Converting 16-bit to 8-bit issue

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GoldWave Inc.
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Re: Converting 16-bit to 8-bit issue

Post by GoldWave Inc. »

8 bit files are inherently noisy. A new Noise Gate filter effect in v6.19 removes noise in quiet/silent sections of the audio. That may give somewhat cleaner sound in some cases.

Increasing the volume to the point just before distortion becomes audible can help as well. Minor clipping of the audio is generally less distracting that the quantization noise. The increased volume of the file would require the listener to use a lower volume setting, making the noise quieter (you gain relative quality/resolution by sacrificing peaks).

As a last resort, there is an 8 bit dither setting (Options | Plug-in | File | GoldWave*, "Use triangular dither...") to make the quantization noise more uniform.
2leftfeet
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Re: Converting 16-bit to 8-bit issue

Post by 2leftfeet »

You cannot make 8 bit recordings easily, so the best thing you can do is to try what has already been suggested. I think that it might be a good idea to filter the original audio first, using the spectrum filter, rolling off at 8000Hz to 10,000Hz. This removes frequencies which are above that which a sample rate of 22050 can accept. Now reduce the noise, resample & save it at 8 bit resolution. LIke I said before, I save all my stuff at 90% of maximum, no one will really notice in the situation you are going to use it for.The audio file which I made here sounded pretty good. I found that compressing did not help, in fact it sounded worse. So do not go out and buy an expensive mike yet!
marera
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Re: Converting 16-bit to 8-bit issue

Post by marera »

Hi all!

After trying all of your clever suggestions, i came the following conclusion:

8-Bit is of poor quality. Zoooooming far into the waveform reveals the "stairs"-waveform of the amplitude sliced into only 256 steps.
There is a chance of keep this poorness in limits, if the recording is as good as possible.

"good recording" means 100% volume, no clipping, low noise.

With the help of you, I got the sound as good as one can obviously expect from 8-Bit recordings.

Thanks a lot!

Marc
DewDude420
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Re: Converting 16-bit to 8-bit issue

Post by DewDude420 »

marera wrote:
8-Bit is of poor quality. Zoooooming far into the waveform reveals the "stairs"-waveform of the amplitude sliced into only 256 steps.
What you have to remember is how PCM stores the audio data. The sample rate says how many samples you have per second; the bit-depth is how many bits each sample takes up. This is why the amplitude of an 8-bit file only has "256 steps"; you can only represent 256 values in an 8-bit integer.

The way you're *supposed* to work around this before exporting to 8-bit is by noise-shaping or dithering. In this process; you're adding just enough noise to keep the "lowest" amplitude within the dynamic range. If properly done; a constant "hiss" is the result of dithering. Usually, however; no one does that and simply chops off 8 bits; leaving you with all kinds of nasty quantization noise that's "around the edges" of louder volume stuff; and begins to swamp lower amplitude.

Still, 8 bit is a pretty lousy format and I'm not even sure if anything really uses it anymore. Historically...it was due to space limitations...some games used 8-bit wavs for sound effects. In those though; there's little dynamic range and the levels are maxed out using hard-limiting so you don't notice it.
pseudogfx
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Re: Converting 16-bit to 8-bit issue

Post by pseudogfx »

Is there a way to perform quantization in GW? Like if I wanted to convert the source sample to 4 bits/16 levels or any other number of levels. Perhaps even with some dithering options.
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Re: Converting 16-bit to 8-bit issue

Post by GoldWave Inc. »

GoldWave doesn't have a quantization effect, but you could use the Expression Evaluator to quantize the audio. For 4 bit (8 positive and 8 negative), you'd use:

Code: Select all

int(wave(n)*8)/8
With a random rectangular dither I think you could use:

Code: Select all

int(wave(n)*8+(rand(1)-0.5))/8
There currently isn't a way to save the audio as 4 bit, but the 4 bit quantized levels would be saved at whatever resolution was selected.
pseudogfx
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Re: Converting 16-bit to 8-bit issue

Post by pseudogfx »

Thanks!
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