From 4eb55942953bd4edba674625a0100aea348bb4c4 Mon Sep 17 00:00:00 2001
From: Ramiro Polla <ramiro.polla@gmail.com>
Date: Fri, 9 Aug 2024 13:26:09 +0200
Subject: [PATCH] swscale: add nv24/nv42 to yuv420p unscaled converter

---
 libswscale/swscale_unscaled.c | 45 +++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/libswscale/swscale_unscaled.c b/libswscale/swscale_unscaled.c
index a5c9917799..239258ab8c 100644
--- a/libswscale/swscale_unscaled.c
+++ b/libswscale/swscale_unscaled.c
@@ -221,6 +221,48 @@ static int nv24ToPlanarWrapper(SwsContext *c, const uint8_t *src[],
     return srcSliceH;
 }
 
+static void nv24_to_yuv420p_chroma(uint8_t *dst1, int dstStride1,
+                                   uint8_t *dst2, int dstStride2,
+                                   const uint8_t *src, int srcStride,
+                                   int w, int h)
+{
+    const uint8_t *src1 = src;
+    const uint8_t *src2 = src + srcStride;
+    // average 4 pixels into 1 (interleaved U and V)
+    for (int y = 0; y < h; y += 2) {
+        for (int x = 0; x < w; x++) {
+            dst1[x] = (src1[4 * x + 0] + src1[4 * x + 2] +
+                       src2[4 * x + 0] + src2[4 * x + 2]) >> 2;
+            dst2[x] = (src1[4 * x + 1] + src1[4 * x + 3] +
+                       src2[4 * x + 1] + src2[4 * x + 3]) >> 2;
+        }
+        src1 += srcStride * 2;
+        src2 += srcStride * 2;
+        dst1 += dstStride1;
+        dst2 += dstStride2;
+    }
+}
+
+static int nv24ToYuv420Wrapper(SwsContext *c, const uint8_t *src[],
+                               int srcStride[], int srcSliceY, int srcSliceH,
+                               uint8_t *dstParam[], int dstStride[])
+{
+    uint8_t *dst1 = dstParam[1] + dstStride[1] * srcSliceY / 2;
+    uint8_t *dst2 = dstParam[2] + dstStride[2] * srcSliceY / 2;
+
+    copyPlane(src[0], srcStride[0], srcSliceY, srcSliceH, c->srcW,
+              dstParam[0], dstStride[0]);
+
+    if (c->srcFormat == AV_PIX_FMT_NV24)
+        nv24_to_yuv420p_chroma(dst1, dstStride[1], dst2, dstStride[2],
+                               src[1], srcStride[1], c->srcW / 2, srcSliceH);
+    else
+        nv24_to_yuv420p_chroma(dst2, dstStride[2], dst1, dstStride[1],
+                               src[1], srcStride[1], c->srcW / 2, srcSliceH);
+
+    return srcSliceH;
+}
+
 static int planarToP01xWrapper(SwsContext *c, const uint8_t *src8[],
                                int srcStride[], int srcSliceY,
                                int srcSliceH, uint8_t *dstParam8[],
@@ -2206,6 +2248,9 @@ void ff_get_unscaled_swscale(SwsContext *c)
         c->convert_unscaled = yuyvToYuv422Wrapper;
     if (srcFormat == AV_PIX_FMT_UYVY422 && dstFormat == AV_PIX_FMT_YUV422P)
         c->convert_unscaled = uyvyToYuv422Wrapper;
+    if (dstFormat == AV_PIX_FMT_YUV420P &&
+        (srcFormat == AV_PIX_FMT_NV24 || srcFormat == AV_PIX_FMT_NV42))
+        c->convert_unscaled = nv24ToYuv420Wrapper;
 
 #define isPlanarGray(x) (isGray(x) && (x) != AV_PIX_FMT_YA8 && (x) != AV_PIX_FMT_YA16LE && (x) != AV_PIX_FMT_YA16BE)
     /* simple copy */