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  1. #1

    captures occasionally hog cpu

    I have a Hauppauge WinTV PVR 150 and I'm using the ivtv drivers (version 0.3.. After some months of trying, on and off, to track down a problem, I believe I have finally found it and it's not really a PVR 150 or IVTV problem.

    The problem is that when I'm doing captures (which I normally do via: cat /dev/video > movie.mpg), from time to time, the CPU usage will shoot up to 40-50% for the process. Normally the CPU usage is under 1%. Once it goes up to 40+%, it stays there for the remainder of the capture. When this happens, the captures start dropping frames, very noticeably, probably from insufficient buffer space.

    I suspected all sorts of things, driver issues, heat, etc. It now appears that the problem is disk related, and I suspect, since the drives seem to function fine otherwise, that it's actually more of a file system issue.

    Captures consume a good deal of disk space, which I think is somewhere between 1 and 2 megabytes per second.

    This wasn't a problem for a long time, but over time, it has become more and more of a problem. If it were Windows, I'd suspect file fragmentation as the problem and I suppose that might be happening here as well.

    I'm not really sure what I can do to diagnose and fix the problem.

    To diagnose it to this point, instead of doing:

    cat /dev/video > movie.mpg
    I tried:

    cat /dev/video > /dev/null
    And I have yet to see the CPU usage go up above 1%

    hda - 200GB - udma6
    hdb - 122GB - udma6
    hdc - 250GB - udma5

    All 3 drives are mapped as a single logical partition:


    This was the default setup that Fedora Core 3 gave me.

    I don't want to repartition the drives and I'd be willing to simply stick a 4th drive in and give it its own partition if that will fix the problem for me.

    But I'd like to see if I have other options (as I'm not even sure that will fix my problem). I'd certainly be interested in finding out if there's some way I can more accurately diagnose the problem.

    Anyway, any help anyone could offer would be great.


  2. #2

    Additional information

    Some information regarding the file system I'm using (ext3). From dumpe2fs, the following features are set:

    has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file

    Blocks are 4K, Inode size is 128

    I still have 69 million free out of a total of 70 million inodes, so I'm not running out of inodes..

  3. #3
    It appears the problem was the ext3 fs itself. Apparently there can be problems dumping the quantity of data that captures do with ext3. I'm not sure the exact mechanism, but it basically ends up doing huge writes that cause the tv capture buffer to overflow and you lose data.

    I added an 80gb drive that I had lying around and put reiserfs on it and it's working great.

  4. $spacer_open

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