An issue with: pwc, v4l2, VIDIOC_DQBUF and mplayer

An issue with: pwc, v4l2, VIDIOC_DQBUF and mplayer

[audetto]

Sorry if the message arrives twice, but when sending from gmail I 
always get
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=====================================================

Hi,

I have a Logitech QuickCam 4000 Pro USB and I am trying to use mplayer 
to play the video.
This is the command I use

mplayer -tv width=640:height=480:driver=v4l2 -fps 15 tv://

But when I quit mplayer hangs in the following line, while shutting 
down the video

        /* unqueue all remaining buffers */
        memset(&buf,0,sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        while (!ioctl(priv->video_fd, VIDIOC_DQBUF, &buf));

Which is more or less at line 1111 of stream/tvi_v4l2.c.

The problem is that the ioctl call VIDIOC_DQBUF never returns.
Reading the doc for VIDIOC_DQBUF
http://www.linuxtv.org/downloads/video4linux/API/V4L2_API/spec/r8849.
htm

The function should stop if there is no block to unqueue, unless it 
has been opened with O_NONBLOCK.
mplayer DOES NOT use O_NONBLOCK, so the call is allowed to block.

The problems are 2

1) I've tried to open with O_NONBLOCK and the ioctl blocks anyway.
pwc-v4l.c at line 1120 does not check for O_NONBLOCK.
Is this a bug?

2) should mplayer handle the situation in a different way? is there a 
way to check if there are queued blocks?

Andrea



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