Waitvsync and Audio Issues Resolved (Xevious and others)

Update April 2022: After finding a perfect configuration for flawless scrolling in MAME (see separate post), I update this waitvsync entry.

In the default configuration of MAME, the scrolling of some vertical shooters, such as the famous Xevious, tend to stutter or bleed. Lines to not scroll down smoothly from time to time. Here waitvsync helps a lot - especially if combined with -nothrottle, as explained in the other post.

Step 1: Enable waitvsync for all games (general configuration)

In mame.ini, head for the 

# OSD VIDEO OPTIONS

waitvsync         1

Old hint for QMC2 Users: In QMC2: Tools/Options/Emulator/Video/waitvsync - 1 (enabled)
In my configuration, this immedately smoothens the video output, perfect vertical scrolling. However, the audio output suddenly gets some hickups. Some forums explain this effect and it seems that sound samples get out of sync.

Step 2: Adjust speed in specific games that have crackled audio
Create a game-specific configuration file by duplicating mame.ini - rename it to the desired game rom file name, e.g. gyruss.ini - in this game-specific ini file, head for the 

# CORE PERFORMANCE OPTIONS

speed               0.99

Old hint for QMC2 Users: In QMC2, choose Xevious from the games list and toggle the machine specific configuration:



Here I reduced the game-specific speed from 1,00 to 0,99 - et voila, the audio stuttering was gone.

A hint from a M.A.M.E forum, many thanks for this! 

Advanced tip: The best way to read out the speed is to launch the game from the Terminal, play it for a while and then stop it and read the average speed - example Moon Patrol:

Without throttle and with waitvsync, the game runs slightly too fast. For smooth audio, you set the speed to 1.057, and the sound is nearly perfect.

List of Games where waitvsync makes a difference (will further update if needed, but again, read the Terminal Average Speed to check this in your own system; if Average Speed has a 1% deviation, it's time to set speed for clear audio):

1942 (no speed adjustment required)
1943 (no speed adjustment required)
Amidar (Speed 0,99)

Cheeky Mouse (no speed adjustment required)
Elevator Action (no speed adjustment required)

Galaxian (Speed 0.99)

Gyruss (Speed 0,99)

Juno First (Speed 0,99)

Moon Patrol (Speed 1,057)

Pacman (Speed 0.99)

Phoenix (Speed 0,98)
Scramble (Speed 0.99)
Shinobi (no speed adjustment required)
Wonderboy in Monster Land (Speed 0,99)
Xevious (Speed 0,99)