On Thu, Jan 12, 2006 at 05:56:18PM +0100, Tim Braun wrote: > Hi folks, > > I need to transmit webcam images over a very low bandwidth connection > (at most 100kbit/s) and therefore want to directly get the compressed > image from the pwc driver, transmit this and decompress it at the remote > end. so a 1fps, the image need to be under 12kbytes. You must have a very good compression ration to send image, i hope not in full resolution. > Unfortunately, I'm unable to find much documentation, although I'm > pretty sure that I read something about this maybe 2 years ago. Right > now, all I have is a link to a (now outdated?) small program that just > grabs the raw stream: > > http://lists.saillard.org/pipermail/pwc/attachments/20050426/c1069c26/pwcgrab.c > > and some decompression(?) routines in the 'libpwc'-package on the > webpage. I did not find any further documentation about these programs.
Ok, the driver can now report the buffer in two formats: YUV420P, and PWC2 (see the exact name in videodev2.h). The buffer size is dynamic, but i always return the size of the buffer in fmt.bytesused. Now use the library to uncompress and convert the raw image to YUV420P or RGB. I've put two programs: one capture.c that is the application sample to grab an image with V4L2. This program capture the image in PWC2 format, or YUV420P. In the library package, i've put a test program to convert the image into a YUV420P or RGB. > Also, does anyone know how high the compression factor of the built-in > algorithm is? Just play with resolution, and compression factor, and check your kernel log. I print the size of 4 lines. Just multiply by your number of lines and you have the size of the buffer. Luc _______________________________________________ pwc mailing list [email protected] http://lists.saillard.org/mailman/listinfo/pwc
