DirectSound capturing 8/16 bit wave PCM
-
Dear programmers, I am capturing audio PCM with 8-bit and 16-bit from DirectSound. As you see below zero values are 128 for 8-bit and 0 for 16-bit. BITS VALUE RANGE ZERO VALUE ---- ----------- ---------- 8-bit 0 to 255 128 16-bit -32768 to +32767 0 Recently, I examined captured audio data sream for both 8 and 16 bits and I notify a strange result. When I capturing 8-bit audio the audio signal is oscilation near the 0x80 (128). It is OK. But, when I capture 16-bit audio PCM; the data is oscilating periodically from 0 to 0xffff. I copy/paste below 22050 KHZ 16-bit MONO audio PCM which is captured from microphone[ there is no high volume noise or sound source while recording]. The PCM data is consist of only air & EM noise. But there are peaks near the 0xFFFF, it is not normal. What may cause to this high amplitude audio peaks. I tried this with two different SoundBlaster but nothing has changed. What may offer you. Thanks and best regard. ff f0 (peak) 00 14 00 1e ff eb (peak) 00 16 00 2c ff f8 (peak) 00 1a ff fe (peak) 00 11 00 07 ff e4 (peak) 00 13 00 04 ff ea (peak) 00 0c 00 40 00 2d 00 15 00 15 00 08 00 1b 00 0c 00 0e 00 1d ff ff (peak)