Circus Convoy PAL - color loss in Duck Shoot sideshow

[Dionoid]

Hi, while playing Circus Convoy (the PAL version) I noticed CRT color loss while in the Duck Shoot sideshow. As soon as I exit the Duck Shoot screen, all colors are fine again.

When entering the Duck Shoot screen, everything is black & white. Then after a few seconds the colors come back, but they are constantly changing, which is kind of annoying. This is typically something you see in PAL games where the number of scanlines is uneven.

 

Is there someone on this forum who has bought the PAL Collectors Edition (incl. digital download) and can verify in Stella if the number of scanlines are uneven in the Duck Shoot sideshow?

[Thomas Jentzsch]

Sounds like an inconsistent framerate.

[Dionoid]

 

[+Karl G]

Have you reported it as a bug to them yet?

[Dionoid]

8 minutes ago, Karl G said:

Have you reported it as a bug to them yet?

Good idea; I just reported it using their contact form.

[Lord Innit]

I'm getting the exact same issue with my PAL copy on my AV modded 2600jr.  

 

Also reported.

Edited April 26, 2021 by Lord Innit

[root42]

Same problem here with the Collector‘s Edition on a PAL Vader. 
I sent them a message via contact form, too. 

[PitfallCreator]

Thank you to those who reported the issue, and the speculation is correct. Even with 2000 hours of Beta Testing, we missed a frame rate anomaly on the Duck Shoot game.  (In our testers' defense, it has an insignificant effect on NTSC and only really shows up on PAL.  And even then only on real hardware - the color effect does not show up on emulation.)

 

Unfortunately, the ROM is what it is, and we can't fix it in your physical cartridge from halfway across the world.  (If it helps, Collector Edition owners can now download a fresh copy from the MANAGE page of the Audacity Games™ Web Portal.)

 

We had only one tester in a PAL territory playing on actual hardware.  But we can fix that!  Which of you wants to sign up as a Beta Tester later in the year for Casey's Gold™?

 

David Crane

[root42]

1 hour ago, PitfallCreator said:

We had only one tester in a PAL territory playing on actual hardware.  But we can fix that!  Which of you wants to sign up as a Beta Tester later in the year for Casey's Gold™?

Count me in! You already have my email... 

 

And thanks for the quick fix!

[+SpiceWare]

22 hours ago, PitfallCreator said:

the color effect does not show up on emulation

 

Stella has a Developer Setting that emulates the PAL Color Loss.

 

Hit TAB to bring up in game options, then click on Developer button:

 

 

Click the Video tab:

 

Click Developer settings:

 

PAL Color loss will now occur for odd scanline counts provided the game is PAL.

Air Sea-Battle output 261 scanines, but is NTSC so does not show up as B&W:

 

I changed the game's TV format to PAL60:

 

Then reloaded the game (CONTROL-R) for PAL60 and the PAL color loss to take effect:

 

[Thomas Jentzsch]

PAL color loss is a bit more complicated than Stella currently emulates. Odd scanlines play a role, but also a changing number of scanlines. 

 

But I am pretty sure the CC color loss would be detected by Stella. Maybe someone who owns a PAL ROM can try.

Edited May 2, 2021 by Thomas Jentzsch

[+skr]

22 hours ago, PitfallCreator said:

We had only one tester in a PAL territory playing on actual hardware.  But we can fix that!  Which of you wants to sign up as a Beta Tester later in the year for Casey's Gold™?

I play on unmodded Lightsixer on an 80s color TV and would do Beta Testing.

 

I also use Harmony and PLUSCART to play .bins on the real machine. Also use Stella sometimes on OS X Big Sur.

[PitfallCreator]

Thanks for that, Darrell.  Stella, the labor of love and wonderful tool it has always been, never ceases to amaze!

 

Part of the problem with Circus Convoy is that there is so much depth of game play it was very difficult to make sure every scanline count (that might have been affected by a page boundary shift from the smallest change) on every game screen remained consistent.  I had checked it in every sideshow throughout development, but apparently Duck Shoot slipped by due to some late change.

