First post, by mcihelka
I have set up a PC for running emulators. It's way overkill for the task but it's what I had in spare parts:
• Intel DP67BA mainboard
• Intel Core i7-2600 3.4 GHz CPU
• 4GB DDR3 1333 RAM
• Onboard sound
• Dell GeForce 9300 GE PCI-E video card
• Windows XP SP3 fresh install + updates
• Latest DOSBox 0.74
I'm using this old Dell video card because it has S-Video output which means I can connect the PC to an old-school CRT television. The intention is to obtain an authentic experience with Commodore 64 and Playstation emulators. The TV output is more than good enough to play DOS games too like Epic Pinball, Lemmings, Alone in the Dark, Comanche, etc.
And that's where the problems start. On S-Video connection, in full-screen mode, DOSBox is jerky/stuttery and sound effects broken up. The gameplay speed isn't consistent (for example in Epic Pinball the game slows down as the table/ball moves around and speeds back up at moments where things are not happening). Other games are affected in a similar way.
So far as I can see, only DOSBox seems to be affected. YouTube videos, movie DVDs, x264 AVI files, other emulators all play back beautifully over S-Video.
I have tried different desktop resolutions - 640x480, 800x600, 1024x768. This is not a multi-monitor setup, the TV is the only thing connected. Incidentally it seems the video card sets itself to 50Hz refresh rate on the S-Video output because that's the PAL standard. Does DOSBox care about video card refresh rates?
I have tried surface, overlay, DirectDraw, and OpenGL output. OpenGL seems somewhat better than the rest but still not good. Double buffering makes things even worse. Adjusting sound buffers doesn't help. Adjusting the type of CPU emulation, cycles, turning off all unneeded emulated devices, etc. doesn't help.
If I unplug the TV and use a monitor over DVI, DOSBox runs beautifully!
To exclude the possibility of a dodgy video card, I sparked up an old Core2 Duo machine with an EVGA GeForce 6200 PCI video card that also has S-Video output. Guess what – exactly the same problem. DOSBox was perfect over VGA or DVI, jerky/stuttery over S-Video.
So that's two NVIDIA cards from different manufacturers exhibiting the same issue. I wish I had a Radeon card with S-Video output to compare but alas I do not.
So I'm wondering if anyone else has experienced anything like this? Or examples of successful S-Video setups? Or just further ideas of what I could/should try to do to fix it.
Many thanks in advance for your help 😀