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Topic: Upsample or Downsample? (Read 7759 times) previous topic - next topic
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Upsample or Downsample?

I know that this is not a recommended practice, but in the given case in which I am transfering Audio CD files to DVD or LPCM files to Audio CD, which is the best: Upsample 44.1 to 48, or Downsample 48 to 44.1 ? Which case will there be audible artifacts?

As for 16 and 24 bit, does it get bad to convert a 24-bit WAV to a 16-bit WAV?
What's the effect to convert 16-bit WAV to 24-bit WAV.

Upsample or Downsample?

Reply #1 –
Downsample is worse than upsample. But in the cases you mentioned you are not likely to hear a difference either way.

Upsample or Downsample?

Reply #2 –
Quote from: Bourne on
I know that this is not a recommended practice, but in the given case in which I am transfering Audio CD files to DVD or LPCM files to Audio CD, which is the best: Upsample 44.1 to 48, or Downsample 48 to 44.1 ? Which case will there be audible artifacts?

As for 16 and 24 bit, does it get bad to convert a 24-bit WAV to a 16-bit WAV?
What's the effect to convert 16-bit WAV to 24-bit WAV.

Unless you have hearing like a bat, you're won't notice any difference between 44.1 and 48 sample rates.

When converting 24-bit to 16-bit you loose 8 bits of resolution.  This means about 48db of dynamic range.  As a practical matter your original program likely doesn't make use of the full 24-bit resolution anyway.

Try it and tell us what you hear.

Upsample or Downsample?

Reply #3 –
Quote from: Bourne on
As for 16 and 24 bit, does it get bad to convert a 24-bit WAV to a 16-bit WAV?
Not bad, really, but it's an undesirable thing to do. On paper, you lose a lot of data, but not a lot of quality.

Quote from: Bourne on
What's the effect to convert 16-bit WAV to 24-bit WAV.
Basically nothing. The values are represented in a different manner, but the values stay the same (or at least they should).

Upsample or Downsample?

Reply #4 –
If you are using decent resampling software, there will never be any audible difference.

Upsample or Downsample?

Reply #5 –
I would use foobar2000 Resampler (PPHS). But I don't know if I should use the (x) Ultra Mode option.

Upsample or Downsample?

Reply #6 –
Use foobar2000's SSRC resampler if you're performing file conversions. Garf once mentioned that PPHS is more suited for on-the-go listening when playing audio with soundcards that resample poorly.

Upsample or Downsample?

Reply #7 –
As I understand it, PPHS is much faster, but SSRC is theoretically higher quality.

Upsample or Downsample?

Reply #8 –
I agree that you shouldn't hear the difference in any case, if done properly.

When you upsample from 44.1kHz to 48kHz, or downsample from 48 to 44.1, the new samples have to be interpolated, because the sample rates don't "divide evenly".  (They don't exist at the same points in time.)

When you downsample from 48 to 44.1, you have the additional concern of aliasing if you don't filter-out any signal above 24kHz before downsampling.  So, all downsampling programs include an anti-aliasing filter.  (Aliasing is not a problem when upsampling.)

When you convert from 24-bit to 16-bit, you generally need to normalize first, so that you only loose the bottom 8-bits.    If you don't do this and your 16-bit file doesn't reach 0dB, then you are not taking advantage of the full 16-bit dynamic range.

P.S.
There are times when you don't want to normalize (i.e. If you want a "quiet track" on a CD.)

And, there are times when it is advantagous to increase the bit-depth to 24-bits, from 16-bits.  (i.e. When you are mixing or doing lots of processing, and the additional headroom will prevent clipping.)