FFmpeg/libavformat/hlsenc.c

/*
 * Apple HTTP Live Streaming segmenter
 * Copyright (c) 2012, Luca Barbato
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"
#include <float.h>
#include <stdint.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif

#if CONFIG_GCRYPT
#include <gcrypt.h>
#elif CONFIG_OPENSSL
#include <openssl/rand.h>
#endif

#include "libavutil/avassert.h"
#include "libavutil/mathematics.h"
#include "libavutil/parseutils.h"
#include "libavutil/avstring.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/random_seed.h"
#include "libavutil/opt.h"
#include "libavutil/log.h"
#include "libavutil/time_internal.h"

#include "avformat.h"
#include "avio_internal.h"
#include "internal.h"
#include "os_support.h"

typedef enum {
  HLS_START_SEQUENCE_AS_START_NUMBER = 0,
  HLS_START_SEQUENCE_AS_SECONDS_SINCE_EPOCH = 1,
  HLS_START_SEQUENCE_AS_FORMATTED_DATETIME = 2,  // YYYYMMDDhhmmss
} StartSequenceSourceType;

#define KEYSIZE 16
#define LINE_BUFFER_SIZE 1024
#define HLS_MICROSECOND_UNIT   1000000

typedef struct HLSSegment {
    char filename[1024];
    char sub_filename[1024];
    double duration; /* in seconds */
    int discont;
    int64_t pos;
    int64_t size;

    char key_uri[LINE_BUFFER_SIZE + 1];
    char iv_string[KEYSIZE*2 + 1];

    struct HLSSegment *next;
} HLSSegment;

typedef enum HLSFlags {
    // Generate a single media file and use byte ranges in the playlist.
    HLS_SINGLE_FILE = (1 << 0),
    HLS_DELETE_SEGMENTS = (1 << 1),
    HLS_ROUND_DURATIONS = (1 << 2),
    HLS_DISCONT_START = (1 << 3),
    HLS_OMIT_ENDLIST = (1 << 4),
    HLS_SPLIT_BY_TIME = (1 << 5),
    HLS_APPEND_LIST = (1 << 6),
    HLS_PROGRAM_DATE_TIME = (1 << 7),
    HLS_SECOND_LEVEL_SEGMENT_INDEX = (1 << 8), // include segment index in segment filenames when use_localtime  e.g.: %%03d
    HLS_SECOND_LEVEL_SEGMENT_DURATION = (1 << 9), // include segment duration (microsec) in segment filenames when use_localtime  e.g.: %%09t
    HLS_SECOND_LEVEL_SEGMENT_SIZE = (1 << 10), // include segment size (bytes) in segment filenames when use_localtime  e.g.: %%014s
    HLS_TEMP_FILE = (1 << 11),
    HLS_PERIODIC_REKEY = (1 << 12),
} HLSFlags;

typedef enum {
    SEGMENT_TYPE_MPEGTS,
    SEGMENT_TYPE_FMP4,
} SegmentType;

typedef enum {
    PLAYLIST_TYPE_NONE,
    PLAYLIST_TYPE_EVENT,
    PLAYLIST_TYPE_VOD,
    PLAYLIST_TYPE_NB,
} PlaylistType;

typedef struct HLSContext {
    const AVClass *class;  // Class for private options.
    unsigned number;
    int64_t sequence;
    int64_t start_sequence;
    uint32_t start_sequence_source_type;  // enum StartSequenceSourceType
    AVOutputFormat *oformat;
    AVOutputFormat *vtt_oformat;

    AVFormatContext *avf;
    AVFormatContext *vtt_avf;

    float time;            // Set by a private option.
    float init_time;       // Set by a private option.
    int max_nb_segments;   // Set by a private option.
#if FF_API_HLS_WRAP
    int  wrap;             // Set by a private option.
#endif
    uint32_t flags;        // enum HLSFlags
    uint32_t pl_type;      // enum PlaylistType
    char *segment_filename;
    char *fmp4_init_filename;
    int segment_type;
    int fmp4_init_mode;

    int use_localtime;      ///< flag to expand filename with localtime
    int use_localtime_mkdir;///< flag to mkdir dirname in timebased filename
    int allowcache;
    int64_t recording_time;
    int has_video;
    int has_subtitle;
    int new_start;
    double dpp;           // duration per packet
    int64_t start_pts;
    int64_t end_pts;
    double duration;      // last segment duration computed so far, in seconds
    int64_t start_pos;    // last segment starting position
    int64_t size;         // last segment size
    int64_t max_seg_size; // every segment file max size
    int nb_entries;
    int discontinuity_set;
    int discontinuity;

    HLSSegment *segments;
    HLSSegment *last_segment;
    HLSSegment *old_segments;

    char *basename;
    char *base_output_dirname;
    char *vtt_basename;
    char *vtt_m3u8_name;
    char *baseurl;
    char *format_options_str;
    char *vtt_format_options_str;
    char *subtitle_filename;
    AVDictionary *format_options;

    int encrypt;
    char *key;
    char *key_url;
    char *iv;
    char *key_basename;

    char *key_info_file;
    char key_file[LINE_BUFFER_SIZE + 1];
    char key_uri[LINE_BUFFER_SIZE + 1];
    char key_string[KEYSIZE*2 + 1];
    char iv_string[KEYSIZE*2 + 1];
    AVDictionary *vtt_format_options;

    char *method;

    double initial_prog_date_time;
    char current_segment_final_filename_fmt[1024]; // when renaming segments
    char *user_agent;
} HLSContext;

static int get_int_from_double(double val)
{
    return (int)((val - (int)val) >= 0.001) ? (int)(val + 1) : (int)val;
}

static int mkdir_p(const char *path) {
    int ret = 0;
    char *temp = av_strdup(path);
    char *pos = temp;
    char tmp_ch = '\0';

    if (!path || !temp) {
        return -1;
    }

    if (!strncmp(temp, "/", 1) || !strncmp(temp, "\\", 1)) {
        pos++;
    } else if (!strncmp(temp, "./", 2) || !strncmp(temp, ".\\", 2)) {
        pos += 2;
    }

    for ( ; *pos != '\0'; ++pos) {
        if (*pos == '/' || *pos == '\\') {
            tmp_ch = *pos;
            *pos = '\0';
            ret = mkdir(temp, 0755);
            *pos = tmp_ch;
        }
    }

    if ((*(pos - 1) != '/') || (*(pos - 1) != '\\')) {
        ret = mkdir(temp, 0755);
    }

    av_free(temp);
    return ret;
}

static void set_http_options(AVFormatContext *s, AVDictionary **options, HLSContext *c)
{
    const char *proto = avio_find_protocol_name(s->filename);
    int http_base_proto = proto ? (!av_strcasecmp(proto, "http") || !av_strcasecmp(proto, "https")) : 0;

    if (c->method) {
        av_dict_set(options, "method", c->method, 0);
    } else if (http_base_proto) {
        av_log(c, AV_LOG_WARNING, "No HTTP method set, hls muxer defaulting to method PUT.\n");
        av_dict_set(options, "method", "PUT", 0);
    }
    if (c->user_agent)
        av_dict_set(options, "user_agent", c->user_agent, 0);

}

static int replace_int_data_in_filename(char *buf, int buf_size, const char *filename, char placeholder, int64_t number)
{
    const char *p;
    char *q, buf1[20], c;
    int nd, len, addchar_count;
    int found_count = 0;

    q = buf;
    p = filename;
    for (;;) {
        c = *p;
        if (c == '\0')
            break;
        if (c == '%' && *(p+1) == '%')  // %%
            addchar_count = 2;
        else if (c == '%' && (av_isdigit(*(p+1)) || *(p+1) == placeholder)) {
            nd = 0;
            addchar_count = 1;
            while (av_isdigit(*(p + addchar_count))) {
                nd = nd * 10 + *(p + addchar_count) - '0';
                addchar_count++;
            }

            if (*(p + addchar_count) == placeholder) {
                len = snprintf(buf1, sizeof(buf1), "%0*"PRId64, (number < 0) ? nd : nd++, number);
                if (len < 1)  // returned error or empty buf1
                    goto fail;
                if ((q - buf + len) > buf_size - 1)
                    goto fail;
                memcpy(q, buf1, len);
                q += len;
                p += (addchar_count + 1);
                addchar_count = 0;
                found_count++;
            }

