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displaying video — Parallax Forums

displaying video

Daniel MeeksDaniel Meeks Posts: 2
edited 2007-06-15 22:28 in Propeller 1
Hey all I'm new to the forms and I just ordered my Propellor chip and clip!
·· What I want to do is send digital video data(mpeg4) from my computer to the usb to the propellor and out to a vga monitor. I've lurked the forms and seen a lot of impressive vga stuff but I haven't read of anyone sending real videos( like a home video or something). For clarification the video isn't going to be stored on· the propellor kinda streamed from the computer.·Anyways I'm just wondering how hard this would be with the propellor, thanks for any help.
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Comments

  • Paul BakerPaul Baker Posts: 6,351
    edited 2007-06-15 15:43
    Is your plan to have the Propeller do the mpeg4 decoding or would another chip provide that function? I've never dealt with mpg4 streams so I dont know how complex the decoding process is. But please keep us updated with your project, it's very interesting.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
  • Lord SteveLord Steve Posts: 206
    edited 2007-06-15 15:45
    MPEG4 decoding at any reasonable frame size is beyond the current Propeller.
  • Daniel MeeksDaniel Meeks Posts: 2
    edited 2007-06-15 15:48
    ok, what format would be the easiest read for the chip as I can change that programmatically from the computer. Thanks for the quick responses guys.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-06-15 16:01
    This is not likely to work for you for several reasons:

    1) The built-in video hardware only supports a limited number of colors for each pixel. Although there are ways around that, they are messy and require a lot of understanding of the video hardware and assembly language, etc.

    2) The memory available is quite limited for a VGA frame buffer which limits the resolution and the number of available colors. There is a very nice external memory card that's now available for the Hydra (which is mostly just a Propeller with some nice "frills" including a socket for the memory card). The Hydra uses the same I/O pins for the memory card as for the VGA output so you might be better off adding your own memory card interface to something like a Propeller Protoboard. There are no VGA drivers currently written that use this extra memory. You'd have to write your own.

    3) I believe the MPEG4 decoder is fairly complex. Do you understand it well enough to write a new decoder in Propeller assembly language ... Spin won't be fast enough for many parts of it. Do have a look at the "Large Memory Model" stuff in this forum. This provides a way to write largish programs in assembly language with only a modest speed penalty over normal assembly language (which is limited by the 512 word COG memory size).
  • mirrormirror Posts: 322
    edited 2007-06-15 22:28
    "Large Memory Model" assembler. Hmmm, interesting concept. Has anybody produced an example (anything slightly non-trivial) to demonstrate the final result and how to go about it?

    I've read some of the large memory model posts. There seems to be a fair number of ideas but not a whole lot of glue. Or are we waiting for ImageCraft to come up with their C compiler to actually implement this large memory model?

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    It's not all that hard to count the number of grains of sand on the beach. The hardest part is making a start - after that it just takes time.·· Mirror - 15 May 2007
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