> On Jan 6, 2023, at 01:34, Vignesh Venkatasubramanian
> <vigneshv-at-google....@ffmpeg.org> wrote:
>
> On Thu, Jan 5, 2023 at 1:45 AM "zhilizhao(赵志立)" <quinkbl...@foxmail.com>
> wrote:
>>
>>
>>
>>> On Jan 5, 2023, at 06:16, Vignesh Venkatasubramanian
>>> <vigneshv-at-google....@ffmpeg.org> wrote:
>>>
>>> The HEIF specification permits specifying the looping behavior of
>>> animated sequences by using the EditList (elst) box. The track
>>> duration will be set to the total duration of all the loops (or
>>> infinite) and the duration of a single loop will be set in the edit
>>> list box.
>>>
>>> The default behavior is to loop infinitely.
>>>
>>> Compliance verification:
>>> * This was added in libavif recently [1] and the files produced by
>>> ffmpeg after this change have EditList boxes similar to the ones
>>> produced by libavif (and avifdec is able to parse the loop count as
>>> intended).
>>> * ComplianceWarden is ok with the produced files.
>>> * Chrome is able to play back the produced files.
>>>
>>> Signed-off-by: Vignesh Venkatasubramanian <vigne...@google.com>
>>> ---
>>> libavformat/movenc.c | 35 +++++++++++++++++++++++++++++++----
>>> libavformat/movenc.h | 1 +
>>> 2 files changed, 32 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
>>> index 36c76f7f60..8d31317838 100644
>>> --- a/libavformat/movenc.c
>>> +++ b/libavformat/movenc.c
>>> @@ -3287,7 +3287,7 @@ static int mov_write_tkhd_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>> int64_t duration = av_rescale_rnd(calc_pts_duration(mov, track),
>>> mov->movie_timescale, track->timescale,
>>> AV_ROUND_UP);
>>> - int version = duration < INT32_MAX ? 0 : 1;
>>> + int version;
>>> int flags = MOV_TKHD_FLAG_IN_MOVIE;
>>> int group = 0;
>>>
>>> @@ -3295,6 +3295,14 @@ static int mov_write_tkhd_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>> size_t display_matrix_size;
>>> int i;
>>>
>>> + if (mov->mode == MODE_AVIF)
>>> + if (!mov->avif_loop_count)
>>> + duration = INT64_MAX;
>>> + else
>>> + duration *= mov->avif_loop_count;
>>> +
>>> + version = duration < INT32_MAX ? 0 : 1;
>>> +
>>> if (st) {
>>> if (mov->per_stream_grouping)
>>> group = st->index;
>>> @@ -3414,7 +3422,10 @@ static int mov_write_tapt_tag(AVIOContext *pb,
>>> MOVTrack *track)
>>> return update_size(pb, pos);
>>> }
>>>
>>> -// This box seems important for the psp playback ... without it the movie
>>> seems to hang
>>> +// This box is written in the following cases:
>>> +// * Seems important for the psp playback. Without it the movie seems to
>>> hang.
>>> +// * Used for specifying the looping behavior of animated AVIF (as
>>> specified
>>> +// in Section 9.6 of the HEIF specification ISO/IEC 23008-12).
>>> static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
>>> MOVTrack *track)
>>> {
>>> @@ -3425,6 +3436,7 @@ static int mov_write_edts_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>> int entry_size, entry_count, size;
>>> int64_t delay, start_ct = track->start_cts;
>>> int64_t start_dts = track->start_dts;
>>> + int flags = 0;
>>>
>>> if (track->entry) {
>>> if (start_dts != track->cluster[0].dts || start_ct !=
>>> track->cluster[0].cts) {
>>> @@ -3440,6 +3452,17 @@ static int mov_write_edts_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>>
>>> delay = av_rescale_rnd(start_dts + start_ct, mov->movie_timescale,
>>> track->timescale, AV_ROUND_DOWN);
>>> +
>>> + if (mov->mode == MODE_AVIF) {
>>> + delay = 0;
>>> + // Section 9.6.3 of ISO/IEC 23008-12: flags specifies repetition
>>> of the
>>> + // edit list as follows: (flags & 1) equal to 0 specifies that the
>>> edit
>>> + // list is not repeated, while (flags & 1) equal to 1 specifies
>>> that the
>>> + // edit list is repeated.
