Different image sizes and userptr

[Ralph Majer <majer (at) vitracom.com>]

Hello,

as already posted in the last few months I'm still writing an
application based on V4L2. But now I got stuck in the next problem,
perhaps you can give me some advice.

My Problem is that I want grab images from an bttv grabber (PAL, Kernel
2.6.15) at different sizes in USERPTR mode. For example I want to grab
an image at 96x72 Pixels (or 192x144).

So I execute an ioctl VIDEOC_S_FMT with:
  video_format.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  video_format.fmt.pix.width       = 96;
  video_format.fmt.pix.height      = 72;
  video_format.fmt.pix.pixelformat = "GREY";
  video_format.fmt.pix.field       = V4L2_FIELD_ANY;

But when I do this in the USERPTR mode this isn't working (STREAM_OFF
was called before and buffers were resized and re-queued successfully).
At the next call of DQBUF -1 is returned. This happens not with the
following image sizes 256x192 (??), 384x288, 768x576.

When I switch to MMAP mode everything works. I can't figure out the
difference between the USERPTR and MMAP mode in this case. Could you
please give me some more infos or are there known bugs in the userptr
mode??

Thanks,
Ralph Majer


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