Convert 16bit to 8bit 11025 Hz? -Sound Forge - PC - MAGIX Community Forums Archive

Subject:Convert 16bit to 8bit 11025 Hz? Posted by: abooblika Date:1/8/2002 1:33:46 PM We are a Speech Recognition (IVR) and typically need to convert 44 Khz, 16bit, mono wav files to 11025 Hz, 8 bit mono wave files so they can be telephone quality. We need to have them in this format in order for our voice application to work properly. When we convert to the lower quality we get lots of noise and pops. We have soundforge 5 and the Native Gold 3.0 bundle from Waves. But we are newbies and don't have any idea which plugins to use and what settings. Any Suggestions?
Subject:RE: Convert 16bit to 8bit 11025 Hz? Reply by: Chienworks Date:1/8/2002 2:51:18 PM First of all, make sure your file is normalized. The conversion from 16 bits to 8 bits simply lops off the lower byte, and if your signal is low, a large part of the important data is in this lower byte. You may also want to use dynamics first to lower peaks so that normalization can bring the quiet parts up higher. 8 bits have only 1/256th the dynamic range of 16 bits. If your sound is too quiet, parts of the wave will simply disappear when converted to 8 bit. This probably causes the pops you are hearing. When resampling, i always set the Interpolation accuracy to High (4). This can take a little longer, but it's definately worth it. Also check Apply an anti-alias filter during resample. Sound Forge is VERY smart and really understands quite a bit about the waveform it's working with. Instead of just cutting out data when reducing the sample rate, it seems to understand the shape of the wave it's working with and preserve that at the lower sample rate. I've converted CD audio files to 8 bit 8,000Hz and still have quite acceptable quality music.

First of all, make sure your file is normalized. The conversion from 16
bits to 8 bits simply lops off the lower byte, and if your signal is low, a
large part of the important data is in this lower byte. You may also want
to use dynamics first to lower peaks so that normalization can bring the
quiet parts up higher. 8 bits have only 1/256th the dynamic range of 16
bits. If your sound is too quiet, parts of the wave will simply disappear
when converted to 8 bit. This probably causes the pops you are hearing.

When resampling, i always set the Interpolation accuracy to High (4).
This can take a little longer, but it's definately worth it. Also check
Apply an anti-alias filter during resample. Sound Forge is VERY smart
and really understands quite a bit about the waveform it's working with.
Instead of just cutting out data when reducing the sample rate, it seems
to understand the shape of the wave it's working with and preserve that
at the lower sample rate. I've converted CD audio files to 8 bit 8,000Hz
and still have quite acceptable quality music.