First scene is missing in Switch/Panic intro

[Former user]

Original issue 313 created by iceknightmail on 2012-12-17T00:18:11.000Z:

What steps will reproduce the problem?
1.Load any version of the game
2.Wait for the SEGA logo and the intro to start

What is the expected output? What do you see instead?
Following the SEGA logo, the intro music starts with a black screen before anything shows up. There should be a first scene with some guy flying a plane.

What version of the emulator are you using (official, SVN revision,...)?
I think this has been happening since Mega CD support was added (I just forgot about it until I played it again using real hardware).

Please provide any additional information below (Emulator settings, Console
setting,...)
Any settings, to my knowledge.

[Former user]

Comment # 1 originally posted by ekeeke31 on 2012-12-17T19:42:07.000Z:

Weird, the exact same thing happens in Kega actually (in Gens, it simply hangs at Sega logo, even with perfect sync). There is indeed a black (well, more grey with some strange black marks) screen before the intro starts then it starts directly with the guy on motorcycle.

I don't have tested a full image with CD tracks so I cannot say anything about music but could you make a video recording of how real hardware behaves ?

[Former user]

Comment # 2 originally posted by iceknightmail on 2012-12-17T20:45:42.000Z:

Sure, here's a video of it.

[Former user]

Comment # 3 originally posted by ekeeke31 on 2012-12-17T21:31:21.000Z:

Thanks, i will have a look at it when i got some time.

[Former user]

Comment # 5 originally posted by ekeeke31 on 2013-01-02T16:02:19.000Z:

Hmm, i could not figure out what is wrong, the game engine does not seem to miss anything or to do anything wrong... although i am not really confident about that, there is still the possibility the isos available on the internet are corrupted, did you burn yours to test on real hardware or dumped an image from a real disc ?

[Former user]

Comment # 6 originally posted by iceknightmail on 2013-01-02T18:10:04.000Z:

I got the US version from the internet, and ripped the Japanese version from the original disc I own. Both act the same in the emu and real hardware when burned...

Could this be related with subchannel reading, perhaps?

[Former user]

Comment # 7 originally posted by ekeeke31 on 2013-01-04T09:44:37.000Z:

I doubt it, Kega Fusion emulates subcodes but has the same issue.

Seems more like a timing issue (missing or delayed event like an interrupt, etc) which leads to some communication mistakes between Main & Sub CPUs (Word-RAM handshake, etc) but honestly, at that state, i haven't found anything

[Former user]

Comment # 8 originally posted by ekeeke31 on 2013-04-06T18:21:24.000Z:

Some progress on this one: I figured it was caused by CRAM (Color RAM) being filled with 000 instead of the correct palette values, at least for the first frames of the intro (during when the airplane is normally showed).

I noticed that if I hack the emulator to ignore CRAM writes if data=000, I got the missing scene displayed (although the color palette is wrong off course).

[Former user]

Comment # 9 originally posted by ekeeke31 on 2013-04-06T18:45:50.000Z:

[Former user]

Comment # 10 originally posted by ekeeke31 on 2013-04-28T16:38:25.000Z:

Damn, this one was pretty hard to debug but I finally figured it.

It actually needs drive SEEK time to be emulated correctly (currently, the emulator only emulated drive access and seek latency when a PLAY command was received, but this game also relies on latency when a SEEK command is received).

Precisely, when the intro scene program/data is loaded from disc to RAM and is ready to be displayed by MAIN-CPU, SUB-CPU will:

1) seek the audio track to be played during intro

2) when the audio track is reached by the drive, send a command to MAIN-CPU side so it starts processing the video scenes

3) start audio track playback

The thing is that between 1) and 2), MAIN-CPU is supposed to slowly increase Color RAM values from black to the desired color palette required by the video scene (some kind of fade in effect) so, if 2) happens too fast, Color palette do not have the time to be properly setup and all pixels appear in black or dark grey. Further scenes do not have the issue because color palette is later adjusted for specific sequences.

[Former user]

Comment # 11 originally posted by ekeeke31 on 2013-04-28T18:38:48.000Z:

Fixed in r774

[Former user]

Comment # 12 originally posted by iceknightmail on 2013-05-02T21:59:37.000Z:

Wow, once more, great work! Makes you wonder why on earth would they purposely make it so the palette stops fading in as soon as the track starts playing.

Out of curiosity, what would happen if the drive took to long to find the track? Do the colors stay at the correct brightness or do they keep getting brighter?

[Former user]

Comment # 13 originally posted by ekeeke31 on 2013-05-03T07:08:11.000Z:

it's not really done on purpose, just the way the intro is sequenced and synced to audio, it just appears that the last step before the audio starts was used to setup the palette during the wait.

and no, the code only updates the palette up to a programmed limit