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SachaG01
02-04-2008, 03:24 AM
As part of my troubleshooting for this:

http://www.newtek.com/forums/showthread.php?t=76178

I noticed that the audio being sent from the output of the VT[5] mixer to the windows capture driver is (about) 24db too high - i.e. if I put a tone on the VT mixer at 0db input, and run unity gain all the way through to the output at 0db, a scope plugin placed on the input of an audio app shows about 12db of clipping (i.e. 12db above even the headroom expected at 0db).

Any suggestions what I can do - (dropping the audio driver input level does not work - all it does is drop the already clipped audio)

I'm aware that NT don't recommend using the windows driver at all, but I'm sure this could be resolved...

Thanks

Sacha Goodwin
University of Bath

Gordon
02-04-2008, 11:53 AM
If I remember correctly, for us here in NTSC land, we had a problem like that with VT3 & VT4. WMEncoder seemed to be always under volume and and yet easily overdriven - similar to a mis-match between consumer level gear (-10dB) and pro level gear (+4dB). I'm sorry I can't remember the exact details now, but I do remember it was a significant problem getting the audio levels just right in WME. Here is one of the new features of VT5:

There are completely re-written audio and video capture drivers for use with encoding applications (e.g. Windows Media Encoder, Flash Encoder, etc...) that are far more reliable and significantly improve VT[5] stability when these are running.
Even now, the WME audio levels are not matching perfectly, but they are improved a great deal. Perhaps your VT5 driver installation has been overwritten as far as the audio capture drivers. Maybe this happened by installing Windows, WME, WMP or other audio software updates/programs.

SachaG01
02-05-2008, 02:28 AM
If I was to hazard a guess as to the reason it might be a mathematical/truncation problem. The VT mixer, for example might be running a 32-bit (or more) mix path, and in order to pass it to the windows capture driver, some bits have to be lopped off the output in order to fit into (say) a 24-bit driver model at the output.

This would cause mismatches in levels and a reduced S/N at the point it leaves the VT mixer and hits the driver. As I'm not a programmer and don't know the first thing about WDM I'm not sure how true this might be - but it might be somewhere to start.

<rant>
I must admit one of the things that has bugged me about all the VT models is there is no real indication of the levels travelling through the system, i.e. what gain is being used at any one time, where is unity actually, what is the headroom above 0db?, are the inputs -10db or +4? (should be +4).

I mean, the knobs and sliders on the mixer go from 'nothing' to 'lots' with 'middle' in between and no detent to know if you hit 0 - huh? The graduations on the sliders are in what db steps?

Any professional mixer manufacturer would be shot if they didn't bother to put any numbers on the panel...

Having this info would go an awful long way making it easy to improve the quality of audio in VT productions, and I think it's a shame that NT didn't put a little more thought into the details... it is a fixable problem to my mind.

</rant>

CreatvGnius
02-14-2008, 10:53 AM
<rant>
I must admit one of the things that has bugged me about all the VT models is there is no real indication of the levels [traveling] through the system, i.e. what gain is being used at any one time, where is unity actually, what is the headroom above 0db?, are the inputs -10db or +4? (should be +4).

I mean, the knobs and sliders on the mixer go from 'nothing' to 'lots' with 'middle' in between and no detent to know if you hit 0 - huh? The graduations on the sliders are in what db steps?

Any professional mixer manufacturer would be shot if they didn't bother to put any numbers on the panel...


Judging from the Audio Mixer's NORMAL mode here (VT[4] version 4.6c), here's what I can ascertain:

Tick-marks on the meters indicate Infinity, -30dB, -10dB, 0dB (Unity), +10dB (I.e., the unmarked lines on channel meters apparently relate to the numbered marks on the channel faders. (refer also to the Front/Back Input and Output Meters).

To get the TRIM, fader and the AUX knob within each channel strip to Infinity, you just double click; but for 0dB (Unity Gain), I just discovered that SHIFT+Double-Click takes care of that for you (whew)!

I don't know to what degree, the use of "Floating-Point" audio, negates the need for some of your requests above, but I answered only what I felt knowledgeable about. Here's hoping this humble reply was of at least a source of help in the area I've marked in bold type.

I must concede the knobs should allow for some means of identifying where you've set them (e.g., Low, Mid & Hi Mid EQ control: What frequency range is being affected, and by how much).

Perhaps left-clicking on it while "rotating" could provide visual feedback in terms of "frequency" and "level") (The preset for the mixer is certainly a welcome feature, so you can reproduce your settings (whatever they may be), howbeit I've never used that function (yet).
-PeterG