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  1. Member
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    Originally Posted by davexnet View Post
    Yes, the opus audio (251) is reduced to 2 channel and the level is low - that's the audio I get on my low res monitor.
    The aac audio (256) is the 6 channel mix (downloaded with youtube-dl) this sounds OK

    Did you upload a 6 channel audio file? Then the Youtube down conversion must be to blame

    Here are some examples of using ffmpeg to do the down conversion to stereo yourself
    https://itectec.com/superuser/properly-downmix-5-1-to-stereo-using-ffmpeg/

    for example
    Code:
    ffmpeg -i "Video muxed-rXcmKJE4Fn0-6ch.mp4"  -vol 420 -b:a 224K -af "pan=stereo|FL=0.5*FC+0.707*FL+0.707*BL+0.5*LFE|FR
    =0.5*FC+0.707*FR+0.707*BR+0.5*LFE" -c:v copy "stereomix.mp4"
    Yep I upload 5.1 channel audio files, but as mentioned before, I tried downmixing to stereo with no luck.

    I don't know which videos you're referring to because I've uploaded a few.

    I have absolutely no clue how to use that code
    Last edited by WAusJackBauer; 17th Jun 2021 at 05:37.
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    I'm willing to pay someone $50 if they can resolve this.
    Last edited by WAusJackBauer; 21st Jun 2021 at 20:02.
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    Raising this to $100
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    Originally Posted by WAusJackBauer View Post
    Raising this to $100
    try this - https://support.google.com/youtube/thread/34577124/why-is-my-video-volume-so-low-after...ploading?hl=en
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  5. Davexnet has already given you a solution in post #28. You might want to play with the coefficients to get the mix you want.

    Attached is your 5.1 audio from post #8 downmixed to stereo using his coefficients. Try uploading it to youtube and see how it sounds.
    Image Attached Files
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    Originally Posted by jagabo View Post
    Davexnet has already given you a solution in post #28. You might want to play with the coefficients to get the mix you want.

    Attached is your 5.1 audio from post #8 downmixed to stereo using his coefficients. Try uploading it to youtube and see how it sounds.
    As I said, I have absolutely no idea how to use the thing he suggested.
    Last edited by WAusJackBauer; 2nd Jul 2021 at 02:26.
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  7. Download ffmpeg. Put a copy of ffmpeg.exe in C:\Windows\System32\.

    Start Notepad. Copy/Paste this text into it (slight changes from davexnet's post).

    Code:
    ffmpeg -i %1  -vol 420 -af "pan=stereo|FL=0.5*FC+0.707*FL+0.707*BL+0.5*LFE|FR=0.5*FC+0.707*FR+0.707*BR+0.5*LFE" -c:v copy -b:a 224K "stereomix.mp4"
    Save that to the folder with the file you want to downmix. But when you do, add ".bat" to the filename: like "downmix.bat".

    In Explorer drag/drop your video onto the batch file. In a while (depending on the length of your file) you'll have a file called stereomix.mp4.

    In the ffmpeg command the "vol=420" means multiply the volume by a factor of 420/256, about 1.64.

    The "pan=stereo" arguments specify how the channels should be mixed.

    FC is the front center channel
    FL is the front left channel
    FR is the front right channel
    BL is the back left channel
    BR ir the back right channel
    LFE is the sub channel (Low Frequency Effects)

    so "FL=0.5*FC+0.707*FL+0.707*BL+0.5*LFE" means the front left channel should be a mix of:

    0.5 times the front center channel
    plus 0.707 times the front left channel
    plus 0.707 times the back left channel
    plus 0.5 * the sub channel

    "FR=0.5*FC+0.707*FR+0.707*BR+0.5*LFE" does the same for the front right channel except right channels are used instead of the left.

    An audio codec wasn't specified bus since ffmpeg was told to create an mp4 file it will default to aac. "-b:a 224K" tell it to use an audio bitrate of 224 Kbps.

    The standard ATSC downmix is:

    Code:
    ffmpeg -i %1 -af "pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR" -c:v copy -b:a 224K "stereomix.mp4"
    That's also the default when you don't specify the individual parameters:

    Code:
    ffmpeg -i %1 -c:v copy  -ac 2 -b:a 224K "stereomix.mp4"
    "-ac 2" here means downmix to 2 channels (stereo). You can add "-vol N" to increase or decrease the overall volume. -vol 256 is no change in volume. Smaller numbers will decrease the overall volume, larger number will increase it.

    Some other useful information: https://superuser.com/questions/852400/properly-downmix-5-1-to-stereo-using-ffmpeg
    Last edited by jagabo; 2nd Jul 2021 at 09:04.
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    Originally Posted by jagabo View Post
    Download ffmpeg. Put a copy of ffmpeg.exe in C:\Windows\System32\.

    Start Notepad. Copy/Paste this text into it (slight changes from davexnet's post).
    Thank you for the reply! Looks complicated but I'll get onto it sometime soon and let you know how it goes.
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