Re: 24-bit/96KHz LPCM audio

Thu Apr 10 2003, Dave Chapman wrote:

> Ogle (and vlc and mplayer) fail to correctly play this, but I propose to
> add support to Ogle to fix this.
> 

Great, I don't have any 96/24 audio on the dvds I have tried so far
so I haven't been able to test it.
What dvd is it?

> I have managed to hack ogle to correctly play the audio via OSS by
> converting it to a 16-bit/48KHz LPCM stream inside the OSS driver.  I
> also had to hack "conversion.c" so that it would pass the entire
> (unmodified) stream to the OSS driver.
> 
> I want to handle the conversion from 24-bits to 16-bits and the
> resampling from 96KHz to 48KHz separately.  Both 24/48 and 16/96 audio
> streams are perfectly legal on a DVD.
>

this should be put into conversion.c I think.

 
> As far as I can tell, there is no support for software conversion of 
> LPCM streams to different formats at the moment.  Do other developers 
> have any ideas about how this should be implemented?
>
 
We had a naive resampling routine for a while to be able to
convert 48kHz to 44.1 but it was removed in a rewrite (partly because
the sound quality was bad and no one had the time to write a better).

There are requantisation/resampling libraries available that one could use.
I haven't looked at them for a while so I don't know which ones
are suitable for this.

> I would also like to add support for 24/96 soundcards in the future 
> (when I buy one!) and this would include using libmad's ability to 
> output mpeg audio with 24-bit resolution.
> 
This shouldn't be to hard to fix. Just add some more code to chose
which output format should be used and add handling in the output drivers.


/Björn