max/ffmpeg
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

avformat/hls: fix seeking in EVENT playlists that start mid-stream

Browse Source 
HLS EVENT playlists (e.g. Twitch VODs) are seekable but not finished,
so live_start_index causes playback to begin near the end. The first
packet's DTS then becomes first_timestamp, creating a wrong mapping
between timestamps and segments.

Fix this by subtracting the cumulative duration of skipped segments from
first_timestamp so it reflects the true start of the playlist.

Also set per-stream start_time from first_timestamp so correct time is
reported, reset pts_wrap_reference on seek to prevent bogus wrap
arounds.

Signed-off-by: Kacper Michajłow <kasper93@gmail.com>
This commit is contained in:
Kacper Michajłow
2026-03-24 23:55:14 +01:00
parent ef13a29d08
commit 6d98a9a2e8
1 changed files with 42 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
libavformat/hls.c
+42 -5
View File
@@ -1111,6 +1111,17 @@ fail:
!(c->variants[0]->playlists[0]->finished ||
c->variants[0]->playlists[0]->type == PLS_TYPE_EVENT))
c->ctx->ctx_flags |= AVFMTCTX_UNSEEKABLE;
if (c->n_variants && c->variants[0]->n_playlists &&
c->variants[0]->playlists[0]->type == PLS_TYPE_EVENT &&
!c->variants[0]->playlists[0]->finished) {
struct playlist *p = c->variants[0]->playlists[0];
int64_t duration = 0;
for (int i = 0; i < p->n_segments; i++)
duration += p->segments[i]->duration;
c->ctx->duration = duration;
}
return ret;
}
@@ -2182,9 +2193,10 @@ static int hls_read_header(AVFormatContext *s)
}
}
/* If this isn't a live stream, calculate the total duration of the
* stream. */
if (c->variants[0]->playlists[0]->finished) {
/* Calculate the total duration of the stream if all segments are
* available (finished or EVENT playlists). */
if (c->variants[0]->playlists[0]->finished ||
c->variants[0]->playlists[0]->type == PLS_TYPE_EVENT) {
int64_t duration = 0;
for (i = 0; i < c->variants[0]->playlists[0]->n_segments; i++)
duration += c->variants[0]->playlists[0]->segments[i]->duration;
@@ -2549,9 +2561,24 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
}
if (c->first_timestamp == AV_NOPTS_VALUE &&
pls->pkt->dts != AV_NOPTS_VALUE)
pls->pkt->dts != AV_NOPTS_VALUE) {
int64_t seg_idx = pls->cur_seq_no - pls->start_seq_no;
c->first_timestamp = av_rescale_q(pls->pkt->dts,
get_timebase(pls), AV_TIME_BASE_Q);
/* EVENT playlists preserve all segments from the start */
if (pls->type == PLS_TYPE_EVENT) {
for (int64_t k = 0; k < seg_idx && k < pls->n_segments; k++)
c->first_timestamp -= pls->segments[k]->duration;
for (unsigned k = 0; k < s->nb_streams; k++) {
AVStream *st = s->streams[k];
if (st->start_time == AV_NOPTS_VALUE)
st->start_time = av_rescale_q(c->first_timestamp,
AV_TIME_BASE_Q, st->time_base);
}
}
}
}
seg = current_segment(pls);
@@ -2717,6 +2744,11 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
seek_pls->cur_seq_no = seq_no;
seek_pls->seek_stream_index = stream_subdemuxer_index;
/* Reset PTS wrap detection so backward seeks don't get misinterpreted
* as a forward PTS wrap. */
for (i = 0; i < (int)s->nb_streams; i++)
ffstream(s->streams[i])->pts_wrap_reference = AV_NOPTS_VALUE;
for (i = 0; i < c->n_playlists; i++) {
/* Reset reading */
struct playlist *pls = c->playlists[i];
@@ -2732,8 +2764,11 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
/* Reset the pos, to let the mpegts/mov demuxer know we've seeked. */
pb->pos = 0;
/* Flush the packet queue of the subdemuxer. */
if (pls->ctx)
if (pls->ctx) {
ff_read_frame_flush(pls->ctx);
for (j = 0; j < (int)pls->ctx->nb_streams; j++)
ffstream(pls->ctx->streams[j])->pts_wrap_reference = AV_NOPTS_VALUE;
}
if (pls->is_subtitle)
avformat_close_input(&pls->ctx);
@@ -2752,6 +2787,8 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
pls->seek_stream_index = -1;
pls->seek_flags |= AVSEEK_FLAG_ANY;
}
pls->last_seq_no = pls->cur_seq_no;
}
c->cur_timestamp = seek_timestamp;