[PR] avutil/hwcontext_cuda: fix yuv420p V/U plane overlap in cuda_get_buffer() (PR #23637)

PR #23637 opened by nyanmisaka
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23637
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23637.patch

# Summary of changes

Odd-height yuv420p result in incorrect calculations of the U-plane
address offset. The last row of the V-plane overlapped with and was
overwritten by the first row of the U-plane, leading to chroma artifacts.

```
ffmpeg -init_hw_device cuda=cu -filter_hw_device cu -f lavfi -i \
testsrc=s=1920x1081,format=yuv420p -vf hwupload -c:v hevc_nvenc \
-vframes 1 -y <OUTPUT>
```

Signed-off-by: nyanmisaka <[email protected]>

Inspired by ffe0104

<img src="/attachments/7abec1e4-9608-4a0a-a423-e3a6347a6795" height="250">


>From 209747824d9862be43c2c09ce6571e35a692074f Mon Sep 17 00:00:00 2001
From: nyanmisaka <[email protected]>
Date: Mon, 29 Jun 2026 15:32:00 +0800
Subject: [PATCH] avutil/hwcontext_cuda: fix yuv420p V/U plane overlap in
 cuda_get_buffer()

Odd-height yuv420p result in incorrect calculations of the U-plane
address offset. The last row of the V-plane overlapped with and was
overwritten by the first row of the U-plane, leading to chroma artifacts.

```
ffmpeg -init_hw_device cuda=cu -filter_hw_device cu -f lavfi -i \
testsrc=s=1920x1081,format=yuv420p -vf hwupload -c:v hevc_nvenc \
-vframes 1 -y <OUTPUT>
```

Signed-off-by: nyanmisaka <[email protected]>
---
 libavutil/hwcontext_cuda.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
index 6342683a17..f93bdcab9c 100644
--- a/libavutil/hwcontext_cuda.c
+++ b/libavutil/hwcontext_cuda.c
@@ -209,7 +209,7 @@ static int cuda_get_buffer(AVHWFramesContext *ctx, AVFrame *frame)
     if (ctx->sw_format == AV_PIX_FMT_YUV420P) {
         frame->linesize[1] = frame->linesize[2] = frame->linesize[0] / 2;
         frame->data[2]     = frame->data[1];
-        frame->data[1]     = frame->data[2] + frame->linesize[2] * (ctx->height / 2);
+        frame->data[1]     = frame->data[2] + frame->linesize[2] * AV_CEIL_RSHIFT(ctx->height, 1);
     }
 
     frame->format = AV_PIX_FMT_CUDA;
-- 
2.52.0

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