Audio 90 degrees out of phase

I recently had a post house master a tape for me, it was edited in 2 channel stereo. I sent off to the station to show, and they rejected the tape. They said the audio was 90 degrees out of phase. What the heck does that mean? Why would a post house get this wrong?

Analog out, mis-wired, better to lay off SDI

With the audio out of phase 1 track will cancel another, hence muted sound.

Can you explain what 'better to lay off SD' means?

It means output using serial digital with embedded audio.

SDI- serial digital interface. SDI is a professional tape signal that carries an uncompressed SD video signal and up to 8 tracks of embedded audio signal.

>They said the audio was 90 degrees out of phase

This means that there is a delay in the signal on one track, and you a phase cancellation issue. Basically when 2 identical waveforms are played out in phase, you'll have a +3.02 dB increment in your signal. When one one track is out of phase, one signal will cancel out the other, resulting in silence.



www.strypesinpost.com

Did they say 90 degrees? Normally audio that has one channel out of phase will have that channel ~180 degrees out. That is a more or less common problem in analog audio. Most the the time is is caused by reversing the hot an common lead in a cable, or hitting the phase reverse switch on a console.

90 degrees is far less common. It is possible, but it implies a time delay. Maybe having two mics on set that both here a single talent from different distances, and are then mixed together. Or adding a delay to only one channel of the audio.

I suspect that the technician that told you that may have inserted the "90 degree" bit just to pad his part. If not ask how they measured the delay. I would be very interested to know how that is done. The only way I know involves an oscilloscope and some math. Not a normal TV station test.

That is what they said: 90 degrees. The post house confirmed that the problem was due to a cable from the Digibeta deck to the Beta SP deck. What exactly happened, I don't know.