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  1. Hi,

    I converted a .mov file to DVD using the standard settings of ffmpegX (I used DVD mpeg2enc). Everything is fine, except that the audio of the resulting dvd has an ugly background noise. Can anybody help, please?
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  2. Explorer Case's Avatar
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    Could you post a few seconds of that noisy audio and a few seconds of the source audio for reference?
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  3. Hi,

    I attached to this message few seconds of the sound track of the source (the audio track of the .mov file) and a few second of the sound track of the dvd created with ffmpegX (the ac3 file).

    Ciao.
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  4. Explorer Case's Avatar
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    Thanks for the samples.

    1/ The sampling depth/sampling size of the MP3 is 32 bit, not the common 16 bit. That may be of influence to the distortion.
    2/ When I convert just this MP3 to AC3, then the output is without distortion. Not sure why that is different.

    I'll search a bit more, but the above is what I found so far.
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  5. Sorry, before I make you waste more time, I should tell you that the depth/sampling size of the MP3 I uploaded may be a byproduct of the conversion I did in order to extract the audio file from the source (since you asked for a sampling of the audio file of the source, I used a converter to extract the audio file from the .mov file and I chose the mp3 format as output).

    I don't know what the depth/sampling size of the audio track of the .mov file is (Quicktime does not give me this info).

    I attach to this message a tiny sample of the .mov file, in case it can be of help. This is (a portion of) the source video (with audio) file that I converted to dvd with ffmpegX (and the result was a dvd with the background noise).

    Thanks.
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  6. Explorer Case's Avatar
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    Your source file has mpeg-4 AAC audio with 5.1 channels.
    When you convert this to AC3 5.1, then you get the distortion.
    When you convert this to AC3 2.0 (stereo), you do not get the distortion.

    The older versions of ffmpeg, like in ffmpegX, were known to have trouble with such. Choosing stereo would avoid this problem.
    One of the things that were added and improved in recent versions of ffmpeg (not yet in ffmpegX) is: channel mapping, so that you can reliably convert 5.1 from one audio codec to another, which may have its channels differently numbered.

    Unfortunately, I don't think the current version of ffmpegX is able to do AAC 5.1 to AC3 5.1 when converting a movie.
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  7. Dear Case,

    thanks for the advice! As you said, setting the channel to stereo eliminates the distortion. The result is acceptable for me.

    Ciao.
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