        } else
            addchar_count = 1;

        while (addchar_count--)
            if ((q - buf) < buf_size - 1)
                *q++ = *p++;
            else
                goto fail;
    }
    *q = '\0';
    return found_count;
fail:
    *q = '\0';
    return -1;
}

static void write_styp(AVIOContext *pb)
{
    avio_wb32(pb, 24);
    ffio_wfourcc(pb, "styp");
    ffio_wfourcc(pb, "msdh");
    avio_wb32(pb, 0); /* minor */
    ffio_wfourcc(pb, "msdh");
    ffio_wfourcc(pb, "msix");
}

static int hls_delete_old_segments(AVFormatContext *s, HLSContext *hls) {

    HLSSegment *segment, *previous_segment = NULL;
    float playlist_duration = 0.0f;
    int ret = 0, path_size, sub_path_size;
    char *dirname = NULL, *p, *sub_path;
    char *path = NULL;
    AVDictionary *options = NULL;
    AVIOContext *out = NULL;
    const char *proto = NULL;

    segment = hls->segments;
    while (segment) {
        playlist_duration += segment->duration;
        segment = segment->next;
    }

    segment = hls->old_segments;
    while (segment) {
        playlist_duration -= segment->duration;
        previous_segment = segment;
        segment = previous_segment->next;
        if (playlist_duration <= -previous_segment->duration) {
            previous_segment->next = NULL;
            break;
        }
    }

    if (segment && !hls->use_localtime_mkdir) {
        if (hls->segment_filename) {
            dirname = av_strdup(hls->segment_filename);
        } else {
            dirname = av_strdup(hls->avf->filename);
        }
        if (!dirname) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        p = (char *)av_basename(dirname);
        *p = '\0';
    }

    while (segment) {
        av_log(hls, AV_LOG_DEBUG, "deleting old segment %s\n",
                                  segment->filename);
        path_size =  (hls->use_localtime_mkdir ? 0 : strlen(dirname)) + strlen(segment->filename) + 1;
        path = av_malloc(path_size);
        if (!path) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }

        if (hls->use_localtime_mkdir)
            av_strlcpy(path, segment->filename, path_size);
        else { // segment->filename contains basename only
            av_strlcpy(path, dirname, path_size);
            av_strlcat(path, segment->filename, path_size);
        }

        proto = avio_find_protocol_name(s->filename);
        if (hls->method || (proto && !av_strcasecmp(proto, "http"))) {
            av_dict_set(&options, "method", "DELETE", 0);
            if ((ret = hls->avf->io_open(hls->avf, &out, path, AVIO_FLAG_WRITE, &options)) < 0)
                goto fail;
            ff_format_io_close(hls->avf, &out);
        } else if (unlink(path) < 0) {
            av_log(hls, AV_LOG_ERROR, "failed to delete old segment %s: %s\n",
                                     path, strerror(errno));
        }

        if ((segment->sub_filename[0] != '\0')) {
            sub_path_size = strlen(segment->sub_filename) + 1 + (dirname ? strlen(dirname) : 0);
            sub_path = av_malloc(sub_path_size);
            if (!sub_path) {
                ret = AVERROR(ENOMEM);
                goto fail;
            }

            av_strlcpy(sub_path, dirname, sub_path_size);
            av_strlcat(sub_path, segment->sub_filename, sub_path_size);

            if (hls->method || (proto && !av_strcasecmp(proto, "http"))) {
                av_dict_set(&options, "method", "DELETE", 0);
                if ((ret = hls->avf->io_open(hls->avf, &out, sub_path, AVIO_FLAG_WRITE, &options)) < 0) {
                    av_free(sub_path);
                    goto fail;
                }
                ff_format_io_close(hls->avf, &out);
            } else if (unlink(sub_path) < 0) {
                av_log(hls, AV_LOG_ERROR, "failed to delete old segment %s: %s\n",
                                         sub_path, strerror(errno));
            }
            av_free(sub_path);
        }
        av_freep(&path);
        previous_segment = segment;
        segment = previous_segment->next;
        av_free(previous_segment);
    }

fail:
    av_free(path);
    av_free(dirname);

    return ret;
}

static int randomize(uint8_t *buf, int len)
{
#if CONFIG_GCRYPT
    gcry_randomize(buf, len, GCRY_VERY_STRONG_RANDOM);
    return 0;
#elif CONFIG_OPENSSL
    if (RAND_bytes(buf, len))
        return 0;
#else
    return AVERROR(ENOSYS);
#endif
    return AVERROR(EINVAL);
}

static int do_encrypt(AVFormatContext *s)
{
    HLSContext *hls = s->priv_data;
    int ret;
    int len;
    AVIOContext *pb;
    uint8_t key[KEYSIZE];

    len = strlen(hls->basename) + 4 + 1;
    hls->key_basename = av_mallocz(len);
    if (!hls->key_basename)
        return AVERROR(ENOMEM);

    av_strlcpy(hls->key_basename, s->filename, len);
    av_strlcat(hls->key_basename, ".key", len);

    if (hls->key_url) {
        av_strlcpy(hls->key_file, hls->key_url, sizeof(hls->key_file));
        av_strlcpy(hls->key_uri, hls->key_url, sizeof(hls->key_uri));
    } else {
        av_strlcpy(hls->key_file, hls->key_basename, sizeof(hls->key_file));
        av_strlcpy(hls->key_uri, hls->key_basename, sizeof(hls->key_uri));
    }

    if (!*hls->iv_string) {
        uint8_t iv[16] = { 0 };
        char buf[33];

        if (!hls->iv) {
            AV_WB64(iv + 8, hls->sequence);
        } else {
            memcpy(iv, hls->iv, sizeof(iv));
        }
        ff_data_to_hex(buf, iv, sizeof(iv), 0);
        buf[32] = '\0';
        memcpy(hls->iv_string, buf, sizeof(hls->iv_string));
    }

    if (!*hls->key_uri) {
        av_log(hls, AV_LOG_ERROR, "no key URI specified in key info file\n");
        return AVERROR(EINVAL);
    }

    if (!*hls->key_file) {
        av_log(hls, AV_LOG_ERROR, "no key file specified in key info file\n");
        return AVERROR(EINVAL);
    }

    if (!*hls->key_string) {
        if (!hls->key) {
            if ((ret = randomize(key, sizeof(key))) < 0) {
                av_log(s, AV_LOG_ERROR, "Cannot generate a strong random key\n");
                return ret;
            }
        } else {
            memcpy(key, hls->key, sizeof(key));
        }

        ff_data_to_hex(hls->key_string, key, sizeof(key), 0);
        if ((ret = s->io_open(s, &pb, hls->key_file, AVIO_FLAG_WRITE, NULL)) < 0)
            return ret;
        avio_seek(pb, 0, SEEK_CUR);
        avio_write(pb, key, KEYSIZE);
        avio_close(pb);
    }
    return 0;
}


static int hls_encryption_start(AVFormatContext *s)
{
    HLSContext *hls = s->priv_data;
    int ret;
    AVIOContext *pb;
    uint8_t key[KEYSIZE];

    if ((ret = s->io_open(s, &pb, hls->key_info_file, AVIO_FLAG_READ, NULL)) < 0) {
        av_log(hls, AV_LOG_ERROR,
                "error opening key info file %s\n", hls->key_info_file);
        return ret;
    }

    ff_get_line(pb, hls->key_uri, sizeof(hls->key_uri));
    hls->key_uri[strcspn(hls->key_uri, "\r\n")] = '\0';

    ff_get_line(pb, hls->key_file, sizeof(hls->key_file));
    hls->key_file[strcspn(hls->key_file, "\r\n")] = '\0';

    ff_get_line(pb, hls->iv_string, sizeof(hls->iv_string));
    hls->iv_string[strcspn(hls->iv_string, "\r\n")] = '\0';

    ff_format_io_close(s, &pb);

    if (!*hls->key_uri) {
        av_log(hls, AV_LOG_ERROR, "no key URI specified in key info file\n");
        return AVERROR(EINVAL);
    }

    if (!*hls->key_file) {
        av_log(hls, AV_LOG_ERROR, "no key file specified in key info file\n");
        return AVERROR(EINVAL);
    }

    if ((ret = s->io_open(s, &pb, hls->key_file, AVIO_FLAG_READ, NULL)) < 0) {
        av_log(hls, AV_LOG_ERROR, "error opening key file %s\n", hls->key_file);
        return ret;
    }

    ret = avio_read(pb, key, sizeof(key));
    ff_format_io_close(s, &pb);
    if (ret != sizeof(key)) {
        av_log(hls, AV_LOG_ERROR, "error reading key file %s\n", hls->key_file);
        if (ret >= 0 || ret == AVERROR_EOF)
            ret = AVERROR(EINVAL);
        return ret;
    }
    ff_data_to_hex(hls->key_string, key, sizeof(key), 0);

    return 0;
}

static int read_chomp_line(AVIOContext *s, char *buf, int maxlen)
{
    int len = ff_get_line(s, buf, maxlen);
    while (len > 0 && av_isspace(buf[len - 1]))
        buf[--len] = '\0';
    return len;
}

static int hls_mux_init(AVFormatContext *s)
{
    AVDictionary *options = NULL;
    HLSContext *hls = s->priv_data;
    AVFormatContext *oc;
    AVFormatContext *vtt_oc = NULL;
    int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);
    int i, ret;

    ret = avformat_alloc_output_context2(&hls->avf, hls->oformat, NULL, NULL);
    if (ret < 0)
        return ret;
    oc = hls->avf;

    oc->filename[0]        = '\0';
    oc->oformat            = hls->oformat;
    oc->interrupt_callback = s->interrupt_callback;
    oc->max_delay          = s->max_delay;
    oc->opaque             = s->opaque;
    oc->io_open            = s->io_open;
    oc->io_close           = s->io_close;
    av_dict_copy(&oc->metadata, s->metadata, 0);

