Friday, November 12, 2010

Codec2 Improvements

David VK5DGR is actively improving Codec2 in a process that he describes on his website. Until I became interested in this process, I hadn't realized how developing a codec is a pretty qualitative and subjective process.

Anyway, some recent patches to the alpha code aim to get rid of crackles from the encoding, and I think I can provide evidence that they have done just that. Last weekend I recorded myself describing my QTH, etc. in typical long-winded ham fashion. I then encoded and decoded this raw audio file to see how intelligible it was after being passed through Codec 2. The result was quite impressive. I think the greatest criticism could be the clicks that appear on my name, 'Bruce' and when I draw my breath in early in the QSO.

After reading that the recent changes aimed to eliminate those noises, I updated my repository, rebuilt the code, and then round-tripped this same file. Listen to the new file, and you'll hear that it has fewer distracting clicks, especially in the two sections I mentioned.

If you are testing Codec2, consider recording your audio files with a boom mike or something similar, not with a mic that will pick up echos and ambient noise. Currently the codec suffers quite a bit if such distractions are around. This is interesting, of course, and important, but unless you are planning to test these problems, you might want to have them set aside for now.

No comments:

Post a Comment