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authorwm4 <nfxjfg@googlemail.com>2015-02-10 12:18:13 +0100
committerMichael Niedermayer <michaelni@gmx.at>2015-02-10 16:03:04 +0100
commitc247fc63e4dcf49995f5ba14021d0dfea6737b74 (patch)
tree230381cc11edcb1cb3b21a2c1a05af671f7699b7 /libavutil
parent92e3a6fdac73f7e1d69d69717219a7538877d7a0 (diff)
downloadffmpeg-c247fc63e4dcf49995f5ba14021d0dfea6737b74.tar.gz
pixdesc: clarify AV_PIX_FMT_FLAG_ALPHA doxygen
Also make clear that PAL8 can have alpha. Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Diffstat (limited to 'libavutil')
-rw-r--r--libavutil/pixdesc.h13
-rw-r--r--libavutil/pixfmt.h4
2 files changed, 14 insertions, 3 deletions
diff --git a/libavutil/pixdesc.h b/libavutil/pixdesc.h
index c8e32518a8..c4d0548ad6 100644
--- a/libavutil/pixdesc.h
+++ b/libavutil/pixdesc.h
@@ -139,8 +139,19 @@ typedef struct AVPixFmtDescriptor {
* An example of a pseudo-paletted format is AV_PIX_FMT_GRAY8
*/
#define AV_PIX_FMT_FLAG_PSEUDOPAL (1 << 6)
+
/**
- * The pixel format has an alpha channel.
+ * The pixel format has an alpha channel. This is set on all formats that
+ * support alpha in some way. The exception is AV_PIX_FMT_PAL8, which can
+ * carry alpha as part of the palette. Details are explained in the
+ * AVPixelFormat enum, and are also encoded in the corresponding
+ * AVPixFmtDescriptor.
+ *
+ * The alpha is always straight, never pre-multiplied.
+ *
+ * If a codec or a filter does not support alpha, it should set all alpha to
+ * opaque, or use the equivalent pixel formats without alpha component, e.g.
+ * AV_PIX_FMT_RGB0 (or AV_PIX_FMT_RGB24 etc.) instead of AV_PIX_FMT_RGBA.
*/
#define AV_PIX_FMT_FLAG_ALPHA (1 << 7)
diff --git a/libavutil/pixfmt.h b/libavutil/pixfmt.h
index 5d443ce9a4..73d4cc987a 100644
--- a/libavutil/pixfmt.h
+++ b/libavutil/pixfmt.h
@@ -44,11 +44,11 @@
* big-endian CPUs.
*
* @par
- * When the pixel format is palettized RGB (AV_PIX_FMT_PAL8), the palettized
+ * When the pixel format is palettized RGB32 (AV_PIX_FMT_PAL8), the palettized
* image data is stored in AVFrame.data[0]. The palette is transported in
* AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is
* formatted the same as in AV_PIX_FMT_RGB32 described above (i.e., it is
- * also endian-specific). Note also that the individual RGB palette
+ * also endian-specific). Note also that the individual RGB32 palette
* components stored in AVFrame.data[1] should be in the range 0..255.
* This is important as many custom PAL8 video codecs that were designed
* to run on the IBM VGA graphics adapter use 6-bit palette components.