Re: [FFmpeg-devel] [PATCH 2/2] lavc/d3d12va_encode: trim header alignment at output

[Tong Wu <wutong1208@outlook.com>]

Lynne:
>Subject: Re: [FFmpeg-devel] [PATCH 2/2] lavc/d3d12va_encode: trim header
>alignment at output
>
>On 28/07/2024 15:06, Tong Wu wrote:
>> Tong Wu:
>>> Subject: [FFmpeg-devel][PATCH 2/2] lavc/d3d12va_encode: trim header
>>> alignment at output
>>>
>>> It is d3d12va's requirement that the FrameStartOffset must be aligned
>>> as per hardware limitation. However, we could trim this alignment at
>>> output to reduce coded size. A aligned_header_size is added to
>D3D12VAEncodePicture.
>>>
>>> Signed-off-by: Tong Wu <wutong1208@outlook.com>
>>> ---
>>> libavcodec/d3d12va_encode.c | 18 ++++++++++++------
>>> libavcodec/d3d12va_encode.h |  1 +
>>> 2 files changed, 13 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/libavcodec/d3d12va_encode.c
>>> b/libavcodec/d3d12va_encode.c index
>>> 9f7a42911e..9ee9da41e3 100644
>>> --- a/libavcodec/d3d12va_encode.c
>>> +++ b/libavcodec/d3d12va_encode.c
>>> @@ -308,9 +308,9 @@ static int d3d12va_encode_issue(AVCodecContext
>*avctx,
>>>          }
>>>
>>>          pic->header_size = (int)bit_len / 8;
>>> -        pic->header_size = pic->header_size % ctx-
>>>> req.CompressedBitstreamBufferAccessAlignment ?
>>> -                           FFALIGN(pic->header_size, ctx-
>>>> req.CompressedBitstreamBufferAccessAlignment) :
>>> -                           pic->header_size;
>>> +        pic->aligned_header_size = pic->header_size % ctx-
>>>> req.CompressedBitstreamBufferAccessAlignment ?
>>> +                                   FFALIGN(pic->header_size, ctx-
>>>> req.CompressedBitstreamBufferAccessAlignment) :
>>> +                                   pic->header_size;
>>>
>>>          hr = ID3D12Resource_Map(pic->output_buffer, 0, NULL, (void **)&ptr);
>>>          if (FAILED(hr)) {
>>> @@ -318,7 +318,7 @@ static int d3d12va_encode_issue(AVCodecContext
>*avctx,
>>>              goto fail;
>>>          }
>>>
>>> -        memcpy(ptr, data, pic->header_size);
>>> +        memcpy(ptr, data, pic->aligned_header_size);
>>>          ID3D12Resource_Unmap(pic->output_buffer, 0, NULL);
>>>      }
>>>
>>> @@ -344,10 +344,10 @@ static int d3d12va_encode_issue(AVCodecContext
>>> *avctx,
>>>
>>>      input_args.PictureControlDesc.PictureControlCodecData = pic->pic_ctl;
>>>      input_args.PictureControlDesc.ReferenceFrames         = d3d12_refs;
>>> -    input_args.CurrentFrameBitstreamMetadataSize          = pic->header_size;
>>> +    input_args.CurrentFrameBitstreamMetadataSize          = pic-
>>>> aligned_header_size;
>>>
>>>      output_args.Bitstream.pBuffer                                    = pic->output_buffer;
>>> -    output_args.Bitstream.FrameStartOffset                           = pic->header_size;
>>> +    output_args.Bitstream.FrameStartOffset                           = pic-
>>>> aligned_header_size;
>>>      output_args.ReconstructedPicture.pReconstructedPicture           = pic-
>>>> recon_surface->texture;
>>>      output_args.ReconstructedPicture.ReconstructedPictureSubresource = 0;
>>>      output_args.EncoderOutputMetadata.pBuffer                        = pic-
>>>> encoded_metadata;
>>> @@ -663,6 +663,12 @@ static int
>>> d3d12va_encode_get_coded_data(AVCodecContext *avctx,
>>>          goto end;
>>>      ptr = pkt->data;
>>>
>>> +    memcpy(ptr, mapped_data, pic->header_size);
>>> +
>>> +    ptr += pic->header_size;
>>> +    mapped_data += pic->aligned_header_size;
>>> +    total_size -= pic->header_size;
>>> +
>>>      memcpy(ptr, mapped_data, total_size);
>>>
>>>      ID3D12Resource_Unmap(pic->output_buffer, 0, NULL); diff --git
>>> a/libavcodec/d3d12va_encode.h b/libavcodec/d3d12va_encode.h index
>>> 1a0abc5bd0..51440428e4 100644
>>> --- a/libavcodec/d3d12va_encode.h
>>> +++ b/libavcodec/d3d12va_encode.h
>>> @@ -43,6 +43,7 @@ typedef struct D3D12VAEncodePicture {
>>>      FFHWBaseEncodePicture base;
>>>
>>>      int             header_size;
>>> +    int             aligned_header_size;
>>>
>>>      AVD3D12VAFrame *input_surface;
>>>      AVD3D12VAFrame *recon_surface;
>>> --
>>> 2.45.1.windows.1
>>
>>
>> The first patch in this patchset has been merged earlier. Will merge this patch if
>there's no more comment.
>>
>> -Tong
>>
>>
>>
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>
>Somehow I missed that patch. You should've ping me when I pushed the first one.
>
>Pushed.
>In Vulkan, we expose the raw packet we've just encoded by wrapping it as an
>AVBufferRef, you should consider doing this.

Thank you very much!

There's already a AVBufferRef of output buffer in D3D12VAEncodePicture. I guess you might mean that.

Thanks,
Tong
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