 

As many of you know, the 2600 was reduced to the cheapest system that would output some semblance of a TV signal.  It was considered perfectly acceptable to use a non-interlace signal for NTSC, and then PAL was a double kludge - completely ignoring the alternating phase requirement.  It worked on consumer TVs, and that was good enough.  The point is that it is arguably surprising that more TVs and monitors view colors correctly than those that don't.

 

Re the non-standard 2600 video signal, for those who like stories from the old days, keep reading.

 

For the Laser Blast commercial, our child actor had to start out looking bored while earning millions of points without even looking at the game screen of some "other space game."  To achieve this I had to write a self-playing, single-screen space game with a big on-screen score and provide it to the commercial production team.  And, of course, I used a 2600 for this since I had the development system; a 2600 was portable; we had extras we could send to LA, etc.

 

Digital effects added in post production were not common then, so they wanted the game to be on the kid's TV screen for the shoot.  Enter Genlock - a studio-wide standard sync signal driven into every TV camera, monitor, etc.  (You can tell when Genlock is not used when you look at a TV in the scene and a black sync bar drifts through the picture.)  Of course, not only is a 2600 not equipped with Genlock, it doesn't even output an interlaced sync signal.  Taking that as a challenge, I first gave the imaginary game an interlaced signal in software, changing the sync code to put out 262.5 scan lines so that alternating frames provided the required 1/2 line offset for interlacing.  I then wired up an unused joystick input to read the Genlock signal and trigger each frame to keep the sync bar out of frame.

 

All that for 4 seconds of the commercial.  (It worked so well I then had to put the same mods into a Laser Blast cart so they could capture game play footage. And yes, I know, I should have saved that cart.)

 

 

[5x7]

Wow! Great story!!

[Dionoid]

On 5/1/2021 at 9:00 PM, PitfallCreator said:

Thank you to those who reported the issue, and the speculation is correct. Even with 2000 hours of Beta Testing, we missed a frame rate anomaly on the Duck Shoot game.  (In our testers' defense, it has an insignificant effect on NTSC and only really shows up on PAL.  And even then only on real hardware - the color effect does not show up on emulation.)

No worries; even the best can make mistakes

However, the defense that there is no effect on NTSC and the issue doesn't show up on Stella doesn't help me much, as I have bought the standard edition PAL cartridge. 

 

Well, at least I got a nice story from the old days for reporting the issue ?

 

[+SpiceWare]

20 hours ago, PitfallCreator said:

Thanks for that, Darrell.  Stella, the labor of love and wonderful tool it has always been, never ceases to amaze!

 

You're welcome! Back in the 90s I maintained the OS/2 port of Stella, but stopped maintaining it after switching to Macs in 2003. It has certainly come a long way since then with all the emulation accuracy improvements and developer features.

 

 

Quote

Of course, not only is a 2600 not equipped with Genlock, it doesn't even output an interlaced sync signal.  Taking that as a challenge, I first gave the imaginary game an interlaced signal in software, changing the sync code to put out 262.5 scan lines so that alternating frames provided the required 1/2 line offset for interlacing.  I then wired up an unused joystick input to read the Genlock signal and trigger each frame to keep the sync bar out of frame.

 

That's really cool!  I know the homebrew community has done some experiments with generating a 480i signal, this is an AtariAge news entry about it from 2002: https://www.atariage.com/news/Interlacing/

 

 

[+Andrew Davie]

11 hours ago, SpiceWare said:

That's really cool!  I know the homebrew community has done some experiments with generating a 480i signal, this is an AtariAge news entry about it from 2002: https://www.atariage.com/news/Interlacing/

 

Yes, I think back then we thought it was the first time it had ever been demonstrated. I was most impressed that it actually worked. More recently I put interlacing on the chess binaries from last year - you could turn it on/off by one of the game switches on the back. It's really hard to decide if it's a plus or a minus - interlacing - you get more flicker but wider scanlines.

 

[+Andrew Davie]

20 hours ago, PitfallCreator said:

... it was very difficult to make sure every scanline count (that might have been affected by a page boundary shift from the smallest change) on every game screen remained consistent.  I had checked it in every sideshow throughout development, but apparently Duck Shoot slipped by due to some late change.

