Don't let Live resample your audio!

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:09 pm

Ok, so to day I got curious (and bored) and I wondered how well live handled files that were not at the session native rate. I.E., playing back 96k sample at 44.1k and 44.1k samples at 96k. It did not do well. At all. [high quality mode is active]

What these files show is a sine wave frequency sweep from the highest representable frequency range, down to 0Hz, then back to maximum again. They were generated with Adobe Audition and recorded as 32Bit floating point waves.

Here's a picture of my 'perfect' 22050Hz to 0Hz to 22050Hz .wav file. I.E. the full range of 44.1Khz audio

Now here's what happens when you render it in Ableton at 96K

As you can see, there are many, many artefacts. But wait, there's worse to come.

Here is my 'perfect' 48000Hz to 0Hz to 48000Hz .wav file. Or, the full range of 96Khz audio.

Now here's what happens in Ableton when you render 96K at 44.1K

As you can see, the 96k-44.1k is butchered. Very audible artefacts.. So what can we do to prevent this? Well, you can try only rendering at the rates you record at. Sadly, not everyone has the ability/means to record/process at 96k, and 44.1 is fine for playback but not at all good for processing.
The second option is to resample whatever audio OUTSIDE of Live. The best (free) resampler is Voxengo's R8Brain (http://www.voxengo.com/product/r8brain/). It's an amazing resampler and doesn't cost a penny.

Tone Deft · Post by **Tone Deft** » Tue Aug 07, 2007 8:21 pm

what do the plot lines represent?

typically it's one plot of magnitude vs. frequency.

Tarekith · Post by **Tarekith** » Tue Aug 07, 2007 8:23 pm

These were 24 bit files weren't they? I discovered the same thing back when we were comparing Live to other DAW's (though sans your nice charts) and was told it was an issue Live has with resampling at 24bit. Doesn't affect 16 or 32 bit apparently....

kineticUk · Post by **kineticUk** » Tue Aug 07, 2007 8:24 pm

Tarekith wrote:These were 24 bit files weren't they? I discovered the same thing back when we were comparing Live to other DAW's (though sans your nice charts) and was told it was an issue Live has with resampling at 24bit. Doesn't affect 16 or 32 bit apparently....

Lets hope this bug gets fixed soon then...

Daim · Post by **Daim** » Tue Aug 07, 2007 8:26 pm

wow this really sux

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:26 pm

These were 32bit files, sorry I should have stated that earlier. Also, the graphs are time/horizontal and frequency/vertical.

Tone Deft · Post by **Tone Deft** » Tue Aug 07, 2007 8:27 pm

kineticUk wrote:
Tarekith wrote:These were 24 bit files weren't they? I discovered the same thing back when we were comparing Live to other DAW's (though sans your nice charts) and was told it was an issue Live has with resampling at 24bit. Doesn't affect 16 or 32 bit apparently....
Lets hope this bug gets fixed soon then...

there are bugs and then there's the nature of the beast.

what answer do you get when you divide 22 by 7? sample rate conversion is a bitch.

the answer is that as a 'producer' or 'mastering engineer' you should know these topics and know what sample rate to render at. saying that this is a bug is like complaining that your hammer won't work on screws.

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:28 pm

Also, I am not slating Ableton, most DAWs are totally bad at resampling. This is why it should be done by a dedicated application. As far as native DAW resampling goes, Ableton is about mid table. You can see more test here http://src.infinitewave.ca/

Tone Deft · Post by **Tone Deft** » Tue Aug 07, 2007 8:29 pm

Funkstar De Luxe wrote:These were 32bit files, sorry I should have stated that earlier. Also, the graphs are time/horizontal and frequency/vertical.

sure, but when you do a frequency sweep there's one line, why the multiple lines? is that a logarithmic or linear plot?

just curious because I make those kinds of measurements as part of my job and I'm not understanding what I'm looking at.

it's cool, I know you're not slating, it's interesting to get to know Live better, I'm just curious.

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:30 pm

And it's not a bug in anyway, it's just not a high quality system.

