Index: docs/nut4cc.txt
===================================================================
--- docs/nut4cc.txt	(revision 669)
+++ docs/nut4cc.txt	(working copy)
@@ -134,6 +134,39 @@
 Y4[11][ 8]  Planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)            [NOT in AVI]
 Y2[00][ 8]  8bit gray, 8bit alpha [NOT in AVI]
 
+For RGB[A] packed formats the scheme used for defining new packed pixel
+format is the following.
+
+The first three bytes represent the number and order of components
+used by the pixel format:
+rgb  -> RGB
+bgr  -> BGR
+rba  -> RGBA
+arb  -> ARGB 
+abr  -> ABGR
+
+The character representing the green component is omitted in the three
+bytes when there is an alpha component, since its position is always
+assumed to be between the red and blue components.
+
+The fourth bytes represents the number of bits per component, assuming
+all the components use the same amount of bits.
+
+If the total number of bits does not suffice to fill all the bits of
+an integer number of bytes, the most significant bits of the most
+significat byte are unused (and ignored).
+
+If the order of bytes is inverted, that means that each component has
+to be read big-endian.
+
+Follows the list of the supported RGB[A] packed format FourCCs created
+using this scheme:
+
+rgb[16]    Packed RGB 4:4:4, 16bpp, (msb)4U 4R 4G 4B(lsb), little-endian, most significant bits unused
+[16]bgr    Packed RGB 4:4:4, 16bpp, (msb)4U 4R 4G 4B(lsb), big-endian   , most significant bits unused
+bgr[16]    Packed BGR 4:4:4, 16bpp, (msb)4U 4B 4G 4R(lsb), little-endian, most significant bits unused
+[16]rgb    Packed BGR 4:4:4, 16bpp, (msb)4U 4B 4G 4R(lsb), big-endian   , most significant bits unused
+
 Raw audio: [x] is an byte with value x,  [NOT in AVI]
 ALAW    A-LAW
 ULAW    MU-LAW