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pal <> NTSC convertor

Discussion in 'Electronic Design' started by Vincent Himpe, Jan 11, 2004.

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  1. anyone knows what is inside the PAL <> NTSC boxes they sell on the market ?
    i'm interested in the chips used.

    Or if anyone has a schematic laying around. the image quality is very
    important as it will be used to convert hires imagery ( microscopy
    application )
     
  2. I read in sci.electronics.design that Vincent Himpe
    'Hi-res' and NTSC are incompatible. (Ducks!)
     
  3. hehe. got me there. i know . but still i have this video microsocopy system
    that comes with a NTSC video camera ( its a liquid cooled camera that looks
    for infrared signals : heat generated by Chips for defect analysis )

    Problem is i need to adapt this so i have a PAL signal i can tape or send
    into a DV capturing system for post processing.
    So i need to be able to do NTSC to PAL conversion.( i need the color
    information as it is a color map showing different temperatures . So thats
    what i mean with hires. I know the Never The Same Color System is not the
    best choice but hey i didn't design this thing :)

    So anyway the question still stands. What is inside these off-the shelf
    NTSc to PAL / PAL to NTSC boxes ? Or how can i do it myself ?

    I want to find out the technicalities and look up the datasheets of the
    chips used before i buy such a thing so i can asses the quality of
    conversion.
     
  4. Zak

    Zak Guest

    Well, a color map is not very accurate to begin with due to the limited
    bandwidth in NTSC and PAL video. Also, mind stuff like time offset
    between chroma and luma, making the colors shift over the picture. Could
    be confusing.

    I'd connect it to an NTSC input on a computer directly, whether that
    would be a DV camera or a TV card.

    Then you can play the 60 Hz frames at 50 Hz, with black bars below and
    above. Minimal processing. The playback runs slow, but I guess that
    doesn't matter much.

    Decent TV cards are cheap enough.


    Thomas
     
  5. jep. all true what you are saying but that does not answer my questions.
    How to convert NTSc to PAL and what is inside the commercial boxes they
    sell at bestbuy and circuit city?

    The signal is not captured by computer but using a DVcam tapedeck and those
    things only take in S-Video PAL signals !

    Frame rate conversion is necessary.
    TV cards are useless for my application due to lack of resolution and use
    of lossy compression.

    I have done the test using a DV tapedeck ( NTSC version ) and the DV
    quality works for my purpose.

    Only problem is i have a PAL deck and need ot record NTSC so i need a
    convertor.
     
  6. I read in sci.electronics.design that Vincent Himpe
    Proprietary devices, not available on the components market.
    By spending perhaps ten times the cost of buying one.
    You won't find the data sheets of proprietary devices. The best you can
    do is borrow a converter and measure it.
     
  7. Zak

    Zak Guest

    These sometimes produce "PAL at 60 Hz" for an NTSC input. Your recorder
    will not like that but it is much nicer on TV than a real frame rate
    converter.
    Frame rate conversion is lossy too. In any case, a BT848 or 878 based TV
    card can do full resolution video quite well. It does not do compression
    in hardware; if you want to measure frams I'd that that is the way to go.


    Thomas
     
  8. Nope can't believe that. Proprietary devices and low cost mass production
    don't mix very well ( believe me i know. I design IC's for a living for
    number 3 in the world )
    Oh yes i will. and reverse engineering is no problem either. :)


    No but serious i was hoping that someone would be able to point me in the
    right direction as to who makes such things commercially

    In the mean time i have found VHDL that describes video transcoders from
    PAL to NTSc and NTSC to PAL. I'll probably have to tweak it a bit and blast
    it in an altera or xilinx gate array. But that is like re-inventing the
    wheel.
    Thanks for the input anyway
     
  9. Yep i know. but that is not usable for me.
    I'm more in favor of the new CX2xxx family as they have a 12 bit A/d
    instead of an 8 bit.

    But then again that solution is not usable for me. I need something that
    does video in video out in realtime . No computer needed.

    I found a couple of chips from TI that i might be able to use, along with
    some VHDL code that i can synthesize in a gate array.

