Eva files

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Par [D-Tail]

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23-02-2006, 13:58

Video encoding is just like the sound encoding: zero. It's just raw YJK data (or RGB data, depending on your EVA file) which is sent directly to the Video RAM. It's said (though because of lack of experience I can't confirm) that pumping the video data to the VRAM is the most time consuming process. Calculate for yourself: 128*106 pixels * 8bpp * 12fps = 159kB/s, or 13,25kB/frame. Then there's also the 10FPS variant of the EVA movie, which has a slightly different file format. I encorporated both in EVAcon - I could send you the Java source, if you would be interested in it.

To be honest, I'm dying to have a decent EVA replayer for MSXDOS(2) - with usable controls and the like. But due to my lack of skill in the ASM department, I can't make it myself. Smile

Par ARTRAG

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23-02-2006, 14:47

How do you play the data?
Do you store the full file in the ram ?
Do you play the file directly from the HD disk?

In 0,083333333 secs I should

load form the disk 13568 bytes
send to the Vram 13568 bytes
load from the disk 4000 bytes (3*16KHz * 0.0833333, I am thinking to PCMENC audio)
out to the PSG 4000 bytes

does it work in this way?

Par Sonic_aka_T

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23-02-2006, 15:30

I don't know exactly how the IDE device is controlled, so I don't really know how the EVA data is loaded... My guess would be that it's streamed from the disk, and it gets the data as needed. I could be entirely wrong tho... ^_^ Anyhow, have a look at the sources of the MSX replayer idd, you should be able to figure something out... I have info on the file format if that's what you need, but you can also easily obtain that by looking at the source. Audio and video data is interleaved in the 12fps format, having small chunks of video data followed by a few bytes of audio. The 10FPS format seperates the audio data from the video data completely, suggesting the data is either not streamed, or is streamed from RAM with a frame delay. Like said, I don't know enough about the IDE to really know what's going on, perhaps you do. Let me know if you need the format info.

Par NYYRIKKI

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23-02-2006, 16:34

EVA video is sent to VDP directly from IDE-controller using OTI and OTD commands, so there is no RAM buffering except in 10fps format where the next frame sound is buffered.

ARTRAG: It may be a bit hard to implement decent PSG playback to EVA. I would suggest, you make your own movie format, that implements PSG playback and uses SCREEN 2 to play video. This way you can use even more space for audio as full 256*212 screen of SC2 data is only 13824 bytes and color pallette is 45 nibbles.

Par Sonic_aka_T

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23-02-2006, 18:30

yeah, why those out-decrement commands?

Par [D-Tail]

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23-02-2006, 18:40

BTW - there should be some EVA replayer for MEGA-SCSI, yet I haven't been able to find it...

Par NYYRIKKI

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23-02-2006, 19:13

yeah, why those out-decrement commands?

Because you don't want to move out of IDE I/O area.

BTW - there should be some EVA replayer for MEGA-SCSI, yet I haven't been able to find it...
If I'm correct, original EVA-player was made for Mega-SCSI. AFAIK also first EVA movies have been recorded on MSX tR & HBI-V1 video digitizer.

Par ARTRAG

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23-02-2006, 19:33

Could I have a short description of the IDE or SCSI HW, in order to have, broadly specking an idea of the complexity of a direct disk to vram or disk to PSG I/O?

Par NYYRIKKI

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23-02-2006, 19:56

Short description of IDE HW: Nice and working.

More info for people interested in programming the device:
www.msx.ch/sunformsx/download/idetxt/idetech.html

Par ARTRAG

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24-02-2006, 08:59

Is it possible to emulate an IDE HD on blemsx or openmsx?

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