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Is timecode output by DVD players?

Discussion in 'Embedded' started by no-reply-john, Jan 23, 2007.

  1. Hi,
    I want to extract timecode from a DVD player video output, and use it
    to trigger events and to control various loads. I plan to build a PIC
    based unit to do this, but I can't find out how widely available a
    timecode signal output might be across the extensive DVD player market.

    Anyone know how often is timecode present on commercial DVD movies?

    If it is available, and output by the DVD player, on which connector,
    S-Video or SCART, or both?

    Is it VITC (vertical interval time code) - I have found a chip to
    decode this - ICS2008b

    There are a few pro-sumer DVD players with RS232 ports, but even for
    these I can't determine whether a timecode signal is available. In any
    event I would prefer to use 'ordinary' players.

    Thanks for any help.

    J
     
    no-reply-john, Jan 23, 2007
    #1
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  2. no-reply-john

    larwe Guest

    I would say, likely never. The DVD MPEG-2 data stream only includes the
    actual picture (plus overscan, of course). If there is any timing
    information in the analog signal output, then it is being inserted by
    the DVD player itself; it's not part of the software you're playing.
     
    larwe, Jan 24, 2007
    #2
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  3. no-reply-john

    Tom Guest

    I would be very surprised if any commercial DVD movies had it.
    VITC is used primarily in analog-only recording systems or broadcasts. In
    digital recordings like DVD or mini-DV the timecodes are recorded as part of
    the binary data stream so there is no need to put them into the vertical
    blanking interval of the video.
    Your best bet might be to try to extract a relative simestamp from the digital
    audio stream. If your DVD player can output raw audio through the SPDIF output
    (either optical or coaxial cable) then there might be a timecode in there. If
    it only outputs PCM or has no digital audio output at all then you're out of
    luck. I'm not even certain if any of the verious raw streams like AC3 or DTS
    would contain an absoulute timestamp. Start by looking at IEC61937 which
    describes how the raw audio streams are sent over SPDIF. Then check the
    standards that describe AC3 and DTS to see if the frames contain a timestamp.
    MPEG 1 Layer 2 frames do NOT contain timestamps in the headers so if you
    happen to get a DVD that uses only this audio format then you're also out of
    luck.

    --Tom.
     
    Tom, Jan 24, 2007
    #3
  4. I would be very surprised if any commercial DVD movies had it.
    VITC is used primarily in analog-only recording systems or broadcasts. In
    digital recordings like DVD or mini-DV the timecodes are recorded as part of
    the binary data stream so there is no need to put them into the vertical
    blanking interval of the video.
    Your best bet might be to try to extract a relative simestamp from the digital
    audio stream. If your DVD player can output raw audio through the SPDIF output
    (either optical or coaxial cable) then there might be a timecode in there.
    --Tom.[/QUOTE]

    Hi Tom, I was browsing the SPDIF spec, late last week, for something
    I'm working on and there is no obvious time stamp in it. It's a very
    simple protocol, Checkout CS8406 data sheet from Cirrus or ebu.ch for
    the official docs

    I would suggest that the easiest(?) way would be via an RS232 control,
    pause the sequence to played, send play command, and count the frame
    pulses in the video (LM1881 etc). It may not be that accurate or
    repeatable . A bit like control track video editing, before LTC became
    popular


    martin
     
    martin griffith, Jan 24, 2007
    #4
  5. The SPDIF output from a CD player does typically include the subcode channels from the disc, one of
    which ( Q I think) includes the timecode - many years ago I made a box to extract and display it.

    I just tried plugging this box into the SPDIF out on a DVD player, and even with an audio CD I don't
    get any time info - I suspect that as it's a DVD player it has more digital processing between the
    disk and the socket, and the subcode doesn't make it through - this may vary between players I
    suppose.
     
    Mike Harrison, Jan 24, 2007
    #5
  6.  
    martin griffith, Jan 24, 2007
    #6
  7. Thanks all for your suggestions. I'm currently looking at using a pro
    player with an RS232 port - that is as soon as I can find one in the UK
    :)

    J
     
    no-reply-john, Jan 24, 2007
    #7
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