Re: volume extremely low when combining many files

[Bob S <bsabiston@gmail.com>]

>> 
>>  I am using sox to automatically assemble a soundtrack which described by a bunch of keyframes, each of which specifies a small sound file to be played at a certain pitch and volume.  When there are many keyframes, the overall soundtrack volume becomes very low.  I do a first pass to generate a sound file for each keyframe with the sound at the specified volume and pitch and with padding to place it at the right place in the overall soundtrack.  Then in a second pass I assemble all the files. (I was doing this with pipes and one big sox call, but the process was being terminated due to using too many resources on the server.)
>> 
>> I want the volume settings on the individual sounds to be respected, but the overall output file should be normal volume.  Right now even if all my keyframes are full volume, the combined result is very quiet.  
>> 
>> I read a little bit about this in the documentation, and I tried using the —norm argument to normalize the final sound, but it isn’t working. 
>> 
>> My call looks something like this:
>> 
>> sox -V —norm -m sound0.wav sound1.wav sound2.wav sound3.wav … sound100.wav  -r 44100  -e signed -b 16 output.wav trim 0 30.0
>> 
>> Can anyone tell me what I am doing wrong?  Should I not try to set the volume on each sub-file and then set the volume when I am doing the final combine?  
>> Thanks!
>> Bob

> 
> the problem is, that "norm" is invoked on the input files, which are
> then mixed and decreased in volume to prevent clipping. Try something like
> 
> sox -V -m sound0.wav sound1.wav sound2.wav sound3.wav … sound100.wav  -r
> 44100  -e signed -b 16 output.wav trim 0 30.0 norm
> 
> instead.
> 
> Cheers, Erich
> 
> On 22.09.2016 01:10, Bob S wrote:

Thanks for the reply.  Actually it sort of started working the way I had it.  I think I had something else wrong.  But the problem now, both with the way I wrote it above and if I try it the way you suggest, is the same:  The volume is loud, but there is also a loud hissing noise all the way through, static where there should be silence.  I also get that same result if I try the ‘mix-power’ argument, and if I set the volume for each track in the final call when I combine them together.

It seems like this might be from raising a low-volume sound way up, but I don’t really know why it would need to do that.  I have like a hundred little tracks being mixed together, and they are all mostly silence except for the part in each one where the sound effect plays.  Anyone have a suggestion for how to fix that?

Thanks,
Bob


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