anti-aliasing

Scrivello wrote on 1/30/2021, 9:03 AM

Hello,

For a while I've been using Sound Forge Pro 3.0 to downsample 48kHz files to 44.1kHz for every day use. Recently, I've been finding out about the need for anti-aliasing when doing this. All the files I've done so far over the years in Sound Forge used the native sample rate and bit depth converter set to maximum / mastering quality. Never has there been a direct option to use anti-aliasing.

Does this mean that all this time I have been creating aliasing artefact or is anti-aliasing automatically done using the above settings?

Thanks.

Comments

emmrecs wrote on 1/30/2021, 10:07 AM

@Scrivello

Welcome to the Magix user to user forums.

"Antialiasing" is a term most commonly applied to graphic objects (images and the like). For audio, and this is what I think you mean, we talk about Dithering.

(If you want a rather technical description of the process, read this Wikipedia page.)

As to whether you need to use it and whether the fact you haven't has had any detrimental effect on what you have previously done: what is the source of those 48kHz files which you have been downsampling? If they are "commercial" recordings they have quite possibly had dithering applied when they were mastered. In those circumstances, for you to use, or not use Dithering, is highly unlikely to make the slightest difference to the finished sound.

Just as a matter of interest, you say you have been doing this downsampling for everyday use. Is this so you can burn the files to audio CD? If so, do be aware that, speaking legally, this could be seen as copyright infringement!

Jeff
Forum Moderator

Scrivello wrote on 1/30/2021, 2:22 PM

Hi Jeff,

Thanks for the reply, but I'm talking about anti-aliasing for digital audio, i.e. prior to reducing bit rate, the frequencies the new bit rate will be unable to reproduce are removed, so to avoid artefact (alias) created when the new reduced bit rate tries to recreate them.

I'd like to know if the native sample rate and bit depth converter on SF 3.0 set to maximum / mastering quality does this automatically or not.

And yes, I appreciate it is likely that the audible difference is undetectable to non teenage humans, but if I'm producing CD ready 44.1/16 files from 48/24 multitracks I don't want to look bad. And on that note, these are my multitracks created in Logic so nothing illegal!

johnebaker wrote on 1/30/2021, 4:23 PM

@Scrivello

To put a precise definition on the feature you are describing, it is an Anti Aliasing Filter - check the manual for the version you have - it is under Izotope 64bit SRC.

HTH

John EB

Scrivello wrote on 1/31/2021, 12:37 AM

it is under Izotope 64bit SRC.

Hi John, indeed it is; I've just discovered that. But I'm still wondering: Does the native sample rate and bit depth converter on SF 3.0 set to maximum / mastering quality use an anti-aliasing filter automatically or not?

I've been using this method for a long time before becoming aware of the Izotope SRC plug-in.

Thanks

Scrivello wrote on 2/1/2021, 2:42 PM

In case anyone is interested, just got this back from Magix support, very nice of them:

Greetings from Sound Forge Support,

Thank you for contacting us. To the best of my knowledge, this happens automatically in Pro Mac 3, however I must admit that I haven't used the Mac version in a few years...I have written the head developer to make sure so if he gives me an answer to the contrary, I will let you know immediately. Thank you for your time and patience, and have a great day!

johnebaker wrote on 2/1/2021, 4:06 PM

@Scrivello

Thanks for the update, like the Magix respondee, I have not used Sound Forge for many years.

John EB