iTunes 11 HD video playback slow/choppy/stutter/skipping in OSX

What year macbook? I have a 2012 13" and it plays movies perfectly, even when I play them on a 1080p screen with hdmi adapter.

I'm having the same problem. I updated Flash. Still having the problem. I'm leaning toward blaming the drive, and would love to replace it with a LaCie 4GB model; but I need to determine that it's something else and not the drive.

I was having this same problem, and found one cause.

I have an extensive library on a Drobo FS. None of the AppleTV's in the house have any problem streaming full 1080p from it, but my new iMac does. Choppy / laggy video play. Movies and TV shows right from the iTunes store. I can have 3 TV's streaming, and even a 4th laptop, all streaming from the iMac iTunes using the Drobo. They all have zero issues. No lag, no choppy, nothing. iMac has the issue even when nothing else is running. Every time.

BTW, it's happend on my old iMac and the brand new one, both with iTunes 11.

I was told to try setting up a second account on my iMac, and try playing video there. It worked. No problems at all. Weird.

So I started looking at differences between the new account, and my standard. I'd already made sure nothing unusual was running, and no processor hogs (not that anything short of Handbrake at full settings has come close to pegging out the processers on the new box). I found one thing, that made a difference. I had Timemachine backups, going to the same Drobo FS (though a different partition) turned on on the iMac.

Timemachine was running the whole time, and didn't impact any other streaming from the same machine, but it did make iTunes video playback of 1080p movies skip like my 6 year old daughter on the iMac. I turned it off.... no more skipping. I've watched 5 TV shows and 2 movies on that account, and not had another single incident.

Obviously, there is still a problem. The iMac and Drobo have enough bandwidth that they can do all the work at the same time (or I'd be seeing the problem on the other devices while streaming), but they are not playing well together on the same account. I've also checked the throughput to the Drobo FS from the iMac... way more than necessary. If it were a read / write thing on the Drobo, then I'd expect other devices to see the issue when I'm watching something on the iMac that is skipping, but there was still no skipping on any other device at that same time...

But, as I said, I found the root cause in my case. I can turn off Timemachine backups while I'm watching a movie on the iMac, or I can move where I write the Timemachine backups to (going to try this over the weekend to be sure it works). If moving the Timemachine backup to a different drive doesn't work, it's a bigger problem.

I'd really love to see Apple fix this and the issue where I have to turn iTunes on in 32bit mode when using an external library (of it gives the funky quicktime error until you delete and readd the movie).

Hope this helps some of you, if not all.

I took the time to try playing vids in a different video player. They skipped. I then tried transferring g video files from the external drive to a folder on my desktop. The transfer paused and restarted intermittently.

I went to the MacMall store in Chicago and bought a G-Technology 2GB drive. No more Western Digital external drives for me. They work well for others, for me they're crap.

Moving my library to an internal drive fixed the problem for me. I have Promise Pegasus R4 and R6 RAIDS using Thunderbolt connectivity, but for some reason video won't play smoothly across this setup on my 2012 iMac. Playing from the internal drive fixes all the pausing, stuttering and fast-forward to catch up issues.