Sample Rate Conversion for Digital Output

[TascMan]

Hi all. I was so happy to see the forums back when I registered at "TheTascamForums" only to find out that this site was up and running. Funny to think there are now Two sites dedicated to this purpose, when I thought we wouldn't see another forum for a long time. Thanks to everyone involved to get the forums back online!! I Just registered here today, but had posted this topic on the other forum site yesturday.

The simple part:
I perfer to record at 88.2, but my outboard digital based effects typically only accept S/PDif at 44.1K or 48K. Can I remain at 88.2K but somehow send a 44.1K clocked audio out to these effects by somehow setting something in the DM? (Fs Conver doesn't work for outputs and "OUT SPEED" on the project page only effects the clock output signal, not the audio sample rate output)

Long part:
I have a few outboard effects (Lexicon MX200, TC Helicon Voice Works, TC C300) that I like to use for some projects. But they have a sample rate limitation, through S/PDif, of 44.1K or 48K. What I usually have to do is record my tracks at 88.2K, then set the DM to 44.1K and reboot, playback the tracks I have recorded then send them out to the desired effect and record that track in a new track. Then shutdown the DM and reboot back into 88.2K. PITA!
I have had the 3200 for quite some time now, since 2007, and have not been able to figure out how to send out audio at a different sample rate than what I am recording at. Now the Fs Convert button works just fine for converting the digital ins to my current sample rate but doesn't not work for the outputs. I do have a Lucid GENx 192 that will pass audio through the AES input to the S/PDif outs, and WILL convert the AES clock to any other desired rate to the outputs but will NOT effect the audio's actual sample rate. It remains at 88.2K out of the Lucid's S/PDif outputs.
Any Help? Thanks

 

[TascMan]

Well it seems that Jarno has indirectly answered my question when he replied to another post about headphone outputs......"Unfortunately there's no sample rate converion in DM's digital outputs...." So, I will be buying a SRC for the DM Digital outs.

 

[captdan]

What I usually have to do is record my tracks at 88.2K, then set the DM to 44.1K and reboot, playback the tracks I have recorded then send them out to the desired effect and record that track in a new track. Then shutdown the DM and reboot back into 88.2K. PITA!

And intriguing.

I'm wondering: when you play back your 88.2k material through the DM clocked at 44.1, aren't you hearing the material at half speed? Or am I missing something?

CaptDan

 

[TascMan]

Good Point. So I did an experiment....
I did a trial by recording my voice into Reaper with the DM set to 44.1K. Reaper showed the Audio in SR at 44.1K. Then I rebooted the DM and reset the clock to 88.2K. I recorded my voice into track two. That one played back just fine and Reaper was also showing audio input SR at 88.2K. Track one played back just fine and normal as well. Then I set the DMs clock to 96K, recorded my voice into track three, and then played back all three tracks. No Problems. Everything sounded normal. and played back at normal speed. I don't know the phyics behind this other than to say that perhaps reaper sees each track as it's own session with it's own speed and can compensate to normal playback speeds? No Idea, but it works.

THEN I tried doing the same thing in Adobe Audition 3. Same sample rates as previous and what I found was that AA has a specific set session sample rate speed for all tracks. I set that to 88.2 and recorded my voice at 88.2. Obviously, playback was fine. Then I rebooted the DM to 44.1K and recorded my voice again. Wouldn't you know it, it played back at half speed. I was unable to record at 96K into audition without opening up a new session. (because the session speed was still at 88.2)

So, maybe it's a function of newer daws, (since AA's roots go back to around 2000 and Reaper's engine was fully updated a couple of years ago with constant updates happening every couple of weeks) but I had no problems recording into Reaper at different sample rates into the same session. This is why I have not had any problems doing what I have been doing with my outboard gear. Nonetheless, I have a new SR converter on the way so I can stay at 88.2 all the time, but send 44.1 out to my effects. The board will convert that back to 88.2.
interesting topic, this SRC stuff.

