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avformat/hls: Implement support for using AVSEEK_FLAG_BACKWARD when seeking

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Before, seeking in hls streams would always seek to the next keyframe
after the given timestamp. With this fix, if seeking in videostream and
AVSEEK_FLAG_BACKWARD is set, seeking will be to the first keyframe of
the segment containing the given timestamp. This fixes #7485.

Signed-off-by: Gustav Grusell <gustav.grusell@gmail.com>
This commit is contained in:
Gustav Grusell
2022-01-28 21:23:20 +01:00
committed by Steven Liu
parent 2727ff069e
commit e78d0810d1
1 changed files with 17 additions and 7 deletions
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24
libavformat/hls.c
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@@ -1653,7 +1653,8 @@ static void add_metadata_from_renditions(AVFormatContext *s, struct playlist *pl
/* if timestamp was in valid range: returns 1 and sets seq_no /* if timestamp was in valid range: returns 1 and sets seq_no
* if not: returns 0 and sets seq_no to closest segment */ * if not: returns 0 and sets seq_no to closest segment */
static int find_timestamp_in_playlist(HLSContext *c, struct playlist *pls, static int find_timestamp_in_playlist(HLSContext *c, struct playlist *pls,
int64_t timestamp, int64_t *seq_no) int64_t timestamp, int64_t *seq_no,
int64_t *seg_start_ts)
{ {
int i; int i;
int64_t pos = c->first_timestamp == AV_NOPTS_VALUE ? int64_t pos = c->first_timestamp == AV_NOPTS_VALUE ?
@@ -1668,6 +1669,9 @@ static int find_timestamp_in_playlist(HLSContext *c, struct playlist *pls,
int64_t diff = pos + pls->segments[i]->duration - timestamp; int64_t diff = pos + pls->segments[i]->duration - timestamp;
if (diff > 0) { if (diff > 0) {
*seq_no = pls->start_seq_no + i; *seq_no = pls->start_seq_no + i;
if (seg_start_ts) {
*seg_start_ts = pos;
}
return 1; return 1;
} }
pos += pls->segments[i]->duration; pos += pls->segments[i]->duration;
@@ -1691,7 +1695,7 @@ static int64_t select_cur_seq_no(HLSContext *c, struct playlist *pls)
* playlist) and this is a complete file, find the matching segment * playlist) and this is a complete file, find the matching segment
* by counting durations. */ * by counting durations. */
if (pls->finished && c->cur_timestamp != AV_NOPTS_VALUE) { if (pls->finished && c->cur_timestamp != AV_NOPTS_VALUE) {
find_timestamp_in_playlist(c, pls, c->cur_timestamp, &seq_no); find_timestamp_in_playlist(c, pls, c->cur_timestamp, &seq_no, NULL);
return seq_no; return seq_no;
} }
@@ -2362,7 +2366,7 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
int i, j; int i, j;
int stream_subdemuxer_index; int stream_subdemuxer_index;
int64_t first_timestamp, seek_timestamp, duration; int64_t first_timestamp, seek_timestamp, duration;
int64_t seq_no; int64_t seq_no, seg_start_ts;
if ((flags & AVSEEK_FLAG_BYTE) || (c->ctx->ctx_flags & AVFMTCTX_UNSEEKABLE)) if ((flags & AVSEEK_FLAG_BYTE) || (c->ctx->ctx_flags & AVFMTCTX_UNSEEKABLE))
return AVERROR(ENOSYS); return AVERROR(ENOSYS);
@@ -2372,8 +2376,7 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
seek_timestamp = av_rescale_rnd(timestamp, AV_TIME_BASE, seek_timestamp = av_rescale_rnd(timestamp, AV_TIME_BASE,
s->streams[stream_index]->time_base.den, s->streams[stream_index]->time_base.den,
flags & AVSEEK_FLAG_BACKWARD ? AV_ROUND_DOWN);
AV_ROUND_DOWN : AV_ROUND_UP);
duration = s->duration == AV_NOPTS_VALUE ? duration = s->duration == AV_NOPTS_VALUE ?
0 : s->duration; 0 : s->duration;
@@ -2394,9 +2397,16 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
} }
/* check if the timestamp is valid for the playlist with the /* check if the timestamp is valid for the playlist with the
* specified stream index */ * specified stream index */
if (!seek_pls || !find_timestamp_in_playlist(c, seek_pls, seek_timestamp, &seq_no)) if (!seek_pls || !find_timestamp_in_playlist(c, seek_pls, seek_timestamp, &seq_no, &seg_start_ts))
return AVERROR(EIO); return AVERROR(EIO);
if (s->streams[stream_index]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
flags & AVSEEK_FLAG_BACKWARD && !(flags & AVSEEK_FLAG_ANY)) {
/* Seeking to start of segment ensures we seek to a keyframe located
* before the given timestamp. */
seek_timestamp = seg_start_ts;
}
/* set segment now so we do not need to search again below */ /* set segment now so we do not need to search again below */
seek_pls->cur_seq_no = seq_no; seek_pls->cur_seq_no = seq_no;
seek_pls->seek_stream_index = stream_subdemuxer_index; seek_pls->seek_stream_index = stream_subdemuxer_index;
@@ -2423,7 +2433,7 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
if (pls != seek_pls) { if (pls != seek_pls) {
/* set closest segment seq_no for playlists not handled above */ /* set closest segment seq_no for playlists not handled above */
find_timestamp_in_playlist(c, pls, seek_timestamp, &pls->cur_seq_no); find_timestamp_in_playlist(c, pls, seek_timestamp, &pls->cur_seq_no, NULL);
/* seek the playlist to the given position without taking /* seek the playlist to the given position without taking
* keyframes into account since this playlist does not have the * keyframes into account since this playlist does not have the
* specified stream where we should look for the keyframes */ * specified stream where we should look for the keyframes */