Re: [FFmpeg-devel] [PATCH v3] avformat/mov: add interleaved_read option

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On Sep 14, 2023, at 09:41, Steven Liu <lingjiujianke@gmail.com> wrote:
> 
> Zhao Zhili <quinkblack@foxmail.com> 于2023年9月12日周二 01:10写道：
>> 
>> From: Zhao Zhili <zhilizhao@tencent.com>
>> 
>> For bad interleaved files, manually interleave multiple tracks at the
>> demuxer level can trigger seeking back and forth, which can be
>> dramatically slow depending on the protocol. Demuxer level interleave
>> can be useless sometimes, e.g., reading mp4 via http and then
>> transcoding/remux to DASH. Disable this option when you don't need the
>> demuxer level interleave, and want to avoid the IO penalizes.
>> 
>> Co-authored-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
>> Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
>> ---
>> v3: update doc
>> v2: rename option
>> 
>> This issue is well known. Two samples can be found at here
>> http://ffmpeg.org/pipermail/ffmpeg-devel/2022-December/304951.html
>> 
>> doc/demuxers.texi     | 7 +++++++
>> libavformat/isom.h    | 1 +
>> libavformat/mov.c     | 5 ++++-
>> libavformat/version.h | 2 +-
>> 4 files changed, 13 insertions(+), 2 deletions(-)
>> 
>> diff --git a/doc/demuxers.texi b/doc/demuxers.texi
>> index 2d33b47a56..ca1563abb0 100644
>> --- a/doc/demuxers.texi
>> +++ b/doc/demuxers.texi
>> @@ -779,6 +779,13 @@ cast to int32 are used to adjust onward dts.
>> 
>> Unit is the track time scale. Range is 0 to UINT_MAX. Default is @code{UINT_MAX - 48000*10} which allows upto
>> a 10 second dts correction for 48 kHz audio streams while accommodating 99.9% of @code{uint32} range.
>> +
>> +@item interleaved_read
>> +Interleave packets from multiple tracks at demuxer level. For badly interleaved files, this prevents playback issues
>> +caused by large gaps between packets in different tracks, as MOV/MP4 do not have packet placement requirements.
>> +However, this can cause excessive seeking on very badly interleaved files, due to seeking between tracks, so disabling
>> +it may prevent I/O issues, at the expense of playback.
>> +
>> @end table
>> 
>> @subsection Audible AAX
>> diff --git a/libavformat/isom.h b/libavformat/isom.h
>> index 4b1cd42f0f..3d375d7a46 100644
>> --- a/libavformat/isom.h
>> +++ b/libavformat/isom.h
>> @@ -327,6 +327,7 @@ typedef struct MOVContext {
>>         int64_t extent_offset;
>>     } *avif_info;
>>     int avif_info_size;
>> +    int interleaved_read;
>> } MOVContext;
>> 
>> int ff_mp4_read_descr_len(AVIOContext *pb);
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index aa1d9e4ccc..8ad5f0b646 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -8780,6 +8780,8 @@ static AVIndexEntry *mov_find_next_sample(AVFormatContext *s, AVStream **st)
>>     AVIndexEntry *sample = NULL;
>>     int64_t best_dts = INT64_MAX;
>>     int i;
>> +    MOVContext *mov = s->priv_data;
>> +    int no_interleave = !mov->interleaved_read || !(s->pb->seekable & AVIO_SEEKABLE_NORMAL);
>>     for (i = 0; i < s->nb_streams; i++) {
>>         AVStream *avst = s->streams[i];
>>         FFStream *const avsti = ffstream(avst);
>> @@ -8788,7 +8790,7 @@ static AVIndexEntry *mov_find_next_sample(AVFormatContext *s, AVStream **st)
>>             AVIndexEntry *current_sample = &avsti->index_entries[msc->current_sample];
>>             int64_t dts = av_rescale(current_sample->timestamp, AV_TIME_BASE, msc->time_scale);
>>             av_log(s, AV_LOG_TRACE, "stream %d, sample %d, dts %"PRId64"\n", i, msc->current_sample, dts);
>> -            if (!sample || (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) && current_sample->pos < sample->pos) ||
>> +            if (!sample || (no_interleave && current_sample->pos < sample->pos) ||
>>                 ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
>>                  ((msc->pb != s->pb && dts < best_dts) || (msc->pb == s->pb && dts != AV_NOPTS_VALUE &&
>>                  ((FFABS(best_dts - dts) <= AV_TIME_BASE && current_sample->pos < sample->pos) ||
>> @@ -9282,6 +9284,7 @@ static const AVOption mov_options[] = {
>>     { "enable_drefs", "Enable external track support.", OFFSET(enable_drefs), AV_OPT_TYPE_BOOL,
>>         {.i64 = 0}, 0, 1, FLAGS },
>>     { "max_stts_delta", "treat offsets above this value as invalid", OFFSET(max_stts_delta), AV_OPT_TYPE_INT, {.i64 = UINT_MAX-48000*10 }, 0, UINT_MAX, .flags = AV_OPT_FLAG_DECODING_PARAM },
>> +    { "interleaved_read", "Manually interleave between multiple tracks", OFFSET(interleaved_read), AV_OPT_TYPE_BOOL, {.i64 = 1 }, 0, 1, .flags = AV_OPT_FLAG_DECODING_PARAM },
>> 
>>     { NULL },
>> };
>> diff --git a/libavformat/version.h b/libavformat/version.h
>> index cb67e0a1f8..e41362ac9d 100644
>> --- a/libavformat/version.h
>> +++ b/libavformat/version.h
>> @@ -32,7 +32,7 @@
>> #include "version_major.h"
>> 
>> #define LIBAVFORMAT_VERSION_MINOR  12
>> -#define LIBAVFORMAT_VERSION_MICRO 100
>> +#define LIBAVFORMAT_VERSION_MICRO 101
>> 
>> #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
>>                                                LIBAVFORMAT_VERSION_MINOR, \
>> --
>> 2.34.1
>> 
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> 
> 
> lgtm

Pushed with a little modification on the option description. Thanks!

> 
> Thanks
> Steven
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