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

[averne <averne381@gmail.com>]

Le 08/04/2025 à 11:19, Zhao Zhili a écrit :
> Sorry for the long delay.

No problem, thank you for the review.

> 
>> 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.

That's a good point, I will send a revised patch shortly.

> 
>> +
>> +    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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> 

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