[PATCH 0/2] fix for seeking in HLS with TS/FMP4 media
I am resubmitting a patch which fixes the following two tickets: https://trac.ffmpeg.org/ticket/7359 https://trac.ffmpeg.org/ticket/7485 The patch consists of 2 parts. The first is necessary to fix the case of HLS seeking when the HLS package consists of ts files. The second fixes HLS seeking when the HLS package consists of fmp4 files. Note that the first can be applied without the second, and HLS seeking with fmp4 files will remain broken, but in a different manner. The first patch works because it relies on correct behaviour implemented in mpegts.c, the second patch mirrors this behaviour in mov.c. The issues can be demonstrated as follows: ./ffmpeg -ss 3 -i http://vectronic.io/hls_seek_issue/ts/in.m3u8 -t 2 out.mp4 ./ffmpeg -ss 3 -i http://vectronic.io/hls_seek_issue/fmp4/in.m3u8 -t 2 out.mp4 These both produce zero duration output files. With the first patch applied, the ts example produces a 2 second output file as expected. However the fmp4 example results in a conversion error. With the second patch applied, both the ts and fmp4 examples produce 2 second output files as expected. Patch 1: Change to logic in hls.c for seeking After performing a rough seek in hls.c hls_read_seek() to the nearest segment, the logic for hls_read_packet() was to discard packets until a DTS after the accurate seek point is discovered. This was done even if AVSEEK_FLAG_ANY was not specified in the initial seek request. The patch changes this so that if AVSEEK_FLAG_ANY has not been specified, it will instead return the first keyframe discovered after the rough seek point. Patch 2: Change to logic in mov.c for reading packets after an HLS seek Within hls.c when hls_read_seek() is called it resets the stream position as follows: /* Reset the pos, to let the mpegts demuxer know we've seeked. */ pls->pb.pos = 0; There is support for this in the mpegts handle_packets() code to check if the position has been reset and clear out any PES packets: if (avio_tell(s->pb) != ts->last_pos) { int i; av_log(ts->stream, AV_LOG_TRACE, "Skipping after seek\n"); /* seek detected, flush pes buffer */ This behaviour needed to be mirrored in the mov demuxer. In mov.c it now detects if the pos has been reset in mov_read_packet(). It clears fragments and indexes and searches for the next root i.e. the next fragment via mov_switch_root(). vectronic (2): avformat hls fix to seek logic avformat mov fix to detect if stream position has been reset libavformat/hls.c | 8 +++++--- libavformat/mov.c | 36 +++++++++++++++++++++++++++++++++--- 2 files changed, 38 insertions(+), 6 deletions(-) -- 2.24.2 (Apple Git-127)
ensure a keyframe is returned if AVSEEK_FLAG_ANY is not specified Signed-off-by: vectronic <hello.vectronic@gmail.com> --- libavformat/hls.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/libavformat/hls.c b/libavformat/hls.c index fc45719d1c..4e59142c99 100644 --- a/libavformat/hls.c +++ b/libavformat/hls.c @@ -2146,8 +2146,10 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt) ts_diff = av_rescale_rnd(pls->pkt.dts, AV_TIME_BASE, tb.den, AV_ROUND_DOWN) - pls->seek_timestamp; - if (ts_diff >= 0 && (pls->seek_flags & AVSEEK_FLAG_ANY || - pls->pkt.flags & AV_PKT_FLAG_KEY)) { + /* If AVSEEK_FLAG_ANY, keep reading until ts_diff is greater than 0 + * otherwise return the first keyframe encountered */ + if ((ts_diff >= 0 && (pls->seek_flags & AVSEEK_FLAG_ANY)) || + (!(pls->seek_flags & AVSEEK_FLAG_ANY) && (pls->pkt.flags & AV_PKT_FLAG_KEY))) { pls->seek_timestamp = AV_NOPTS_VALUE; break; } @@ -2291,7 +2293,7 @@ static int hls_read_seek(AVFormatContext *s, int stream_index, pls->pb.eof_reached = 0; /* Clear any buffered data */ pls->pb.buf_end = pls->pb.buf_ptr = pls->pb.buffer; - /* Reset the pos, to let the mpegts demuxer know we've seeked. */ + /* Reset the pos, to let the mpegts/mov demuxer know we've seeked. */ pls->pb.pos = 0; /* Flush the packet queue of the subdemuxer. */ ff_read_frame_flush(pls->ctx); -- 2.24.2 (Apple Git-127)
