audio sampling rate question
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From: Ben Bradley on 6 May 2008 22:25 On Tue, 29 Apr 2008 07:25:29 -0800, glen herrmannsfeldt <gah(a)ugcs.caltech.edu> wrote: >DigitalSignal wrote: >>>I agree. I now have a 24 bit WAV file and a C program I wrote to reduce >>>it to 16 bit with the appropriate shift. > >> On average how much compression ratio have you achieved? > >The advantage is that you don't have to guess as accurately >what the record level will be. > >I don't know about the OP, I was recently using a Roland R1 >recorder. It has the choice of 16 or 24 bit WAV, and some >choices of MP3. With 24 bits, I then wrote a C program to >find the minimum and maximum sample values, along with a some >other statistical values. I then did the conversion to 16 bits >by rounding and shifting the appropriate number of bits. This doesn't sound right. If you want the best quality possible in the final 16-bit signal, look into dithering and noise-shaping rather than doing rounding, and it's best to do all your processing in floating point (that way you can change the level to any arbitrary value, rather than only in the 3dB steps that bit shifting gives). OTOH, the difference can be subtle, and many people can't tell even under the best listening conditions. > >-- glen
From: glen herrmannsfeldt on 7 May 2008 00:51
Ben Bradley wrote: (snip, I wrote) >>I don't know about the OP, I was recently using a Roland R1 >>recorder. It has the choice of 16 or 24 bit WAV, and some >>choices of MP3. With 24 bits, I then wrote a C program to >>find the minimum and maximum sample values, along with a some >>other statistical values. I then did the conversion to 16 bits >>by rounding and shifting the appropriate number of bits. > This doesn't sound right. If you want the best quality possible in > the final 16-bit signal, look into dithering and noise-shaping rather > than doing rounding, and it's best to do all your processing in > floating point (that way you can change the level to any arbitrary > value, rather than only in the 3dB steps that bit shifting gives). > OTOH, the difference can be subtle, and many people can't tell even > under the best listening conditions. I thought about it, but so far I haven't tried. By finding the peak and appropriate shifting, the quietest parts aren't so far down. It is a recording with a live audience, and the background isn't all that quiet, anyway. It would be nice, though. Do others do it? -- glen |