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What is the format on our dvds!?

Discussion in 'Projectors, Screens & Video Processors' started by buns, Feb 7, 2004.

  1. buns

    buns
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    I dont know that this is necessarily the place to ask, but I cant think of a better forum.

    I have been doing a bit of reading up on things video related. Whilst I have come across many fascinating bits of info, there is still much confusing me. The biggest thing is on our video standards. Whilst most people are happy enough to simply state PAL or NTSC, this really is rather ambiguous. So, what are we actually using on a dvd? Given that all info i find on and PAL/NTSC/SECAM formats actually include audio standard, i wonder whether we are actually correct to describe a dvd as any of these formats since the dvd audio (such as dd/dts) doesnt actually fall under any of the format specs I have seen.

    So assuming the audio is being ignored, there is still question in my mind. NTSC seems simple since there is but one format, M/NTSC. But of course there is the question of setup which is easily forgotten. Im told that at some point, setup was removed from NTSC, but can find no definite statement of this for both or either standard broadcast NTSC or dvd NTSC. So do we know how things stand with NTSC setup? (yes i know jap NTSC should be zero setup, it is US NTSC i infact was talking about) Now for PAL, a touch more complex. There are a load of standards with different scanning, subcarrier frequencies and video bandwidths. So which is encoded to dvd? I assume the scanning is 576i/25 since this is what almost everyone accepts as being PAL. What about the subcarrier frequency? 5 of 7 of the standards use 4.434 (ish) MHz, so is this what's used on dvds? Then finally, video bandwidth, I can really only make guesses at this so i wont bother, can anyone tell me otherwise?

    thanks

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  2. buns

    buns
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    and a slightly related thing...... sdi, this seems defined by smpte259m. But this defines 4 different interfaces, so is the sdi we use the A, B, C or D version? I presume it must be C or D since A and B are composite and PAL/NTSC specific, but do we know which one it is?

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  3. RichardA

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    Ad,

    To your first question, the answer is none of the above!

    The format on DVD's is component and not composite so there is no relationship to broadcast PAL, NTSC or SECAM in terms of sub-carrier, separation, audio, etc...

    The terms PAL and NTSC are purely used to indicate 525/60 or 625/50 encoding - it's technically wrong but is used as it indicates compatibility with 'PAL' countries and 'NTSC' countries.

    The format on DVDs is M-PEG encoded 4:2:0 MP@ML of either 720x576 @50Hz (PAL Video material), 720x576 @ 25Hz (PAL Film material), 720x480 @60Hz (NTSC Video material) or 720x480 @24Hz (NTSC Film material)

    The DVD player encodes the component signal to composite and s-video and this is where any decisions on exact output standard are made.

    Setup is not encoded on DVDs but is again added in the DVD player depending on the area set (i.e. NTSC or NTSC-J)

    Video Bandwith for DVD is 6.75MHz.

    I am actually not familiar with the A,B,C and D terms you've used with SMPTE 259M but there are deinitions within the standard for Composite and Component as well as standard and widescreen.

    The widescreen versions are almost universally not used by anyone anymore so they can be discounted.

    The Standard you would find used with DVD is Component (and is often referred to as D1 after the original tape format that supported it in studios etc..)

    The Composite version is widely used mainly in US broadcasters and is often refered to as D2 after it's tape format again.

    Hope this helps!
     
  4. buns

    buns
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    Thanks Richard,

    I had a feeling there was a differentiation between composite and component versions, i havent got to the point of following the component yet. But basically what you say is that the use of PAL and NTSC terminology simply is to define the scanning? So what happens with M/PAL countries which would, by this definition, actually be NTSC since its scanning is 525/59.94?

    With respect to setup, do all US type NTSC machines add setup? This is a point which greatly confuses me for calibration. Some tell me there is no NTSC setup on dvds while others disagree and then further others say sometimes there will be and sometimes there wont. In any case, knowing what is actually the case would make calibration simpler in my mind.

    The sdi versions, A and B are composite 4fsc NTSC and PAL, C and D are 4:2:2 component with D being 16:9. Having looked a bit further, there also appear to be a 4:2:2p dual link system and a single link 4:2:0p system. then even further, there is an interface for 4:4:4:4 component standardised by smpte344m.... so im getting more confused all the time! It sure isnt simple for a novice to come in here and try to understand things!

    I guess id best keep reading! Thnks for your help

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  5. Chris Muriel

    Chris Muriel
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    If you want a good reference book on video-related matters
    I can highly recommend the book Video Demystified.

    Info at : http://www.video-demystified.com/

    Chris Muriel, Manchester.
     
  6. buns

    buns
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    i actually do have a very good book, 'Digital video and HDTV' but with something as complex, its impossible to go cover to cover without your head pickling so you miss bits! Thanks though

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  7. StooMonster

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    RichardA, isn't the format MPEG-2?

    Shudders with thought of MPEG-1.

    StooMonster
     
  8. RichardA

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    Damn, yes I forgot to put on the -2 !
     
  9. bugster

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    Mpeg-1 at VCD resolutions, CBR up 1850Kbps is DVD compliant.

    Most commercial DVD's are mpeg-2.

    Mpeg-1 and mpeg-2 use EXACTLY the same compression methods. its just that mpeg-2 takes the allowable bitrates and resolutions to higher numbers whilst adding things like intelace support and 3:2 pulldown.

    or 704 * 576/480
    or 352 * 576/480
    or 352 * 288/240
     
  10. Magsy

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    How is a film based DVD stored on disc, is it interlaced or not?

    3:2 pulldown refers to making a interlaced film source, progessive?

    S'all a bit confusing :)
     
  11. salacious

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    Video can be stored on DVDs either as interlaced or progressive. They have markers will tell the chipset what way it is encoded. They also have flags through the bitstream to tell it when to repeat frames when doing 3:2 pulldown. Some progressive bitstream decoders only look at the actual data on the disc and this can produce video artifacts.

    Some links and info can be found here http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html
     
  12. buns

    buns
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    btw it should be 2-3 pulldown, not 3-2. This is because smpte standards assign A,B,C and D frames to sets of 4; the A-frame is associated with the frame without duplicate (or redundant) field. So its better describer as 2-3 not 3-2.

    To answer Magsy, It is the transfer of film to 480i29.97.

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  13. rscott4563

    rscott4563
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    So are there actually any DVD's which have the film stored as progressive frames, as the article at the link above says that this is possible, as mpeg can handle either.
    If there are does this mean that DVD players have interlacers as well as deinterlacers, also if there are any DVD's that are progressive in nature, does this mean they would bypass the deinterlacer in a DVD player and hence should give the best possible progressive scan output, i.e no deinterlacing or 2:3 pull down for ntsc??
     
  14. StooMonster

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    I'm a fan of Fractal Wavelet hybrid codecs myself.

    StooMonster
     
  15. Plump

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    Thanks god (or whoever else is in charge) there are people like Richard Ansell, who know everything (or almost everything) and always find the best way to explain it to us!

    See also
    http://www.avforums.com/forums/showthread.php?threadid=81609

    Thanks again Richard for sharing your time with us!

    Kastrup
     

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