Phase shifts correction implementation !?!

Bug report and feature request
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Phase shifts correction implementation !?!

Post by forart.eu » Fri Nov 14, 2008 9:59 pm

I wanna revive here an IMHO old but interesting discussion.

The problem is to find the best way to convert stereo to mono.

I discovered this, at that time:
If recordings are converted from stereo to mono using traditional methods, some sounds will get lost in the process, making the result sound less 'full' or even distorted. FlatStereo, a technology created especially for Weird Titan Radio, completely solves this problem.

The sound is converted to mono in two steps:
  • Remove phase shifts between left and right channel.
    This results in a recording where each channel sounds exactly the same as it did before, but a part of the stereo effect is lost. (The phase for the left and right channel is equalized)
  • Convert the two channels to one channel using traditional stereo-to-mono methods (similar to pressing the 'MONO' button on an amplifier).
    This results in a mono signal, where all sounds from the original recording are still present.
I can't find any open source tool to remove the phase shifts, so it would be great to implement it in MC.

Dunno if useful, but the only windows tool available to achieve this is the adbandoned Advanced Audio Corrector by Dmitry Sknarev that claims:
If during manufacturing of an audio soundtrack there is an analog stage (recording to a tape or to a gramophone disk in an analog mode), an inevitable consequence will be the appearance of a phase shift between stereo-channels. In an uncompressed soundtrack these distortions are inaudible but only become apparent when stored in a compressed format (for example in MP3 Joint Stereo). These distortions are heard as unpleasant high-frequency sounds.

Advanced Audio Corrector allows you to save a soundtrack (WAV-file) from these distortions for the subsequent coding to MP3 format.

Advanced audio corrector v2.0 allows to remove phase distortions in high-quality audio files (WAV, 16-bit Stereo) before coding to a format MP3. The program works in a batch mode.
Hope that helps (or at leas inspires). :roll:
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Post by stanley » Sun Nov 16, 2008 11:40 pm

Thanks. But that software is a trial. Wouldn't it expire?
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Post by forart.eu » Wed Nov 19, 2008 9:17 pm

stanley wrote:Thanks. But that software is a trial. Wouldn't it expire?
Of course, it's just an example and is not open source.

I'm claiming that would be great to have an open source phase shift corrector tool... :roll:
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Post by forart.eu » Sun Dec 07, 2008 11:43 am

Freeware (closed source) solution found:

Stereo Tool - Command line version
VERY useful for converting to MONO, the resulting sound can be downmixed to mono without any distortion or loss of sounds, which occur in normal stereo to mono conversion. This creates a much fuller and undistorted mono sound.
8)
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Post by stanley » Mon Dec 08, 2008 3:12 am

It also supports stdin/stdout and input and output so it can be integrated more easily.
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