[mythtv] [mythtv-commits] Ticket #4804: Add software amplification support to libmyth/AudioOutput

Mark Spieth mark at digivation.com.au
Wed Apr 16 01:57:44 UTC 2008

>Then perhaps the right approach is to make the software preamp available
>in the audio output class, but to use the decoders native preamp if one
>exists.  Another possibility is to extend the AudioOutput class to
>accept floating point input as well, and to make decoders use this when
>access to the floating point data is available.

all codecs currently output 16bit 2ch audio. changing that would be an lavc 
IMO I dont think this is an option.

>Regardless of the approach, I'm not convinced that the errors involved
>in rounding before amplifying are significant; typical preamp values
>(looking at the ReplayGain values across my collection of music) are
>going to be within +/- 10 dB, so we're talking about errors of at most 2
>units per 32,768, or an error of at most 0.006% per sample value.

note 12dB is 2 bits when amplifying.

so are we talking about every audio codec type having a preamp value to 
provide volume normalization?
If this is so, I would still change the gain values in lavc so that it 
happens at the correct place.

I know mpeg1 layer2 audio is currently softer than it should be.
music from mythmusic is usually loud and almost saturated (using 

also which codecs are we talking about? video only modes? or music modes 


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