Sound - Debugging

The biggest drawback for me when working with sound is that I don't know that much what I am doing. What I mean is that I have spent many years, for example, working with graphics, transformations etc. and I know the language, terminology and have encountered many problems. The upshot of this is that when working with graphics I have a context to put things into and looking through the code it "makes sense", as do the problems. With sound everything is new. In this regard OSX is basically as unfamiliar as MFC.

My one good stoke of luck is, as ever, that the code is beautfully written and well commented. From the code I know that WAV files are converted to PCM. These files are then consumed by Cello's own ADPCM converter and appear in the final output file.

Having looked through Apple's sample there is a sample SCAudioCompress command line tool that converts sounds. It also has an optional UI that means it is posible to play around with settings. Hacking this in to a class that was based on the original WAV source was not hard. My approach was to just get it in to see if I was on the right track. Once I had something working there would be an opportunity to refine.

My first test file was a short movie with a phrase from Peter Griffin (from "Family Guy").

Adding the code was not too bad. The existing tool wrote a file and loading a buffer wit the contents of a file is quite straight forward. The results were disappointing - the first sound that Cello published was short and unintelligible. Not understanding much about sound I felt a certain amount of despair - where to start?

To debug it I compared the two builds in the debugger. Running Visual Studio under VMware means that I can look at the two builds side-by-side. I also compared the two log files that are created during publishing. My discovery was that the OSX build outputted roughly a 10th of the sound than the PC build. The bug was that in calculating the duration of sound I was out by a factor of 8 - the difference between 8 bits and 1 byte. After fixing this the sound appeared. The unintelligibility of the first part of the sound was due to he strange form of Peter Griffin's voice. If I had chosen a voice like Brian - my life would have been less fraught.