Sound quality using G.711

[Philippe Torrelli]

Hello, 

This in on windows with the latest autobuilds, on a lan.

Trying to talk from minisip and an Oxo here, I notice the audio sent from
the Oxo restituted in minisip is very metallic and saturated.  The audio
sent by minisip was very clear actually .
However the quality for minisip-to-minisip conversations is OK, as are
minisip to snom ..  This is with G.711 PCMA codec.. 

I replay the capture with ethereal, the quality is OK, so it's a problem of
restitution. Trying to investigate this, I noticed the Oxo sends bigger
packets than minisip does ( 240  byte payload versus 160 for minisip ).

I think I found something wrong in BasicSoundSource::pushSound in 

for( int32_t nSamples = nMonoSamples; nSamples > 0; ){
			int32_t cur = nSamples;

			if( cur > (int32_t)iFrames )
				cur = iFrames;
			memset( temp, 0, iFrames * oNChannels ); 
			for( int32_t i = 0; i<cur; i++ ) {
				tempVal = i*oNChannels;
				temp[ tempVal ] = samples[i];
				tempVal ++;
				temp[ tempVal ] = samples[i];
			}
			writeRet = cbuff->write( temp, cur * 2, true );
samples += cur ; // PTI
			nSamples -= cur;

}

as only the only part of samples that is used is the first interval modulo
iFrame  [0.. iFrames [  is added to the circular buffer ( and more than once
)...  Fixing it to use every sample makes the sound much better...  


Philippe Torrelli