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Topic: Best Free-software or no charge proprietary tool to downsample to 44.1 (Read 18831 times) previous topic - next topic
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Best Free-software or no charge proprietary tool to downsample to 44.1

Reply #25 –
Quote from: saratoga on
If you are just resampling you don't need dither, but if you are also decreasing the dit depth it is a good idea.

Thanks for clarifying that.

Quote from: saratoga on
I would probably not enable alaising if down sampling from a much higher sampling rate.

So like from 192 to 48, or 176.4 to 44.1, aliasing would be undesirable; but not necessarily from 96 to 48, or 88.2 to 44.1? Why is that?

I know alias is a "bad word" among audiophiles, but from what I've read it cleans up the ultrasonic frequencies, so I figure why not do it? As an added bonus, it actually makes the operation faster, too. If I'm missing something here though, I'm all ears.  (Or if I'm confusing this concept with that of dither, I apologize.)

Best Free-software or no charge proprietary tool to downsample to 44.1

Reply #26 –
@ArtistOfMind:  About aliasing:

The option in SOX allows the (necessary) filter used for doing the resampling to be softer, which in the end means allowing aliasing in the transition range of frequencies (which in this case means a small zone at the top frequencies).
This is a tradeoff so that the filter doesn't need to be as long (plus other details that i don't remember precisely).

As for the concept of alias, sometimes there is confusion between the concept ( alias as in mirroring outside of the delimited frequencies when no filter is present ), and the effect ( if it is not filtered and there is resampling, the alias moves into the valid frequencies in a way similar to a mirror).

You can think about it like looking at a mirror and moving it. If you look at it straight, it would be like a brickwall filter. If you rotate a bit the mirror, you'll start to see things that you didn't see before. (The analogy is not complete, because aliasing is added to the existing frequencies, while moving the mirror just "displaces the frequencies").

Best Free-software or no charge proprietary tool to downsample to 44.1

Reply #27 –
There's also QSoX, for anyone who wants an easy to use GUI. (Note that the included SoX files are outdated and should be replaced with more recent ones.)