Possible quality loss when bouncing in place? [SOLVED]

Somehow I got the idea that bouncing in place (bip) always means a (tiny) loss in quality. Is this correct?

If it's correct: any ideas on how often one can bip before it becomes an audible issue?

 

Example: I've done a drumtrack with RMX (= Midi). I bip it to use Stutter Edit on it. I bip this mangled track to another audio track. I edit this track to create the final track and bip it again. Finally I export the track (sort of fourth bip). All bips are done in 24bit and 44,1kHz. In this case I'm not able to hear any loss in quality - which doesn't mean there isn't any.

The fact that you do some sort of processing on every generation makes the question moot, since the processing will always have more significant impact anyway.

The only way to find out is to approach it scientifically: bip 20 generations, and do a null test between the original and the 2nd, and 6th, and 11th and 15 th and 20th generations. No processing though, that'll invalidate any result.

If you bouce a 24/44.1 file unprocessed, you should get a clone. Theoretically, even the 20th generation clone should null (be identical) against the first.

Digital can "stand" much more generations than analog ever could, because, for starters, there is no accumulative carrier (tape) noise.

Thank you - so I was wrong. BIP (of course without any processing) is just like copying and doesn't somehow "pass through" Logic's audio engine. I assumed that when bip-ing Logic will do some "calculating" too due to running it through the audio engine ...

In case it's useful (for the original poster, or others reading this thread later), here's a technical explanation.

 

As I understand it, a typical pro DAW's mix engine (in simplified form, and leaving out plugins) does this:

 

For each sample:

1) Set up a temporary "sample storage" place (let's call it S) and reset it to 0

2) For each track:

----a) Note that track's current sample value (let's call it T)

----b) Multiply T by whatever the track's fader is set to (i.e. 0dB = x1, -6dB = x0.5, -infinity = x0)

----c) Add the result to whatever is in S, and store the sum in S

----d) Repeat a-c for the next track until done

3) Record what ended up in S as that sample for the mixdown

4) Repeat 1-3 for the next sample until done

 

At least in the circumstance of only one track and all relevant faders at 0dB, even samples that DO pass through the audio engine come out with the same values as went in (multiply by 1, add 0) and therefore the exact same audio, even after countless generations.

 

There are so many things that make hugely more of a difference to the sound of a track than any digital generation loss or mix engine coloration (if those things are even audible at all in your specific circumstances), that it's generally not worth worrying about - unless you're clipping during the bounce process (to fixed-point), using lossy compression per pass, or something like that.

 

If you do run into situations where you or someone else suspects digital generation loss as a source of quality loss, I'd be inclined to be extra thorough testing other causes first. It would take an awful lot to convince me that generation loss was the culprit, as opposed to some other thing that someone overlooked.

Excellent explanation - thx for taking the time!!

I was searching the forum before posting this. There are several threads dealing with quality issues when bouncing - but none of them related to bouncing without processing. So, I guess we're done here.

Thank you - so I was wrong. BIP (of course without any processing) is just like copying and doesn't somehow "pass through" Logic's audio engine. I assumed that when bip-ing Logic will do some "calculating" too due to running it through the audio engine ...

You will get a difference between a 32 bit floating point signal and a fixed 24 bit ditto, but it's extremely low level. It will look like a null unless you have higher resolution meters than Logic's.

 

I wouldn't worry too much about it.

My "final meter" are always my ears - and I knew I couldn't hear any difference. But I was curious too.