vgmrips

The forum about vgm files
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PostPosted: 2017-08-03, 23:37:29 

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Can you characterize the idle time commands? I'd like to filter those out to save bandwidth.

Edit: in fact, is it possible to see a vgm2txt of the idle commands? And perhaps the test mode ones as well? Thanks


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PostPosted: 2017-08-04, 17:07:07 

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It occurred to me that I can use a diode OR gate to mix /CS and /WR together and this way trigger less DMA requests.


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PostPosted: 2017-08-05, 12:38:32 

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Here is another log, I think I got rid of the 0xffff waits. This time the format is:

0x61, 0xb5, 16 x (wait time, 16 bit, LSB first, address, data)

This format is meant to save some bandwidth, that's why it's not VGM commands this time.

Example:

Code:
61b5
0000 0201
0000 007d
0100 0205
0000 0031
0f00 0114
0000 0202
0000 0021
0000 0203
0000 0003
0100 0205
0000 0030
0d00 0115
0000 0200
0000 0008
0100 0202
0000 0001


Attachments:
song.cap.gz [624.46 KiB]
Downloaded 6 times
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PostPosted: 2017-08-05, 17:30:24 

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Is the YM3413 emulated? Aparently the SY77 keyboard uses it, which I also own.

Also, the unused pins on IC21 tells me that it is used in other products as well.


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PostPosted: 2017-08-05, 20:58:16 

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The led outputs on the gate array (IC21) are probably for the CBX-T3, which is a budget version of the TG100 without an LCD display.

The YM3413 ("LDSP") is not emulated. We need to reverse engineer it, somehow. I think it can probably only do a few fixed functions...


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PostPosted: 2017-08-05, 22:09:41 

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Well, that DSP chip is in several cheap Yamaha products. Some info here http://www.dtech.lv/techarticles_yamaha_chips.html

I wonder what they mean 'programs are only 32 cycles long', perhaps the programs are stored in the CPU ROM and just sent over to the DSP chip?


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PostPosted: 2017-08-05, 23:06:30 

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it seems like any commands to it go through the sound chip, so any hints on how the LDSP is programmed would be contained in your chip capture logs... There is also another test in the test mode dedicated to the LDSP chip and it seems like you can use MIDI sysex commands to mess with it as well.


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PostPosted: 2017-08-06, 1:15:52 

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ctr wrote:
it seems like any commands to it go through the sound chip, so any hints on how the LDSP is programmed would be contained in your chip capture logs... There is also another test in the test mode dedicated to the LDSP chip and it seems like you can use MIDI sysex commands to mess with it as well.


Ah I hadn't thought of that. I'll wait for ValleyBell to examine the latest log file to see if the VGM logger is accurate now.


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PostPosted: 2017-08-06, 14:02:29 

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I'm leaving tomorrow for a week or so, here is the latest capture file.


Attachments:
song.cap.gz [1.33 MiB]
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PostPosted: 2017-08-06, 15:47:28 

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here is a tool to convert the latest capture into VGM. It can even insert the (8-bit) sample ROM into the VGM.
The archive also contains the startup/testmode VGM. It's really just the VGM header and the raw capture data slapped together.

The new capture is bit a bit fast (but seems fine else) and there are about 3 major lags. (65535 sample delays)

EDIT: When I said "new", I meant the log from yesterday.
Also, the tool requires the "sync" word to start at an even offset. The log you just posted fails there.


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PostPosted: 2017-08-06, 16:09:19 

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Thanks, my hands are all over your tool.


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