Re: [FFmpeg-devel] [PATCH v1 5/8] avformat/mov_muxer: Extended MOV muxer to handle APV video content

[Dawid Kozinski/Multimedia (PLT) /SRPOL/Staff Engineer/Samsung Electronics]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of James
> Almer
> Sent: środa, 23 kwietnia 2025 16:44
> To: ffmpeg-devel@ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH v1 5/8] avformat/mov_muxer: Extended
> MOV muxer to handle APV video content
> 
> On 4/23/2025 11:13 AM, Dawid Kozinski wrote:
> > @@ -2757,6 +2789,8 @@ static int mov_write_video_tag(AVFormatContext
> *s, AVIOContext *pb, MOVMuxContex
> >       }
> >       else if (track->par->codec_id ==AV_CODEC_ID_EVC) {
> >           mov_write_evcc_tag(pb, track);
> > +    } else if (track->par->codec_id ==AV_CODEC_ID_APV) {
> > +        mov_write_apvc_tag(pb, track);
> >       } else if (track->par->codec_id == AV_CODEC_ID_VP9) {
> >           mov_write_vpcc_tag(mov->fc, pb, track);
> >       } else if (track->par->codec_id == AV_CODEC_ID_AV1) { @@ -6713,6
> > +6747,18 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
> >           memset(trk->vos_data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
> >       }
> >
> > +    if (par->codec_id == AV_CODEC_ID_APV && !trk->vos_len) {
> > +            ret = ff_isom_create_apv_dconf_record(&trk->vos_data, &trk-
> >vos_len);
> > +            if (!trk->vos_data) {
> > +                ret = AVERROR(ENOMEM);
> > +                goto err;
> > +            }
> > +    }
> > +
> > +    if (par->codec_id == AV_CODEC_ID_APV && trk->vos_len) {
> > +        ret = ff_isom_fill_apv_dconf_record(trk->vos_data, pkt->data, 
> > size);
> > +    }
> > +
> >       if (par->codec_id == AV_CODEC_ID_AAC && pkt->size > 2 &&
> >           (AV_RB16(pkt->data) & 0xfff0) == 0xfff0) {
> >           if (!trk->st->nb_frames) {
> 
> Instead of this, add APV to the list in
> https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/movenc.c;h=4bc8b
> d1b2ab765c2b9f5f5dfc2dcb77361f2b944;hb=HEAD#l6697
> so the first packet is always copied to trk->vos_data in case
> par->extradata is not set.
> 
> After that, ff_isom_write_apvc() can either write the extradata as is if it's
> already a configuration record, or generate it if it's just a packet of PBUs 
> (See
> ff_isom_write_hvcc()).

Previously, I had this implemented as follows:

if ((par->codec_id == AV_CODEC_ID_DNXHD ||
     par->codec_id == AV_CODEC_ID_H264 ||
     par->codec_id == AV_CODEC_ID_HEVC || 
     par->codec_id == AV_CODEC_ID_VVC ||
     par->codec_id == AV_CODEC_ID_VP9 ||
     par->codec_id == AV_CODEC_ID_EVC ||
     par->codec_id == AV_CODEC_ID_APV ||
     par->codec_id == AV_CODEC_ID_TRUEHD) && !trk->vos_len &&

AV_CODEC_ID_APV was included in the list at
https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/movenc.c;h=4bc8bd1b2ab765c2b9f5f5dfc2dcb77361f2b944;hb=HEAD#l6697.

It was exactly as you described, which caused the first packet to be copied to 
trk->vos_data when par->extradata was not set.

However, I had to change this because I was unable to fill the 
APVDecoderConfigurationRecord structure in the ff_isom_write_apvc() function 
based on the data from trk->vos_data (data from a single packet - data only 
from the first AU). The structure is defined as follows:
https://github.com/AcademySoftwareFoundation/openapv/blob/main/readme/apv_isobmff.md.

The structure contains the fields number_of_configuration_entry and 
number_of_frame_info[i]. It seems to me that filling in correctly the 
APVDecoderConfigurationRecord structure requires analyzing the entire stream.

number_of_configuration_entry - this value corresponds to the number of 
different PBU types in all AUs (PBU types for frames: 1 - primary frame; 2 - 
non-primary frame; 25 - preview frame; 26 - depth frame; 27 - alpha frame).
number_of_frame_info[i] - indicates the number of variations of the frame 
header information; for each configuration, there can be one or more variations 
of frame_info.

Examples:
--------------
Case 1:
======
If we have a stream containing only primary frames and if each primary frame 
has the same data in frame_info, then we have:

number_of_configuration_entry = 1
number_of_frame_info[0] = 1 (if all primary frames have the same frame_info)

Case 2:
======
If we have a stream containing both primary frames and non-primary frames, and 
if each primary and non-primary frame has the same data in frame_info, then we 
have:

number_of_configuration_entry = 2
number_of_frame_info[0] = 1 (if all primary frames have the same frame_info)
number_of_frame_info[1] = 1 (if all non-primary frames (type: 2) have the same 
frame_info)
Case 3:
======

number_of_configuration_entry = 1
number_of_frame_info[0] = 2 (if primary frames have 2 kinds of frame_info)

To correctly fill in number_of_configuration_entry and number_of_frame_info[i], 
we need to check all AUs one by one. The number_of_configuration_entry will 
equal the number of PBU types in the stream (only those that contain 
frame_info, such as 1, 2, 25, 26, 27). Therefore, if the stream contains PBU 
types 1 and 2, then number_of_configuration_entry = 2. For each of these types, 
there can be different number_of_frame_info. If in the stream we have a certain 
number of primary frame PBUs with Full HD resolution, followed by a certain 
number of primary frame PBUs with UHD resolution, then for the configuration 
related to the primary frame, we will have number_of_frame_info[i] = 2.

Please correct me if I'm wrong.


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