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Author Topic: [MD/GENESIS] A few Mega Drive ROM issues on hardware  (Read 3389 times)

Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« on: September 14, 2015, 01:40:06 PM »
(Note: All the tracks here were made with Deflemask 10c.)

In my travels through YM2612 Land, I've come across some odd issues relating to playback on hardware (my region-modded VA6 PAL Mega Drive, to be precise):

- The main issue I'm noticing is that most of my tracks are playing at a slower tempo on hardware than in Deflemask/as VGM files. I played around with the setting of a recent track (Stone_2612), and it appears to have something to do with the Speed setting. Originally I had the track set to Base Time 02 and Speed 03/03 - the lower Base Time setting seemed to make it even slower on hardware!

(DMF file attached to post - hardware recording for comparison: http://www.mediafire.com/listen/dqvopjzra4qbjz3/%5BMD%5DStone_2612%28TempoIssue%29.mp3)

- Another thing is that I'm getting a small pause before the loop point when playing certain tracks on hardware (in this case, CASSO_HANGAR). I've played around with the command placement and double-checked my work, but I'm not sure at all what causes this.

(DMF attached to post - hardware recording: http://www.mediafire.com/listen/5a8kx07z2rk5z51/%5BMD%5DCASSO_HANGAR%28LoopGapIssue%7D.mp3)

- Finally, an odd one: in the track "CASSO_BOSS," there's a low, growling instrument hard-panned left and right in the first verse of the song (after the "DA-DA-DA!" from the kick drum). After the song loops back to this verse, the instrument turns into a more straight-forward "brassy" sound, and stays like that for every loop afterwards. What's interesting is this happens with ROM file exports of the track as well as VGM file exports! The instrument only stays "dark and growly" in Deflemask.

(DMF and VGM file attached - hardware recording: http://www.mediafire.com/listen/ux4dkk09dnakh41/%5BMD%5DCASSO_BOSS%28InstrumentIssue%7D.mp3)

---

I should note that I've also tried the first last two tracks on a friend's NTSC Genesis, as well as my own NTSC-J VA1 Mega Drive. The problems persist on both.

Anybody else encounter similar problems?
« Last Edit: September 14, 2015, 01:56:16 PM by Heavy Viper »

Offline Delek

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #1 on: September 14, 2015, 11:34:43 PM »
I will look at this with MJS (author of the ROM export feature used by DefleMask) to see what we can do.

Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #2 on: September 16, 2015, 07:56:20 AM »
Good to hear, thanks!

Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #3 on: December 29, 2015, 06:03:34 AM »
Could you please update your original thread bug report with a more specific example?, I mean only one channel running at different timing (in order to make the debugging easily)

I've taken the time to record some samples at different speed settings, using ROMs exported from Deflemask AND VGMs converted to ROMs using MDVgmPlayer 3.30. Should also note I was using Deflemask v11.1pre during this.

Everything's zipped up and waiting right here!

Offline TheDeadFish

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #4 on: December 30, 2015, 08:09:47 AM »
I am writing a new player designed just for playback of Tracker generated vgms, its timing will be allot easier to verify. The old VgmPlay is extremely complex and was designed to play real vgm dumps, support for streamed samples was tacked on and is rather hackish. Might be done today.

Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #5 on: December 30, 2015, 01:39:55 PM »
Awesome news, cheers for your hard work!

Offline mihaelkyeah

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #6 on: January 12, 2016, 04:13:45 AM »
I am writing a new player designed just for playback of Tracker generated vgms, its timing will be allot easier to verify. The old VgmPlay is extremely complex and was designed to play real vgm dumps, support for streamed samples was tacked on and is rather hackish. Might be done today.
Wow! Please make this happen! It would be great to see a new ROM builder with better PCM encoding and compatibility with vgm_cmp (otherwise we would have to ask Delek to make the vgm_cmp pass optional). Hopefully in this next version some looping bugs would also be fixed?

Offline Delek

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #7 on: January 12, 2016, 11:48:11 AM »
Wow! Please make this happen! It would be great to see a new ROM builder with better PCM encoding and compatibility with vgm_cmp (otherwise we would have to ask Delek to make the vgm_cmp pass optional). Hopefully in this next version some looping bugs would also be fixed?
I think the loop bugs have nothing to do with the rom builder, they are also present in .vgm expors right?

Offline mihaelkyeah

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #8 on: January 12, 2016, 10:22:15 PM »
No. Maybe I should send MJS an email with example files. What I mean is, when I loop VGMs with vgm_trim, many of them (mainly the ones with all FM and no samples) take a while before looping in the exported ROM, making the last notes stay sustained for longer, whereas in Winamp or foobar2000 (both with their derivative in_vgm/VGMplay extensions) they sound fine. I also tried trimming with VGMTool's old "safe" code and the same thing happens with MJS's ROM builder.
« Last Edit: January 12, 2016, 10:23:48 PM by kyusawamura »

Offline Delek

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #9 on: January 17, 2016, 11:37:04 AM »
TheDeadFish already sent me the new rom builder code, you can test it out in the windows version of the pre-release here.
Linux and OSX version are coming if there's no bug reports in the Windows one.

Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #10 on: February 03, 2016, 08:59:28 AM »
Posting this here since it's related and saves making a new thread.

After testing VGMs in this thread with the current build, I exported all the same tracks as ROMs for hardware testing. On a few tracks, there seems to be a small pause or gap just before a pattern with a loop command pointing to it, both on first playback and on loops. It only shows up in ROMs, not the tracker or VGMs.

I've attached a example along with the related ROM export. If you listen to the ROM first, you can hear the loop point skipping about 10-12 seconds in.

Something I noticed is that if I blank the PSG channels and export a ROM, the skip SEEMS to go away. That's just me going by ear, though.

Offline TheDeadFish

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #11 on: February 04, 2016, 01:58:04 AM »
Does this issue occur only on Hardware or also emulators? I have been listning in emulation and I cannot hear the pause. If its a hardware only issue that would be weird. For now I will work on the assumption that the pause is in emulation also and I am just deaf to the problem. I am analyzing an emulator vgm dump to try and match it up to the source vgm.

Offline TheDeadFish

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #12 on: February 04, 2016, 02:57:56 AM »
Ok I finally see the problem, there is no bug with my player, its a bug with the file. So many register writes occur at the loop-point that one or more timer events are lost. Those register writes are duplicates and should not be there. I will consult with Delek.



Offline Heavy Viper

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #13 on: February 04, 2016, 03:56:55 AM »
Does this issue occur only on Hardware or also emulators? I have been listning in emulation and I cannot hear the pause. If its a hardware only issue that would be weird. For now I will work on the assumption that the pause is in emulation also and I am just deaf to the problem. I am analyzing an emulator vgm dump to try and match it up to the source vgm.

Sorry, should have mentioned this! The pause shows up on my hardware (PAL VA6 Mega Drive 1) using a Mega Everdrive, and in Kega Fusion 3.64.

Offline TheDeadFish

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[MD/GENESIS] A few Mega Drive ROM issues on hardware
« Reply #14 on: February 04, 2016, 04:10:41 AM »
As I later found out the problem is due to there being far too many writes at the loop point, it does not show when playing the vgm file because those players do not emulate the fact that it takes quite a long time to write a register. It takes about 19us to write a register, the problem file has 2500 register writes at the loop point. This end up in taking 3 frames to write.

I could not hear the pause, but that's not surprising, I could not even tell when I had an issue with percussion samples being cut 50% too short. Its funny that I work mostly in audio stuff but am totally deaf to rhythm and timing!