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FFmpeg/libavformat/srtdec.c

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/*
* SubRip subtitle demuxer
* Copyright (c) 2010 Aurelien Jacobs <aurel@gnuage.org>
* Copyright (c) 2015 Clément Bœsch <u pkh me>
*
* 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 "avformat.h"
#include "internal.h"
#include "subtitles.h"
#include "libavutil/bprint.h"
#include "libavutil/intreadwrite.h"
typedef struct {
FFDemuxSubtitlesQueue q;
} SRTContext;
static int srt_probe(AVProbeData *p)
{
int v;
char buf[64], *pbuf;
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FFTextReader tr;
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ff_text_init_buf(&tr, p->buf, p->buf_size);
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while (ff_text_peek_r8(&tr) == '\r' || ff_text_peek_r8(&tr) == '\n')
ff_text_r8(&tr);
/* Check if the first non-empty line is a number. We do not check what the
* number is because in practice it can be anything.
* Also, that number can be followed by random garbage, so we can not
* unfortunately check that we only have a number. */
if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0 ||
strtol(buf, &pbuf, 10) < 0 || pbuf == buf)
return 0;
/* Check if the next line matches a SRT timestamp */
if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0)
return 0;
pbuf = buf;
if (buf[0] == '-')
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pbuf++;
if (pbuf[0] >= '0' && pbuf[0] <= '9' && strstr(buf, " --> ")
&& sscanf(buf, "%*d:%*d:%*d%*1[,.]%*d --> %*d:%*d:%*d%*1[,.]%d", &v) == 1)
return AVPROBE_SCORE_MAX;
return 0;
}
struct event_info {
int32_t x1, x2, y1, y2;
int duration;
int64_t pts;
int64_t pos;
};
static int get_event_info(const char *line, struct event_info *ei)
{
int hh1, mm1, ss1, ms1;
int hh2, mm2, ss2, ms2;
ei->x1 = ei->x2 = ei->y1 = ei->y2 = ei->duration = -1;
ei->pts = AV_NOPTS_VALUE;
ei->pos = -1;
if (sscanf(line, "%d:%d:%d%*1[,.]%d --> %d:%d:%d%*1[,.]%d"
"%*[ ]X1:%"PRId32" X2:%"PRId32" Y1:%"PRId32" Y2:%"PRId32,
&hh1, &mm1, &ss1, &ms1,
&hh2, &mm2, &ss2, &ms2,
&ei->x1, &ei->x2, &ei->y1, &ei->y2) >= 8) {
const int64_t start = (hh1*3600LL + mm1*60LL + ss1) * 1000LL + ms1;
const int64_t end = (hh2*3600LL + mm2*60LL + ss2) * 1000LL + ms2;
ei->duration = end - start;
ei->pts = start;
return 0;
}
return -1;
}
static int add_event(FFDemuxSubtitlesQueue *q, AVBPrint *buf, char *line_cache,
const struct event_info *ei, int append_cache)
{
if (append_cache && line_cache[0])
av_bprintf(buf, "%s\n", line_cache);
line_cache[0] = 0;
while (buf->len > 0 && buf->str[buf->len - 1] == '\n')
buf->str[--buf->len] = 0;
if (buf->len) {
AVPacket *sub = ff_subtitles_queue_insert(q, buf->str, buf->len, 0);
if (!sub)
return AVERROR(ENOMEM);
av_bprint_clear(buf);
sub->pos = ei->pos;
sub->pts = ei->pts;
sub->duration = ei->duration;
if (ei->x1 != -1) {
uint8_t *p = av_packet_new_side_data(sub, AV_PKT_DATA_SUBTITLE_POSITION, 16);
if (p) {
AV_WL32(p, ei->x1);
AV_WL32(p + 4, ei->y1);
AV_WL32(p + 8, ei->x2);
AV_WL32(p + 12, ei->y2);
}
}
}
return 0;
}
static int srt_read_header(AVFormatContext *s)
{
SRTContext *srt = s->priv_data;
AVBPrint buf;
AVStream *st = avformat_new_stream(s, NULL);
int res = 0;
char line[4096], line_cache[4096];
int has_event_info = 0;
struct event_info ei;
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FFTextReader tr;
ff_text_init_avio(s, &tr, s->pb);
if (!st)
return AVERROR(ENOMEM);
avpriv_set_pts_info(st, 64, 1, 1000);