    if(hls->vtt_oformat) {
        ret = avformat_alloc_output_context2(&hls->vtt_avf, hls->vtt_oformat, NULL, NULL);
        if (ret < 0)
            return ret;
        vtt_oc          = hls->vtt_avf;
        vtt_oc->oformat = hls->vtt_oformat;
        av_dict_copy(&vtt_oc->metadata, s->metadata, 0);
    }

    for (i = 0; i < s->nb_streams; i++) {
        AVStream *st;
        AVFormatContext *loc;
        if (s->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE)
            loc = vtt_oc;
        else
            loc = oc;

        if (!(st = avformat_new_stream(loc, NULL)))
            return AVERROR(ENOMEM);
        avcodec_parameters_copy(st->codecpar, s->streams[i]->codecpar);
        if (!oc->oformat->codec_tag ||
            av_codec_get_id (oc->oformat->codec_tag, s->streams[i]->codecpar->codec_tag) == st->codecpar->codec_id ||
            av_codec_get_tag(oc->oformat->codec_tag, s->streams[i]->codecpar->codec_id) <= 0) {
            st->codecpar->codec_tag = s->streams[i]->codecpar->codec_tag;
        } else {
            st->codecpar->codec_tag = 0;
        }

        st->sample_aspect_ratio = s->streams[i]->sample_aspect_ratio;
        st->time_base = s->streams[i]->time_base;
        av_dict_copy(&st->metadata, s->streams[i]->metadata, 0);
    }
    hls->start_pos = 0;
    hls->new_start = 1;
    hls->fmp4_init_mode = 0;

    if (hls->segment_type == SEGMENT_TYPE_FMP4) {
        if (hls->max_seg_size > 0) {
            av_log(s, AV_LOG_WARNING, "Multi-file byterange mode is currently unsupported in the HLS muxer.\n");
            return AVERROR_PATCHWELCOME;
        }
        hls->fmp4_init_mode = !byterange_mode;
        set_http_options(s, &options, hls);
        if ((ret = s->io_open(s, &oc->pb, hls->base_output_dirname, AVIO_FLAG_WRITE, &options)) < 0) {
            av_log(s, AV_LOG_ERROR, "Failed to open segment '%s'\n", hls->fmp4_init_filename);
            return ret;
        }

        if (hls->format_options_str) {
            ret = av_dict_parse_string(&hls->format_options, hls->format_options_str, "=", ":", 0);
            if (ret < 0) {
                av_log(s, AV_LOG_ERROR, "Could not parse format options list '%s'\n",
                       hls->format_options_str);
                return ret;
            }
        }

        av_dict_copy(&options, hls->format_options, 0);
        av_dict_set(&options, "fflags", "-autobsf", 0);
        av_dict_set(&options, "movflags", "frag_custom+dash+delay_moov", 0);
        ret = avformat_init_output(oc, &options);
        if (ret < 0)
            return ret;
        if (av_dict_count(options)) {
            av_log(s, AV_LOG_ERROR, "Some of the provided format options in '%s' are not recognized\n", hls->format_options_str);
            av_dict_free(&options);
            return AVERROR(EINVAL);
        }
        av_dict_free(&options);
    }
    return 0;
}

static HLSSegment *find_segment_by_filename(HLSSegment *segment, const char *filename)
{
    while (segment) {
        if (!av_strcasecmp(segment->filename,filename))
            return segment;
        segment = segment->next;
    }
    return (HLSSegment *) NULL;
}

static int sls_flags_filename_process(struct AVFormatContext *s, HLSContext *hls, HLSSegment *en, double duration,
                                         int64_t pos, int64_t size)
{
    if ((hls->flags & (HLS_SECOND_LEVEL_SEGMENT_SIZE | HLS_SECOND_LEVEL_SEGMENT_DURATION)) &&
        strlen(hls->current_segment_final_filename_fmt)) {
        av_strlcpy(hls->avf->filename, hls->current_segment_final_filename_fmt, sizeof(hls->avf->filename));
        if (hls->flags & HLS_SECOND_LEVEL_SEGMENT_SIZE) {
            char * filename = av_strdup(hls->avf->filename);  // %%s will be %s after strftime
            if (!filename) {
                av_free(en);
                return AVERROR(ENOMEM);
            }
            if (replace_int_data_in_filename(hls->avf->filename, sizeof(hls->avf->filename),
                filename, 's', pos + size) < 1) {
                av_log(hls, AV_LOG_ERROR,
                       "Invalid second level segment filename template '%s', "
                        "you can try to remove second_level_segment_size flag\n",
                       filename);
                av_free(filename);
                av_free(en);
                return AVERROR(EINVAL);
            }
            av_free(filename);
        }
        if (hls->flags & HLS_SECOND_LEVEL_SEGMENT_DURATION) {
            char * filename = av_strdup(hls->avf->filename);  // %%t will be %t after strftime
            if (!filename) {
                av_free(en);
                return AVERROR(ENOMEM);
            }
            if (replace_int_data_in_filename(hls->avf->filename, sizeof(hls->avf->filename),
                filename, 't',  (int64_t)round(duration * HLS_MICROSECOND_UNIT)) < 1) {
                av_log(hls, AV_LOG_ERROR,
                       "Invalid second level segment filename template '%s', "
                        "you can try to remove second_level_segment_time flag\n",
                       filename);
                av_free(filename);
                av_free(en);
                return AVERROR(EINVAL);
            }
            av_free(filename);
        }
    }
    return 0;
}

static int sls_flag_check_duration_size_index(HLSContext *hls)
{
    int ret = 0;

    if (hls->flags & HLS_SECOND_LEVEL_SEGMENT_DURATION) {
         av_log(hls, AV_LOG_ERROR,
                "second_level_segment_duration hls_flag requires use_localtime to be true\n");
         ret = AVERROR(EINVAL);
    }
    if (hls->flags & HLS_SECOND_LEVEL_SEGMENT_SIZE) {
         av_log(hls, AV_LOG_ERROR,
                "second_level_segment_size hls_flag requires use_localtime to be true\n");
         ret = AVERROR(EINVAL);
    }
    if (hls->flags & HLS_SECOND_LEVEL_SEGMENT_INDEX) {
        av_log(hls, AV_LOG_ERROR,
               "second_level_segment_index hls_flag requires use_localtime to be true\n");
        ret = AVERROR(EINVAL);
    }

    return ret;
}

static int sls_flag_check_duration_size(HLSContext *hls)
{
    const char *proto = avio_find_protocol_name(hls->basename);
    int segment_renaming_ok = proto && !strcmp(proto, "file");
    int ret = 0;

    if ((hls->flags & HLS_SECOND_LEVEL_SEGMENT_DURATION) && !segment_renaming_ok) {
         av_log(hls, AV_LOG_ERROR,
                "second_level_segment_duration hls_flag works only with file protocol segment names\n");
         ret = AVERROR(EINVAL);
    }
    if ((hls->flags & HLS_SECOND_LEVEL_SEGMENT_SIZE) && !segment_renaming_ok) {
         av_log(hls, AV_LOG_ERROR,
                "second_level_segment_size hls_flag works only with file protocol segment names\n");
         ret = AVERROR(EINVAL);
    }

    return ret;
}

static void sls_flag_file_rename(HLSContext *hls, char *old_filename) {
    if ((hls->flags & (HLS_SECOND_LEVEL_SEGMENT_SIZE | HLS_SECOND_LEVEL_SEGMENT_DURATION)) &&
        strlen(hls->current_segment_final_filename_fmt)) {
        ff_rename(old_filename, hls->avf->filename, hls);
    }
}

static int sls_flag_use_localtime_filename(AVFormatContext *oc, HLSContext *c)
{
    if (c->flags & HLS_SECOND_LEVEL_SEGMENT_INDEX) {
        char * filename = av_strdup(oc->filename);  // %%d will be %d after strftime
        if (!filename)
            return AVERROR(ENOMEM);
        if (replace_int_data_in_filename(oc->filename, sizeof(oc->filename),
#if FF_API_HLS_WRAP
            filename, 'd', c->wrap ? c->sequence % c->wrap : c->sequence) < 1) {
#else
            filename, 'd', c->sequence) < 1) {
#endif
            av_log(c, AV_LOG_ERROR, "Invalid second level segment filename template '%s', "
                    "you can try to remove second_level_segment_index flag\n",
                   filename);
            av_free(filename);
            return AVERROR(EINVAL);
        }
        av_free(filename);
    }
    if (c->flags & (HLS_SECOND_LEVEL_SEGMENT_SIZE | HLS_SECOND_LEVEL_SEGMENT_DURATION)) {
        av_strlcpy(c->current_segment_final_filename_fmt, oc->filename,
                   sizeof(c->current_segment_final_filename_fmt));
        if (c->flags & HLS_SECOND_LEVEL_SEGMENT_SIZE) {
            char * filename = av_strdup(oc->filename);  // %%s will be %s after strftime
            if (!filename)
                return AVERROR(ENOMEM);
            if (replace_int_data_in_filename(oc->filename, sizeof(oc->filename), filename, 's', 0) < 1) {
                av_log(c, AV_LOG_ERROR, "Invalid second level segment filename template '%s', "
                        "you can try to remove second_level_segment_size flag\n",
                       filename);
                av_free(filename);
                return AVERROR(EINVAL);
            }
            av_free(filename);
        }
        if (c->flags & HLS_SECOND_LEVEL_SEGMENT_DURATION) {
            char * filename = av_strdup(oc->filename);  // %%t will be %t after strftime
            if (!filename)
                return AVERROR(ENOMEM);
            if (replace_int_data_in_filename(oc->filename, sizeof(oc->filename), filename, 't', 0) < 1) {
                av_log(c, AV_LOG_ERROR, "Invalid second level segment filename template '%s', "
                        "you can try to remove second_level_segment_time flag\n",
                       filename);
                av_free(filename);
                return AVERROR(EINVAL);
            }
            av_free(filename);
        }
    }
    return 0;
}

