From: "audetto@tiscali.it" <audetto@tiscali.it>
To: video4linux-list@redhat.com
Subject: An issue with: pwc, v4l2, VIDIOC_DQBUF and mplayer
Date: Sat, 5 Jul 2008 00:37:35 +0200 (CEST) [thread overview]
Message-ID: <16342448.1215211055980.JavaMail.root@ps11> (raw)
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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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reply other threads:[~2008-07-04 22:38 UTC|newest]
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