a-law PCM wav

Posted: Sat Jun 21, 2008 2:23 pm

Hi folks,
Recently i did an IVR project for the 1st time in my life (I have been doing usual voice recording for corporates without much trouble for quite some time now). Their technical peaple demanded a file encoded with a-law PCM wav. Having done the final exports of my processed vocal content at 44.1k/16 bits (with 16 bit dither), I imported the files into Soundforge & exported them back to a-law PCM wav.
Obviously the 44.1k/16 bit files sounded awesome & the a-law PCM wav files which are 8k/8bits, sounded like bull crap on my studio monitors.
When these files (a-law PCM wav) were loaded onto the client's IVR switch, they sounded even worse!!
I have heard IVRs of other companies & they sound fine although even those were a-law PCM wav files loaded onto their respective switches.
I'd like to know if there is any special treatment that is done to the files that are to be exported as a-law PCM wav?
Can someone please shed some light on where I am going horribly wrong?

Regards,
Swapnil

Posted: Sun Jun 22, 2008 3:14 pm

A-Law specifies a method of data compression where (broadly) the quieter sounds get more resolution at the expense of the louder ones. It says nothing about reducing the sampling rate. 8-bit A-Law compressed tracks can sound reasonable at the same data rate as the original.

It's likely that the poor sound quality you experienced was principally due to the reduction fom 44.1K to 8K sps and not to the A-Law compression from 16 to 8 bits.

Posted: Tue Jun 24, 2008 9:48 am

Hi. thanx for the reply

Quote:

It's likely that the poor sound quality you experienced was principally due to the reduction fom 44.1K to 8K sps and not to the A-Law compression from 16 to 8 bits.

So this brings me back to my basic question as to what would be the correct process during the course of recording/mixing to avoid the poor sound quality caused due to sample reduction?

Posted: Tue Jun 24, 2008 10:44 am

You say they specify A-law compression, but you do not say they specify an 8k sample rate. Did they specify a samplerate at all? If not leave it at 44.1k: in SF set Format = A-Law, Attributes = 44.1KHz, 8-bit, Mono or Stereo

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