/* Create a new segment and append it to the segment list */
static int hls_append_segment(struct AVFormatContext *s, HLSContext *hls, double duration,
                              int64_t pos, int64_t size)
{
    HLSSegment *en = av_malloc(sizeof(*en));
    const char  *filename;
    int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);
    int ret;

    if (!en)
        return AVERROR(ENOMEM);

    ret = sls_flags_filename_process(s, hls, en, duration, pos, size);
    if (ret < 0) {
        return ret;
    }

    filename = av_basename(hls->avf->filename);

    if (hls->use_localtime_mkdir) {
        filename = hls->avf->filename;
    }
    if ((find_segment_by_filename(hls->segments, filename) || find_segment_by_filename(hls->old_segments, filename))
        && !byterange_mode) {
        av_log(hls, AV_LOG_WARNING, "Duplicated segment filename detected: %s\n", filename);
    }
    av_strlcpy(en->filename, filename, sizeof(en->filename));

    if(hls->has_subtitle)
        av_strlcpy(en->sub_filename, av_basename(hls->vtt_avf->filename), sizeof(en->sub_filename));
    else
        en->sub_filename[0] = '\0';

    en->duration = duration;
    en->pos      = pos;
    en->size     = size;
    en->next     = NULL;
    en->discont  = 0;

    if (hls->discontinuity) {
        en->discont = 1;
        hls->discontinuity = 0;
    }

    if (hls->key_info_file || hls->encrypt) {
        av_strlcpy(en->key_uri, hls->key_uri, sizeof(en->key_uri));
        av_strlcpy(en->iv_string, hls->iv_string, sizeof(en->iv_string));
    }

    if (!hls->segments)
        hls->segments = en;
    else
        hls->last_segment->next = en;

    hls->last_segment = en;

    // EVENT or VOD playlists imply sliding window cannot be used
    if (hls->pl_type != PLAYLIST_TYPE_NONE)
        hls->max_nb_segments = 0;

    if (hls->max_nb_segments && hls->nb_entries >= hls->max_nb_segments) {
        en = hls->segments;
        hls->initial_prog_date_time += en->duration;
        hls->segments = en->next;
        if (en && hls->flags & HLS_DELETE_SEGMENTS &&
#if FF_API_HLS_WRAP
                !(hls->flags & HLS_SINGLE_FILE || hls->wrap)) {
#else
                !(hls->flags & HLS_SINGLE_FILE)) {
#endif
            en->next = hls->old_segments;
            hls->old_segments = en;
            if ((ret = hls_delete_old_segments(s, hls)) < 0)
                return ret;
        } else
            av_free(en);
    } else
        hls->nb_entries++;

    if (hls->max_seg_size > 0) {
        return 0;
    }
    hls->sequence++;

    return 0;
}

static int parse_playlist(AVFormatContext *s, const char *url)
{
    HLSContext *hls = s->priv_data;
    AVIOContext *in;
    int ret = 0, is_segment = 0;
    int64_t new_start_pos;
    char line[1024];
    const char *ptr;
    const char *end;

    if ((ret = ffio_open_whitelist(&in, url, AVIO_FLAG_READ,
                                   &s->interrupt_callback, NULL,
                                   s->protocol_whitelist, s->protocol_blacklist)) < 0)
        return ret;

    read_chomp_line(in, line, sizeof(line));
    if (strcmp(line, "#EXTM3U")) {
        ret = AVERROR_INVALIDDATA;
        goto fail;
    }

    hls->discontinuity = 0;
    while (!avio_feof(in)) {
        read_chomp_line(in, line, sizeof(line));
        if (av_strstart(line, "#EXT-X-MEDIA-SEQUENCE:", &ptr)) {
            int64_t tmp_sequence = strtoll(ptr, NULL, 10);
            if (tmp_sequence < hls->sequence)
              av_log(hls, AV_LOG_VERBOSE,
                     "Found playlist sequence number was smaller """
                     "than specified start sequence number: %"PRId64" < %"PRId64", "
                     "omitting\n", tmp_sequence, hls->start_sequence);
            else {
              av_log(hls, AV_LOG_DEBUG, "Found playlist sequence number: %"PRId64"\n", tmp_sequence);
              hls->sequence = tmp_sequence;
            }
        } else if (av_strstart(line, "#EXT-X-DISCONTINUITY", &ptr)) {
            is_segment = 1;
            hls->discontinuity = 1;
        } else if (av_strstart(line, "#EXTINF:", &ptr)) {
            is_segment = 1;
            hls->duration = atof(ptr);
        } else if (av_stristart(line, "#EXT-X-KEY:", &ptr)) {
            ptr = av_stristr(line, "URI=\"");
            if (ptr) {
                ptr += strlen("URI=\"");
                end = av_stristr(ptr, ",");
                if (end) {
                    av_strlcpy(hls->key_uri, ptr, end - ptr);
                } else {
                    av_strlcpy(hls->key_uri, ptr, sizeof(hls->key_uri));
                }
            }

            ptr = av_stristr(line, "IV=0x");
            if (ptr) {
                ptr += strlen("IV=0x");
                end = av_stristr(ptr, ",");
                if (end) {
                    av_strlcpy(hls->iv_string, ptr, end - ptr);
                } else {
                    av_strlcpy(hls->iv_string, ptr, sizeof(hls->iv_string));
                }
            }

        } else if (av_strstart(line, "#", NULL)) {
            continue;
        } else if (line[0]) {
            if (is_segment) {
                is_segment = 0;
                new_start_pos = avio_tell(hls->avf->pb);
                hls->size = new_start_pos - hls->start_pos;
                av_strlcpy(hls->avf->filename, line, sizeof(line));
                ret = hls_append_segment(s, hls, hls->duration, hls->start_pos, hls->size);
                if (ret < 0)
                    goto fail;
                hls->start_pos = new_start_pos;
            }
        }
    }

fail:
    avio_close(in);
    return ret;
}

static void hls_free_segments(HLSSegment *p)
{
    HLSSegment *en;

    while(p) {
        en = p;
        p = p->next;
        av_free(en);
    }
}

static void write_m3u8_head_block(HLSContext *hls, AVIOContext *out, int version,
                                  int target_duration, int64_t sequence)
{
    avio_printf(out, "#EXTM3U\n");
    avio_printf(out, "#EXT-X-VERSION:%d\n", version);
    if (hls->allowcache == 0 || hls->allowcache == 1) {
        avio_printf(out, "#EXT-X-ALLOW-CACHE:%s\n", hls->allowcache == 0 ? "NO" : "YES");
    }
    avio_printf(out, "#EXT-X-TARGETDURATION:%d\n", target_duration);
    avio_printf(out, "#EXT-X-MEDIA-SEQUENCE:%"PRId64"\n", sequence);
    av_log(hls, AV_LOG_VERBOSE, "EXT-X-MEDIA-SEQUENCE:%"PRId64"\n", sequence);
}

static void hls_rename_temp_file(AVFormatContext *s, AVFormatContext *oc)
{
    size_t len = strlen(oc->filename);
    char final_filename[sizeof(oc->filename)];

    av_strlcpy(final_filename, oc->filename, len);
    final_filename[len-4] = '\0';
    ff_rename(oc->filename, final_filename, s);
    oc->filename[len-4] = '\0';
}

static int hls_window(AVFormatContext *s, int last)
{
    HLSContext *hls = s->priv_data;
    HLSSegment *en;
    int target_duration = 0;
    int ret = 0;
    AVIOContext *out = NULL;
    AVIOContext *sub_out = NULL;
    char temp_filename[1024];
    int64_t sequence = FFMAX(hls->start_sequence, hls->sequence - hls->nb_entries);
    int version = 3;
    const char *proto = avio_find_protocol_name(s->filename);
    int use_rename = proto && !strcmp(proto, "file");
    static unsigned warned_non_file;
    char *key_uri = NULL;
    char *iv_string = NULL;
    AVDictionary *options = NULL;
    double prog_date_time = hls->initial_prog_date_time;
    int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);

    if (byterange_mode) {
        version = 4;
        sequence = 0;
    }

    if (hls->segment_type == SEGMENT_TYPE_FMP4) {
        version = 7;
    }

    if (!use_rename && !warned_non_file++)
        av_log(s, AV_LOG_ERROR, "Cannot use rename on non file protocol, this may lead to races and temporary partial files\n");

    set_http_options(s, &options, hls);
    snprintf(temp_filename, sizeof(temp_filename), use_rename ? "%s.tmp" : "%s", s->filename);
    if ((ret = s->io_open(s, &out, temp_filename, AVIO_FLAG_WRITE, &options)) < 0)
        goto fail;

