[LAD] Best way to insert DSP module in audio chain in Linux

Kim Therkelsen kim_t26 at hotmail.com
Mon Aug 30 12:00:45 UTC 2010


Hi,

I want to make is a DSP module that improves the sound quality 
of the sound coming from the laptop builtin speakers by applying DSP 
(FIR/IIR filters). 
I want to route all audio played back (from for 
instance an offline WAV or MP3 file, from a movie, or streamed from the internet) to 
pass through the 
DSP plugin whenever headphones are NOT connected. When headphones are connected no processing should be applied. 
I 
want to place the DSP module as close to the hardware as possible to 
make sure all audio is really routed through the DSP plugin so I always 
can enjoy 
the DSP improvements made to the sound. 

Where should I place this module/DSP code? 
- As a plugin to PulseAudio? 

- As a plugin to ALSA? 
- As its own virtual sound card?

- In the audio driver for my built-in sound card?
- As a kernel module? 
 

I have tried loading the LADSPA-module using the module-ladspa-sink in PulseAudio but I am not sure this is the best solution. 
I need to remove some limitations in module-ladspa-sink to get it working properly ( multichannel audio, only DSP processing for internal speakers).

 

My requirements:

1) Must be able to detect if headphones are connected

2) Must be able to process stereo and multichannel (5.1/7.1) formats. I 
need the multichannel formats to perform binaural downmixing to 
stereo. 
So it is important that I can receive multichannel audio and mix it down to stereo and output it to a stereo soundcard.

/Kim
 		 	   		  
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