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FFmpeg/libavformat/assdec.c

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/*
* SSA/ASS demuxer
* Copyright (c) 2008 Michael Niedermayer
* Copyright (c) 2014 Clément Bœsch
*
* 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 <stdint.h>
#include "avformat.h"
#include "internal.h"
#include "subtitles.h"
#include "libavcodec/internal.h"
#include "libavutil/bprint.h"
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typedef struct ASSContext {
FFDemuxSubtitlesQueue q;
unsigned readorder;
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} ASSContext;
static int ass_probe(const AVProbeData *p)
{
char buf[13];
FFTextReader tr;
ff_text_init_buf(&tr, p->buf, p->buf_size);
while (ff_text_peek_r8(&tr) == '\r' || ff_text_peek_r8(&tr) == '\n')
ff_text_r8(&tr);
ff_text_read(&tr, buf, sizeof(buf));
if (!memcmp(buf, "[Script Info]", 13))
return AVPROBE_SCORE_MAX;
return 0;
}
static int ass_read_close(AVFormatContext *s)
{
ASSContext *ass = s->priv_data;
ff_subtitles_queue_clean(&ass->q);
return 0;
}
static int read_dialogue(ASSContext *ass, AVBPrint *dst, const uint8_t *p,
int64_t *start, int *duration)
{
int pos = 0;
int64_t end;
int hh1, mm1, ss1, ms1;
int hh2, mm2, ss2, ms2;
if (sscanf(p, "Dialogue: %*[^,],%d:%d:%d%*c%d,%d:%d:%d%*c%d,%n",
&hh1, &mm1, &ss1, &ms1,
&hh2, &mm2, &ss2, &ms2, &pos) >= 8 && pos > 0) {
/* This is not part of the sscanf itself in order to handle an actual
* number (which would be the Layer) or the form "Marked=N" (which is
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* the old SSA field, now replaced by Layer, and will lead to Layer
* being 0 here). */
const int layer = atoi(p + 10);
end = (hh2*3600LL + mm2*60LL + ss2) * 100LL + ms2;
*start = (hh1*3600LL + mm1*60LL + ss1) * 100LL + ms1;
*duration = end - *start;
av_bprint_clear(dst);
av_bprintf(dst, "%u,%d,%s", ass->readorder++, layer, p + pos);
/* right strip the buffer */
while (dst->len > 0 &&
dst->str[dst->len - 1] == '\r' ||
dst->str[dst->len - 1] == '\n')
dst->str[--dst->len] = 0;
return 0;
}
return -1;
}
static int64_t get_line(AVBPrint *buf, FFTextReader *tr)
{
int64_t pos = ff_text_pos(tr);
av_bprint_clear(buf);
for (;;) {
char c = ff_text_r8(tr);
if (!c)
break;
av_bprint_chars(buf, c, 1);
if (c == '\n')
break;
}
return pos;
}
static int ass_read_header(AVFormatContext *s)
{
ASSContext *ass = s->priv_data;
AVBPrint header, line, rline;
int res = 0;
AVStream *st;
FFTextReader tr;
ff_text_init_avio(s, &tr, s->pb);
st = avformat_new_stream(s, NULL);
if (!st)
return AVERROR(ENOMEM);
avpriv_set_pts_info(st, 64, 1, 100);
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_ASS;
av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
av_bprint_init(&line, 0, AV_BPRINT_SIZE_UNLIMITED);
av_bprint_init(&rline, 0, AV_BPRINT_SIZE_UNLIMITED);
ass->q.keep_duplicates = 1;
for (;;) {
int64_t pos = get_line(&line, &tr);
int64_t ts_start = AV_NOPTS_VALUE;
int duration = -1;
AVPacket *sub;
if (!line.str[0]) // EOF
break;
if (read_dialogue(ass, &rline, line.str, &ts_start, &duration) < 0) {
av_bprintf(&header, "%s", line.str);
continue;
}
sub = ff_subtitles_queue_insert(&ass->q, rline.str, rline.len, 0);
if (!sub) {
res = AVERROR(ENOMEM);
goto end;
}
sub->pos = pos;
sub->pts = ts_start;
sub->duration = duration;
}
res = ff_bprint_to_codecpar_extradata(st->codecpar, &header);
if (res < 0)
goto end;
ff_subtitles_queue_finalize(s, &ass->q);
end:
av_bprint_finalize(&header, NULL);
av_bprint_finalize(&line, NULL);
av_bprint_finalize(&rline, NULL);
return res;
}
static int ass_read_packet(AVFormatContext *s, AVPacket *pkt)
{
ASSContext *ass = s->priv_data;
return ff_subtitles_queue_read_packet(&ass->q, pkt);
}
static int ass_read_seek(AVFormatContext *s, int stream_index,
int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
{
ASSContext *ass = s->priv_data;
return ff_subtitles_queue_seek(&ass->q, s, stream_index,
min_ts, ts, max_ts, flags);
}
AVInputFormat ff_ass_demuxer = {
.name = "ass",
.long_name = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
.priv_data_size = sizeof(ASSContext),
.read_probe = ass_probe,
.read_header = ass_read_header,
.read_packet = ass_read_packet,
.read_close = ass_read_close,
.read_seek2 = ass_read_seek,
};