    for (en = hls->segments; en; en = en->next) {
        if (target_duration <= en->duration)
            target_duration = get_int_from_double(en->duration);
    }

    hls->discontinuity_set = 0;
    write_m3u8_head_block(hls, out, version, target_duration, sequence);
    if (hls->pl_type == PLAYLIST_TYPE_EVENT) {
        avio_printf(out, "#EXT-X-PLAYLIST-TYPE:EVENT\n");
    } else if (hls->pl_type == PLAYLIST_TYPE_VOD) {
        avio_printf(out, "#EXT-X-PLAYLIST-TYPE:VOD\n");
    }

    if((hls->flags & HLS_DISCONT_START) && sequence==hls->start_sequence && hls->discontinuity_set==0 ){
        avio_printf(out, "#EXT-X-DISCONTINUITY\n");
        hls->discontinuity_set = 1;
    }
    for (en = hls->segments; en; en = en->next) {
        if ((hls->encrypt || hls->key_info_file) && (!key_uri || strcmp(en->key_uri, key_uri) ||
                                    av_strcasecmp(en->iv_string, iv_string))) {
            avio_printf(out, "#EXT-X-KEY:METHOD=AES-128,URI=\"%s\"", en->key_uri);
            if (*en->iv_string)
                avio_printf(out, ",IV=0x%s", en->iv_string);
            avio_printf(out, "\n");
            key_uri = en->key_uri;
            iv_string = en->iv_string;
        }

        if (en->discont) {
            avio_printf(out, "#EXT-X-DISCONTINUITY\n");
        }

        if ((hls->segment_type == SEGMENT_TYPE_FMP4) && (en == hls->segments)) {
            avio_printf(out, "#EXT-X-MAP:URI=\"%s\"", hls->fmp4_init_filename);
            if (hls->flags & HLS_SINGLE_FILE) {
                avio_printf(out, ",BYTERANGE=\"%"PRId64"@%"PRId64"\"", en->size, en->pos);
            }
            avio_printf(out, "\n");
        } else {
            if (hls->flags & HLS_ROUND_DURATIONS)
                avio_printf(out, "#EXTINF:%ld,\n",  lrint(en->duration));
            else
                avio_printf(out, "#EXTINF:%f,\n", en->duration);
            if (byterange_mode)
                avio_printf(out, "#EXT-X-BYTERANGE:%"PRId64"@%"PRId64"\n",
                            en->size, en->pos);
        }
        if (hls->flags & HLS_PROGRAM_DATE_TIME) {
            time_t tt, wrongsecs;
            int milli;
            struct tm *tm, tmpbuf;
            char buf0[128], buf1[128];
            tt = (int64_t)prog_date_time;
            milli = av_clip(lrint(1000*(prog_date_time - tt)), 0, 999);
            tm = localtime_r(&tt, &tmpbuf);
            strftime(buf0, sizeof(buf0), "%Y-%m-%dT%H:%M:%S", tm);
            if (!strftime(buf1, sizeof(buf1), "%z", tm) || buf1[1]<'0' ||buf1[1]>'2') {
                int tz_min, dst = tm->tm_isdst;
                tm = gmtime_r(&tt, &tmpbuf);
                tm->tm_isdst = dst;
                wrongsecs = mktime(tm);
                tz_min = (abs(wrongsecs - tt) + 30) / 60;
                snprintf(buf1, sizeof(buf1),
                         "%c%02d%02d",
                         wrongsecs <= tt ? '+' : '-',
                         tz_min / 60,
                         tz_min % 60);
            }
            avio_printf(out, "#EXT-X-PROGRAM-DATE-TIME:%s.%03d%s\n", buf0, milli, buf1);
            prog_date_time += en->duration;
        }
        if (!((hls->segment_type == SEGMENT_TYPE_FMP4) && (en == hls->segments))) {
            if (hls->baseurl)
                avio_printf(out, "%s", hls->baseurl);
            avio_printf(out, "%s\n", en->filename);
        }
    }

    if (last && (hls->flags & HLS_OMIT_ENDLIST)==0)
        avio_printf(out, "#EXT-X-ENDLIST\n");

    if( hls->vtt_m3u8_name ) {
        if ((ret = s->io_open(s, &sub_out, hls->vtt_m3u8_name, AVIO_FLAG_WRITE, &options)) < 0)
            goto fail;
        write_m3u8_head_block(hls, sub_out, version, target_duration, sequence);

        for (en = hls->segments; en; en = en->next) {
            avio_printf(sub_out, "#EXTINF:%f,\n", en->duration);
            if (byterange_mode)
                 avio_printf(sub_out, "#EXT-X-BYTERANGE:%"PRIi64"@%"PRIi64"\n",
                         en->size, en->pos);
            if (hls->baseurl)
                avio_printf(sub_out, "%s", hls->baseurl);
            avio_printf(sub_out, "%s\n", en->sub_filename);
        }

        if (last)
            avio_printf(sub_out, "#EXT-X-ENDLIST\n");

    }

fail:
    av_dict_free(&options);
    ff_format_io_close(s, &out);
    ff_format_io_close(s, &sub_out);
    if (ret >= 0 && use_rename)
        ff_rename(temp_filename, s->filename, s);
    return ret;
}

static int hls_start(AVFormatContext *s)
{
    HLSContext *c = s->priv_data;
    AVFormatContext *oc = c->avf;
    AVFormatContext *vtt_oc = c->vtt_avf;
    AVDictionary *options = NULL;
    char *filename, iv_string[KEYSIZE*2 + 1];
    int err = 0;

    if (c->flags & HLS_SINGLE_FILE) {
        av_strlcpy(oc->filename, c->basename,
                   sizeof(oc->filename));
        if (c->vtt_basename)
            av_strlcpy(vtt_oc->filename, c->vtt_basename,
                  sizeof(vtt_oc->filename));
    } else if (c->max_seg_size > 0) {
        if (replace_int_data_in_filename(oc->filename, sizeof(oc->filename),
#if FF_API_HLS_WRAP
            c->basename, 'd', c->wrap ? c->sequence % c->wrap : c->sequence) < 1) {
#else
            c->basename, 'd', c->sequence) < 1) {
#endif
                av_log(oc, AV_LOG_ERROR, "Invalid segment filename template '%s', you can try to use -use_localtime 1 with it\n", c->basename);
                return AVERROR(EINVAL);
        }
    } else {
        if (c->use_localtime) {
            time_t now0;
            struct tm *tm, tmpbuf;
            time(&now0);
            tm = localtime_r(&now0, &tmpbuf);
            if (!strftime(oc->filename, sizeof(oc->filename), c->basename, tm)) {
                av_log(oc, AV_LOG_ERROR, "Could not get segment filename with use_localtime\n");
                return AVERROR(EINVAL);
            }

            err = sls_flag_use_localtime_filename(oc, c);
            if (err < 0) {
                return AVERROR(ENOMEM);
            }

            if (c->use_localtime_mkdir) {
                const char *dir;
                char *fn_copy = av_strdup(oc->filename);
                if (!fn_copy) {
                    return AVERROR(ENOMEM);
                }
                dir = av_dirname(fn_copy);
                if (mkdir_p(dir) == -1 && errno != EEXIST) {
                    av_log(oc, AV_LOG_ERROR, "Could not create directory %s with use_localtime_mkdir\n", dir);
                    av_free(fn_copy);
                    return AVERROR(errno);
                }
                av_free(fn_copy);
            }
        } else if (replace_int_data_in_filename(oc->filename, sizeof(oc->filename),
#if FF_API_HLS_WRAP
                   c->basename, 'd', c->wrap ? c->sequence % c->wrap : c->sequence) < 1) {
#else
                   c->basename, 'd', c->sequence) < 1) {
#endif
            av_log(oc, AV_LOG_ERROR, "Invalid segment filename template '%s' you can try to use -use_localtime 1 with it\n", c->basename);
            return AVERROR(EINVAL);
        }
        if( c->vtt_basename) {
            if (replace_int_data_in_filename(vtt_oc->filename, sizeof(vtt_oc->filename),
#if FF_API_HLS_WRAP
                c->vtt_basename, 'd', c->wrap ? c->sequence % c->wrap : c->sequence) < 1) {
#else
                c->vtt_basename, 'd', c->sequence) < 1) {
#endif
                av_log(vtt_oc, AV_LOG_ERROR, "Invalid segment filename template '%s'\n", c->vtt_basename);
                return AVERROR(EINVAL);
            }
       }
    }
    c->number++;

    set_http_options(s, &options, c);

    if (c->flags & HLS_TEMP_FILE) {
        av_strlcat(oc->filename, ".tmp", sizeof(oc->filename));
    }

    if (c->key_info_file || c->encrypt) {
        if (c->key_info_file && c->encrypt) {
            av_log(s, AV_LOG_WARNING, "Cannot use both -hls_key_info_file and -hls_enc,"
                  " will use -hls_key_info_file priority\n");
        }

