video chroma: add a Nv12 copy function which outputs I420

modules/video_chroma/copy.c

@@ -438,6 +438,18 @@ void CopyFromNv12ToNv12(picture_t *dst, uint8_t *src[2], size_t src_pitch[2],
               width, height/2);
 }
 
+void CopyFromNv12ToI420(picture_t *dst, uint8_t *src[2], size_t src_pitch[2],
+                        unsigned width, unsigned height)
+{
+    CopyPlane(dst->p[0].p_pixels, dst->p[0].i_pitch,
+              src[0], src_pitch[0],
+              width, height);
+    SplitPlanes(dst->p[1].p_pixels, dst->p[1].i_pitch,
+                dst->p[2].p_pixels, dst->p[2].i_pitch,
+                src[1], src_pitch[1],
+                width/2, height/2);
+}
+
 void CopyFromYv12(picture_t *dst, uint8_t *src[3], size_t src_pitch[3],
                   unsigned width, unsigned height,
                   copy_cache_t *cache)

modules/video_chroma/copy.h

@@ -47,4 +47,7 @@ void CopyFromNv12ToNv12(picture_t *dst, uint8_t *src[2], size_t src_pitch[2],
                         unsigned width, unsigned height,
                         copy_cache_t *cache);
 
+void CopyFromNv12ToI420(picture_t *dst, uint8_t *src[2], size_t src_pitch[2],
+                        unsigned width, unsigned height);
+
 #endif