Out of phase Audio

[Thope]

Hi all...

Just completed a mini camera test with the RED and my 744T.

Setup was similar to some other posts but i'll list it anyway.

416 plugged into sounddevices 442. 442 outputs into 744T and RED camera channel 1 at LINE level. Timecode o/p from 744t to timecode i/p RED.

Jam sync seemed to work straight away. Strangely the red doesn't display rolling frames until the camera itself rolls. Mins and seconds do roll when the camera is stopped.

In FCP we imported both audio from 744t and video files from RED
Frames are out by 2 frames as found by most other users.

I exported an OMF from FCP and imported into pro tools to listen to differences in audio quality. They actually sounded better then i expected from reading other peoples posts. Couldn't hear a significant difference at all.. I found the audio i/p at line level perfectly usable.

Here's the problem! When comparing the waveforms of the 744T audio and the RED audio they are completely phase reversed! I'm 100% sure this is not a problem with my cables as i've made them all myself. Has anyone else experienced this. I'll do more testing next week.

cheers


Trev

 

[ChristopherKenworthy]

Audio out of phase Image

Audio out of phase Image

I worked with Thope on the above, so here's a screenshot from FCP showing exactly what he means. This shows the Channel 1 Red Audio on top, and the 744t on the bottom. They are a mirror image of each other.

 

[ChristopherKenworthy]

It's a bit depressing that audio is so ignored on this forum. This has been up for a couple of days, and nobody has any input. This is, from what I can tell, a pretty major issue. If this is an in-camera wiring problem, that's huge. If it's one cable, it's minor. But we need to know.

 

[Georg Misch]

Oh yes, audio issues are always a bit neglected. I'll test this on my camera as soon as I can, it could be wrong wiring on the adapter cable as well, did you check that?

Georg

 

[Stuart English]

Audio displayed FCP

Audio displayed FCP

I worked with Thope on the above, so here's a screenshot from FCP showing exactly what he means. This shows the Channel 1 Red Audio on top, and the 744t on the bottom. They are a mirror image of each other.

Looking into it guys...

 

[Finner]

It's a bit depressing that audio is so ignored on this forum. This has been up for a couple of days, and nobody has any input. This is, from what I can tell, a pretty major issue. If this is an in-camera wiring problem, that's huge. If it's one cable, it's minor. But we need to know.

I can see in your diagram what "phase reversed" is but I don't understand what the difference is in what you actually hear? Sorry, I am kust a bit of an audio newbey.

 

[Adrian T.]

I can see in your diagram what "phase reversed" is but I don't understand what the difference is in what you actually hear? Sorry, I am kust a bit of an audio newbey.

As long as you only have a single mono recording it doesn't matter. But as soon as you combine channels (multichannel setups, mixing of several mono sources etc.) it can be disastrous.

 

[Elizabeth Lowrey]

In addition to the phase issue, there appears to be a new DC offset (negative) as well. IIRC, the DC offset others discovered before was positive.

ETA: After thinking about it a minute, something's weird because the DC offset is present in both channels. Wasn't the bottom (R) channel recorded on another device?

 

[Adrian T.]

In addition to the phase issue, there appears to be a new DC offset (negative) as well. IIRC, the DC offset others discovered before was positive.

ETA: After thinking about it a minute, something's weird because the DC offset is present in both channels. Wasn't the bottom (R) channel recorded on another device?

How can you see a DC offset in this small screenshot? Just in case: the beveled line you see there is not supposed to be centerpoint of the waveform.

 

[Elizabeth Lowrey]

How can you see a DC offset in this small screenshot? Just in case: the beveled line you see there is not supposed to be centerpoint of the waveform.

I don't use FCP, so I guess I mistook the beveled line for the midline. I use Sony Vegas, where there is a thin line running at the zero point of the waveform.

What does that line represent?

 

[Adrian T.]

I don't use FCP, so I guess I mistook the beveled line for the midline. I use Sony Vegas, where there is a thin line running at the zero point of the waveform.

What does that line represent?

I have no idea. Never thought about that. I suppose it's just a design element. The same beveled line also appears in video tracks.

 

[Elizabeth Lowrey]

Back to the topic post, could ChristopherKenworthy or Thope post short clips of each sample (RED-recorded and Sound Devices-recorded)? Would love to compare the two myself.

 

[ChristopherKenworthy]

Audio Clips

Audio Clips

Back to the topic post, could ChristopherKenworthy or Thope post short clips of each sample (RED-recorded and Sound Devices-recorded)? Would love to compare the two myself.

Thope is getting married today, so I've done what I can. Rather than post the RD3, which is huge, I extracted the audio from the QT. There's also the audio from Thope's device. The latter is much longer, as he rolled way before I did. You'll hear a lot of fan noise - it's my Mac Pro in the background, not the Red One. You'll also hear me drop the Clapper, but the less said about that the better.

From Thope's Sound Recording equipment
http://www.christopherkenworthy.com/RED-TESTT13_1.WAV

From the camera. (Extracted from the QT)
http://www.christopherkenworthy.com/REDTEST13ExtractedQT.mov

 

[Craig Bowman]

Hi all...

Just completed a mini camera test with the RED and my 744T.

Setup was similar to some other posts but i'll list it anyway.

416 plugged into sounddevices 442. 442 outputs into 744T and RED camera channel 1 at LINE level. Timecode o/p from 744t to timecode i/p RED.

Jam sync seemed to work straight away. Strangely the red doesn't display rolling frames until the camera itself rolls. Mins and seconds do roll when the camera is stopped.

In FCP we imported both audio from 744t and video files from RED
Frames are out by 2 frames as found by most other users.

I exported an OMF from FCP and imported into pro tools to listen to differences in audio quality. They actually sounded better then i expected from reading other peoples posts. Couldn't hear a significant difference at all.. I found the audio i/p at line level perfectly usable.

Here's the problem! When comparing the waveforms of the 744T audio and the RED audio they are completely phase reversed! I'm 100% sure this is not a problem with my cables as i've made them all myself. Has anyone else experienced this. I'll do more testing next week.

cheers


Trev

I hope you realize that the wiring of Red's supplied standard XLR to mini XLR phase reverses the connection back to normal. This means you can't do a pass through if you make your own cables.

 

[Elizabeth Lowrey]

I hope you realize that the wiring of Red's supplied standard XLR to mini XLR phase reverses the connection back to normal. This means you can't do a pass through if you make your own cables.

This is related to Anders Holck's thread here about phase reversal in the RED XLR to miniXLR cables. The question is, why is phase on the RED such that it has to be "reversed back to normal" in the cables?

 

[Thope]

Whats really worrying here is the resistor bridge talked about in Anders post..

Does someone from RED want to explain firstly why it is neccesary.. secondly why it not mentioned in the manual.. I had an audio snake made while i've been away thats probably not going to work! thats infuriating!

Maybe Chris could clear this up but the cable we used for that test was the one supllied with the camera.. i think its the RED one.

Trev

 

[ChristopherKenworthy]

Whats really worrying here is the resistor bridge talked about in Anders post..

Does someone from RED want to explain firstly why it is neccesary.. secondly why it not mentioned in the manual.. I had an audio snake made while i've been away thats probably not going to work! thats infuriating!

Maybe Chris could clear this up but the cable we used for that test was the one supllied with the camera.. i think its the RED one.

Trev

Yep, the one we used for the test was the RED one.