Practical Technology

for practical people.

Do you really need to upgrade your Apple TV’s hard drive?


Let’s head deep into Apple TV video geekiness shall we?

Many users, and I was one of them, looked at the Apple TV’s 40 GB hard drive, and said, “You’ve got to be kidding.”

In what seemed like a matter of hours, other Apple TV fans came up with hardware hacks to add a bigger hard drive. Heck, within days, there were Apple authorized resellers who could add a bigger hard drive for you and not blow away your warranty at the same time. But, now I really wonder if you need to go to all that trouble.

I took a long, hard look at the Apple TV’s actual video output, at its networking capabilities, and what happened in the real world when I watched movies and TV by streaming them instead of storing them on my Apple TV’s hard drive. Here’s what I found.

First, without any software hacking, the Apple TV supports both MPEG-4 and H.264-encoded files. Video content, even with the compressed formats, takes up room, a lot of room.

MPEG-4 was designed to deliver DVD and HDTV quality video, usually transmitted or stored in MPEG-2 format, at lower data rates and smaller file sizes. It’s also become the format of choice for delivering HDTV over satellites in the future. For example, DirecTV is switching to MPEG-4 so that it can deliver far more HD channels than it does currently.

Not everyone is happy about this development. Some people are, with reason, concerned that their current MPEG-2 HDTV equipment won’t work with the new technology.

Be that as it may, in the Apple TV, Apple uses it own variations on these video codices, MPEG-4 part 2 (aka MPEG-4 simple profile) and MPEG-4 part 10, better known to us Apple TV users as H.264.

MPEG-4 on the Apple TV can handle up to 3 Mbps of video content with a maximum resolution: 720 by 432 pixels at 30 fps (frames per second). On the audio side, Apple TV delivers AAC-LC (Advanced Audio Coding Advanced Audio Coding) audio up to 160 Kbp (kilobits per second) and a maximum sampling rate of 44.1 kHz for both MPEG-4 and H.264.

In practice, what this means is that you can stream 480i and 480p content of slightly less than DVD quality in my experience over a decent quality 802.11g connection. As the connection worsens, say for example if you were trying to use 802.11b or a less than optimal 802.11g hook-up, Apple TV will put delivering fps at a higher priority over resolution. The end result is, to my eyes, a grainer display but one that tends to avoid fast moving action artifacts.

The moral of this part of my tale is that while you can run an Apple TV on a slow Wi-Fi connection, you really don’t want to try it.

Now, with H.264, we can get progressive video with B-Frames with a maximum sustained bitrate of 5Mbps (Megabits per second).

That means for those of us in front of the television, we can get 720p HDTV at 24 fps. Once more, if your connection gets iffy, Apple TV will put delivering high fps over resolution. At this point, you’re just asking for trouble if you’re using 802.11b. On a good day, with the wind blowing the right way, 802.11b can deliver 4 to 5 Mbps. Don’t count on it.

Yes, I know 802.11b is supposed to go 11 Mbps and 802.11g, without any fancy extras, should go 54 Mbps. Boy, do I know how Wi-Fi is supposed to work. But, the simple truth is that they don’t. If you want to see 720p HDTV, your Apple TV won’t be the bottleneck. It will be your Wi-Fi connection.

That said, a good 802.11g connection can easily handle Apple TV’s minimum requirement of 5 Mbps. Of course, that predisposes that you’re not using your network bandwidth’s for something else. Even with a great connection, you can’t expect to get a good video stream if you’re also downloading megabytes of files on your PC and your kid-brother is playing World of Warcraft on his box.

Now, the Apple TV also supports 802.11n, which is faster still. And, true 802.11n can 108 Mbps and faster rates. The problem is that, even now, 802.11n isn’t a true, finalized standard. 802.11n is getting closer to being a real standard, but it’s not there yet. Given the vendors’ checkered history of infighting (PDF link), I’m not counting on it.

If you decide to give 802.11n a try, get Apple’s own new MA073LL/A AirPort Extreme Base Station. I’ve learned the hard way that draft 802.11n APs (access point) may not work worth a darn with a device or network card using someone else’s 802.11n technology.

Come the day 802.11n is a real standard, it may well be worth getting. As it happens, I also found that an Apple TV can deal with up to 12 Mbps transmission bursts. Don’t get any ideas about Apple TV handling 1080p anytime soon. It can’t, in my playing with it, seem to consistently handle those peaks. I will say, however, that you may be pleasantly surprised at how well Apple TV handles bursts of furious video action in your movies.

What I think is really important about all this is that, with a good network, you can quite happily view videos without syncing them to your Apple TV. Yes, you can hack your Apple TV to add a bigger hard drive, but based on what I’m seeing with Apple TV’s video and networking capabilities you don’t really need to do it.

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