DD 5.1 downmixed to 2-channel

Discussion in 'Archived Threads 2001-2004' started by Mike Wilhoit, Jul 27, 2001.

  1. Mike Wilhoit

    Mike Wilhoit Auditioning

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    I just have a 'primitive' 2-channel stereo amp (1980s JVC model, 100 Watt/channel) I use for TV/home theater purposes. I'm wondering about some things i've noticed with DD 5.1 DVDs using this amp and my Pioneer DV-333 player.
    Basically, music on DVDs like '2010', or 'Charlies Angels', or other musical passages on DVDs in DD 5.1, often "doesn't sound right" on my 2-channel stereo. It seems like the 5.1 -->2-channel downmixing is losing or muddying some of the sound (especially high freqs), for lack of a better description. If the disc has a 2-channel soundtrack available, then music usually sounds much better using that soundtrack than music on the 5.1 soundtrack. Of course many DVDs only have 5.1 with no 2-channel track.
    Other sound effects, dialogue etc. seem livable with 5.1 but music just doesn't seem to downconvert well. Is this 'normal' for all DVD players, or do some players downconvert 5.1 sound to 2-channel better than others?
    Another issue, which may or may not be related to downconversion, sometimes DVD sound just feels more compressed than it should. Dialogue is a bit fuzzy & unclear compared to regular cable TV or VHS. Like listening to someone's voice on on a cheap phone, it seems to filter out subtle tonalities and makes the audio a miniscule bit more difficult for my brain to recognize. (Of course I'm also one of those people who think CD's sound "sampled" compared to a turntable...but that's another story...)
    Thanks for any replies...
     
  2. Roger Dressler

    Roger Dressler Stunt Coordinator

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    The downmixing process in virtually all DVD players turns on the DRC (dymnanic range control) function of Dolby Digital. This allows the downmix to happen without peak overload as the signals are added together. There is no frequency rolloff of bass/treble, but the LFE signal is not included in the downmix. I would not expect this to affect the music so much as you report.
    One suggestion to try (if your player allows it) is to select the "stereo" or "normal" downmix as opposed to the "surround" downmix. Not all players offer this option, and default to surround mode. The stereo downmix might seem nicer in stereo playback as it does not phase encode the surrounds. But the dynamics will be just the same as before. The only way to hear the full dynamics is to use a Dolby Digital surround decoder or a DVD player with 5.1-ch analog outputs.
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    Roger Dressler
    Dolby Laboratories
     
  3. Jon D

    Jon D Stunt Coordinator

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    I think the biggest problem is that it is creating a pro logic mix on the fly. This is naturally going to result in some funkiness. Pro logic DVD tracks are encoded using a 4 channel master whereas the downmix has to create and encode a mix using a 5.1 master, all without any human intervention. Some DVD 5.1 tracks are altered so the downmix sounds better, but even then, it usually is no match for a hand made pro logic track. Your best bet in this situation is to stick to the 2.0 track, if available.
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    Gee, I hope this doesn't lower your opinion of me
     

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