Audacity - Noise Removal & 2.0 mono tracks

[ecc]

If a 2.0 mono track has two channels of the same information, would it be faster (after having converted the ac3 to WAV) to delete one of the tracks, perform the noise removal on the remaining track and just duplicate the track to make it 2-channel again?

I noticed that in both normalizing and in noise removal that (at least in the illustration of the peaks in Audacity), that it seems to perform actions on one channel and then the other. Does having done the first channel make it faster to perform the same action on the second channel or do the filters just re-analyze the audio over again on the second channel?

[jman98]

Excellent question. I don't use Audacity (I use Cool Edit), but I can tell you that what you say (doing one channel at a time) is exactly how Cool Edit does it. If nobody knows for sure, I'd say try only doing one channel. It should be faster. Logically, how could doing one channel instead of two not be faster?

[ecc]

Yeah, I guess it would be shorter logically. It takes about 20 minutes (longer if I'm doing other things on the computer) to perform noise removal on a 2.0 mono feature length track.

[SLK001]

You are assuming that the noise is identical on both channels (although it quite possibly is). If the channels are ident, then the delete-reduce-duplicate would be quicker - neither program has any idea as to the content of the individual channels being identical, so it will treat them each as unique.

[ecc]

I'm assuming that when the transfer was done, they just duplicated the same track to two channels rather than a 1.0 mono track because that seems to be standard. I guess two tracks could pick up non-identical noise as part of generational loss during some sort of copying but I'm also assuming that since it is dual mono, there is not one sound on one channel (that belongs there - i.e. not tape hiss, pops, or clicks) that isn't also on the other channel.

[jman98]

The tracks should just be duplicated. Back in the early days of DVD, Criterion did release some DVDs with 1.0 mono, but even they moved away from it to 2.0. There seems to be a consumer preference for 2.0 mono as I guess it sounds more natural coming from those locations than a single central speaker as in 1.0 mono. I can't imagine why anyone would not simply duplicate a single track to get 2.0 mono.

[ecc]

I think Criterion still does 1.0 mono tracks. The most recent discs I've bought from them (YOJIMBO/SANJURO, the HIROSHI TESHIGAHARA set) still mention that the 1.0 signal is decoded to the center channel in 5.1 systems and say that viewers can switch to 2-channel playback optionally (I think a 1.0 track would decode to left and right if you just have 2-channel playback if your DVD player doesn't have much in the way of setup (my player's setup allows you to playback dual mono or place it in the left or right speaker).

I'm thinking Criterion does 1.0 tracks because it allows them to dedicate more of the target bitrate to the video portion of the film.

[olyteddy]

Actually I'd think you'd want to clean one track and duplicate to ensure that your mono is pure. If there were a difference in the original two tracks that would eliminate it, whereas the noise reduction process might increase the difference.