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MP3...in Surround Sound

Posted by Hemos on from the THX-We're-Coming-For-You dept.

A number of people sent in the latest news from the fine folks at Frauhofer that they are expecting to have surround sound working for MP3s by July. The details are pretty sketchy in the article, but supposedly it won't be much more space per MP3s, and existing players will work with it.

5 of 247 comments (clear)

  1. conversion by tomocoo · · Score: 5, Informative

    You couldn't convert your mp3's to surround because the source is stereo... if you want surround just run it through PL2 for pretty good on the spot surround sound.

  2. Nothing to see here. by sokk · · Score: 5, Informative

    Ogg Vorbis have had support for this for some while.

    What I'm not sure of is if the support for "joint" surround is there. (Like joint stereo, only for surround)

    Who wants to use a proprietary sound format, when they can use a much more appealing open format.

  3. Vorbis can already do this :P by Anonymous Coward · · Score: 5, Informative

    Vorbis is also intended for lower and higher sample rates (from 8kHz telephony to 192kHz digital masters) and a range of channel representations (monaural, polyphonic, stereo, quadraphonic, 5.1, ambisonic, or up to 255 discrete channels)

    http://xiph.org/ogg/vorbis/doc/vorbis-spec-intro.h tml

  4. Some Additional Tech by Effugas · · Score: 5, Informative

    Here's the deal.

    By far, the most popular algorithm in use for surround sound encoding is Dolby's AC3 (I can say this, because it's on pretty much every DVD, and nothing comes close to its penetration even in the audio space -- not even DVD-Audio). AC3 itself is a pretty fascinating codec; one of the more interesting things about it is that each additional channel requires less and less bandwidth to tack on. This is because there tends to be massive correlation between channels -- either the same sound is coming from multiple directions, or a sound is coming from one direction and all the others are silent, or some combination therein. AC3 encodes this quite efficiently, and thus gets really high quality surround sound in surprisingly few bits.

    I suspect they're engineering a similar mode for MP3 -- hopefully something a little nicer than Joint Stereo, which basically works by doing a mono mix and specifying which frequencies are louder in which channel. No, this doesn't work very well. Concievably, we could see something like VBR on a per-channel basis, but I suspect this would cause existing decoders to collapse. I do believe it's possible to place extra data between MP3 granules; I suppose they'll get their backwards compatible surround mode worked into there.

    --Dan

    1. Re:Some Additional Tech by mudrat · · Score: 5, Informative
      I suspect they're engineering a similar mode for MP3 -- hopefully something a little nicer than Joint Stereo, which basically works by doing a mono mix and specifying which frequencies are louder in which channel. No, this doesn't work very well. Concievably, we could see something like VBR on a per-channel basis, but I suspect this would cause existing decoders to collapse. I do believe it's possible to place extra data between MP3 granules; I suppose they'll get their backwards compatible surround mode worked into there.

      That is precisely how MP3 mid side stereo mode works. It takes the sum of the channels (the common sounds) and encodes with a higher bitrate than the sounds that differ. Joint stereo is a mode where the encoder decides whether to use Mid-Side or true stereo for each frame depending on the stereo seperation. Joint stereo gives better results than true stereo at the same bitrate.

      The mode you describe (mono with frequency info) is Intensity Stereo which few encoders even support.