most common: buggy audio driver! - try to use different drivers, try ALSA OSS emulation with -ao oss, also try -ao sdl, sometimes it helps. If your file plays fine with -nosound, then you can be sure it's sound card (driver) problem.
audio buffer problems (buffer size badly detected)
Workaround: MPlayer's -abs option
samplerate problems - maybe your card doesn't support the samplerate used in your files - try the resampling filter (-af resample=...)
slow machine (CPU or VGA)
try with -vo null, if it plays well, then you have slow VGA card/driver
Workaround: buy a faster card or read this documentation about how to speed up
Also try -framedrop
bad file
Workaround:
-ni or -nobps option (for non-interleaved or bad files)
and/or
-mc 0 (required for files with badly interleaved VBR audio)
and/or
-delay or +/- keys at runtime to adjust delay
If none of these help, please upload the file, we'll check (and fix).
your sound card doesn't support 48kHz playback
Workaround: buy a better sound card... or try to decrease fps by 10% (use -fps 27 for a 30fps movie) or use the resample filter
slow machine (if A-V is not around 0, and the last number in the status line increasing)
Workaround: -framedrop
your file uses an unsupported audio codec
Solution: read the documentation and help us adding support for it
your file uses an unsupported video codec
Solution: read the documentation and help us adding support for it
auto-selected codec can't decode the file, try to select another using -vc or -vfm options
First note that the options -fs, -vm and -zoom are not supported by all drivers. Plus, not all drivers support scaling/zooming in hardware.
OSD/sub flickering.
x11 driver: sorry, it can't be fixed now
xv driver: use -double option
Green image using mga_vid (-vo mga / -vo xmga).
mga_vid misdetected your card's RAM amount, reload it using mga_ram_size option.