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I have a flatscreen iMac, 10.5.8, 1.8GHz PowerPC G5, 1.25 GB RAM

I noticed that when I watch HD TV shows downloaded from iTunes, that there seems to be some minor video choppiness.

Is this system too slow for HD video? I checked the Apple site and existing questions here, and I did not see any info.

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up vote 4 down vote accepted


Playing HD-quality videos purchased on the iTunes Store requires a 2.0GHz Intel Core 2 Duo or faster processor

Your system is on the verge of the minimum requirements.. It might help to quit any other open applications, but I imagine it will still struggle on faster moving scenes.

I don't recall if this works, but you could try viewing the purchased video in Quicktime Player, which might have a tiny bit less overhead than iTunes..

H.264 is a CPU intensive format to decode, there's not really any way around that.. GPU acceleration would help, but support for that is being added in Snow Leopard, which isn't compatible with PPC machines..

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A 2.0 Ghz Intel Core 2 Duo has two cores versus the 1.8Ghz iMac has only one core. Geekbench wise the Core 2 Duo scores 2665 whereas the G5 scores 1032 – Chealion Aug 18 '09 at 22:55
dbr: thanks. I didn't find that article when I searched... Chealion: great info. I knew the chips use different instruction sets, so I didn't know the relative power. – benc Aug 19 '09 at 8:44

Depends on your Mac's specific video card, the resolution you're running on your screen and the exact file you're trying to play.

The video card's capacity is the limiting factor. Try lowering the display resolution as a test to see if the file will play at a lower resolution. If so, then most likely the video card is simply not powerful enough to handle this specific file.

There may be other HD content that your computer can play if the file's format is more conducive to your system.

If it still stutters at a lower resolution, you might have a codec/player or other software problem that may be "fixable"

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