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Emulating MT-32 on an RPi2

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Reply 221 of 242, by Dunuin

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Nice, I've got an spare Raspi3+ laying around, because I build a real home server and don't need my Raspi-server anymore.
Does Munt got a API for user inputs? Its no problem to add a letter LCD and some buttons to the Pi, so it could look and feel more like the real MT-32, as long as Munt would allow that.

Reply 222 of 242, by gdjacobs

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It generally doesn't require any input once the client is up. I initially patched mt32d to output text to an LCD, but the better, more modular approach has been using software layers on top to sniff and display SYSEX messages, switch to GM synth engines, etc.

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Reply 225 of 242, by appiah4

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One thing I noticed is that if I leave the Pi turned on overnight, and/or powercycle the computer, MT32D no longer receives MIDI messages. I believe this is a quirk related to the USB MIDI interface I'm using, but regardless, in either case I have to powercycle the Pi as well before the setup starts to function.

It's not a huge deal, but a strange quirk nonetheless.

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Reply 226 of 242, by 7F20

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gdjacobs,

i have gotten this up and running, but i sometimes get PCM recover, underrun errors upon exiting dosbox. So far, it hasn't been a deal breaker, but I suspect it coincides with game hangs and sound stutters I occasionally get. I set Munt to -m -i 25& to get a solid 25ms buffer (which is apparently the default for dosbox mixer) and I set all of dosbox's emulated instruments to 48000kHz (which is apparently the alsa native default).

What's your experience with these settings, and did you find that there is a correct way to arrange all of that?

Thanks,

Reply 229 of 242, by gdjacobs

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USB audio issues were not uncommon and sometimes required tweaking of fast IRQ (FIQ) parameters. You can try adding fiq_fix_enable=0 to the kernel parameter list which trades off some CPU usage for greater USB I/O. Are you running dosbox off the SD card or a USB device?

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Reply 230 of 242, by 7F20

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I installed dosbox on the sd card, but I have all my games and such on a usb 3 memory stick. With my raspi 3, I just used an ssd on the usb ports, but now using the 4, so no USB boot yet. I will try adding that line to the kernel params. Sorry, but I'm new-ish to linux so just learning some of this. Could you please confirm I should add that to: /boot/cmdline.txt ?

Thanks

Reply 232 of 242, by 7F20

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After adding that line, there's been a reduction (not complete elimination) of the usb audio errors reported. Today, I finally overclocked the pi4 (mildly), and I think that smoothed things out a bit as well, or at least helped with the cpu tradeoff.

Reply 233 of 242, by gdjacobs

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Good to hear. Network mounting your DOS games might be a little nicer as well. IIRC, the Pi 4 has a dedicated I/O channel for LAN instead of it being on the USB bus with the earlier models.

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Reply 234 of 242, by appiah4

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I might just be deaf to it but the regular Pi audio out is fine for just stereo MT-32 audio IMO. Adding a USB sound card simply complicates the setup..

Retronautics: A digital gallery of my retro computers, hardware and projects.

Reply 235 of 242, by gdjacobs

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THD is fairly high due to relatively low frequency PWM. I wish they'd spend 50 cents for either a PCM DAC onboard or a higher clocked PWM DAC. They don't need super high bit rates, but proper CD quality would be nice.

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Reply 237 of 242, by Serious Callers Only

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The Pi mesa driver recently had a few percents performance bump by changing hash algorithms on gpu limited workflows too. I like the little device, even if the hardware is lacking in comparison with proprietary phones (28 nm, terribly simple gpu from the ruins of broadcom ambitions), the open source software support is making it punch above its weight with dreamcast level emulation on the RPi4, verging on gamecube being a near certainty in the future.

Reply 238 of 242, by digger

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7F20 wrote on 2020-01-07, 02:26:

Hopefully don't sound too picky, but I am an audio centric person and the difference is pretty noticable to me.
Even if I'm getting a little tearing or a frame rate drop, it's worth it.

Aren't there quite a few high quality sound cards for the Raspberry Pi out there that connect through GPIO pins as opposed to USB? Wouldn't that work even better?

Reply 239 of 242, by 7F20

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digger wrote on 2020-02-17, 00:03:

Aren't there quite a few high quality sound cards for the Raspberry Pi out there that connect through GPIO pins as opposed to USB? Wouldn't that work even better?

i haven't pursued that for a couple of reasons:

1) I usually use the GPIO for a 24bit VGA adapter that hooks up to an old RGB monitor for arcade games

2) I'm not sure how well such a solution would work with Lakka (or if it would work at all)

3) Those solutions are a good deal more expensive than my $5 usb adapter from amazon.

4) They sound better, but the $5 one actually sounds pretty good.

however, it's an interesting idea that i may look into in the future. i have one setup that goes from the HDMI to a VGA adapter and out to a monitor, but there is a whole different set of problems with that setup. (mostly that lakka is incompatible with HDMI-VGA adapters)