On Thu, Apr 13, 2023 at 3:50 PM Muni Sekhar <munisekharrms@xxxxxxxxx> wrote: > > Hi all, > > I recorded the silence on the default audio card by running "arecord > -d 5 test.wav." > > Once it exited, I checked the contents by running "hexdump test.wav," > and I see that silence is recorded as a sequence of 0x80 instead of > 0x00. > > 0000000 4952 4646 0024 8000 4157 4556 6d66 2074 > 0000010 0010 0000 0001 0001 1f40 0000 1f40 0000 > 0000020 0001 0008 6164 6174 0000 8000 8080 8080 > 0000030 8080 8080 8080 8080 8080 8080 8080 8080 > 0000040 8080 8080 8080 8080 8080 8080 8080 8080 > ... > > What might be the reason for silence being recorded as 0x80 instead of 0x0? > > > -- > Thanks, > Sekhar This is what I found after Googling a bit: Since you didn't specify a format, arecord defaults to 8 bit format (U8). Being unsigned, a negative value for maximum negative amplitude is impossible. Therefore the value is given a bias of 128, making 0 the maximum negative amplitude, 255 the maximum positive, and 128 the center point (or silence). Best Regards, Luke
