0

I open two webcams using v4l2. With 30 fps everything works fine. With 60 fps, begining troubles. FPS on first cam about 20, FPS on second cam about 0-3. I try to run in different threads(and different processor kernels) - the same problem. I think problem in v4l2 driver.

My task is very simple - capture data from two webcams on one computer with 60 fps. Is it possible? In what could be the problem? I may show the code, but it is big.

Sorry for my english.

herolover
  • 733
  • 3
  • 9
  • 18

1 Answers1

0

It should be possible. Problems can be:

  • you have DMA capable hardware, but you are not using DMA. With high FPS your performance can decrease.
  • you have too short buffer queue. You are acquiring more buffers than you have allocated in the queue
  • others, it depends by your implementation
Federico
  • 3,782
  • 32
  • 46
  • Thanks for answer. But how I can to use DMA? Now I use just v4l2 API. If problem in short buffer queue, then increasing buffers number will not to solve the problem. So or performance is enough, or performance is not enough and then nothing will help. – herolover Mar 20 '13 at 08:57
  • You can use DMA if your hardware can do DMA. V4L2 offers the VideoBuf2 framework to handle buffers. Here you can find different DMA memory allocator vb2-dma-contig, vb2-dma-sg. Obviously, if your webcams are faster than your processor a long buffer queue does not resolve the problem. But if you have a queue of 10 buffers and you acquiring 15 frames at time, you can set 10 buffers, but you must wait to set the other 5. – Federico Mar 20 '13 at 09:45