Re: [FFmpeg-devel] [PATCH] nvdec/vc1: add marker insertion logic

[Zhao Zhili <quinkblack-at-foxmail.com@ffmpeg.org>]

Sorry for the long delay.

> On Mar 5, 2025, at 01:17, averne <averne381@gmail.com> wrote:
> 
> 
> ---
> Insert the relevant marker into the bitstream on
> slice submission.
> This is analogous to the logic found in DXVA and
> D3D hwaccels.
> 
> Fixes decoding of various VC-1 streams, eg.:
> https://drive.google.com/file/d/1WJyiRhcdU4FHTW3sVMitS7UdrZM1NBy-/view?usp=sharing

I have tested and the patch works to fix the issue.

> 
> This was investigated using my nvdec tracing tool:
> https://github.com/averne/NvdecTrace
> 
> Signed-off-by: averne <averne381@gmail.com>
> ---
> libavcodec/nvdec_vc1.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 48 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/nvdec_vc1.c b/libavcodec/nvdec_vc1.c
> index fbfba1ecb43421573ef8fea1e37a2425c272edc9..2726574a26583b0cfc28bdec5595c15bdc465ff8 100644
> --- a/libavcodec/nvdec_vc1.c
> +++ b/libavcodec/nvdec_vc1.c
> @@ -22,6 +22,7 @@
> 
> #include "config_components.h"
> 
> +#include "libavutil/mem.h"
> #include "avcodec.h"
> #include "hwaccel_internal.h"
> #include "internal.h"
> @@ -107,6 +108,51 @@ static int nvdec_vc1_start_frame(AVCodecContext *avctx, const uint8_t *buffer, u
>     return 0;
> }
> 
> +static int nvdec_vc1_decode_slice(AVCodecContext *avctx, const uint8_t *buffer,
> +                                  uint32_t size)
> +{
> +    NVDECContext *ctx = avctx->internal->hwaccel_priv_data;
> +    const VC1Context *v = avctx->priv_data;
> +    uint32_t marker;
> +    int marker_size;
> +    void *tmp;
> +
> +    if (avctx->codec_id != AV_CODEC_ID_VC1) {
> +        marker_size = 0;
> +    } else {
> +        if (ctx->bitstream_len)
> +            marker = VC1_CODE_SLICE;
> +        else if (v->profile == PROFILE_ADVANCED && v->fcm == ILACE_FIELD && v->second_field)
> +            marker = VC1_CODE_FIELD;
> +        else
> +            marker = VC1_CODE_FRAME;
> +
> +        marker_size = (size >= sizeof(marker) && AV_RB32(buffer) != marker) ? sizeof(marker) : 0;
> +    }

I’m not familiar with VC1 or WMV3, but if the maker only needed for VC1, you can remove the check on
codec_id, and keep ff_wmv3_nvdec_hwaccel as before (use ff_nvdec_simple_decode_slice).

Otherwise LGTM, thanks.

> +
> +    tmp = av_fast_realloc(ctx->bitstream_internal, &ctx->bitstream_allocated,
> +                          ctx->bitstream_len + size + marker_size);
> +    if (!tmp)
> +        return AVERROR(ENOMEM);
> +    ctx->bitstream = ctx->bitstream_internal = tmp;
> +
> +    tmp = av_fast_realloc(ctx->slice_offsets, &ctx->slice_offsets_allocated,
> +                          (ctx->nb_slices + 1) * sizeof(*ctx->slice_offsets));
> +    if (!tmp)
> +        return AVERROR(ENOMEM);
> +    ctx->slice_offsets = tmp;
> +
> +    if (marker_size)
> +        AV_WB32(ctx->bitstream_internal + ctx->bitstream_len, marker);
> +
> +    memcpy(ctx->bitstream_internal + ctx->bitstream_len + marker_size, buffer, size);
> +    ctx->slice_offsets[ctx->nb_slices] = ctx->bitstream_len;
> +    ctx->bitstream_len += size + marker_size;
> +    ctx->nb_slices++;
> +
> +    return 0;
> +}
> +
> static int nvdec_vc1_frame_params(AVCodecContext *avctx,
>                                   AVBufferRef *hw_frames_ctx)
> {
> @@ -121,7 +167,7 @@ const FFHWAccel ff_vc1_nvdec_hwaccel = {
>     .p.pix_fmt            = AV_PIX_FMT_CUDA,
>     .start_frame          = nvdec_vc1_start_frame,
>     .end_frame            = ff_nvdec_simple_end_frame,
> -    .decode_slice         = ff_nvdec_simple_decode_slice,
> +    .decode_slice         = nvdec_vc1_decode_slice,
>     .frame_params         = nvdec_vc1_frame_params,
>     .init                 = ff_nvdec_decode_init,
>     .uninit               = ff_nvdec_decode_uninit,
> @@ -136,7 +182,7 @@ const FFHWAccel ff_wmv3_nvdec_hwaccel = {
>     .p.pix_fmt            = AV_PIX_FMT_CUDA,
>     .start_frame          = nvdec_vc1_start_frame,
>     .end_frame            = ff_nvdec_simple_end_frame,
> -    .decode_slice         = ff_nvdec_simple_decode_slice,
> +    .decode_slice         = nvdec_vc1_decode_slice,
>     .frame_params         = nvdec_vc1_frame_params,
>     .init                 = ff_nvdec_decode_init,
>     .uninit               = ff_nvdec_decode_uninit,
> 
> ---
> base-commit: f76195ff656d6bea68feee783160652e2b3e3d60
> change-id: 20250304-nvdec-vc1-marker2-53d6bd30ee99
> 
> Best regards,
> -- 
> averne <averne381@gmail.com>
> 
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