[pulseaudio-discuss] Crash and/or distortion when remapping a remapped sink.

[Colin Guthrie]

'Twas brillig, and Lennart Poettering at 07/08/09 23:13 did gyre and gimble:
> On Fri, 24.07.09 17:07, Colin Guthrie (gmane at colin.guthr.ie) wrote:
> 
>> Hi Lennart,
>>
>> From IRC, but as you're busy and I suspect this wont get immediate  
>> attention, I'll post the details here for later :)
>>
>> <coling> mezcalero, found a reliable way to produce some nasty  
>> distortion that should not happen....
>> <coling> 1) >>> load-module module-remap-sink sink_name=mono  
>> master=<alsa sink name> channels=1 master_channel_map=front-left  
>> channel_map=mono
>> <coling> 2) >>> load-module module-remap-sink sink_name=fakestereo  
>> master=mono channels=2 master_channel_map=mono,mono  
>> channel_map=front-left,front-right
>> <coling> 3) PULSE_SINK=fakestereo paplay foo.wav
>> <coling> That's it.
>> <coling> Pretty nasty :s
>> <coling> mezcalero, incidentally, the above process also causes an  
>> assert half the time too.
>> <coling> E: sink.c: Assertion '!s->thread_info.rewind_requested' failed  
>> at pulsecore/sink.c:843, function pa_sink_render(). Aborting.
> 
> This fix should be fixed now in r7d49163. Please verify.

Seems to be OK now, thanks. :)

> The distortion is probably caused because the handling of having two
> mono channels is not what you expect. i.e. we probably just add them,
> effectively amplifiyng the original signal 2x, which might easily
> trigger clipping.
> 
> If you run PA in debug mode the resamplers/remixers will dump a little
> table that tells you how each input channel is added up for the output
> channels. Could you please find out that table and check out if that
> triggers your problem? (i.e. both input mono channels are multiplied
> by factor 1.0 instead of 0.5?)
> 
> Lennart

Here's the full output.

http://pastebin.com/me868948

 From what I can see, yes when the second sink is loaded there is a 
factor of 1.0 involved.

I presume there is no way to do what I originally wanted? (Incidentally 
I don't specifically want this... it was more an experiment for a user 
on the list who wanted to mix everything to the left channel but still 
have a balance control - he was deaf in one ear).

Col

-- 

Colin Guthrie
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http://colin.guthr.ie/

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