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Downmixing dolby 5.1 to stereo problem.

Discussion in 'High resolution audio' started by kenders, May 12, 2004.

  1. kenders

    kenders Member

    May 12, 2004
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    I am downmixing 5.1 into stereo, using the LoRo option as I want to create an 5.1 ac3 stream where the matadata flags will force the stereo downmix level of the surround and centre channels to a specific value. My problem occurs because I cannot (not through lack of trying!) find any software that might be able to do this, or . I was wondering if there any programs that would be able to change metadata values within a bit stream or must the stream be re-encoded from scratch to do this. And if which programs might give control over these flags when encoding or changing the metadata.
    Any help would be greatly appreciated!
  2. wilkes

    wilkes Regular member

    May 31, 2003
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    Okay - firstly this is a high res forum, and Dolby Digital is far from high res. but I will have a go for you anyway..
    5.1 Dolby Digital will automatically downmix into stereo when played on a stereo system. Do not worry about the Lo/Ro options.
    The metadata flags are all there when you encode with a Dolby Labs encoder - you can choose one of 3 settings for centre channel - no attenuation, 0.707 of original and 0.5 of original. You get similar options in the Surround channels as well.
    I use the Nuendo Dolby Digital Encoder, as this is a genuine licensed encoder. The trouble with most of the free ones is that they are not Dolby approved, and are AC3 "clone" encoders.
    Once the file is encoded, you cannot change the metadata. The only recourse is to re encode the file from scratch. Dolby Labs may be able to alter the metadata embedded in the bitstream, but we cannot. Period.
    The software you need for this AFAIK is one of 2.
    The Nuendo DDE, which only encodes from Nuendo, or the SurCode DDE which has full control over the metadata too. Bad news is these are very expensive. Nuendo DDE is €1500 and the SurCode is about the same.
    Or you could use Dolby Labs hardware.

    If you are lucky enough to be able to afford Scenarist, the Daikin DDE included will also let you set the downmix flags.

    Lo/Ro will never give you a surround option, as it is a stereo format hence "o" as in "only".

    Hope this helps.
    If there are any more questions can you PM as this really is not the right forum for this.

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