        if (c->number <= 1 || (c->flags & HLS_PERIODIC_REKEY)) {
            if (c->key_info_file) {
                if ((err = hls_encryption_start(s)) < 0)
                    goto fail;
            } else {
                if ((err = do_encrypt(s)) < 0)
                    goto fail;
            }
        }
        if ((err = av_dict_set(&options, "encryption_key", c->key_string, 0))
                < 0)
            goto fail;
        err = av_strlcpy(iv_string, c->iv_string, sizeof(iv_string));
        if (!err)
            snprintf(iv_string, sizeof(iv_string), "%032"PRIx64, c->sequence);
        if ((err = av_dict_set(&options, "encryption_iv", iv_string, 0)) < 0)
           goto fail;

        filename = av_asprintf("crypto:%s", oc->filename);
        if (!filename) {
            err = AVERROR(ENOMEM);
            goto fail;
        }
        err = s->io_open(s, &oc->pb, filename, AVIO_FLAG_WRITE, &options);
        av_free(filename);
        av_dict_free(&options);
        if (err < 0)
            return err;
    } else
        if ((err = s->io_open(s, &oc->pb, oc->filename, AVIO_FLAG_WRITE, &options)) < 0)
            goto fail;
    if (c->vtt_basename) {
        set_http_options(s, &options, c);
        if ((err = s->io_open(s, &vtt_oc->pb, vtt_oc->filename, AVIO_FLAG_WRITE, &options)) < 0)
            goto fail;
    }
    av_dict_free(&options);

    if (c->segment_type == SEGMENT_TYPE_FMP4 && !(c->flags & HLS_SINGLE_FILE)) {
            write_styp(oc->pb);
    } else {
        /* We only require one PAT/PMT per segment. */
        if (oc->oformat->priv_class && oc->priv_data) {
            char period[21];

            snprintf(period, sizeof(period), "%d", (INT_MAX / 2) - 1);

            av_opt_set(oc->priv_data, "mpegts_flags", "resend_headers", 0);
            av_opt_set(oc->priv_data, "sdt_period", period, 0);
            av_opt_set(oc->priv_data, "pat_period", period, 0);
        }
    }

    if (c->vtt_basename) {
        err = avformat_write_header(vtt_oc,NULL);
        if (err < 0)
            return err;
    }

    return 0;
fail:
    av_dict_free(&options);

    return err;
}

static const char * get_default_pattern_localtime_fmt(AVFormatContext *s)
{
    char b[21];
    time_t t = time(NULL);
    struct tm *p, tmbuf;
    HLSContext *hls = s->priv_data;

    p = localtime_r(&t, &tmbuf);
    // no %s support when strftime returned error or left format string unchanged
    // also no %s support on MSVC, which invokes the invalid parameter handler on unsupported format strings, instead of returning an error
    if (hls->segment_type == SEGMENT_TYPE_FMP4) {
        return (HAVE_LIBC_MSVCRT || !strftime(b, sizeof(b), "%s", p) || !strcmp(b, "%s")) ? "-%Y%m%d%H%M%S.m4s" : "-%s.m4s";
    }
    return (HAVE_LIBC_MSVCRT || !strftime(b, sizeof(b), "%s", p) || !strcmp(b, "%s")) ? "-%Y%m%d%H%M%S.ts" : "-%s.ts";
}

static int hls_write_header(AVFormatContext *s)
{
    HLSContext *hls = s->priv_data;
    int ret, i;
    char *p = NULL;
    const char *pattern = "%d.ts";
    const char *pattern_localtime_fmt = get_default_pattern_localtime_fmt(s);
    const char *vtt_pattern = "%d.vtt";
    AVDictionary *options = NULL;
    int basename_size = 0;
    int vtt_basename_size = 0;

    if (hls->segment_type == SEGMENT_TYPE_FMP4) {
        pattern = "%d.m4s";
    }
    if ((hls->start_sequence_source_type == HLS_START_SEQUENCE_AS_SECONDS_SINCE_EPOCH) ||
        (hls->start_sequence_source_type == HLS_START_SEQUENCE_AS_FORMATTED_DATETIME)) {
        time_t t = time(NULL); // we will need it in either case
        if (hls->start_sequence_source_type == HLS_START_SEQUENCE_AS_SECONDS_SINCE_EPOCH) {
            hls->start_sequence = (int64_t)t;
        } else if (hls->start_sequence_source_type == HLS_START_SEQUENCE_AS_FORMATTED_DATETIME) {
            char b[15];
            struct tm *p, tmbuf;
            if (!(p = localtime_r(&t, &tmbuf)))
                return AVERROR(ENOMEM);
            if (!strftime(b, sizeof(b), "%Y%m%d%H%M%S", p))
                return AVERROR(ENOMEM);
            hls->start_sequence = strtoll(b, NULL, 10);
        }
        av_log(hls, AV_LOG_DEBUG, "start_number evaluated to %"PRId64"\n", hls->start_sequence);
    }

    hls->sequence       = hls->start_sequence;
    hls->recording_time = (hls->init_time ? hls->init_time : hls->time) * AV_TIME_BASE;
    hls->start_pts      = AV_NOPTS_VALUE;
    hls->current_segment_final_filename_fmt[0] = '\0';

    if (hls->flags & HLS_PROGRAM_DATE_TIME) {
        time_t now0;
        time(&now0);
        hls->initial_prog_date_time = now0;
    }

    if (hls->format_options_str) {
        ret = av_dict_parse_string(&hls->format_options, hls->format_options_str, "=", ":", 0);
        if (ret < 0) {
            av_log(s, AV_LOG_ERROR, "Could not parse format options list '%s'\n", hls->format_options_str);
            goto fail;
        }
    }

    for (i = 0; i < s->nb_streams; i++) {
        hls->has_video +=
            s->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO;
        hls->has_subtitle +=
            s->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE;
    }

    if (hls->has_video > 1)
        av_log(s, AV_LOG_WARNING,
               "More than a single video stream present, "
               "expect issues decoding it.\n");

    if (hls->segment_type == SEGMENT_TYPE_FMP4) {
        hls->oformat = av_guess_format("mp4", NULL, NULL);
    } else {
        hls->oformat = av_guess_format("mpegts", NULL, NULL);
    }

    if (!hls->oformat) {
        ret = AVERROR_MUXER_NOT_FOUND;
        goto fail;
    }

    if(hls->has_subtitle) {
        hls->vtt_oformat = av_guess_format("webvtt", NULL, NULL);
        if (!hls->oformat) {
            ret = AVERROR_MUXER_NOT_FOUND;
            goto fail;
        }
    }

    if (hls->segment_filename) {
        hls->basename = av_strdup(hls->segment_filename);
        if (!hls->basename) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
    } else {
        if (hls->flags & HLS_SINGLE_FILE) {
            if (hls->segment_type == SEGMENT_TYPE_FMP4) {
                pattern = ".m4s";
            } else {
                pattern = ".ts";
            }
        }

        if (hls->use_localtime) {
            basename_size = strlen(s->filename) + strlen(pattern_localtime_fmt) + 1;
        } else {
            basename_size = strlen(s->filename) + strlen(pattern) + 1;
        }
        hls->basename = av_malloc(basename_size);
        if (!hls->basename) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }

        av_strlcpy(hls->basename, s->filename, basename_size);

        p = strrchr(hls->basename, '.');
        if (p)
            *p = '\0';
        if (hls->use_localtime) {
            av_strlcat(hls->basename, pattern_localtime_fmt, basename_size);
        } else {
            av_strlcat(hls->basename, pattern, basename_size);
        }
    }

    if (av_strcasecmp(hls->fmp4_init_filename, "init.mp4")) {
        int fmp4_init_filename_len = strlen(hls->fmp4_init_filename) + 1;
        hls->base_output_dirname = av_malloc(fmp4_init_filename_len);
        if (!hls->base_output_dirname) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        av_strlcpy(hls->base_output_dirname, hls->fmp4_init_filename, fmp4_init_filename_len);
    } else {
        hls->base_output_dirname = av_malloc(basename_size);
        if (!hls->base_output_dirname) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }

        av_strlcpy(hls->base_output_dirname, s->filename, basename_size);
        p = strrchr(hls->base_output_dirname, '/');
        if (p) {
            *(p + 1) = '\0';
            av_strlcat(hls->base_output_dirname, hls->fmp4_init_filename, basename_size);
        } else {
            av_strlcpy(hls->base_output_dirname, hls->fmp4_init_filename, basename_size);
        }
    }

    if (!hls->use_localtime) {
        ret = sls_flag_check_duration_size_index(hls);
        if (ret < 0) {
             goto fail;
        }
    } else {
        ret = sls_flag_check_duration_size(hls);
        if (ret < 0) {
             goto fail;
        }
    }
    if(hls->has_subtitle) {

        if (hls->flags & HLS_SINGLE_FILE)
            vtt_pattern = ".vtt";
        vtt_basename_size = strlen(s->filename) + strlen(vtt_pattern) + 1;
        hls->vtt_basename = av_malloc(vtt_basename_size);
        if (!hls->vtt_basename) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        hls->vtt_m3u8_name = av_malloc(vtt_basename_size);
        if (!hls->vtt_m3u8_name ) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        av_strlcpy(hls->vtt_basename, s->filename, vtt_basename_size);
        p = strrchr(hls->vtt_basename, '.');
        if (p)
            *p = '\0';

