[FFmpeg-trac] #1454(undetermined:new): FFMPEG Volume not working as documented

[FFmpeg]

#1454: FFMPEG Volume not working as documented
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             Reporter:  ramitbhalla  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug: What's the right syntax for -vol

 When I run ffmpeg -h the documentation says:

 -vol volume         change audio volume (256=normal)

 So if I want to double the volume should I use 512 and to half should I
 use 128?

 The website: http://ffmpeg.org/ffmpeg.html#volume
 Says:

 If vol is expressed as a decimal number, the output audio volume is given
 by the relation:
 output_volume = vol * input_volume
 If vol is expressed as a decimal number followed by the string "dB", the
 value represents the requested change in decibels of the input audio
 power, and the output audio volume is given by the relation:
 output_volume = 10^(vol/20) * input_volume
 Otherwise vol is considered an expression and its evaluated value is used
 for computing the output audio volume according to the first relation.
 Default value for vol is 1.0.



 I tried dB but it doesn't work, I tried a decimal it does work.
 I'm confused, what the right way to use it?

 Which documentation is correct and how should it be used to double or half
 the volume? Are there any limits? (should be decimal, integer, max/min,
 mulitples of 2 etc?)

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1454>
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