立你斯學習記錄

http://linuxtv.org/downloads/v4l-dvb-apis/ch02s08.html

Compressed Formats

Table 2.9. Compressed Image Formats
Identifier Code Details
V4L2_PIX_FMT_JPEG	'JPEG'	TBD. See also VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP.
V4L2_PIX_FMT_MPEG	'MPEG'	MPEG multiplexed stream. The actual format is determined by 
extended control V4L2_CID_MPEG_STREAM_TYPE, see Table 1.2, “MPEG Control IDs”.
V4L2_PIX_FMT_H264	'H264'	H264 video elementary stream with start codes.
V4L2_PIX_FMT_H264_NO_SC	'AVC1'	H264 video elementary stream without start codes.
V4L2_PIX_FMT_H263	'H263'	H263 video elementary stream.
V4L2_PIX_FMT_MPEG1	'MPG1'	MPEG1 video elementary stream.
V4L2_PIX_FMT_MPEG2	'MPG2'	MPEG2 video elementary stream.
V4L2_PIX_FMT_MPEG4	'MPG4'	MPEG4 video elementary stream.
V4L2_PIX_FMT_XVID	'XVID'	Xvid video elementary stream.
V4L2_PIX_FMT_VC1_ANNEX_G	'VC1G'	VC1, SMPTE 421M Annex G compliant stream.
V4L2_PIX_FMT_VC1_ANNEX_L	'VC1L'	VC1, SMPTE 421M Annex L compliant stream.



If the device supports read(/write) mode, I suppose you could simply read the device node as
 a file.  'vlc v4l2c:///dev/video0 --demux h264' might work "thanks" to a software bug whereby
 the format is not reset, but I have not tried. V4L2 H.264 is supported in 
VLC version 2.0.2-git: 


vlc v4l2:///dev/video0:chroma=h264

vlc v4l2:///dev/video0:width=320:height=240:chroma=h264




 At least for UVC devices, it's pretty damn straight forward. You just need to  
set pixel format 'H264' with the standard VIDIOC_S_FMT. Then you get the H.264  
elementary stream with the plain normal streaming or read/write modes of V4L2.  

E.g.:  
# v4l2-ctl --set-fmt-video=width=640,height=480,pixelformat=H264 
# vlc v4l2c/h264://

http://ivtvdriver.org/index.php/V4l2-ctl



hw example:

http://bluecherry.zendesk.com/entries/235174-using-the-bluecherry-hardware-compression-open-source-linux-drivers-mpeg-4-h-264


相關參考網址

http://hi.baidu.com/carlson_freec/item/807870f451bf2ddd42c36abc

v4l videocap

http://blog.csdn.net/zgyulongfei/article/details/7529973

Compressed Formats

http://linuxtv.org/downloads/v4l-dvb-apis/ch02s08.html

h264 via V4L2

http://forum.videolan.org/viewtopic.php?f=13&t=87677