> Hi Michael and all, > I have been asking the question whether BT8x8 cards write video data > directly on to the framebuffer many times. But I got the answer from > your mail. If BT8x8 cards write video data directly on to the > framebuffer, how can we read the video data from "/dev/fb0" instead of > "/dev/video0" ? I am using Microwindows (www.microwindows.org) to > develop a tv viewer application like "Xawtv" which uses "/dev/video0" to > read video streams. I have planned to develop a tv viewer application > which reads the data from "/dev/fb0". And while it's soo simple ;-) There are roughly two modes of operation for both v4l2 (with v4l2 it's a bit more subtile btw), capturing to "memory" and capturing to "screen". If you request capturing to "memory" your application can fetch the frames from there, it hasn't been on your display at all. You can even use to read() system call to fetch the data (although not recommended). You can also request capturing to "screen" which will place the frame date directly into frame buffer memory, where you can see it. That's why you see funny artefacts when you move the window the output encapsulates. You can also do both, first capture to memory and then show the frame using normal X11/fb semantics. This is of course slower, but on a remote screen (try xawtv -remote) the only working way. A bit more clear now?
