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Thread: HOWTO: Proper Screencasting on Linux

  1. #131
    Join Date
    May 2011
    Location
    Madison, WI
    Beans
    3
    Distro
    Ubuntu 11.04 Natty Narwhal

    Re: HOWTO: Proper Screencasting on Linux

    In Step 2 Example 1, instead of
    Code:
    ffmpeg -i output.mkv -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -vpre slow -crf 22 -threads 0 our-final-product.mp4
    I had to use
    Code:
    ffmpeg -i output.mkv -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -preset slow -crf 22 -threads 0 our-final-product.mp4
    Not sure if the recent updates are the reason. Quoting from http://ffmpeg.org/index.html
    FFmpeg now accesses x264 presets via libx264. This extends functionality by introducing several new libx264 options including -preset, -tune, and -profile. You can read more detailed information about these options with "x264 --fullhelp".

    The syntax has changed so be sure to update your commands. Example:
    ffmpeg -i input -vcodec libx264 -preset fast -tune film -profile main -crf 22 -threads 0 output
    Thanks.

  2. #132
    Join Date
    Mar 2007
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    Re: HOWTO: Proper Screencasting on Linux

    Hi varunvats,

    I've updated the guide to the new -preset syntax.

    Regarding the low fps, that's probably because you're not using the lossless_ultrafast preset. If you don't specify a preset, it defaults to "medium" which is very slow for encoding on-the-fly. Also, I'm not getting "constant rate-factor is incompatible with 2pass." with lossless preset. Maybe you messed the preset file by editing it?
    Freedom is neither exclusive nor unlimited.

  3. #133
    Join Date
    Jan 2010
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    165

    Re: HOWTO: Proper Screencasting on Linux

    Hi. Im getting the same error the guy got one page ago. I switched to

    Code:
    ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x768 -i :0.0 -acodec pcm_s16le -vcodec libx264 -preset slow -threads 0 big.mkv
    But I get a ridiculously laggy 1-3fps recovering with lossy video. None of the solutions in this thread seem to have remotely helped, and gtk-recordmydesktop has terrible sync issues so there is no using that.. (It also takes a year to encode... >.<)

    Help please?

    Code:
    [libx264 @ 0xaa75500] constant rate-factor is incompatible with 2pass.
    Output #0, matroska, to 'big.mkv':
        Stream #0.0: Video: libx264, yuv420p, 1024x768, q=0-69, pass 1, pass 2, 200 kb/s, 90k tbn, 30 tbc
        Stream #0.1: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, pass 1, pass 2, 1411 kb/s
    Stream mapping:
      Stream #1.0 -> #0.0
      Stream #0.0 -> #0.1
    Error while opening encoder for output stream #0.0 - maybe incorrect parameters such as bit_rate, rate, width or height
    This is the syntax that gives me the error

    Code:
    ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x768 -i :0.0 -acodec pcm_s16le -vcodec libx264 -vpre lossless_ultrafast -threads 0 big.mkv
    Side note, when I do use slow, I get this kind of ****. See brackets.

    Code:
    Stream mapping:
      Stream #1.0 -> #0.0
      Stream #0.0 -> #0.1
    Press [q] to stop, [?] for help
    frame=  122 <<<fps=  1>>> q=13.0 Lsize=    6048kB time=00:00:26.33 bitrate=1881.1kbits/s
    Last edited by Saiko Berry; June 3rd, 2011 at 08:11 PM.

  4. #134
    Join Date
    Mar 2007
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    Re: HOWTO: Proper Screencasting on Linux

    ok, let's try to troubleshoot the problem. In the ffmpeg source folder (from which you compiled ffmpeg), there is a directory calld 'ffpresets'. We are going to instruct ffmpeg to use that preset instead of the one installed on your system.


    Code:
    ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x768 -i :0.0 -acodec pcm_s16le -vcodec libx264 -fpre /home/user/ffmpeg/ffpresets/libx264-lossless_ultrafast.ffpreset -threads 0 big.mkv
    replace "/home/user/ffmpeg/ffpresets/libx264-lossless_ultrafast.ffpreset" with the path to the preset in ffmpeg source directory on your system. Also note we're using "-fpre" not "-vpre".

    Can you reproduce the problem with that method described above?
    Freedom is neither exclusive nor unlimited.

  5. #135
    Join Date
    Sep 2006
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    3,491

    Re: HOWTO: Proper Screencasting on Linux

    I can reproduce this on 32-bit Natty, but not on x86_64 Arch or Lucid. I'm currently attempting a git bisect because this confounds me.

  6. #136
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    Mar 2007
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    Re: HOWTO: Proper Screencasting on Linux

    Quote Originally Posted by FakeOutdoorsman View Post
    I can reproduce this on 32-bit Natty, but not on x86_64 Arch or Lucid. I'm currently attempting a git bisect because this confounds me.
    Thanks for the confirmation FakeOutdoorsman. I'm on Natty 64-bit and can't reproduce the problem.
    Freedom is neither exclusive nor unlimited.

  7. #137
    Join Date
    Sep 2006
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    3,491

    Re: HOWTO: Proper Screencasting on Linux

    Maybe I missed something simple, but it looked like a regression to me, so I filed a bug report:
    https://ffmpeg.org/trac/ffmpeg/ticket/264

  8. #138
    Join Date
    Sep 2006
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    3,491

    Re: HOWTO: Proper Screencasting on Linux

    The bug report I mentioned in my previous post (x11grab w/ libx264 fails on 32-bit) is getting no attention from the developers right now, and I have no idea how to fix it, so if anyone else is being affected by it then it might be a good idea to add a comment to the report.

  9. #139
    Join Date
    Mar 2007
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    Re: HOWTO: Proper Screencasting on Linux

    Ive added a comment to the bug, requesting some developer attention and a fix.
    (p.s. bug number is somewhat unique and related to the bug )
    Freedom is neither exclusive nor unlimited.

  10. #140
    Join Date
    Sep 2006
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    3,491

    Re: HOWTO: Proper Screencasting on Linux

    Thanks for the comments. This bug has been fixed: eval: Fix 32bit unsigned parsing.

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