>>> + flags = mov->avif_loop_count != 1;
>>> + start_ct = 0;
>>> + }
>>> +
>>> version |= delay < INT32_MAX ? 0 : 1;
>>>
>>> entry_size = (version == 1) ? 20 : 12;
>>> @@ -3452,7 +3475,7 @@ static int mov_write_edts_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>> avio_wb32(pb, size - 8);
>>> ffio_wfourcc(pb, "elst");
>>> avio_w8(pb, version);
>>> - avio_wb24(pb, 0); /* flags */
>>> + avio_wb24(pb, flags); /* flags */
>>>
>>> avio_wb32(pb, entry_count);
>>> if (delay > 0) { /* add an empty edit to delay presentation */
>>> @@ -3469,7 +3492,7 @@ static int mov_write_edts_tag(AVIOContext *pb,
>>> MOVMuxContext *mov,
>>> avio_wb32(pb, -1);
>>> }
>>> avio_wb32(pb, 0x00010000);
>>> - } else {
>>> + } else if (mov->mode != MODE_AVIF) {
>>> /* Avoid accidentally ending up with start_ct = -1 which has got a
>>> * special meaning. Normally start_ct should end up positive or zero
>>> * here, but use FFMIN in case dts is a small positive integer
>>> @@ -3670,6 +3693,9 @@ static int mov_write_trak_tag(AVFormatContext *s,
>>> AVIOContext *pb, MOVMuxContext
>>> "Not writing any edit list even though one would have
>>> been required\n");
>>> }
>>>
>>> + if (mov->is_animated_avif)
>>> + mov_write_edts_tag(pb, mov, track);
>>> +
>>> if (track->tref_tag)
>>> mov_write_tref_tag(pb, track);
>>>
>>> @@ -7761,6 +7787,7 @@ static const AVCodecTag codec_f4v_tags[] = {
>>>
>>> static const AVOption avif_options[] = {
>>> { "movie_timescale", "set movie timescale", offsetof(MOVMuxContext,
>>> movie_timescale), AV_OPT_TYPE_INT, {.i64 = MOV_TIMESCALE}, 1, INT_MAX,
>>> AV_OPT_FLAG_ENCODING_PARAM},
>>> + { "loop", "Number of times to loop animated AVIF: 0 - infinite loop",
>>> offsetof(MOVMuxContext, avif_loop_count), AV_OPT_TYPE_INT, {.i64 = 0}, 0,
>>> INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, 0 },
>>
>> The code treat -loop 1 means playback 1 time. It can be misleading
>> to mean 2 times, playback 1 time then repeat/loop 1 time. That’s
>> how ‘-stream_loop’ option works. I’m not English native speaker,
>> I don’t know which one is correct. Better make the offset by 1
>> clear.
>>
>
> libavif uses the term "repetitionCount" instead of "loop" to not have
> this ambiguity.
>
> The behavior of the "loop" parameter in this implementation is similar
> to WebP's "loop" parameter in ffmpeg (i.e.) loop means the number of
> times it will be played back (loop == 1 => 1 playback, loop == 2 => 2
> playbacks and so on).
LGTM then.
>
>>> { NULL },
>>> };
>>> static const AVCodecTag codec_avif_tags[] = {
>>> diff --git a/libavformat/movenc.h b/libavformat/movenc.h
>>> index c6b3313deb..e85d83abdb 100644
>>> --- a/libavformat/movenc.h
>>> +++ b/libavformat/movenc.h
>>> @@ -249,6 +249,7 @@ typedef struct MOVMuxContext {
>>> int64_t avif_extent_pos[2]; // index 0 is YUV and 1 is Alpha.
>>> int avif_extent_length[2]; // index 0 is YUV and 1 is Alpha.
>>> int is_animated_avif;
>>> + int avif_loop_count;
>>> } MOVMuxContext;
>>>
>>> #define FF_MOV_FLAG_RTP_HINT (1 << 0)
>>> --
>>> 2.39.0.314.g84b9a713c41-goog
>>>
>>> _______________________________________________
>>> ffmpeg-devel mailing list
>>> ffmpeg-devel@ffmpeg.org
>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>>
>>> To unsubscribe, visit link above, or email
>>> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
>>
>
>
> --
> Vignesh
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
