VideoHelp Forum


Try StreamFab All-in-One and download Netflix, Amazon Prime, etc! Or Try DVDFab and copy all Blu-rays and DVDs!

Try NordVPN to access Netflix or other streaming services from any country and also surf safely! Try NordVPN!
+ Reply to Thread
Page 2 of 2
FirstFirst 1 2
Results 31 to 48 of 48
Thread
  1. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    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.
    Quote Quote  
  2. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    I'm willing to pay someone $50 if they can resolve this.
    Last edited by WAusJackBauer; 21st Jun 2021 at 20:02.
    Quote Quote  
  3. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    Raising this to $100
    Quote Quote  
  4. Member
    Join Date
    Feb 2006
    Location
    United States
    Search Comp PM
    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
    Quote Quote  
  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
    Quote Quote  
  6. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    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.
    Quote Quote  
  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.
    Quote Quote  
  8. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    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.
    Quote Quote  
  9. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    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).

    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.
    I finally got around to trying this but when I dragged and dropped the file onto the bat, it ran but I got this message so I'm not sure that it worked

    -vol has been deprecated. Use the volume audio filter instead.
    -vol is forwarded to lavfi similarly to -af volume=1.640625.

    Any tips on what to do now?
    Quote Quote  
  10. That's just a warning that the "vol" argument is deprecated (it may someday stop working) and they are recommending that you switch to using the audio filter called volume instead. I guess "-af volume=1.640625" is the equivalent of "vol=420". I'm pretty sure you can switch to the volume filter like this:

    Code:
    ffmpeg -i %1  -af "volume=1.640625,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"
    Note "-vol=420" was removed, and "volume=1.640625," was added at the start of the audio filter string. I don't know if it makes any different to put it at the end of the audio filter string:

    Code:
    ffmpeg -i %1  -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,volume=1.640625" -c:v copy -b:a 224K "stereomix.mp4"
    Try both.
    Quote Quote  
  11. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    I just realised, the steps that I do this in could be important.

    Should I use this ffmpeg downmix on the source audio (big 2 - 3gb 5.1 DTS file) and then trim scenes and encode it the old way I normally would and it should be fine since its already been downmixed properly?

    Or should I trim the scene and encode the way I normally would and then as the last step, use the ffmpeg downmix on the trimmed scene?
    Quote Quote  
  12. If you do the audio downmix first and save it as uncompressed PCM you can edit with the audio in "copy" mode so there will be no further reencoding of the audio. Or only one at the end when you output your final edit.
    Quote Quote  
  13. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    Originally Posted by jagabo View Post
    If you do the audio downmix first and save it as uncompressed PCM you can edit with the audio in "copy" mode so there will be no further reencoding of the audio. Or only one at the end when you output your final edit.
    How do you save it as uncompressed PCM? Also how do you use this copy mode you're talking about.
    Quote Quote  
  14. With ffmpeg you can save as uncompressed PCM in MOV:

    Code:
    ffmpeg -i %1  -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,volume=1.640625" -c:v copy -c:a pcm_s16le "stereomix.mov"
    With audio editors saving as WAV usually gets you uncompressed PCM (WAV can contain compressed audio but that's rarely done).

    A/V editors usually have a "copy" mode for the audio. In VirtualDub it's selected with Audio -> Direct Stream Copy (it's the default). Or you can just set the editor to output uncompressed PCM -- that's essentially a "copy".
    Quote Quote  
  15. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    Originally Posted by jagabo View Post
    Code:
    ffmpeg -i %1  -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,volume=1.640625" -c:v copy -c:a pcm_s16le "stereomix.mov"
    Thank you very much.

    I just realised though, the volume=1.640625 is essentially amplifying the audio. So isn't this what's making my volume louder rather than the downmixing to stereo?

    I believe Youtube supports 5.1 so couldn't I just keep it at 5.1 and use volume=1.640625 by itself if ffmpeg allows it? That way people with 5.1 setups can enjoy true 5.1 sound?
    Last edited by WAusJackBauer; 28th Sep 2021 at 10:25.
    Quote Quote  
  16. You'll have to try both. I suspect the way youtube downmixes 5.1 may reduce the overall volume. So downmixing yourself may work better.
    Quote Quote  
  17. Member
    Join Date
    Nov 2013
    Location
    Western Australia
    Search Comp PM
    Originally Posted by jagabo View Post
    You'll have to try both. I suspect the way youtube downmixes 5.1 may reduce the overall volume. So downmixing yourself may work better.
    Hrrm I tried to use the standard ATSC downmix
    Code:
    "pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR"
    combined with uncompressed PCM but it just wouldn't run when I dragged and dropped. Any idea why?
    Last edited by WAusJackBauer; 5th Oct 2021 at 00:40.
    Quote Quote  
  18. What's your entire command line? What container did you use? MP4 doesn't support PCM. Use MOV or MKV instead.
    Quote Quote