ATV3 movie playback stuttering

[Kenjancef]

I'm not sure if I should post this here or in the Mac Mini forum...

Here is my setup:

Late 2012 Mac Mini, with 400GB iTunes library on USB 3 external drive
Apple TV 3

They are connected by wired gigabit Ethernet.

So my library used to be on the same internal boot drive of the Mini, but because I was running out of room on that drive, I decided to move it to a USB 3 external drive. Since then, 7 out of 10 movies will stutter a lot during playback. The movie will also seem to slow down, then speed up very quickly to catch up to itself. It never did this when the library was on the internal boot drive.

And also, when watching a movie, the Mini isn't doing anything else except running iTunes.

Is there an issue with having the iTunes library on an external drive? I wouldn't think so. The external drive is a USB 3 enclosure with a Seagate 1TB 7200RPM drive inside. I would see that there might be an issue if I was wireless, but I am wired with gigabit.

Oh, and the external drive is directly connected to the Mini, it is not connected with a USB hub.

Any thoughts?

 

[rayward]

Is there an issue with having the iTunes library on an external drive? I wouldn't think so. The external drive is a USB 3 enclosure with a Seagate 1TB 7200RPM drive inside. I would see that there might be an issue if I was wireless, but I am wired with gigabit.

Logic would suggest it's the external drive or, at least, iTunes' interaction with it. I have my 1.5TB iTunes library on a 2TB WD MyBook connected to my iMac by Firewire. I have no problems with this set up. USB 3 should be plenty fast enough, so maybe check the Seagate drive's settings to see if it sleeps. It's possible that it simply may be something mechanical with the drive also.

 

[Kenjancef]

Logic would suggest it's the external drive or, at least, iTunes' interaction with it. I have my 1.5TB iTunes library on a 2TB WD MyBook connected to my iMac by Firewire. I have no problems with this set up. USB 3 should be plenty fast enough, so maybe check the Seagate drive's settings to see if it sleeps. It's possible that it simply may be something mechanical with the drive also.

Yea, I would assume that USB 3 would be fast enough, especially when connected directly to the Mini. I was even thinking of getting a 1TB 2.5" drive and just throw it in the Mini as a second drive.

(I think this is turning into a Mac Mini thread.... sorry...)

 

[priitv8]

That's strange, because my Mac Mini gets the media files from much slower NAS than your USB 3 7200rpm drive and still doesn't stutter.
That's because AppleTV is actually very good at buffering media ahead (you can follow the process by observing fillup of the white bar on the timeline).
What bitrate do these movies have?
If you see that appleTV is not at buffer underflow but the picture still stutters, then it must be overwhelming for the CPU/GPU to process the data.

 

[Kenjancef]

Not sure on how to get the bitrate of the files. Could I just open it in Handbrake, or another program, and there would be a setting to check?

 

[priitv8]

There are special programs for that. I personally am using the Media Inspector, but there ought to bee freeware available as well.

EDIT: Silly me! You can just open the movie in QuickTime Player and you will see the bitrate in Movie Inspector (Cmd+I) field Data Rate:

 

[Kenjancef]

Thanks for that tip!

I tried that with 2 movies that had issues:

E.T. The Extra-Terrestrial: 6.97 Mbit/s
Oz: The Great and Powerful: 3.10 Mbit/s

So even though I am an IT tech, I'm not too well-versed on the movie-side of things. So are those bitrates too high? There are movies that work ok with it, so I am assuming the bitrate may be lower on those?

Thanks again...

 

[priitv8]

So are those bitrates too high?

Actually - no! Up to 10Mbps should be quite chewable for aTV 3.
There must be something else at fault here.
Unfortunately, I know of no good means to graph the data rate of your USB disk. That may be one of the things to check.
Activity Monitor will give you an idea, although it shows a total throughput of all disks.

 

[niteflyr]

Run a blackmagic speed test on the ext. drive. You can get it in the App Store.

 

[Kenjancef]

Run a blackmagic speed test on the ext. drive. You can get it in the App Store.

I'll give that a shot. Could be an issue with the USB enclosure too, I just don't have a spare USB 3 enclosure at the moment. I do have a USB 2 enclosure though. Will the lower speed of USB 2 be a factor?

 

[priitv8]

Will the lower speed of USB 2 be a factor?

Not for movies at that bitrate.

PS One more thing you could check: play the movies back on VLC player, eg on Mini. Open the Media information window (Cmd + I) and observe the Statistics tab. You should see steady numbers at read media and input bitrate, and you should see minimum possible dropped frames.
I still have the impression, that there is the problem with the stream (file, disk media) or getting it to the CPU (disk media, USB, USB controller on MoBo). VLC Statistics should give a hint if this is the case, if you see dropped frames or heavy fluctuations in input bitrate.
For example, I see such numbers when reading the file over wi-fi from a Mac Mini that has USB 3.0 drive connected, where the file is stored.