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:31 pm

Tone Deft wrote:
Funkstar De Luxe wrote:These were 32bit files, sorry I should have stated that earlier. Also, the graphs are time/horizontal and frequency/vertical.
sure, but when you do a frequency sweep there's one line, why the multiple lines? is that a logarithmic or linear plot?

just curious because I make those kinds of measurements as part of my job and I'm not understanding what I'm looking at.

it's cool, I know you're not slating, it's interesting to get to know Live better, I'm just curious.

The multiple lines are what happens when Ableton resamples the audio improperly. It's creating artefacts. What I imagine is happening is this; the high frequencies are not being sufficiently rolled off and thus breaking the highest representable frequency of the sampling rate. IE, trying to represent a frequency higher than 22050Hz @ 44.1Khz will result in problems (the frequencies fold back into lower frequencies - I am struggling to remember the correct terminology).

Edit: it's aliasing.

kineticUk · Post by **kineticUk** » Tue Aug 07, 2007 8:34 pm

Tone Deft wrote:the answer is that as a 'producer' or 'mastering engineer' you should know these topics and know what sample rate to render at.

who is ?

Tone Deft wrote:saying that this is a bug is like complaining that your hammer won't work on screws.

who is ?

Tarekith wrote:and was told it was an issue Live has with resampling at 24bit. Doesn't affect 16 or 32 bit apparently....

I know something but am not trying to act smart.
Just joining in the conversation, please don't talk to me like I'm a div.

Tone Deft · Post by **Tone Deft** » Tue Aug 07, 2007 8:34 pm

Funkstar De Luxe wrote:
Tone Deft wrote:
Funkstar De Luxe wrote:These were 32bit files, sorry I should have stated that earlier. Also, the graphs are time/horizontal and frequency/vertical.
sure, but when you do a frequency sweep there's one line, why the multiple lines? is that a logarithmic or linear plot?

just curious because I make those kinds of measurements as part of my job and I'm not understanding what I'm looking at.

it's cool, I know you're not slating, it's interesting to get to know Live better, I'm just curious.
The multiple lines are what happens when Ableton resamples the audio improperly. It's creating artefacts.

I dig, trust me.

you put in shaped white noise and at the output you measure the amplitude at each frequency. your plot shows multiple measurements. it looks more like a pretty picture done in photoshop than a measurement. plot measurements don't have lines whose endpoints fade in and out.

Tone Deft · Post by **Tone Deft** » Tue Aug 07, 2007 8:37 pm

kineticUk wrote:
Tone Deft wrote:the answer is that as a 'producer' or 'mastering engineer' you should know these topics and know what sample rate to render at.
who is ?
Tone Deft wrote:saying that this is a bug is like complaining that your hammer won't work on screws.
who is ?
Tarekith wrote:and was told it was an issue Live has with resampling at 24bit. Doesn't affect 16 or 32 bit apparently....
I know something but am not trying to act smart.
Just joining in the conversation, please don't talk to me like I'm a div.

no problem. the internet is a pretty shitty form of communication, complete lack of body language, vocal inflection and eye contact can almost guarantee misunderstandings.

Funkstar De Luxe · Post by **Funkstar De Luxe** » Tue Aug 07, 2007 8:38 pm

Tone Deft wrote:
Funkstar De Luxe wrote:
Tone Deft wrote: sure, but when you do a frequency sweep there's one line, why the multiple lines? is that a logarithmic or linear plot?

just curious because I make those kinds of measurements as part of my job and I'm not understanding what I'm looking at.

it's cool, I know you're not slating, it's interesting to get to know Live better, I'm just curious.
The multiple lines are what happens when Ableton resamples the audio improperly. It's creating artefacts.
I dig, trust me.

you put in shaped white noise and at the output you measure the amplitude at each frequency. your plot shows multiple measurements. it looks more like a pretty picture done in photoshop than a measurement. plot measurements don't have lines whose endpoints fade in and out.

It's a frequency sweep sine wave from 22050Hz-0 and back up to 22050 again. Sorry about the lack of detail, but Adobe Audition is a bitch to use like this.

If anyone wants, I can post the two test files here...