Clip indicators are lit, but level seems OK

[MP]

Hi All,

I have a project that has four vsti synths and an audio track. Before I recorded the audio, the VU meters in the mixer looked OK (nothing clipping). I added an audio track without touching anything in the mixer. Now the clip indicators are lit on the Vsti channels and aux channel - even though the actual VU levels are still well below the red. If I disable the effects/synths (turn the power off), the clip indicators do not light.

The audio track is on its own output . . . I can't figure out why it would be affecting the clip indicators for the vsti (and aux) channels.

Any idea what could be going on?

Thanks,
Mike

1 ghz TiBook, 768 ram, Jaguar 10.2.8, coffee, no sleep

[Jerm]

The clip indicator denotes that somewhere in the audio mixing path clipping has occurred. Look at the following example:

Track1->audio
Track2->audio
Track3->VI->audio
Track4->VI->audio

Let's say that these 4 tracks are being summed (mixed) to an audio output. So for every sample the output will be T1+T2+T3+T4. If when adding T1+T2+T3 there is a clip, it will indicate so in T3's fader even if the level of track 3 is very very low.

[MP]

Hi Jeremy,

Thanks for the reply. All tracks are being sent to separate outputs, it's more like this:

Track1->audio output 1
Track2->audio output 2
Track3->VI->audio output 3
Track4->VI->audio output 4

Are you saying that any clipping happening at "audio output 1" will activate the clip indicators for outputs outside of it's audio path?

In this senario, I was expecting to see any clipping due to summing at the master channel's indicator. I appologize if I am not understanding some fundamental aspect of Metro's audio routing.

Thanks,
Mike

[Jerm]

Track1->audio output 1
Track2->audio output 2
Track3->VI->audio output 3
Track4->VI->audio output 4

Yes but those numbers on the end represent channels. They all output to the same physical output so they must be summed together. When a clip occurs it must be indicated somewhere. There are no audio output master faders or clip indicators for each physical output (In Metro at least).

Are you saying that any clipping happening at "audio output 1" will activate the clip indicators for outputs outside of it's audio path?

No or err... perhaps. Remember in Metro the faders go up to 0 db. This means a single audio output (with no plug-ins) can never clip. The audio channel is being summed with other channels to be output to the physical core audio output. If the intermediate sum involving this channel exceeds the clip level, the signal is clipped and the indicator goes on for a short time.

I was expecting to see any clipping due to summing at the master channel's indicator.

The master vu and clip indicator's are approximations since they need to account for MIDI data whose amplitude is unknown and therefore is estimated based on the MIDI volume level (Controller 7), and velocity.

If the master clip indicator is not lighting then perhaps it is a bug.

You might take a look at a plug-in like RMS buddy to check exact levels at any time. This plug-in can be placed on an aux buss and audio can be routed to it.

[MP]

Hi Jeremy,

Thanks for explaining it so well, I now understand what is going on. The mixer work flow is a bit different from what I'm used to (DP), but I can make good sense of it.

It's now clear to me that the master fader is a global control for all faders in the mixer (now that could be a useful feature). As for its clip indicator, I have never seen it light (even when the other channels are clipping).

Thanks again for your help . . . on a weekend, no less!

Mike

[Jerm]

One of the reasons for this design is because it can be rather processor intensive to have specialized clip indicators therefore in our audio engine we detect audio overflow (clips) only during some kind of audio mix operation.