lavf: replace AVStream.codec with AVStream.codecpar Currently, AVStream contains an embedded AVCodecContext instance, which is used by demuxers to export stream parameters to the caller and by muxers to receive stream parameters from the caller. It is also used internally as the codec context that is passed to parsers. In addition, it is also widely used by the callers as the decoding (when demuxer) or encoding (when muxing) context, though this has been officially discouraged since Libav 11. There are multiple important problems with this approach: - the fields in AVCodecContext are in general one of * stream parameters * codec options * codec state However, it's not clear which ones are which. It is consequently unclear which fields are a demuxer allowed to set or a muxer allowed to read. This leads to erratic behaviour depending on whether decoding or encoding is being performed or not (and whether it uses the AVStream embedded codec context). - various synchronization issues arising from the fact that the same context is used by several different APIs (muxers/demuxers, parsers, bitstream filters and encoders/decoders) simultaneously, with there being no clear rules for who can modify what and the different processes being typically delayed with respect to each other. - avformat_find_stream_info() making it necessary to support opening and closing a single codec context multiple times, thus complicating the semantics of freeing various allocated objects in the codec context. Those problems are resolved by replacing the AVStream embedded codec context with a newly added AVCodecParameters instance, which stores only the stream parameters exported by the demuxers or read by the muxers.
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st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
st->codecpar->codec_id = AV_CODEC_ID_SUBRIP;
av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
line_cache[0] = 0;
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while (!ff_text_eof(&tr)) {
struct event_info tmp_ei;
const int64_t pos = ff_text_pos(&tr);
ptrdiff_t len = ff_subtitles_read_line(&tr, line, sizeof(line));
if (len < 0)
break;
if (!len || !line[0])
continue;
if (get_event_info(line, &tmp_ei) < 0) {
char *pline;
if (!has_event_info)
continue;
if (line_cache[0]) {
/* We got some cache and a new line so we assume the cached
* line was actually part of the payload */
av_bprintf(&buf, "%s\n", line_cache);
line_cache[0] = 0;
}
/* If the line doesn't start with a number, we assume it's part of
* the payload, otherwise is likely an event number preceding the
* timing information... but we can't be sure of this yet, so we
* cache it */
if (strtol(line, &pline, 10) < 0 || line == pline)
av_bprintf(&buf, "%s\n", line);
else
strcpy(line_cache, line);
} else {
if (has_event_info) {
/* We have the information of previous event, append it to the
* queue. We insert the cached line if and only if the payload
* is empty and the cached line is not a standalone number. */
char *pline = NULL;
const int standalone_number = strtol(line_cache, &pline, 10) >= 0 && pline && !*pline;
res = add_event(&srt->q, &buf, line_cache, &ei, !buf.len && !standalone_number);
if (res < 0)
goto end;
} else {
has_event_info = 1;
}
tmp_ei.pos = pos;
ei = tmp_ei;
}
}
/* Append the last event. Here we force the cache to be flushed, because a
* trailing number is more likely to be geniune (for example a copyright
* date) and not the event index of an inexistant event */
if (has_event_info) {
res = add_event(&srt->q, &buf, line_cache, &ei, 1);
if (res < 0)
goto end;
}
ff_subtitles_queue_finalize(s, &srt->q);
end:
av_bprint_finalize(&buf, NULL);
return res;
}
static int srt_read_packet(AVFormatContext *s, AVPacket *pkt)
{
SRTContext *srt = s->priv_data;
return ff_subtitles_queue_read_packet(&srt->q, pkt);
}
static int srt_read_seek(AVFormatContext *s, int stream_index,
int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
{
SRTContext *srt = s->priv_data;
return ff_subtitles_queue_seek(&srt->q, s, stream_index,
min_ts, ts, max_ts, flags);
}
static int srt_read_close(AVFormatContext *s)
{
SRTContext *srt = s->priv_data;
ff_subtitles_queue_clean(&srt->q);
return 0;
}
AVInputFormat ff_srt_demuxer = {
.name = "srt",
.long_name = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
.priv_data_size = sizeof(SRTContext),
.read_probe = srt_probe,
.read_header = srt_read_header,
.read_packet = srt_read_packet,
.read_seek2 = srt_read_seek,
.read_close = srt_read_close,
};