        if( hls->subtitle_filename ) {
            strcpy(hls->vtt_m3u8_name, hls->subtitle_filename);
        } else {
            strcpy(hls->vtt_m3u8_name, hls->vtt_basename);
            av_strlcat(hls->vtt_m3u8_name, "_vtt.m3u8", vtt_basename_size);
        }
        av_strlcat(hls->vtt_basename, vtt_pattern, vtt_basename_size);
    }

    if ((hls->flags & HLS_SINGLE_FILE) && (hls->segment_type == SEGMENT_TYPE_FMP4)) {
        hls->fmp4_init_filename  = av_strdup(hls->basename);
        if (!hls->fmp4_init_filename) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
    }

    if ((ret = hls_mux_init(s)) < 0)
        goto fail;

    if (hls->flags & HLS_APPEND_LIST) {
        parse_playlist(s, s->filename);
        hls->discontinuity = 1;
        if (hls->init_time > 0) {
            av_log(s, AV_LOG_WARNING, "append_list mode does not support hls_init_time,"
                   " hls_init_time value will have no effect\n");
            hls->init_time = 0;
            hls->recording_time = hls->time * AV_TIME_BASE;
        }
    }

    if (hls->segment_type != SEGMENT_TYPE_FMP4 || hls->flags & HLS_SINGLE_FILE) {
        if ((ret = hls_start(s)) < 0)
            goto fail;
    }

    av_dict_copy(&options, hls->format_options, 0);
    ret = avformat_write_header(hls->avf, &options);
    if (av_dict_count(options)) {
        av_log(s, AV_LOG_ERROR, "Some of provided format options in '%s' are not recognized\n", hls->format_options_str);
        ret = AVERROR(EINVAL);
        goto fail;
    }
    //av_assert0(s->nb_streams == hls->avf->nb_streams);
    for (i = 0; i < s->nb_streams; i++) {
        AVStream *inner_st;
        AVStream *outer_st = s->streams[i];

        if (hls->max_seg_size > 0) {
            if ((outer_st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) &&
                (outer_st->codecpar->bit_rate > hls->max_seg_size)) {
                av_log(s, AV_LOG_WARNING, "Your video bitrate is bigger than hls_segment_size, "
                       "(%"PRId64 " > %"PRId64 "), the result maybe not be what you want.",
                       outer_st->codecpar->bit_rate, hls->max_seg_size);
            }
        }

        if (outer_st->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
            inner_st = hls->avf->streams[i];
        else if (hls->vtt_avf)
            inner_st = hls->vtt_avf->streams[0];
        else {
            /* We have a subtitle stream, when the user does not want one */
            inner_st = NULL;
            continue;
        }
        avpriv_set_pts_info(outer_st, inner_st->pts_wrap_bits, inner_st->time_base.num, inner_st->time_base.den);
    }
fail:

    av_dict_free(&options);
    if (ret < 0) {
        av_freep(&hls->fmp4_init_filename);
        av_freep(&hls->basename);
        av_freep(&hls->vtt_basename);
        av_freep(&hls->key_basename);
        if (hls->avf)
            avformat_free_context(hls->avf);
        if (hls->vtt_avf)
            avformat_free_context(hls->vtt_avf);

    }
    return ret;
}

static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    HLSContext *hls = s->priv_data;
    AVFormatContext *oc = NULL;
    AVStream *st = s->streams[pkt->stream_index];
    int64_t end_pts = hls->recording_time * hls->number;
    int is_ref_pkt = 1;
    int ret = 0, can_split = 1;
    int stream_index = 0;

    if (hls->sequence - hls->nb_entries > hls->start_sequence && hls->init_time > 0) {
        /* reset end_pts, hls->recording_time at end of the init hls list */
        int init_list_dur = hls->init_time * hls->nb_entries * AV_TIME_BASE;
        int after_init_list_dur = (hls->sequence - hls->nb_entries ) * hls->time * AV_TIME_BASE;
        hls->recording_time = hls->time * AV_TIME_BASE;
        end_pts = init_list_dur + after_init_list_dur ;
    }

    if( st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE ) {
        oc = hls->vtt_avf;
        stream_index = 0;
    } else {
        oc = hls->avf;
        stream_index = pkt->stream_index;
    }
    if (hls->start_pts == AV_NOPTS_VALUE) {
        hls->start_pts = pkt->pts;
        hls->end_pts   = pkt->pts;
    }

    if (hls->has_video) {
        can_split = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
                    ((pkt->flags & AV_PKT_FLAG_KEY) || (hls->flags & HLS_SPLIT_BY_TIME));
        is_ref_pkt = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO;
    }
    if (pkt->pts == AV_NOPTS_VALUE)
        is_ref_pkt = can_split = 0;

    if (is_ref_pkt) {
        if (hls->new_start) {
            hls->new_start = 0;
            hls->duration = (double)(pkt->pts - hls->end_pts)
                                       * st->time_base.num / st->time_base.den;
            hls->dpp = (double)(pkt->duration) * st->time_base.num / st->time_base.den;
        } else {
            if (pkt->duration) {
                hls->duration += (double)(pkt->duration) * st->time_base.num / st->time_base.den;
            } else {
                av_log(s, AV_LOG_WARNING, "pkt->duration = 0, maybe the hls segment duration will not precise\n");
                hls->duration = (double)(pkt->pts - hls->end_pts) * st->time_base.num / st->time_base.den;
            }
        }

    }
    if (hls->fmp4_init_mode || can_split && av_compare_ts(pkt->pts - hls->start_pts, st->time_base,
                                   end_pts, AV_TIME_BASE_Q) >= 0) {
        int64_t new_start_pos;
        char *old_filename = av_strdup(hls->avf->filename);
        int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);

        if (!old_filename) {
            return AVERROR(ENOMEM);
        }

        av_write_frame(hls->avf, NULL); /* Flush any buffered data */

        new_start_pos = avio_tell(hls->avf->pb);
        hls->size = new_start_pos - hls->start_pos;

        if (!byterange_mode) {
            ff_format_io_close(s, &oc->pb);
            if (hls->vtt_avf) {
                ff_format_io_close(s, &hls->vtt_avf->pb);
            }
        }
        if ((hls->flags & HLS_TEMP_FILE) && oc->filename[0]) {
            if (!(hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size <= 0))
                if ((hls->avf->oformat->priv_class && hls->avf->priv_data) && hls->segment_type != SEGMENT_TYPE_FMP4)
                    av_opt_set(hls->avf->priv_data, "mpegts_flags", "resend_headers", 0);
            hls_rename_temp_file(s, oc);
        }

        if (hls->fmp4_init_mode) {
            hls->number--;
        }

        if (!hls->fmp4_init_mode || byterange_mode)
            ret = hls_append_segment(s, hls, hls->duration, hls->start_pos, hls->size);

        hls->start_pos = new_start_pos;
        if (ret < 0) {
            av_free(old_filename);
            return ret;
        }

        hls->end_pts = pkt->pts;
        hls->duration = 0;

        hls->fmp4_init_mode = 0;
        if (hls->flags & HLS_SINGLE_FILE) {
            hls->number++;
        } else if (hls->max_seg_size > 0) {
            if (hls->start_pos >= hls->max_seg_size) {
                hls->sequence++;
                sls_flag_file_rename(hls, old_filename);
                ret = hls_start(s);
                hls->start_pos = 0;
                /* When split segment by byte, the duration is short than hls_time,
                 * so it is not enough one segment duration as hls_time, */
                hls->number--;
            }
            hls->number++;
        } else {
            sls_flag_file_rename(hls, old_filename);
            ret = hls_start(s);
        }
        av_free(old_filename);

        if (ret < 0) {
            return ret;
        }

        if (!hls->fmp4_init_mode || byterange_mode)
            if ((ret = hls_window(s, 0)) < 0) {
                return ret;
            }
    }

    ret = ff_write_chained(oc, stream_index, pkt, s, 0);

    return ret;
}

static int hls_write_trailer(struct AVFormatContext *s)
{
    HLSContext *hls = s->priv_data;
    AVFormatContext *oc = hls->avf;
    AVFormatContext *vtt_oc = hls->vtt_avf;
    char *old_filename = av_strdup(hls->avf->filename);

    if (!old_filename) {
        return AVERROR(ENOMEM);
    }


    av_write_trailer(oc);
    if (oc->pb) {
        hls->size = avio_tell(hls->avf->pb) - hls->start_pos;
        ff_format_io_close(s, &oc->pb);

        if ((hls->flags & HLS_TEMP_FILE) && oc->filename[0]) {
            hls_rename_temp_file(s, oc);
        }

        /* after av_write_trailer, then duration + 1 duration per packet */
        hls_append_segment(s, hls, hls->duration + hls->dpp, hls->start_pos, hls->size);
    }

    sls_flag_file_rename(hls, old_filename);

    if (vtt_oc) {
        if (vtt_oc->pb)
            av_write_trailer(vtt_oc);
        hls->size = avio_tell(hls->vtt_avf->pb) - hls->start_pos;
        ff_format_io_close(s, &vtt_oc->pb);
    }
    av_freep(&hls->basename);
    av_freep(&hls->base_output_dirname);
    av_freep(&hls->key_basename);
    avformat_free_context(oc);

    hls->avf = NULL;
    hls_window(s, 1);

    av_freep(&hls->fmp4_init_filename);
    if (vtt_oc) {
        av_freep(&hls->vtt_basename);
        av_freep(&hls->vtt_m3u8_name);
        avformat_free_context(vtt_oc);
    }

    hls_free_segments(hls->segments);
    hls_free_segments(hls->old_segments);
    av_free(old_filename);
    return 0;
}

