[MPlayerOSX-devel] Native sound output for MPlayer

[Dan C. <da...@us...>]

Hi,

I've been considering writing a native Mac OS X output module for  
MPlayer - I had a feeling that the SDL plugin added some unnecessary  
overhead. Currently, I'm researching, trying to gather as much info as  
possible and trying to find some code that does the job - I know  
nothing of Apple programming. In this process I stumbled upon some  
_very_ interesting information: Mac OS X is capable of decoding MP3,  
AAC and AC-3 internally, or at least so it seems. And it also supports  
internal resampling. Thus, once an output module is complete, it should  
be possible to write at least a hardware AC-3  output module for  
MPlayer. This might free enough resources to make MPlayer almost as  
fast as VLC or Quicktime.

In a week or so, I may find the time to begin coding, but I thought I'd  
tell you what I was up to :) Since I haven't really written anything  
yet, I thought I'd keep it out of the MPlayer mailing lists.

Having hardware 5.1-channel AC-3 decoding wouldn't be all that bad  
though. Hopefully, slighter faster sound will make MPlayer fast enough  
to play most 640-width DivX-movies on my 400MHz iMac DV. The next step  
if this is ever finished would be writing a native video out, but that  
seems very difficult. SDL doesn't seem like it's hardware accelerated  
at all...

The more I use MPlayer, the more I get impressed by it's potential.

- Dan

Reference:

CoreAudioTypes.h, look for kAudioFormatLinearPCM and the more  
interesting ones below it:
</System/Library/Frameworks/CoreAudio.framework/Versions/A/Headers/ 
CoreAudioTypes.h>

Mac OS X supports internal decoding of AC-3 and MP3:
<http://developer.apple.com/techpubs/macosx/Darwin/IOKit/DeviceDrivers/ 
Audio/WritingAudioDrivers/AudioOnMacOSX/_Mac_OS_X_A_apabilities.html>

Even my bloody old iMac DV decodes AC-3 in hardware:
<http://developer.apple.com/techpubs/hardware/Developer_Notes/ 
Macintosh_CPUs-G3/iMac_Aug00/iMac.pdf>

A native output patch for mpg123, decreases CPU load from 11-13% to  
9-11%:
<http://sourceforge.net/projects/mosx-mpg123/>

Yet another interesting link:
<http://techweb.rfa.org/pipermail/portaudio/2002-August/001122.html>