Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Division Network Operations Group Subject: Re: [linux-audio-user] Fwd: [Jamin] Re: soft clip: Achieving Gain, inconsequential overloads -------- Steve Harris writes: >Actually thats not quite right - AD converters generally work in 1's or >2's complement, depending on the brand/variety, so the middle point is at >0, and the range is slightly larger in the -ve voltage range. Correct. We may be talking about the difference between signed and unsigned number representation. If you have an unsigned value, the only possibilities are from 0 to the maximum value represented by all ones. There are no negative numbers. When you have a signed value, then an 8-bit number, for example can be represented by +1 to +127 or -1 to -128. Now, here is something I am a bit unsure of, myself. I know, from actual observations that a straight PCM output from your basic A/D converter if read as unsigned numbers moves in steps from 0 to all 1's on. I honestly have not tried to interpret those data as signed numbers because it wasn't convenient at the time. If one wants to have a valid representation of what the wave form is doing for graphical or calculation purposes, then the mid-point would have to be what one would call 0 level with -1 being one below and 1 being 1 above, etc. I am certainly not arguing with anyone, but am a wee bit confused as to the correct way to represent the numbers. This is probably off-topic, but any graphical software that shows you your music wave forms or does DSP functions in an arithmetic manner that is based upon an AC model has to behave as if the mid-point value was 0. Maybe someone can set me/us all straight in this manner. G
