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Fix CUDA RGBA to NV12 conversion

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On linux hosts with Nvidia GPU and CUDA support enabled, a CUDA kernel
is used to convert captured RGBA frames to NV12 before encoding. This
kernel contained a bug affecting image quality, in particular when
rendering high-contrast colored text and sharp lines. See [1] for more
information.

This commit fixes the format conversion kernel by taking 2x2 RGBA blocks
to generate 4 luma (Y) values and 1 chroma (UV) pair, ie: 12 bits per
pixel YUV420 (NV12). Previous code incorrectly generated 1 UV pair for
every 2 pixels.

[1] https://github.com/LizardByte/Sunshine/issues/154
This commit is contained in:
Wouter Bijlsma 2022-10-10 20:25:01 +02:00 committed by w0utert
parent 43525415fd
commit 7f53388304
1 changed files with 19 additions and 9 deletions
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26
src/platform/linux/cuda.cu
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@ -160,7 +160,7 @@ __global__ void RGBA_to_NV12(
float scale, const viewport_t viewport, const video::color_t *const color_matrix) {
int idX = (threadIdx.x + blockDim.x * blockIdx.x) * 2;
int idY = (threadIdx.y + blockDim.y * blockIdx.y);
int idY = (threadIdx.y + blockDim.y * blockIdx.y) * 2;
if(idX >= viewport.width) return;
if(idY >= viewport.height) return;
@ -171,18 +171,28 @@ __global__ void RGBA_to_NV12(
idX += viewport.offsetX;
idY += viewport.offsetY;
dstY = dstY + idX + idY * dstPitchY;
uint8_t *dstY0 = dstY + idX + idY * dstPitchY;
uint8_t *dstY1 = dstY + idX + (idY + 1) * dstPitchY;
dstUV = dstUV + idX + (idY / 2 * dstPitchUV);
float3 rgb_l = bgra_to_rgb(tex2D<float4>(srcImage, x, y));
float3 rgb_r = bgra_to_rgb(tex2D<float4>(srcImage, x + scale, y));
float3 rgb_lt = bgra_to_rgb(tex2D<float4>(srcImage, x, y));
float3 rgb_rt = bgra_to_rgb(tex2D<float4>(srcImage, x + scale, y));
float3 rgb_lb = bgra_to_rgb(tex2D<float4>(srcImage, x, y + scale));
float3 rgb_rb = bgra_to_rgb(tex2D<float4>(srcImage, x + scale, y + scale));
float2 uv = calcUV((rgb_l + rgb_r) * 0.5f, color_matrix) * 256.0f;
float2 uv_lt = calcUV(rgb_lt, color_matrix) * 256.0f;
float2 uv_rt = calcUV(rgb_rt, color_matrix) * 256.0f;
float2 uv_lb = calcUV(rgb_lb, color_matrix) * 256.0f;
float2 uv_rb = calcUV(rgb_rb, color_matrix) * 256.0f;
float2 uv = (uv_lt + uv_lb + uv_rt + uv_rb) * 0.25f;
dstUV[0] = uv.x;
dstUV[1] = uv.y;
dstY[0] = calcY(rgb_l, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
dstY[1] = calcY(rgb_r, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
dstY0[0] = calcY(rgb_lt, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
dstY0[1] = calcY(rgb_rt, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
dstY1[0] = calcY(rgb_lb, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
dstY1[1] = calcY(rgb_rb, color_matrix) * 245.0f; // 245.0f is a magic number to ensure slight changes in luminosity are more visisble
}
int tex_t::copy(std::uint8_t *src, int height, int pitch) {
@ -292,7 +302,7 @@ int sws_t::convert(std::uint8_t *Y, std::uint8_t *UV, std::uint32_t pitchY, std:
int sws_t::convert(std::uint8_t *Y, std::uint8_t *UV, std::uint32_t pitchY, std::uint32_t pitchUV, cudaTextureObject_t texture, stream_t::pointer stream, const viewport_t &viewport) {
int threadsX = viewport.width / 2;
int threadsY = viewport.height;
int threadsY = viewport.height / 2;
dim3 block(threadsPerBlock);
dim3 grid(div_align(threadsX, threadsPerBlock), threadsY);