Alle 12:43, sabato 13 gennaio 2007, Vojtech Pavlik ha scritto: > > Yes, and port all the applications to it. Not a small effort. Still the > raw+library approach doesn't convince me entirely. ALSA has used it, and > still a lot of people prefer the legacy /dev/dsp interface.
Consider that many applications are still based on the old V4L1. In one way or the other they would have to be rewritten... > Of course, some bridges (or standards) supply the video data in a stupid > format with headers, which need to be removed to concatenate the > individual chunks into a continuous picture. Then, most likely, > zero-copy is not possible. Exactly. One more reason why you can't map the ISOC transfer buffers directly is that ISOC transfers does not garantuee a fixed number of video bytes per frame. > But those that deliver the whole frame in a Bulk transfer without any > interfering headers, it's trivially possible to avoid the copy. (Yes, > I've done that. I needed it to be able to reach 60fps with a > ovfx2/ov7620 camera. Not using V4L2 yet, though.) Not all the USB controllers support bulk transfers. It's a second choice, when possible, and, globally speaking, they are usually slower than the ISOC transfers. Best regards Luca Risolia _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
