Re: [FFmpeg-devel] [PATCH 3/3] avformat/movenc: Add support for AVIF muxing

[James Zern <jzern-at-google.com@ffmpeg.org>]

On Mon, Mar 28, 2022 at 1:49 PM Vignesh Venkatasubramanian
<vigneshv-at-google.com@ffmpeg.org> wrote:
>
> Add an AVIF muxer by re-using the existing the mov/mp4 muxer.
>
> AVIF Specifiation: https://aomediacodec.github.io/av1-avif
>

Specification

> Sample usage for still image:
> ffmpeg -i image.png -c:v libaom-av1 -avif-image 1 image.avif
>
> Sample usage for animated AVIF image:
> ffmpeg -i video.mp4 animated.avif
>
> We can re-use any of the AV1 encoding options that will make
> sense for image encoding (like bitrate, tiles, encoding speed,
> etc).
>
> The files generated by this muxer has been verified to be valid
> AVIF files by the following:
> 1) Displays on Chrome (both still and animated images).
> 2) Displays on Firefox (only still images, firefox does not support
>    animated AVIF yet).
> 3) Verfied to be valid by Compliance Warden:

Verified

>    https://github.com/gpac/ComplianceWarden
>
> Fixes the encoder/muxer part of Trac Ticket #7621
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> ---
>  configure                |   1 +
>  libavformat/allformats.c |   1 +
>  libavformat/movenc.c     | 337 ++++++++++++++++++++++++++++++++++++---
>  libavformat/movenc.h     |   5 +
>  4 files changed, 319 insertions(+), 25 deletions(-)
>

There might be some other issues, you can try tools/patcheck.

> [...]
> @@ -5068,6 +5231,31 @@ static int mov_write_ftyp_tag(AVIOContext *pb, AVFormatContext *s)
>      // compatible brand a second time.
>      if (mov->mode == MODE_ISM) {
>          ffio_wfourcc(pb, "piff");
> +    } else if (mov->mode == MODE_AVIF) {
> +        const AVPixFmtDescriptor *pix_fmt_desc =
> +            av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> +        const int depth = pix_fmt_desc->comp[0].depth;
> +        if (mov->is_animated_avif) {
> +            // For animated AVIF, major brand is "avis". Add "avif" as a
> +            // compatible brand.
> +            ffio_wfourcc(pb, "avif");
> +            ffio_wfourcc(pb, "msf1");
> +            ffio_wfourcc(pb, "iso8");
> +        }
> +        ffio_wfourcc(pb, "mif1");
> +        ffio_wfourcc(pb, "miaf");
> +        if (depth == 8 || depth == 10) {
> +            // MA1B and MA1A brands are based on AV1 profile. Short hand for
> +            // computing that is based on chroma subsampling type. 420 chroma
> +            // subsampling is MA1B.  444 chroma subsampling is MA1A.
> +            if (pix_fmt_desc->log2_chroma_w == 0 && pix_fmt_desc->log2_chroma_h == 0) {

!... is the preferred style.

> @@ -6773,12 +6983,13 @@ static int mov_init(AVFormatContext *s)
>                          pix_fmt == AV_PIX_FMT_MONOWHITE ||
>                          pix_fmt == AV_PIX_FMT_MONOBLACK;
>              }
> -            if (track->par->codec_id == AV_CODEC_ID_VP9 ||
> -                track->par->codec_id == AV_CODEC_ID_AV1) {
> -                if (track->mode != MODE_MP4) {
> -                    av_log(s, AV_LOG_ERROR, "%s only supported in MP4.\n", avcodec_get_name(track->par->codec_id));
> -                    return AVERROR(EINVAL);
> -                }
> +            if (track->par->codec_id == AV_CODEC_ID_VP9 && track->mode != MODE_MP4) {
> +                av_log(s, AV_LOG_ERROR, "%s only supported in MP4.\n", avcodec_get_name(track->par->codec_id));
> +               return AVERROR(EINVAL);

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