#define OFFSET(x) offsetof(HLSContext, x)
#define E AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
    {"start_number",  "set first number in the sequence",        OFFSET(start_sequence),AV_OPT_TYPE_INT64,  {.i64 = 0},     0, INT64_MAX, E},
    {"hls_time",      "set segment length in seconds",           OFFSET(time),    AV_OPT_TYPE_FLOAT,  {.dbl = 2},     0, FLT_MAX, E},
    {"hls_init_time", "set segment length in seconds at init list",           OFFSET(init_time),    AV_OPT_TYPE_FLOAT,  {.dbl = 0},     0, FLT_MAX, E},
    {"hls_list_size", "set maximum number of playlist entries",  OFFSET(max_nb_segments),    AV_OPT_TYPE_INT,    {.i64 = 5},     0, INT_MAX, E},
    {"hls_ts_options","set hls mpegts list of options for the container format used for hls", OFFSET(format_options_str), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
    {"hls_vtt_options","set hls vtt list of options for the container format used for hls", OFFSET(vtt_format_options_str), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
#if FF_API_HLS_WRAP
    {"hls_wrap",      "set number after which the index wraps (will be deprecated)",  OFFSET(wrap),    AV_OPT_TYPE_INT,    {.i64 = 0},     0, INT_MAX, E},
#endif
    {"hls_allow_cache", "explicitly set whether the client MAY (1) or MUST NOT (0) cache media segments", OFFSET(allowcache), AV_OPT_TYPE_INT, {.i64 = -1}, INT_MIN, INT_MAX, E},
    {"hls_base_url",  "url to prepend to each playlist entry",   OFFSET(baseurl), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       E},
    {"hls_segment_filename", "filename template for segment files", OFFSET(segment_filename),   AV_OPT_TYPE_STRING, {.str = NULL},            0,       0,         E},
    {"hls_segment_size", "maximum size per segment file, (in bytes)",  OFFSET(max_seg_size),    AV_OPT_TYPE_INT,    {.i64 = 0},               0,       INT_MAX,   E},
    {"hls_key_info_file",    "file with key URI and key file path", OFFSET(key_info_file),      AV_OPT_TYPE_STRING, {.str = NULL},            0,       0,         E},
    {"hls_enc",    "enable AES128 encryption support", OFFSET(encrypt),      AV_OPT_TYPE_BOOL, {.i64 = 0},            0,       1,         E},
    {"hls_enc_key",    "hex-coded 16 byte key to encrypt the segments", OFFSET(key),      AV_OPT_TYPE_STRING, .flags = E},
    {"hls_enc_key_url",    "url to access the key to decrypt the segments", OFFSET(key_url),      AV_OPT_TYPE_STRING, {.str = NULL},            0,       0,         E},
    {"hls_enc_iv",    "hex-coded 16 byte initialization vector", OFFSET(iv),      AV_OPT_TYPE_STRING, .flags = E},
    {"hls_subtitle_path",     "set path of hls subtitles", OFFSET(subtitle_filename), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
    {"hls_segment_type",     "set hls segment files type", OFFSET(segment_type), AV_OPT_TYPE_INT, {.i64 = SEGMENT_TYPE_MPEGTS }, 0, SEGMENT_TYPE_FMP4, E, "segment_type"},
    {"mpegts",   "make segment file to mpegts files in m3u8", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_MPEGTS }, 0, UINT_MAX,   E, "segment_type"},
    {"fmp4",   "make segment file to fragment mp4 files in m3u8", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_FMP4 }, 0, UINT_MAX,   E, "segment_type"},
    {"hls_fmp4_init_filename", "set fragment mp4 file init filename", OFFSET(fmp4_init_filename),   AV_OPT_TYPE_STRING, {.str = "init.mp4"},            0,       0,         E},
    {"hls_flags",     "set flags affecting HLS playlist and media file generation", OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = 0 }, 0, UINT_MAX, E, "flags"},
    {"single_file",   "generate a single media file indexed with byte ranges", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SINGLE_FILE }, 0, UINT_MAX,   E, "flags"},
    {"temp_file", "write segment to temporary file and rename when complete", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_TEMP_FILE }, 0, UINT_MAX,   E, "flags"},
    {"delete_segments", "delete segment files that are no longer part of the playlist", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_DELETE_SEGMENTS }, 0, UINT_MAX,   E, "flags"},
    {"round_durations", "round durations in m3u8 to whole numbers", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_ROUND_DURATIONS }, 0, UINT_MAX,   E, "flags"},
    {"discont_start", "start the playlist with a discontinuity tag", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_DISCONT_START }, 0, UINT_MAX,   E, "flags"},
    {"omit_endlist", "Do not append an endlist when ending stream", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_OMIT_ENDLIST }, 0, UINT_MAX,   E, "flags"},
    {"split_by_time", "split the hls segment by time which user set by hls_time", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SPLIT_BY_TIME }, 0, UINT_MAX,   E, "flags"},
    {"append_list", "append the new segments into old hls segment list", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_APPEND_LIST }, 0, UINT_MAX,   E, "flags"},
    {"program_date_time", "add EXT-X-PROGRAM-DATE-TIME", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_PROGRAM_DATE_TIME }, 0, UINT_MAX,   E, "flags"},
    {"second_level_segment_index", "include segment index in segment filenames when use_localtime", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SECOND_LEVEL_SEGMENT_INDEX }, 0, UINT_MAX,   E, "flags"},
    {"second_level_segment_duration", "include segment duration in segment filenames when use_localtime", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SECOND_LEVEL_SEGMENT_DURATION }, 0, UINT_MAX,   E, "flags"},
    {"second_level_segment_size", "include segment size in segment filenames when use_localtime", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SECOND_LEVEL_SEGMENT_SIZE }, 0, UINT_MAX,   E, "flags"},
    {"periodic_rekey", "reload keyinfo file periodically for re-keying", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_PERIODIC_REKEY }, 0, UINT_MAX,   E, "flags"},
    {"use_localtime", "set filename expansion with strftime at segment creation", OFFSET(use_localtime), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, E },
    {"use_localtime_mkdir", "create last directory component in strftime-generated filename", OFFSET(use_localtime_mkdir), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, E },
    {"hls_playlist_type", "set the HLS playlist type", OFFSET(pl_type), AV_OPT_TYPE_INT, {.i64 = PLAYLIST_TYPE_NONE }, 0, PLAYLIST_TYPE_NB-1, E, "pl_type" },
    {"event", "EVENT playlist", 0, AV_OPT_TYPE_CONST, {.i64 = PLAYLIST_TYPE_EVENT }, INT_MIN, INT_MAX, E, "pl_type" },
    {"vod", "VOD playlist", 0, AV_OPT_TYPE_CONST, {.i64 = PLAYLIST_TYPE_VOD }, INT_MIN, INT_MAX, E, "pl_type" },
    {"method", "set the HTTP method(default: PUT)", OFFSET(method), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
    {"hls_start_number_source", "set source of first number in sequence", OFFSET(start_sequence_source_type), AV_OPT_TYPE_INT, {.i64 = HLS_START_SEQUENCE_AS_START_NUMBER }, 0, HLS_START_SEQUENCE_AS_FORMATTED_DATETIME, E, "start_sequence_source_type" },
    {"generic", "start_number value (default)", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_START_SEQUENCE_AS_START_NUMBER }, INT_MIN, INT_MAX, E, "start_sequence_source_type" },
    {"epoch", "seconds since epoch", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_START_SEQUENCE_AS_SECONDS_SINCE_EPOCH }, INT_MIN, INT_MAX, E, "start_sequence_source_type" },
    {"datetime", "current datetime as YYYYMMDDhhmmss", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_START_SEQUENCE_AS_FORMATTED_DATETIME }, INT_MIN, INT_MAX, E, "start_sequence_source_type" },
    {"http_user_agent", "override User-Agent field in HTTP header", OFFSET(user_agent), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,    E},
    { NULL },
};

static const AVClass hls_class = {
    .class_name = "hls muxer",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};


AVOutputFormat ff_hls_muxer = {
    .name           = "hls",
    .long_name      = NULL_IF_CONFIG_SMALL("Apple HTTP Live Streaming"),
    .extensions     = "m3u8",
    .priv_data_size = sizeof(HLSContext),
    .audio_codec    = AV_CODEC_ID_AAC,
    .video_codec    = AV_CODEC_ID_H264,
    .subtitle_codec = AV_CODEC_ID_WEBVTT,
    .flags          = AVFMT_NOFILE | AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
    .write_header   = hls_write_header,
    .write_packet   = hls_write_packet,
    .write_trailer  = hls_write_trailer,
    .priv_class     = &hls_class,
};