 

If you use dasm, there are a few macros available that help you ensure this doesn't happen.  Essentially checking that code is on the same page is pretty simple, and you can "protect" branches and accesses from page crossings with a bit of macro usage.

[Dionoid]

@PitfallCreator Could you elaborate a bit on the tools you've used to develop Circus Convoy? In the homebrew scene, I think most developers use dasm for building the roms and Stella (in developer mode) for debugging. Did you use any custom tools?

[+Philsan]

@PitfallCreator

 

Wouldn't it be better, and easier for developers (only colors must be changed), to use PAL60 instead of PAL50?

 

Nowadays nearly all PAL games use that format.

[JaySab]

PAL copy here and the colours are fine for me on my 7800 on a Trinitron CRT.

 

The cartridge is a horribly tight fit though. 

[Thomas Jentzsch]

There are a few more display bugs in the PAL version, e.g. the gold bars having some black pixel mess below them.

[SavyIsJoshoArts]

G'day all.
I too have got the PAL version of Circus Convoy. I gave the duck shoot minigame a go, It seems to show up alright on my end without any colour loss. Either that or my copy must have been the fixed issue. this is showing on a PAL Atari 2600Jr that is RGB modded using Tim Worthington's 2600RGB kit.
Yes the colours are correct. the phone camera seem to make it look like it's too bright.

I can happily say that as a PAL owner from Australia. The game works without any colour issue on my copy. 
David Crane, first of, welcome to AtariAge. and secondly. You, Gary and Dan Kitchen did a marvelous job with this game. Got absolutely addicted to it the moment I fired this up. I'll definitely will have to buy from yous there at Audacity again once Casey's Gold is released.  

Pheominel work guys.

Cheers,

Josh

Edited September 20, 2021 by SavyIsJoshoArts
to add creditation to David Crane, Gary Kitchen and Dan Kitchen on a fabulous job on the game.

[alex_79]

4 hours ago, SavyIsJoshoArts said:

this is showing on a PAL Atari 2600Jr that is RGB modded using Tim Worthington's 2600RGB kit.

With RGB,  the color information is not encoded using PAL (or NTSC, or SECAM), so by definition it can't show PAL color loss (RGB is not PAL!).

 

Chances are that it won't show the issue even when using the built in composite or S-video outputs of the RGB mod (assuming you had connectors installed for those signals), because that mod completely bypasses the TIA color generation circuit.

 

PAL color loss with an odd number of scanlines is the result of how PAL TIA generates the signal.
For example, the PAL Atari 7800, in 7800 mode, always outputs 313 scanlines and displays colors just fine, because it's using the MARIA chip color generation in that case and not the TIA.

 

The issue only shows with a PAL 2600 if using stock RF, or a composite / S-video mod that still uses the TIA color circuit (the RGB mod is the only mod I'm aware of that uses its own color generation).

 

Note finally that not all TVs will show the color loss. Some more recent CRTs display wrong colors in the top area of the screen instead, and digital TVs might not show the issue at all.

 

[SavyIsJoshoArts]

8 hours ago, alex_79 said:

Chances are that it won't show the issue even when using the built in composite or S-video outputs of the RGB mod (assuming you had connectors installed for those signals)

 

Hi Alex_79. 
I can confirm that Composite Is wired up on my 2600Jr on this mod. Haven't yet wired S-Video however my Sony WEGA Trinitron shown on my photo doesn't have a S-Video jack, only AV and YPbPr. But yes you're correct since Etim's 2600RGB mod seem to bypass the TIA colour generation circuit which would explain why I'm not seeing the colour loss issue with Duck shoot ^^; upon saying that. I'm glad to see there are no issues on my part with my PAL copy of Circus Convoy. I'm very happy with the results nonethless. 

 

8 hours ago, alex_79 said:

With RGB,  the color information is not encoded using PAL (or NTSC, or SECAM), so by definition it can't show PAL color loss (RGB is not PAL!).

 

I'm fully aware of that when I found out some years back on another topic. Still appreciate the info from what you said here nonethless ?