From 4266129964b8238526936d723de65b419d8069c6 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 31 May 2011 16:27:44 -0300 Subject: [media] DocBook: Move all media docbook stuff into its own directory This patch addresses several issues pointed by Randy Dunlap at changeset ece722c: - In the generated index.html file, "media" is listed first, but it should be listed in alphabetical order, not first. - The generated files are (hidden) in .tmpmedia/ - The link from the top-level index.html file to "media" is to media/index.html, but the file is actually in .tmpmedia/media/index.html - Please build docs with and without using "O=builddir" and test that. - Would it be possible for media to have its own Makefile instead of merging into this one? Due to the way cleandocs target works, I had to rename the media DocBook to media_api, otherwise cleandocs would remove the /media directory. Thanks-to: Randy Dunlap Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml | 74 +++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml (limited to 'Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml') diff --git a/Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml b/Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml new file mode 100644 index 0000000..7a2855a --- /dev/null +++ b/Documentation/DocBook/media/v4l/pixfmt-nv12mt.xml @@ -0,0 +1,74 @@ + + + V4L2_PIX_FMT_NV12MT ('TM12') + &manvol; + + + V4L2_PIX_FMT_NV12MT + + Formats with ½ horizontal and vertical +chroma resolution. This format has two planes - one for luminance and one for +chrominance. Chroma samples are interleaved. The difference to +V4L2_PIX_FMT_NV12 is the memory layout. Pixels are +grouped in macroblocks of 64x32 size. The order of macroblocks in memory is +also not standard. + + + + Description + + This is the two-plane versions of the YUV 4:2:0 format where data +is grouped into 64x32 macroblocks. The three components are separated into two +sub-images or planes. The Y plane has one byte per pixel and pixels are grouped +into 64x32 macroblocks. The CbCr plane has the same width, in bytes, as the Y +plane (and the image), but is half as tall in pixels. The chroma plane is also +grouped into 64x32 macroblocks. + Width of the buffer has to be aligned to the multiple of 128, and +height alignment is 32. Every four adjactent buffers - two horizontally and two +vertically are grouped together and are located in memory in Z or flipped Z +order. + Layout of macroblocks in memory is presented in the following +figure. +
+ <constant>V4L2_PIX_FMT_NV12MT</constant> macroblock Z shape +memory layout + + + + + +
+ The requirement that width is multiple of 128 is implemented because, +the Z shape cannot be cut in half horizontally. In case the vertical resolution +of macroblocks is odd then the last row of macroblocks is arranged in a linear +order. + In case of chroma the layout is identical. Cb and Cr samples are +interleaved. Height of the buffer is aligned to 32. + + + Memory layout of macroblocks in <constant>V4L2_PIX_FMT_NV12 +</constant> format pixel image - extreme case + +
+ Example <constant>V4L2_PIX_FMT_NV12MT</constant> memory +layout of macroblocks + + + + + +
+ Memory layout of macroblocks of V4L2_PIX_FMT_NV12MT + format in most extreme case. + + + + + + -- cgit v1.1