 

[captdan]

Thanks for the info. I asked because what you describe about Audition is exactly what I experience.

It's true- AA is essentially a slightly modified version of the venerable Cool Edit Pro with a few extra bells and whistles. I rely on it heavily, though it seems quite tied to earlier 'Micr0$oft' logic.

Can't say what's going on with Reaper - obviously there's some on-the-fly conversion going on. Interesting issue, though.

CaptDan

 

[Arjan P]

Can't say what's going on with Reaper - obviously there's some on-the-fly conversion going on. Interesting issue, though.

Interesting issue indeed. And it would make me very suspicious about a DAW if it converts sample rates behind my back. Which SRC is it? What quality can I expect from it, working real time? Do I have any influence on it? I don't think there's anything 'modern' about it, sounds more like iffy engineering..

 

[TascMan]

Geeesssh,,,,,

From their features page,,,see number two

"Drag and drop to import any supported media format
• Freely mix source audio of any format and sample rate with no offline conversion necessary
• Full support, including rendering, of multichannel (greater-than-stereo) audio formats
• Source audio containing tempo or beat slice location information is automatically imported at project tempo, spaced properly, and pinned to beat locations
• Record, glue, and render directly to any supported format"

AND,,,

" REAPER's audio cuts no corners. The audio signal path is 64-bit from input to output, for maximum resolution and headroom. Hundreds of tracks of audio can be mixed down with no measurable loss of resolution."

 

[Gravity Jim]

Yes, no OFFLINE conversion. It does the conversion in the program, automatically. Because it can't play back audio at more than one sample rate at a time. Nothing can.

Digital Performer and Logic both do this kind of automatic conversion, and there is a preference setting for whether you want the program to do it or not. I'd guess there might be one in Reaper, too.

I completely understand what Dan is saying about being suspicious. I don't know what quality of conversion Reaper is performing. For example, I'll trust Digital Performer's engine for true sample-accurate bouncing much more than Logic's if i had to downsample. They're not all created equal. But when upsampling... from 44.1 to 88.2, for example... you're just getting a lot of extra zeroes that don't affect audio quality.

I scratched my head over this same problem, trying to figure out how to address my Lexicons digitally while recording at HD rates. I finally decided, after reading a pile of research from George Massenburg and others, that:

A) in a system with only one digital device, like mine is now (just the DM/IF-FW card), I was better off letting the unit clock itself, because even a high-quality external clock would screw things up

B) having decided that, using the SPDIF ports would do more harm to the audio in the form of clock hash than simply running them as analog units would (don't use my analog Aux outs for cue mixes, so I just use them to feed the Lexi's).

So instead of replacing my Lucid 48k clock, I sold it and just let the DM clock itself. If my Lexicons were 96K devices, I would have gone the other way. I the very rare occasion I stil need input from a DAT, I bringvit in digitally and let the DM convert the SR on the fly, which it does nicely.... other than that, it's just one streamlined digital unit, which was one of the main reasons I went with the DM console.

 

[captdan]

Despite contentions to the contrary, a digital audio rig with few devices doesn't necessitate an outboard clock. The DM's 'Jet/PLL' clock is rock solid and more than capable of kicking minimal outboard gear into perfect lockstep.

Not trying to launch a discussion about how top-drawer clocks are alleged to improve audio; there've been quite a few of those already. To each his own; whatever works - works. But G. Massenburg ain't a slouch either - he arrived at his conclusions through empirical methods, moderated by a lot of audio years in the trenches.

Jes' sayin.

CaptDan

 

[Gravity Jim]

Agreed, Capt. When I switched to the DM and was able to record at the higher rates, I was sure I'd have to also buy a 96K replacement for my Lucid clock. But after reading what Massenburg had to say on the subject, I decided to ignore everything else I found on the Internet. There's a lot of subjective literature, but George's stuff sounded like pure science to me.

Which is not to say that the OP or anybody made a wrong choice... if it works for you, then it works.

 

[captdan]

Subjectivity in audio? Nawwwwwwwww.

CaptDan