Syntrillium Backup Forums :: View topic

clothesburner · Location: USA

Can someone explain the multitrack latency box under Options >> Device Properites >> Wave In >> Multitrack Latency? I am trying hard to understand.

In Richard Riley's book, he explains as follows:

"To test for latency patch the output of your sound card to the input and record a wave playing back from track one to track two. Place the playback cursor over an area of the wave and zoom in the sample level at which point it should be possible to see and calculate any latency using the Offset feature in Multitrack View.

"In the multitrack view record a metronome beat using a sharp sound such as a drumstick click. Set this track to output one in the track controls.

"Route the output of your sound card to the input using a patch cable. Be sure to mute the monitor outputs in your sound card controls to avoid damaging your equipment. The intention is to play track one and record the result to track two so ensure that device order (Options >> Device Order) is set correctly.

"Arm track two by pressing the R button in track contols and record a few second of the output of track one to track two.

"Set the playback cursor at the front of one of the clicks and use the Zoom To Selection button to zoom right in to the point where the beginning of each click is clearly visible.

"Right click over the waveblock in track two and choose Waveblock Properties from the right click menu. Adjust the offset until the waveforms line up exactly. The difference between the offset value before and after adjusting is the amount of latency. Move to Settings >> Device Properites >> Wave In and enter this value in the latency box."

----------------------------------------------------------------------

Alofoz [from our forum] describes the same technique a different way:

1. In edit view I created a 5 sec waveform with a pulse at about 2 sec, about 1 sec in length. There are several ways to do this, I used the DC bias adjust in the Amplify transform, set to 50%.

2. Insert into MT, track 1 and lock in time. Playback device for this track is 1/2.

3. In track 2, set the recording device to 3/4, left channel and arm the track.

4. Connect output 1 to input 3.

5. Start recording. At the start and end of the pulse a spike will be recorded in track 2.

6. Zoom in until you can clearly see the time difference between the start of the pulse in track 1 and the start of the spike in track 2. At this stage you should see the individual samples.

7. Switch the time format to samples for better accuracy.

8. Drag the mouse from the start of the pulse to the start of the spike. The time, i.e. the latency, will be indicated in the "length" box on the "sel" line in the "sel/view" window.

9. Move to Options >> Device Properties >> Wave In and enter this value (converted to mS) in the latency box.

10. I found that you need to close & restart CEP for this to take effect.

For my card recording at a sampling rate of 44100 I found the time difference to be 72 samples. This is 72/44100 S or 1.63 mS. If I don't use a time format of samples, it rounds the figure down to 1 mS.

----------------------------------------------------------------------

I used a combination of Richard Riley's method and Alofoz's method.

In track one, I recorded the metronome.

After recording it, I locked it in time and ran it out Output 1 into Input 3.

I recorded the metronome onto track two.

At first, I attempted to line the tracks up (which were off slightly) by using Richard Riley's method of right clicking on track two, selecting Wave Block Properties, and entering a value in the Time Offset box, but I couldn't get my tracks to line up this way so I switched over to Alofoz's method of switching the time format to samples and measuring from the start of the pulse to the start of the spike. The time indicated in the "length" box on the "sel" line was 155. The sample rate I was recording at was 48,000. I devided 155 by 48,000 and arrived at a value of 3.23. I entered this value into the Multitrack Latency Box on the Wave In page.

Now, why don't the metronome beats line up when I run out of Track 1 into Track 2? I was expecting once I entered this value in the Multitrack Latency Box for that to be the case. Can someone explain?

clothesburner · Location: USA

bump bump bump... come on, man, what's your setting?

DeluXMan · Location: Canada

mine is 0. Blush

Is that bad?

DeluXMan · Location: Canada

OK. I will remove my latency and advise. 8)

in the meantime... do you use a digital mixer or rack processor? Shock

Just in case it is in the loop some of the time and adding latency...

OK i routed the digital out to the digital in through a pair of Adats, rather than messing with the DI/O of the PC card, and to catch any latency in the Adat lightpipe daisychain, found a latency of 1029, which was succesfully removed by entering 1/[recording Fr. Hz.] times 1029 samples = .0214375 @48kHz. so i entered 21.4375 in this case. I had to use 'samples' and fractional ms. to get accurate enough. Hope this helps. Now all i have to worry about is my digital mixer.