multiple video streams?

evildragon · Post by **evildragon** » Mon Mar 12, 2007 1:55 am

I know the game Make My Video really stunk, but how did it achieve what it did?

It has three video streams working, AND manipulates it! But, how could they have coded that?

I want to do something similar, like a "Multiple angle", type of thing..

TascoDLX · Post by **TascoDLX** » Mon Mar 12, 2007 6:33 am

It's basically a stream composed of three small video frames side-by-side played back at 15 frames per second. Most of the effects are low-impact -- palette or tile effects.

The concept of real-time music video editing was novel at the time but, yeah, the game sucked eggs. Oh well.

evildragon · Post by **evildragon** » Mon Mar 12, 2007 6:35 am

TascoDLX wrote:It's basically a stream composed of three small video frames side-by-side played back at 15 frames per second. Most of the effects are low-impact -- palette or tile effects.

The concept of real-time music video editing was novel at the time but, yeah, the game sucked eggs. Oh well.

thing is, i noticed when you playback your "mix", the playback window, is larger in resolution..

is it still hiding other views? or is it just rapidly changing video streams as I demanded in the mix?

Fonzie · Post by **Fonzie** » Mon Mar 12, 2007 7:53 am

yeah, i noticed that... Probably they packed twice the 3 streams (two files) and decompress only one stream for the larger one.

TascoDLX · Post by **TascoDLX** » Mon Mar 12, 2007 10:53 am

evildragon wrote:
TascoDLX wrote:It's basically a stream composed of three small video frames side-by-side played back at 15 frames per second. Most of the effects are low-impact -- palette or tile effects.

The concept of real-time music video editing was novel at the time but, yeah, the game sucked eggs. Oh well.
thing is, i noticed when you playback your "mix", the playback window, is larger in resolution..

Yes, there are two files. In mix mode, video is 96x56 and is uncompressed. In playback mode, video is 112x96 (which, because of H32 cell mode, is stretched to 140x96) and is compressed in order to keep the framerate.

evildragon wrote:is it still hiding other views? or is it just rapidly changing video streams as I demanded in the mix?

Keep in mind it's really just one big stream but I'll refer to the three video sources as streams anyway.

An ordinary streaming video file is composed of:

a video frame, an audio frame, a video frame, an audio frame, a video frame....

Make My Video's file is composed of:

3 video frames, an audio frame, 3 video frames, an audio frame, 3 video frames....

Here's how it works...

In mix mode:

All three video streams are decoded at once and copied to VRAM; the active stream is copied twice, usually unchanged. There are really only two effects that need to alter the pattern data -- Bigpix and Smear. The other effects alter either the palette or the nametable.

In playback mode:

Only the active stream is copied to VRAM. I'm not sure about the decoding (since I'm not familiar with these specific SGA video packets) but it either (A) decodes the video frames of all streams at once and simply ignores the frames from inactive streams, or (B) decodes the video frame of the active stream only and ignores the encoded frames of inactive streams. If either Bigpix or Smear is engaged, the pattern data is altered before copying to VRAM.

Buffering is used for both modes, so there are always two sets of pattern data in VRAM.

That's it. I think I've covered everything -- more than I ever wanted to know.