Re: [FFmpeg-devel] [PATCH] avcodec/cuviddec: fix AV1 decoding error

[Timo Rothenpieler <timo@rothenpieler.org>]

On 23/06/2022 11:10, Zhao Zhili wrote:
> From: Zhao Zhili <zhilizhao@tencent.com>
> 
> Regression from 45e3b6a68. cuvidParseVideoData report unknown
> error with AV1CodecConfigurationRecord.
> ---
>   libavcodec/cuviddec.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/libavcodec/cuviddec.c b/libavcodec/cuviddec.c
> index cb3cda7e24..584fff40ed 100644
> --- a/libavcodec/cuviddec.c
> +++ b/libavcodec/cuviddec.c
> @@ -953,6 +953,17 @@ static av_cold int cuvid_decode_init(AVCodecContext *avctx)
>           extradata_size = avctx->extradata_size;
>       }
>   
> +#if CONFIG_AV1_CUVID_DECODER && defined(CUVID_HAS_AV1_SUPPORT)
> +    if (avctx->codec->id == AV_CODEC_ID_AV1 &&
> +            extradata_size > 4 &&
> +            extradata && extradata[0] & 0x80) {
> +        // skip AV1CodecConfigurationRecord to keep configOBUs only,
> +        // otherwise cuvidParseVideoData report unknown error.
> +        extradata += 4;
> +        extradata_size -= 4;
> +    }
> +#endif

Checking the defines shouldn't be necessary. The codec ID should never 
be AV1 if it's not enabled, and the code does not contain anything AV1 
specific.

>       ctx->cuparse_ext = av_mallocz(sizeof(*ctx->cuparse_ext)
>               + FFMAX(extradata_size - (int)sizeof(ctx->cuparse_ext->raw_seqhdr_data), 0));
>       if (!ctx->cuparse_ext) {

I'm not quite sure I understand what causes this.
Something about the mp4 demuxer changed, yes.
But what about other containers? Why wasn't this an issue before?

The code that was removed in 45e3b6a68 seems to just have always skipped 
the first 4 byte unconditionally.

A little more info in the commit message would be nice here. Specially a 
sentence or two about the "& 80" part.
Code LGTM otherwise.
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