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2nd July 2014, 14:51 | #1 | Link |
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Reencoding AC3 - Phase Shift
Hi there,
I have a question about the following workflow: Decode AC3 to WAV - some Changes - Encode WAV to AC3 Should I enable "90 degree phase shift" when encoding the new AC3 or have I then a "180 degree phase shift"? What about DTS to WAV - some Changes - Encode WAV to AC3? Thanks a lot Last edited by RRAH; 2nd July 2014 at 14:55. Reason: supplement |
3rd July 2014, 08:11 | #3 | Link |
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I believe if one uses phase shift he should refer to anything else than 180° (or 90°). When a sound engineer hears of phase shift he would think also on temporal displacement of a particular spectrum (say trebles) vs another particular spectrum (eg bass) - because this plagues analogue gear. He would never think of reversed phase (or antiphase).
180° is the reverse phase in other words when the sound of one channel is in antiphase to the other ones (for multiple channels read combinations of). This is mainly due to wrong cabling (for analogue sounds) or wrong starting point for digital synthesised sounds. Anyway, a phase difference of max. 90° (between bass and trebles or between channels) is allowed, provided it serves a purpose (eg the phase difference between channels emphasis the stereo/spatial effect). In other words 90° shifting renders (or cancels ) a stereo effect, a phase shift of 180° makes almost no difference (see below). I am not aware of audio tools within purchasing power of an individual that would change the phase in the musician's understanding - because such a tool would remove cinavia as well . BTW, phase inversion is almost inaudible. How did you find you have one (and therefore need to alter it)?
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3rd July 2014, 13:16 | #4 | Link | ||
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Dolby Digital Professional Encoding Guidelines
http://www.beussery.com/pdf/beussery.dolby.pdf (c) 2000 Dolby Laboratories Inc Quote:
http://www.soundonsound.com/sos/dec0.../surround5.asp Quote:
Last edited by raffriff42; 3rd July 2014 at 13:23. |
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8th July 2014, 15:05 | #5 | Link |
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IMHO this is metadata problem at this stage as downmix type (Lo/Ro or Lt/Rt was selected at source encoding) so to not change anything it is better to just copy metadata.
Selecting particular downmix mode is done anyway in reference to the decoder mode (RF/Theater etc) - there is lot implications to additional processing for such prepared audio. |
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