Quicktime 7 plays movie but skips frames

A 1024 x 768 H.264 movie will probably require a very fast G4 or at least a G5. I'm not certain that either of you G4s will handle that size H.264. As for the Apple Intermediate codec, that should probably be working.

On my 800MHz PowerBook 480p H.264 (848 x 480) is pretty difficult (not 100% smooth) and since 1024 x 768 is nearly twice that size I'd guess that you'd need better than a 1.6GHz G4 to do smooth playback at that larger size.

However, I have no problems with the Apple Intermediate codec even at sizes up to 720p (1280 x 720). The latter is even true under QuickTime 7.0.3 and Tiger.

Are you sure that you don't have a disk related problem? Extreme disk fragmentation could cause what you're seeing but that would seem very unlikely under either Panther or Tiger. More likely would be a problem with having tasks running in the background while you are trying to play the movies or some software conflict.

Have you used Activity Monitor to check for background tasks and disk activity?

I concur with QuickTimeKirk: use the "Audio MIDI Setup" application, in the Utilities folder, to set the audio output format to 44100Hz, but you should also use Audio MIDI Setup to check the Default Input and Default Output settings. Try the "Built-In Audio" setting for all these options, and see if that helps. What's happening here is that sometimes the Mac's audio settings have gotten messed up, and need to be reset (why this interacts with playing movies, and only in Quicktime Player, I don't know). The Sound prefpane also lets you change some of these settings, but sometimes it can't properly do the job.

If that doesn't help, trash the plist file that these settings are stored in--com.apple.audio.DeviceSettings.plist file (at Macintosh HD/Library/Preferences)--it might have gotten damaged. Then restart the Mac and try running Quicktime Player again.

I found what was causing my Mac's problem (that I describe above) with playing MPEG files (even MPEG-1) in a jerky fashion, in Quicktime Player--it's related to this audio settings problem: my Mac's audio hardware (on the logic board) has failed, and without working audio hardware, the audio settings for Input Device, Output Device, etc. as described above, can't be set--Audio MIDI Setup on my Mac just displays "None", "No devices", "Input is not supported", etc. I already knew my audio hardware was dead, but that didn't bother me so much. Quicktime 6.5.2 worked under OS 10.3.9--it was only after I updated to OS 10.4 and Quicktime 7 that this problem started, and it didn't occur to me how dependent Quicktime 7 is on things like audio working properly. I don't know of any software fix that would let Quicktime play smoothly regardless of this hardware problem. I've been thinking of getting an iMic, made by Griffin, to see if that will produce audio with my G4’s logic board (it plugs into the Mac's USB ports), or at least let me select it in the Audio MIDI Setup application, but I doubt it will help, since it's the basic audio-generating chip on my logic board that's dead, not just the audio output amps.