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  1. #1

    Question Can't stereo to mono with mencoder


    I have a video stereo.avi (xvid+mp3) and I want to output a new one in mono so that's what I do with mencoder:

    mencoder stereo.avi -ovc copy -oac mp3lame -lameopts cbr:br=128:mode=3 -o mono.avi

    that doesn't work, it still has 2 channels

    I've also tried:

    mencoder stereo.avi -ovc copy -oac mp3lame -lameopts cbr:br=128:mode=3 -af -pan=1:0.5:0.5 -channels 1 -o mono.avi

    And doesn't work

    What I'm doing wrong? Any help is appreciated.

    Thank you.

  2. #2

    Wink works for me with newer version

    These both worked for me just today under Ubuntu 10.04:

    2007 mencoder -ovc copy -oac mp3lame -af pan=1:0.5:0.5 stereofile.MP4 -o mono-pan.mp4

    2020 mencoder -ovc copy -oac mp3lame -af channels=1 stereofile.MP4 -o mono-chan.MP4

    The first one produced
    Stream #0.1: Audio: mp3, 48000 Hz, mono, s16, 96 kb/s

    And the second produced
    Stream #0.1: Audio: mp3, 48000 Hz, mono, s16, 80 kb/s

    And they both sound like mono. Before, they had only one channel of stereo.

  3. #3
    Also, you can boost the volume at the same time by adding the volume=24:0 to the -af audio filter args.

    Concatenate filters with a comma like this:

    $ mencoder -ovc copy -oac mp3lame -af channels=1,volume=30 infile.mp4 -o outfile.mp4
    One problem I have not solved yet is that the resulting files are not playable by Totem, a popular Linux medi player. My current work-around is to use ffmpeg to process it. Something innocuous like this:

    $ ffmpeg -b 3M -acodec aac -i infile.avi outfile.avi
    BTW, the "2007" and "2010" prefixes in my previous comment are merely artifacts of my running the Linux history command and can be ignored.

  4. $spacer_open

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