Hi Benoit, At 12:25 PM 6/17/02 +0200, Benoit PAPILLAULT wrote: >I'm using this driver on kernel 2.4.18. It seems (from the source code), >that there are several "Quickcam Express" model, even those labeled >Logitech on the box and on the cam may be "Dexxa" model. With mine, I can get a >picture (with some bad pictures sometimes, but the framerate is 5 fps and not 30 fps). (here's some of my experience) There are several quickcam models. Some of them have compression, with which you can get more than 5 fps. The problem is mainly that if you capture (example) RGB24 frames at a resolution of 384x288, you're doing a total of 3x384x288=331.776 byte/frame. given that the total busrate of USB (ideally) is 2 MB/s, you can get at moest 2*1024*1024 MB/s divided by 331776 byte/frame = 6 frames/sec. Since there's also overhead, 5 fps is a pretty practical optimum. So you might get more fps, but only at smaller sizes. Compression allows more (since the transferred data is smaller - compression in the cam), but most manufacturers refuse to give the specs of the compression they use. This is mostly a private non-standard compression which nobody can understand. There is (afaik) a driver which decodes it for one of the quickcam models (quickcam web), and I've had the possibility to try it since my brother has such a cam. ;-). You're getting a pretty good framerate, around 15 fps, maybe more, but the hacked driver is not V4L-compatible (it uses a private interface) and - worse - it does decompressoin in the kernel instead of in userspace, so in total, it was pretty useless and I installed the non-compression driver for him. 5 fps is better than nothing. ;-). (If someone feels lazy - go combine these drivers so that the driver with compression uses the v4l2 kernel interface and gives compressed frames to userspace with proper headers preceeding the frame data). Ronald
