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

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

On Wed, Apr 13, 2022 at 1:40 PM Vignesh Venkatasubramanian
<vigneshv-at-google.com@ffmpeg.org> wrote:
>
> Add an AVIF muxer by re-using the existing the mov/mp4 muxer.
>
> AVIF Specification: https://aomediacodec.github.io/av1-avif
>
> 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) Verified to be valid by Compliance Warden:
>    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(-)
>

It would be good to have a Changelog entry after the ticket is fixed.

> [...]
> @@ -2823,7 +2848,10 @@ static int mov_write_hdlr_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
>
>      if (track) {
>          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
> -        if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
> +        if (track->mode == MODE_AVIF) {
> +            hdlr_type = "pict";
> +            descr = "ffmpeg";

Should this be PictureHandler or blank? What's written for heic?

> [...]
> +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
> +{
> +    int64_t pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "ispe");
> +    avio_wb32(pb, 0); /* Version & flags */
> +    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> +    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> +    return update_size(pb, pos);
> +}
> +
> +

This extra line could be removed.

> [...]
> +    /* AVIF output must have exactly one video stream */
> +    if (mov->mode == MODE_AVIF) {
> +        if (s->nb_streams > 1) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one stream\n");
> +            return AVERROR(EINVAL);
> +        }
> +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output requires one video stream\n");
> +            return AVERROR(EINVAL);
> +        }
> +    }
> +
> +

This one too.
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