    One of these chips 'reads' the composite or Svideo NTSC or PAL or SECAM in
    all their flavours and spit out the data into a field memory ( 24 bit wide
    8 bit each for RGB )
    A second one takes a field memory and re-encodes it to PAL NTSC or SECAM in
    any flavor.

    All i need to make is an interspeeder that resyncs the time difference ( 30
    frames a second for NTSC and 25 for pal ) If i have more time a can even
    make an interpolator that can downsample or upsample field wise.

    As small microprocessor is used to set up the desired standard,
    quantisation params and drive 8 led's and 2 pushbuttons.

    But then again i had hoped to find some off-the shelf thingies i could just
    use without too much work on my part( i'm lazy :) )

    oh well

    thanks anyway.
     
  10. I read in sci.electronics.design that Vincent Himpe
    You cannot possibly be serious.
     
  11. Hi Vincent,

    The application of the (silicon) devices you mention is more difficult
    than you seem to realize. Although you seem familiar with the basic
    building blocks of the convertor, one of many hidden challenges is in
    implementing a proper algorithm for the scaling and scan conversion
    and interpolation filters. Perhaps you should consider one of the
    off-the-shelf items. A decent one may be had for less than $750. You
    can get a cheap one (if quality can suffer a bit) for about $150.
    Google and STW.

    As the manager of the "PC/TV" chipset development for an IBM
    sub-contractor, I learned a lot of interesting details about NTSC and
    PAL television. I believe the advice given by John Woodgate and Thomas
    has been appropriate.

    If you intend to implement the scaling and scan conversion algorithms
    in an Altera, please keep the group posted on your progress.

    Best Regards,

    Frank Raffaeli
    http://www.aomwireless.com/
     
  12. [posted and mailed]

    got it running.

    I didn't need to scale as NTSC is 720 by 480 pixels and pal is 720 by 500-
    something. I just have 2 black bands above and below the video. as for the
    rate conversion. i throw out one in 5 frames. done.

    Made a little board. I use a cyclone EP13. runs ok.
    I use a video A/D from TI and a video D/A for now.

    I just ordered a diVio development kit. this is a CCIr602 to DV over
    firewire chipset. The final goal is to have this thing run the encoding to
    DV so it can be taped using an off the shelf DV deck. Since the Video DAC
    is already using that interface this should be a snap.

    the images can then be loaded into a computer for later analysis.

    thanks to anyone who contributed

    - topic closed for me -
     
  13. Oh, how did you do the color / chroma conversion?
    from 3.58 to 4.43 MHz?
    What are you using for DA?
     
  14. No need for that. its handled by the video A/D and D/A
    The Chips i use can demodulate and remodulate any video format. They spit
    out RGB data in CCIR601 format ( digital stream for video )

    Used parts in the design :

    Texas instruments TVP5145 Pal/NTSc/Secam video decoder with 10 bit AD
    convertor in QFP80 Video
    Texas instruments TVP6000 PAL.NTSC video DAC with encoder
    Altera EP13 programmable gate array. This contains the buffer control (
    pseudo fifo using fast Srams.) the frame rate adjuster ( frame removal/
    insertion depending on NTSC/PAL or PAL/NTSC. )
    I don't do any scaling. The PAL signal has a black band above and below the
    420 lines from the source video signal.

    Cygnal 8051c120 50 mips 8051 processor
    4x 1Meg fast SRam from ISSI
    FTDI FT245BM USB engine ( for system control, 8051 firmware and vhdl
    download )

    To be added soon :

    DiVio DV701 CCIR601 to Firewire transport bridge in 256 pin BGA
    Some more Srams and fifo's for the Divio chip
    Texas instruments TSB41AB3 Firewire Physical layer controller
     
  15. Hey, cool stuff, yes, if demodulating - remodulating you are fine.
    I had that in mind as a last resort, demodulating PAL to get RGB
    with a normal analog chip...

    Might want to try standard conversion one day in my setup, just for fun.
    Got the datasheet now for the TVP5145, mm just had a look, they use
    2 AD, one for chroma and one for Y, I am using 1 (multiplexed).
    I want to do the whole thing (decoding / encoding) in FPGA (xilinx).
    Of cause for the 15 USD lot of work is done for you with this chip.
    Some interesting info in that datasheet.
    Thank you for the info :)
     
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