Re: [FFmpeg-devel] [PATCH v2 1/1] avcodec/libjxlenc: Add libjxl_animated encoder

["Zsolt Vadász via ffmpeg-devel" <ffmpeg-devel@ffmpeg.org>]

On Friday, December 15th, 2023 at 12:20 AM, Leo Izen <leo.izen@gmail.com> wrote:


> > + AVFrame *last;
> 
> 
> I don't see the purpose of keeping this here.
> 

The name is misleading, I should have named it `previous`, since it always contains the previous frame.
I did it this way so I could call JxlEncoderCloseInput when the callback received NULL.
> > +
> > + if(!ctx->last && !avctx->internal->draining) { > + ctx->last = av_frame_clone(frame);
> > + *got_packet = 0;
> > + return AVERROR(EAGAIN);
> 
> It looks like you're trying to emit one packet per image, rather than
> one packet per encoded frame. This is fine, but you should not be
> calling av_frame_clone, and there's no reason to use
> avctx->internal->draining here. If you are doing this, you also have no
> 
> reason to cache ctx->last at all.

It's the opposite, I'm trying to emit a packet for each frame of the animation.
> > +const FFCodec ff_libjxl_animated_encoder = {
> > + .p.name = "libjxl_animated",
> > + CODEC_LONG_NAME("libjxl Animated JPEG XL"),
> > + .p.type = AVMEDIA_TYPE_VIDEO,
> > + .p.id = AV_CODEC_ID_JPEGXL,
> > + .priv_data_size = sizeof(LibJxlEncodeContext),
> > + .init = libjxl_animated_encode_init,
> > + FF_CODEC_ENCODE_CB(libjxl_animated_encode_frame),
> > + .close = libjxl_encode_close,
> > + .p.capabilities = AV_CODEC_CAP_OTHER_THREADS |
> > + AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE |
> > + AV_CODEC_CAP_DELAY,
> > + .caps_internal = FF_CODEC_CAP_NOT_INIT_THREADSAFE |
> > + FF_CODEC_CAP_AUTO_THREADS | FF_CODEC_CAP_INIT_CLEANUP |
> > + FF_CODEC_CAP_ICC_PROFILES | FF_CODEC_CAP_EOF_FLUSH,
> 
> 
> Why FF_CODEC_CAP_EOF_FLUSH?

So the encoder receives a NULL after the last frame has been submitted,
so JxlEncoderCloseInput can be called and the final frame properly emitted.
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