avutil/pixfmt: extend the VUY{A,X} description

Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/pixfmt.h

@@ -398,12 +398,12 @@ enum AVPixelFormat {
     AV_PIX_FMT_P416BE,      ///< interleaved chroma YUV 4:4:4, 48bpp, big-endian
     AV_PIX_FMT_P416LE,      ///< interleaved chroma YUV 4:4:4, 48bpp, little-endian
 
-    AV_PIX_FMT_VUYA,        ///< packed VUYA 4:4:4, 32bpp, VUYAVUYA...
+    AV_PIX_FMT_VUYA,        ///< packed VUYA 4:4:4:4, 32bpp (1 Cr & Cb sample per 1x1 Y & A samples), VUYAVUYA...
 
     AV_PIX_FMT_RGBAF16BE,   ///< IEEE-754 half precision packed RGBA 16:16:16:16, 64bpp, RGBARGBA..., big-endian
     AV_PIX_FMT_RGBAF16LE,   ///< IEEE-754 half precision packed RGBA 16:16:16:16, 64bpp, RGBARGBA..., little-endian
 
-    AV_PIX_FMT_VUYX,        ///< packed VUYX 4:4:4, 32bpp, Variant of VUYA where alpha channel is left undefined
+    AV_PIX_FMT_VUYX,        ///< packed VUYX 4:4:4:4, 32bpp, Variant of VUYA where alpha channel is left undefined
 
     AV_PIX_FMT_P012LE,      ///< like NV12, with 12bpp per component, data in the high bits, zeros in the low bits, little-endian
     AV_PIX_FMT_P012BE,      ///< like NV12, with 12bpp per component, data in the high bits, zeros in the low bits, big-endian