Will any DVD player play an all-Dolby Digital disc?

Discussion in 'Archived Threads 2001-2004' started by Norm Strong, Aug 8, 2001.

  1. Norm Strong

    Norm Strong Stunt Coordinator

    Joined:
    May 7, 1999
    Messages:
    142
    Likes Received:
    0
    A DVD will hold about 20 hours of Dolby Digital audio, sampled at 448kb/s. As far as I know there are no such discs in existence. My question is: Could there be? Will any DVD player go slowly enough so that it takes 20 hours for one pass? Of course it could read the disc in burst mode, filling the buffer on the fly.
    IOW, does anyone here know more about this than I do?!?
    ------------------
    Norm Strong ([email protected])
     
  2. Dan Hitchman

    Dan Hitchman Cinematographer

    Joined:
    Jun 11, 1999
    Messages:
    2,713
    Likes Received:
    0
    I doubt it. DTS beat Dolby to it with DTS CDs (although, at regular playing times of up to 80 minutes), and most audio engineers in the music arena seem to like DTS over Dolby Digital if given a choice.
    Now that DVD-Audio and SACD are out, this even further drives the nails into a DD music disc's coffin.
    Dan
    ------------------
    Stop HDCP and 5C-- Your rights are at risk!
     
  3. Adam Barratt

    Adam Barratt Cinematographer

    Joined:
    Oct 16, 1998
    Messages:
    2,343
    Likes Received:
    1
    Real Name:
    Adam
    This is quite possible, and every DVD player should be able to play these discs. Although I've never heard of a disc containing only Dolby Digital audio, several discs (The Mummy for example) have included 'hidden' soundtracks/film scores using this feature (Dolby Digital audio with no/static video).
    Adam
     
  4. Craig F

    Craig F Second Unit

    Joined:
    Jul 5, 2001
    Messages:
    276
    Likes Received:
    0
    Real Name:
    Craig
    DVD Discs spin at a constant rate. You can't slow them down to make them play longer. A dual layer disc can hold roughly 4 hours of video, if I remember correctly. I would assume that this 4 hours is the time it takes for the laser to traverse the entire disc. Since DVD supports multiple sound tracks, if you had 5 tracks 4 hours long, this would give you the 20 hours you're after. There may be other technical issues that would make this unfeasible though.
     
  5. James Q Jenkins

    James Q Jenkins Stunt Coordinator

    Joined:
    Sep 24, 2000
    Messages:
    167
    Likes Received:
    0
     
  6. Craig F

    Craig F Second Unit

    Joined:
    Jul 5, 2001
    Messages:
    276
    Likes Received:
    0
    Real Name:
    Craig
    Very good point, DVD does support variable bitrate. But I have always heard that it spins at a constant rate. DVD-ROM speeds (like CD-ROM) are specified by 1x, 2x 4x etc. 1x being the DVD-Player spin rate. Any DVD experts out there know the scoop?
     
  7. Maksim Yankovskiy

    Maksim Yankovskiy Auditioning

    Joined:
    Jan 16, 2001
    Messages:
    3
    Likes Received:
    0
    I think the VBR (variable bit rate) is not relevant to the disk speed. VBR is how the data is encoded/decoded not how it is read. VBR data is read in exactly the same way any other data is read, they are just processed differently (becuase each sample may contains different number of bits).
    Moreover, the disk spinning speed has nothing to do with the amount of time it takes the laser to move from the inner edge of the disk to the outer, and back.
    The laser is controlled by the controller hardware/software, which moves the laser head and instructs the laser to read certain sectors of the disk. If needed (for example, to access the disk's TOC - table of content), the laser may have to be moved to the inner edge of the disk, and then back again, and so on. In many cases the data are not recorded sequentially on the disk.
    So, as long as the player's aware of how to read the disk, the laser may have to be moved back and forth multiple times in order to read certain areas of the disk.
    == Maksim
    ------------------
    == Every great accomplishment was once considered impossible ==
     
  8. Dennis Nicholls

    Dennis Nicholls Lead Actor

    Joined:
    Oct 5, 1998
    Messages:
    8,890
    Likes Received:
    329
    Location:
    Boise, ID
    Real Name:
    Dennis
     
  9. Craig F

    Craig F Second Unit

    Joined:
    Jul 5, 2001
    Messages:
    276
    Likes Received:
    0
    Real Name:
    Craig
    I knew there were two types of disc spins CLV and CAV. I wasn't sure which DVD used, thanks for the clarification.
    It also sounds like DVD has to jump around a bit during playback, unlike CDs. I figured it would have to do something like that to support multiple audio tracks etc.
     

Share This Page