An interesting phase issue

reidc · 7th June 2006

I've mixed a lot of tv/film/music in 5.1 & 2.0, and I've finished on a lot of stuff that others have started, but here's an issue I must say I surprisingly haven't come across before. A job walks in the door that is essentially conforming 7 musics tracks to picture. I don't know the provenance of the job (where it was recorded or mixed, etc) but I DO know who mastered the material (a fairly high end/high profile place & mastering engineer in New York).

There are 2 versions of each track: 2.0 (film/tv/dvd lingo for 2 channels of audio, however otherwise configured, i.e. stereo, dual mono, LtRt, etc), in this case simple 2 channel left/right stereo, and a 5.1 version. The 5.1 version makes lots of use of the center & surround channels, but it's clear that L/R is still king, at least in this production. There are sections where there's ONLY L/R on the 5.1 version, for example. When I match the tracks up against the stereo version of the material, it's immediately clear that the L/R in the stereo & the L/R in the 5.1 are phase reversed from each other.

For some reason, this job is a bit politically sensitive, so no one wants to go banging on the mastering house's door to ask what happened. In the end, my client had me provide 2 versions: one with phase as-is, the 2nd with phase reversed on all 6 channels, matching the 2.0 which, according to their "way of doing things", is correctly in phase due to the fact that the first samples of the first cut in the series start out as positive phase, as opposed to the 5.1 L/R/ tracks for the same cut, which start out in negative phase.

Now, the client is afraid to use the phase-modified version of the 5.1 I provided (even though they asked for it) because they're afraid the mastering house will find out & scream at them. Anyone out there come across something like this, and if so, how did you handle it from a technical and/or political perspective?

bob katz · 8th June 2006

Quote:

Originally Posted by reidc

I've mixed a lot of tv/film/music in 5.1 & 2.0, and I've finished on a lot of stuff that others have started, but here's an issue I must say I surprisingly haven't come across before. A job walks in the door that is essentially conforming 7 musics tracks to picture. I don't know the provenance of the job (where it was recorded or mixed, etc) but I DO know who mastered the material (a fairly high end/high profile place & mastering engineer in New York).

There are 2 versions of each track: 2.0 (film/tv/dvd lingo for 2 channels of audio, however otherwise configured, i.e. stereo, dual mono, LtRt, etc), in this case simple 2 channel left/right stereo, and a 5.1 version. The 5.1 version makes lots of use of the center & surround channels, but it's clear that L/R is still king, at least in this production. There are sections where there's ONLY L/R on the 5.1 version, for example. When I match the tracks up against the stereo version of the material, it's immediately clear that the L/R in the stereo & the L/R in the 5.1 are phase reversed from each other.

SNIP. Is this something audible or just visible in the waveform? It seems to me to be academic. I suspect the mastering house used some analog processing with pins 2 and 3 reversed or a device that reversed polarity and "shame on them". It's really not a problem unless it's audible, and most times a simple polarity reversal in this kind of material is not very audible at all and no one can agree on what sounds better.

So the only time it's an issue is if someone combined or folded down or up some of the 2 channel material with some of the 5.1. And that isn't going to happen. I think it's a non-problem problem. The house that's afraid about the polarity-reversed material should only be concerned that it's a generation down (as an academic argument), not that it's audible. You could prove it to yourself if the two versions COMPLETELY cancel against one another with no residue. If so, don't lose any sleep over it, god there are far worse problems we encounter in a day.

How could the mastering house possibly tell? Are they going to put up the waveform and notice? Can this phase reverse actually be heard by even the most critical observer? Even when switching sources?

BK

reidc · 8th June 2006

in my explanatory email to my client, I referred to the problem, in fact, as "largely academic" and suggested that the only way it would be a problem is if the 2.0 & 5.1 were put up together, and that this was unlikely to happen, etc. So your points are well taken, as these had been my thoughts. As to whether the reverse can be heard, I think the answer would be no.

7th June 2006	#1
reidc Gear interested Joined: Mar 2006 Posts: 22 Thread Starter	An interesting phase issue I've mixed a lot of tv/film/music in 5.1 & 2.0, and I've finished on a lot of stuff that others have started, but here's an issue I must say I surprisingly haven't come across before. A job walks in the door that is essentially conforming 7 musics tracks to picture. I don't know the provenance of the job (where it was recorded or mixed, etc) but I DO know who mastered the material (a fairly high end/high profile place & mastering engineer in New York). There are 2 versions of each track: 2.0 (film/tv/dvd lingo for 2 channels of audio, however otherwise configured, i.e. stereo, dual mono, LtRt, etc), in this case simple 2 channel left/right stereo, and a 5.1 version. The 5.1 version makes lots of use of the center & surround channels, but it's clear that L/R is still king, at least in this production. There are sections where there's ONLY L/R on the 5.1 version, for example. When I match the tracks up against the stereo version of the material, it's immediately clear that the L/R in the stereo & the L/R in the 5.1 are phase reversed from each other. For some reason, this job is a bit politically sensitive, so no one wants to go banging on the mastering house's door to ask what happened. In the end, my client had me provide 2 versions: one with phase as-is, the 2nd with phase reversed on all 6 channels, matching the 2.0 which, according to their "way of doing things", is correctly in phase due to the fact that the first samples of the first cut in the series start out as positive phase, as opposed to the 5.1 L/R/ tracks for the same cut, which start out in negative phase. Now, the client is afraid to use the phase-modified version of the 5.1 I provided (even though they asked for it) because they're afraid the mastering house will find out & scream at them. Anyone out there come across something like this, and if so, how did you handle it from a technical and/or political perspective?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread starter	Forum	Replies	Last Post
Setup issue regarding Digi 192 and Apogee DA16x Setup issue:Digi192 and Apogee DA16x	Redsandblu	Music computers	4	19th February 2010 11:58 PM
Linear Phase and Minimum Phase switch?	Cojo	Mastering forum	6	9th September 2006 10:19 PM
interesting little studio client issue... (long post)	karatemanjohnny	The Moan Zone	13	29th January 2004 07:17 AM
G5...This should be interesting	Dean Landon	Music computers	1	21st June 2003 09:58 PM

8th June 2006	#3
reidc Gear interested Joined: Mar 2006 Posts: 22 Thread Starter	in my explanatory email to my client, I referred to the problem, in fact, as "largely academic" and suggested that the only way it would be a problem is if the 2.0 & 5.1 were put up together, and that this was unlikely to happen, etc. So your points are well taken, as these had been my thoughts. As to whether the reverse can be heard, I think the answer would be no.