[FFmpeg-devel] [PATCH 1/3] avcodec/vp8: Enforce key-frame only for WebP

[Andreas Rheinhardt]

Andreas Rheinhardt:
> VP8-in-WebP only uses key frame encoding (see [1]), yet this
> is currently not enforced. This commit does so in order to
> make output reproducible with frame-threading as the VP8 decoder's
> update_thread_context is not called at all when using decoding
> VP8-in-WebP (as this is unnecessary for key frame-only streams).
> 
> [1]: https://developers.google.com/speed/webp/docs/riff_container
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavcodec/vp8.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
> index 83c60adeb0..7972775a1c 100644
> --- a/libavcodec/vp8.c
> +++ b/libavcodec/vp8.c
> @@ -2665,7 +2665,11 @@ int vp78_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame,
>      if (ret < 0)
>          goto err;
>  
> -    if (s->actually_webp) {
> +    if (!is_vp7 && s->actually_webp) {
> +        // VP8 in WebP is supposed to be intra-only. Enforce this here
> +        // to ensure that output is reproducible with frame-threading.
> +        if (!s->keyframe)
> +            return AVERROR_INVALIDDATA;
>          // avctx->pix_fmt already set in caller.
>      } else if (!is_vp7 && s->pix_fmt == AV_PIX_FMT_NONE) {
>          s->pix_fmt = get_pixel_format(s);

Will apply this patchset tomorrow unless there are objections.

- Andreas