Is VOX bit-perfect?

#21

Here is something else Ive notices: when VOX is doing sample rate conversion (where the rate of the file is different than the rate of the system) when a new track is started it will play a small amount of the previous tracks’ audio as if its stuck in a cache. this causes problems because its annoying but also because it triggers meters. as you know I use VOX to play back files to analyze them with meters (that’s a compliment). so when this clip plays it throws off my meters. when the file and system rate are the same, this small amount of the previous track doesn’t play.

brett

On Dec 22, 2016, at 10:34 PM, UsabilityNow brett@usabilitynow.ca wrote:

So an area where VOX could be improved is an honest better sample rate conversion. it’s easy to not know if the sample rate “chain” isn’t creating problems because of rate conversion, because a lot of what goes on is under the hood. but it seems like VOX can essentially control the same rate of the system. so both a better quality sample rate conversion and some kind of warning that its doing conversion would be great. that way the user can be alerted to a problem and resolve it.

just a suggestion based on all our troubleshooting

brett

On Dec 22, 2016, at 5:42 PM, UsabilityNow > wrote:

I found the problem. sample rate conversion. if there are any inputs or outputs in “audio midi” with sample rates other than the file sample rate, sample rate conversion (within VOX?) will cause RoundTrip to report sample clops.

I use Audio Hijack as well. if Audio Midi is set to the right sample rate, it may be that Audio Hijack i(AH) isn’t. AH doesn’t seem to change it’s sample rate once set from initial launch. so if the file rate is 44.1 and the system rates are all 44.1 there will be no sample clipping.

It appears to be s simple sample rate conversion issue. as long as I ensure the output I am using is set to the file rate, there are no sample clips.

I discovered that a track has to be re-started by double-cliking on it if the system sample rate has changed otherwise the file will continue playing at the previous set rate when it was first played.

“Syncronize sample rate with player” helps to solve this problem by forcing the system rate to the file rate. this seems to work.

WHEW! :D

On Dec 22, 2016, at 4:49 PM, soundguy > wrote:

#22

Please specify sample rates of source and output when You noticed clipping bump?

#23

Also, did sample rate conversion take place in Logic also?

#24

I measured the same file with SR conversion from 44.1 to 88.2 and level rise is around 0.2 dB - which is normal since SRC is taking place. We are prepping new major version update (not very soon) where there will be a pack of deeper Hi-Res settings among which is a choice of SRC params

But I don't believe that more sophisticated SRC type will eliminate this level bump radically - because no matter the exact algorithm, to do SRC You need to antialias, which in turn may introduce peaks somewhat higher than in original signal. This is the best way to keep the audio as original as possible, when SRC is on.

If Logic is doing SRC without this tiny peak level bump - I am afraid, they are using level reduction along with it.

I find Your suggestion to indicate that SRC takes place very appropriate and we will include it in v3.0 I think

#25

I think I found the reason:

Why we need SRC at all? because file and output have different sample rates, and for some reason the SR of file is not supported or not switched to in output device.

Logic probably is not doing this SRC, or it is doing it after Audio Units. This is fair/logical because after all it is designed to show the levels of Your original recording, not the monitoring output. The SRC, if any, could take place later between Logic and Core Audio, or, depending on Your setup, straight inside Your hardware.

On the other side, Vox tries not to delegate SRC to Core Audio as BASS has more options to control SRC quality and we use these to the max. You've noticed this when You switched sample rate manually in Audio Midi Setup - the SRC then takes place in Core Audio, because Vox didn't catch the change yet, once You re-start track - SRC goes back to Vox.

The difference here between Logic and Vox is that in later SRC takes place just prior to effects and Audio Units, because we want to process/monitor signal with AU's as close to output as possible. This is exactly not the case with Logic where we want to monitor the levels of file itself, not the output, without any conversion.

And since SRC had inescapable but tiny level changes this is what You see in Vox but don't see in Logic.

Knowing that might help You judging Your levels correctly in Vox. Turns out You can model different SRC modes and see peaks of Your material.
Hope this helps and we are here for any further comments.

Thank You for compliments,
Happy Holidays, btw!

#26

Solved

#27