On Fri, 27 Feb 2009 23:15:54 +0100 Anders Blomdell <anders.blomdell@xxxxxxxxxxxxxx> wrote: > Hi, > > I'm trying to write a driver for a webcam based on Topro TP6801/CX0342 > (06a2:0003). My first attempt (needs gspca) can be found on: > > http://www.control.lth.se/user/andersb/tp6800.c > > Unfortunately the JPEG images (one example dump is in > http://www.control.lth.se/user/andersb/topro_img_dump.txt), seems to > be bogus, they start with (data is very similar to windows data): > > 00000000: 0xff,0xd8,0xff,0xfe,0x28,0x3c,0x01,0xe8,... > ... > 0000c340: ...,0xf4,0xc0,0xff,0xd9 > > Anybody who has a good idea of how to find a DQT/Huffman table that > works with this image data? Hi Anders, Thomas Champagne (See To:) was also writing a driver for this webcam. Maybe you may merge your codes... About the JPEG images, the Huffman table is always the same and the quantization tables depend on the compression quality. >From the USB trace I had from Thomas, I saw that: - when a packet starts with '55 ff d8', it is the first part of the image. This one should start at the offset 8 of the packet. - when a packet starts with 'cc', it is the next part of the image. In the function pkt_scan, when finding the image start, you must add the JPEG header: 'ff d8', DQT, huffman table, SOF0 and SOS. As we don't know the quality used by the webcam, in my test repository, I added a control for that: the JPEG header is created at streamon time, and the quantization tables may be modified by the control on the fly (have a look at stk014.c for an example). This solution is not the right one: the JPEG quality must be set by the VIDIOC_S_JPEGCOMP ioctl instead of VIDIOC_S_CTRL. I think I will update the concerned subdrivers next week. BTW, don't use the video4linux-list@xxxxxxxxxx mailing-list anymore: all the video discussions are now done in linux-media@xxxxxxxxxxxxxxxx Best regards. -- Ken ar c'hentañ | ** Breizh ha Linux atav! ** Jef | http://moinejf.free.fr/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
