Hi Anders and others, I have already tried to create a module for my webcam (Topro TP6800). It have the same usb id (06a2:0003). But I have the same problem as you about the image data. I don't know what is the comment tag (FF:FE). I tried to skip the tag or to skip the comment with the length after this tag but the image is never good. I don't know where start the image. If you want an example of the bad result you can download this image : http://lafeuil.free.fr/webcam/images/1.jpg So, I am also in the dark. If you want to take a look to my code, you can download this file : http://lafeuil.free.fr/webcam/tp6800.c If somebody have an idea how can I transform the data, Tell me ! Good luck Thomas Champagne 2009/2/28 Anders Blomdell <anders.blomdell@xxxxxxxxxxxxxx>: > Jean-Francois Moine wrote: >> >> 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... > > Thomas, if you have DQT/Huffman tables for this camera, please drop me a > note. > >> >> About the JPEG images, the Huffman table is always the same > > Does this mean that it's the same for all JPEG images or only for one > camera? > > If it's the same for all images, it should mean that I have a way to > determine how much I have to chop off after the 0xfffe tag (no illegal > huffman codes -> possibly chop at the correct position). > > Comments anyone? > > >> 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. > > This is even in the docs, and is implemented in the driver. > >> In the function pkt_scan, when finding the image start, you must add >> the JPEG header: 'ff d8', DQT, huffman table, SOF0 and SOS. > > OK, will see if I can find the DQT (and possibly the Huffman table) in the > windows driver (as suggested by Thomas Kaiser). > >> 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. > > I'll look into that monday. > >> BTW, don't use the video4linux-list@xxxxxxxxxx mailing-list anymore: all >> the video discussions are now done in linux-media@xxxxxxxxxxxxxxxx > > OK, so Google hit http://www.linuxtv.org/v4lwiki/index.php/Main_Page is no > hit then... > > > Thanks > > Anders Blomdell > -- 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
