[linux-audio-user] Converting Unsigned Byte Audio to 2-Channel WAV with SOX solved.

Peder Hedlund writes: That created an interesting effect. The original data are unsigned linear 8-bit samples. Silence is represented by 0x7f or 0x80 with 0 being the low extreme and 0xff being the highest extreme. Using uw or unsigned words told sox that this was 8,000 16-bit samples per second. It did that just fine and produced audio that was twice the correct pitch. There is no header on that file so it just says "data." The -u flag appeared to have no effect since sox already understood the data were unsigned linear. sox: resample opts: Kaiser window, cutoff 0.950000, beta 16.000000 sox: Input file cdda.ub: using sample rate 8000 size bytes, encoding unsigned, 1 channel sox: Do not support unsigned with 16-bit data. Forcing to Signed. sox: Writing Wave file: Microsoft PCM format, 2 channels, 44100 samp/sec sox: 176400 byte/sec, 4 block align, 16 bits/samp sox: Output file output.wav: using sample rate 44100 size shorts, encoding signed (2's complement), 2 channels sox: Output file: comment "Processed by SoX" sox: resample: rate ratio 80:441, coeff interpolation not needed sox: Finished writing Wave file, 125728820 data bytes 62864410 samples I began to wonder if the problem was in the resampling algorithm. If you listen to the sound, the glitches are at regular intervals at about 10 hits per second. When there is voice present, it sounds as if the "sixty Minutes" stopwatch was ticking away at around ten ticks per second and there were little segments missing from words. As I previously sed, the pitch was correct. I then tried the following line to change the algorithm: sox -V -r8000 cdda.ub -t wav -c 2 -w -r44100 output.wav polyphase .95 You can't tell any audible difference between the upconverted .wav file and the original unsigned linear data file. Being at 8000 samples/sec, the audio is voice grade and is a recording of two-way radio communications so it isn't the best anyway, but it appears that using the polyphase algorithm fixed the problem. The latest Debian port of sox is sox: Version 12.17.7. I am not sure but what the version was different a couple of years ago when I first wrote that script using the resample algorithm instead of polyphase. Maybe the previous version of sox had some different defaults and it forced polyphase, somehow. Thanks, Peder, for your suggestions on things to try as they got me to look at everything more closely. Martin McCormick WB5AGZ Stillwater, OK Systems Engineer OSU Information Technology Department Network Operations Group