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D3D12_Video_Encoding_ReadableReconpic.md

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D3D12_Video_Encoding_ReadableReconpic.md

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1. D3D12 Video Encoding readable reconstructed pictures

2. General considerations

This spec focuses on the points of extension where the existing D3D12 Video Encode API needs new structures to support reconstructed pictures (EncodeFrame output and DPB reference pictures) being readable, meaning NOT requiring D3D12_RESOURCE_FLAG_VIDEO_ENCODE_REFERENCE_ONLY anymore. The rest of the D3D12 Encode API will remain unmodified for this feature unless explicited in this spec. The next sections detail the API and DDI for video encoding. In many cases, the DDI is extremely similar to the API. The structures and enumerations which are basically the same (differing solely in name convention) are not repeated in the this specification.

3. Video Encoding API

ENUM: D3D12_VIDEO_ENCODER_SUPPORT_FLAGS

typedef enum D3D12_VIDEO_ENCODER_SUPPORT_FLAGS
{
    ...
    // New flags added in this spec
    D3D12_VIDEO_ENCODER_SUPPORT_FLAG_READABLE_RECONSTRUCTED_PICTURE_LAYOUT_AVAILABLE	= ...,
} D3D12_VIDEO_ENCODER_SUPPORT_FLAGS;

Remarks

Driver reports optional support for D3D12_VIDEO_ENCODER_SUPPORT_FLAG_READABLE_RECONSTRUCTED_PICTURE_LAYOUT_AVAILABLE using the associated support cap inputs (e.g the DXGI_FORMAT of the encoding input texture).

  • When the driver does NOT report this flag, D3D12_RESOURCE_FLAG_VIDEO_ENCODE_REFERENCE_ONLY is still mandatory as usual.

  • When the driver DOES report this flag, the reconstructed picture output in D3D12_VIDEO_ENCODER_ENCODEFRAME_OUTPUT_ARGUMENTS.ReconstructedPicture and the pictures in the DPB in D3D12_VIDEO_ENCODE_REFERENCE_FRAMES.ppTexture2Ds can be just regular textures without D3D12_RESOURCE_FLAG_VIDEO_ENCODE_REFERENCE_ONLY. All other existing restrictions still apply (e.g must be the same DXGI_FORMAT, dimensions, etc as D3D12_VIDEO_ENCODER_ENCODEFRAME_INPUT_ARGUMENTS.pInputFrame)

Please note that even when the driver reports D3D12_VIDEO_ENCODER_SUPPORT_FLAG_READABLE_RECONSTRUCTED_PICTURE_LAYOUT_AVAILABLE, the usage of reconstructed pictures with D3D12_RESOURCE_FLAG_VIDEO_ENCODE_REFERENCE_ONLY must be still supported along with also readable textures.

Drivers must only report D3D12_VIDEO_ENCODER_SUPPORT_FLAG_READABLE_RECONSTRUCTED_PICTURE_LAYOUT_AVAILABLE when the reconstructed pictures are in a readable layout, and must not perform any conversions (e.g using shaders) within the driver that would mean a performance hit respect using resources with D3D12_RESOURCE_FLAG_VIDEO_ENCODE_REFERENCE_ONLY. The intent of this feature is to allow users consume the reconstructed pictures where hardware/drivers allow it without any performance hit.