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avformat/hls: refine first_timestamp from the first segment's packets

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first_timestamp is taken from the first packet in mux order, which is
not necessarily the earliest timestamp in the segment. Lower it while
packets of that segment are still arriving, so the seek timeline is
anchored at the true segment start.

Signed-off-by: Kacper Michajłow <kasper93@gmail.com>
This commit is contained in:
Kacper Michajłow
2026-07-08 03:57:33 +02:00
parent 848fb754dd
commit f6fa0d3fda
1 changed files with 42 additions and 8 deletions
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50
libavformat/hls.c
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@@ -131,6 +131,7 @@ struct playlist {
int broken;
int64_t cur_seq_no;
int64_t last_seq_no;
int64_t first_read_seq_no;
int m3u8_hold_counters;
int64_t cur_seg_offset;
int64_t last_load_time;
@@ -232,6 +233,7 @@ typedef struct HLSContext {
int first_packet;
int64_t first_timestamp;
struct playlist *first_timestamp_pls;
int first_timestamp_locked;
int64_t cur_timestamp;
AVIOInterruptCB *interrupt_callback;
AVDictionary *avio_opts;
@@ -355,6 +357,7 @@ static struct playlist *new_playlist(HLSContext *c, const char *url,
av_strlcpy(pls->url, abs_url, sizeof(pls->url));
pls->ts_offset = AV_NOPTS_VALUE;
pls->seek_timestamp = AV_NOPTS_VALUE;
pls->first_read_seq_no = -1;
pls->is_id3_timestamped = -1;
pls->id3_mpegts_timestamp = AV_NOPTS_VALUE;
@@ -1812,6 +1815,8 @@ restart:
}
segment_retries = 0;
just_opened = 1;
if (v->first_read_seq_no < 0)
v->first_read_seq_no = v->cur_seq_no;
}
if (c->http_multiple == -1) {
@@ -1901,6 +1906,8 @@ static int read_data_subtitle_segment(void *opaque, uint8_t *buf, int buf_size)
v->index);
return ret;
}
if (v->first_read_seq_no < 0)
v->first_read_seq_no = v->cur_seq_no;
}
return read_from_url(v, seg, buf, buf_size);
@@ -2294,6 +2301,7 @@ static int hls_read_header(AVFormatContext *s)
c->first_packet = 1;
c->first_timestamp = AV_NOPTS_VALUE;
c->first_timestamp_pls = NULL;
c->first_timestamp_locked = 0;
c->cur_timestamp = AV_NOPTS_VALUE;
if ((ret = ffio_copy_url_options(s->pb, &c->avio_opts)) < 0)
@@ -2621,6 +2629,7 @@ static int recheck_discard_flags(AVFormatContext *s, int first)
pls->needed = 1;
changed = 1;
pls->cur_seq_no = select_cur_seq_no(c, pls);
pls->first_read_seq_no = -1;
pls->pb.pub.eof_reached = 0;
if (c->cur_timestamp != AV_NOPTS_VALUE) {
/* catch up */
@@ -2744,10 +2753,14 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
fill_timing_for_id3_timestamped_stream(pls);
}
if (pls->ts_offset == AV_NOPTS_VALUE &&
pls->pkt->dts != AV_NOPTS_VALUE) {
if (pls->pkt->dts != AV_NOPTS_VALUE &&
(pls->ts_offset == AV_NOPTS_VALUE ||
(!c->first_timestamp_locked &&
c->first_timestamp_pls == pls &&
pls->cur_seq_no <= pls->first_read_seq_no + 1))) {
int adjusted = 0;
/* Packet timestamp rebased onto the start of the segment list. */
int64_t seg_idx = pls->cur_seq_no - pls->start_seq_no;
int64_t seg_idx = pls->first_read_seq_no - pls->start_seq_no;
int64_t ts = av_rescale_q(pls->pkt->pts != AV_NOPTS_VALUE ?
pls->pkt->pts : pls->pkt->dts,
get_timebase(pls), AV_TIME_BASE_Q);
@@ -2758,18 +2771,35 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
if (c->first_timestamp == AV_NOPTS_VALUE) {
c->first_timestamp = ts;
c->first_timestamp_pls = pls;
adjusted = 1;
} else if (c->first_timestamp_pls == pls) {
/* first_timestamp came from the first packet in mux
* order, but another stream in the same segment may
* start earlier. Lower the estimate while packets of
* that segment are still arriving. */
int64_t delta = c->first_timestamp - ts;
/* start_time is the start of the segment list, the
* origin of the timeline used for seeking. */
if (delta > 0 && delta <= pls->target_duration) {
c->first_timestamp = ts;
for (int k = 0; k < c->n_playlists; k++)
if (c->playlists[k]->ts_offset != AV_NOPTS_VALUE)
c->playlists[k]->ts_offset += delta;
adjusted = 1;
}
}
if (pls->ts_offset == AV_NOPTS_VALUE)
pls->ts_offset = ts - c->first_timestamp;
if (adjusted) {
for (unsigned k = 0; k < s->nb_streams; k++)
s->streams[k]->start_time =
av_rescale_q(ts, AV_TIME_BASE_Q,
av_rescale_q(c->first_timestamp, AV_TIME_BASE_Q,
s->streams[k]->time_base);
av_log(s, AV_LOG_DEBUG,
"First timestamp %"PRId64" from playlist %d\n",
ts, pls->index);
c->first_timestamp, pls->index);
}
pls->ts_offset = ts - c->first_timestamp;
}
seg = current_segment(pls);
@@ -2960,6 +2990,9 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
" of playlist %d (start %"PRId64")\n",
seek_timestamp, seq_no, seek_pls->index, seg_start_ts);
/* Keep timeline start fixed from now on. */
c->first_timestamp_locked = 1;
/* set segment now so we do not need to search again below */
seek_pls->cur_seq_no = seq_no;
seek_pls->seek_stream_index = stream_subdemuxer_index;
@@ -2975,6 +3008,7 @@ static int hls_read_seek(AVFormatContext *s, int stream_index,
AVIOContext *const pb = &pls->pb.pub;
ff_format_io_close(pls->parent, &pls->input);
pls->input_read_done = 0;
pls->first_read_seq_no = -1;
pls->input_reuse = 0;
ff_format_io_close(pls->parent, &pls->input_next);
pls->input_next_requested = 0;