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Altera_Forum
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15 years ago

Overlay moving (live) graphics feed on video

I need to mix a live graphics image (Streaming into the FPGA) that has a special pixel value in places where VIDEO should show through. I know that the Alpha Blending Mixer can do this, if I can sample the graphics stream and create an ALPHA Channel with it.

I need to see how to use the alpha channel (I can't find any examples) and use this data to enable the underlying video to overlay the graphics on a video stream.

Thanks, in advance.

Mike

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    try this for liminance.

    output = pixel/256 *(256-alpha) + graphics/256 *alpha

    As for chrominance - good luck. It might be easier to convert it all into the RGB colour space before mixing if you want to mix in colour.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    --- Quote Start ---

    try this for liminance.

    output = pixel/256 *(256-alpha) + graphics/256 *alpha

    As for chrominance - good luck. It might be easier to convert it all into the RGB colour space before mixing if you want to mix in colour.

    --- Quote End ---

    Thanks, but I need ti create the alpha channel and I also need to see an example of how to connect the alpha channel in SOPC.

    MIKE
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    have the same problem:

    i need to configure alpha blending on DE2 without using CPU

    I've found some information about Alpha Blending Mixer over google with next request:

    alpha blending mixer sopc example

    but in every manual NIOS processor is used

    does anyone have sth much useful, like working examples?