lgtm
if pos has been reset, clear fragments and indexes and search for next root Signed-off-by: vectronic <hello.vectronic@gmail.com> --- libavformat/mov.c | 36 +++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) diff --git a/libavformat/mov.c b/libavformat/mov.c index 3d6fef685d..8f051fb9b1 100644 --- a/libavformat/mov.c +++ b/libavformat/mov.c @@ -7796,15 +7796,15 @@ static int mov_switch_root(AVFormatContext *s, int64_t target, int index) if (index >= 0 && index < mov->frag_index.nb_items) target = mov->frag_index.item[index].moof_offset; - if (avio_seek(s->pb, target, SEEK_SET) != target) { + if (target >= 0 && avio_seek(s->pb, target, SEEK_SET) != target) { av_log(mov->fc, AV_LOG_ERROR, "root atom offset 0x%"PRIx64": partial file\n", target); return AVERROR_INVALIDDATA; } mov->next_root_atom = 0; - if (index < 0 || index >= mov->frag_index.nb_items) + if ((index < 0 && target >= 0) || index >= mov->frag_index.nb_items) index = search_frag_moof_offset(&mov->frag_index, target); - if (index < mov->frag_index.nb_items && + if (index >= 0 && index < mov->frag_index.nb_items && mov->frag_index.item[index].moof_offset == target) { if (index + 1 < mov->frag_index.nb_items) mov->next_root_atom = mov->frag_index.item[index + 1].moof_offset; @@ -7856,8 +7856,38 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt) AVStream *st = NULL; int64_t current_index; int ret; + int i; mov->fc = s; retry: + if (s->pb->pos == 0) { + + // Discard current fragment index + if (mov->frag_index.allocated_size > 0) { + av_freep(&mov->frag_index.item); + mov->frag_index.nb_items = 0; + mov->frag_index.allocated_size = 0; + mov->frag_index.current = -1; + mov->frag_index.complete = 0; + } + + for (i = 0; i < s->nb_streams; i++) { + AVStream *avst = s->streams[i]; + MOVStreamContext *msc = avst->priv_data; + + // Clear current sample + mov_current_sample_set(msc, 0); + + // Discard current index entries + if (avst->index_entries_allocated_size > 0) { + av_freep(&avst->index_entries); + avst->index_entries_allocated_size = 0; + avst->nb_index_entries = 0; + } + } + + if ((ret = mov_switch_root(s, -1, -1)) < 0) + return ret; + } sample = mov_find_next_sample(s, &st); if (!sample || (mov->next_root_atom && sample->pos > mov->next_root_atom)) { if (!mov->next_root_atom) -- 2.24.2 (Apple Git-127)
Am Fr., 24. Apr. 2020 um 17:21 Uhr schrieb vectronic <hello.vectronic@gmail.com>:
I am resubmitting a patch which fixes the following two tickets:
https://trac.ffmpeg.org/ticket/7359 https://trac.ffmpeg.org/ticket/7485
Are you Nick Ryan / did you write the attached patches? Carl Eugen
On 25/04/2020 22:42, Carl Eugen Hoyos wrote:
Am Fr., 24. Apr. 2020 um 17:21 Uhr schrieb vectronic <hello.vectronic@gmail.com>:
I am resubmitting a patch which fixes the following two tickets:
Do you not want to commit with your name rather than a handle here?
https://trac.ffmpeg.org/ticket/7359 https://trac.ffmpeg.org/ticket/7485
Are you Nick Ryan / did you write the attached patches?
The LinkedIn on his website suggests he is. -- Josh
participants (4)
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Carl Eugen Hoyos -
Josh de Kock -
Paul B Mahol -
vectronic