In case you missed it (har, har), Apple shipped the iPad in early April. I think one of the best uses of the new device will be for video playback and photo display. In this column, I’ll discuss how to encode video for the iPad. What’s that you ask? Do I have one? Well, sure, certainly. What do I think? Well, I’ve only had it for a grand total of less than a day, but I’ve already formed some strong impressions. Actually, I have a bunch of them, some not my own.
For example, my kids loved it on first sight. But then, what’s not to like if you’re not paying for it? In essence, for them, it’s a huge iPod touch, but it’s much better at games and for surfing the web. My youngest, who’s 9, starting downloading free apps from the App Store. It was kind of fun hanging out and watching her shop and play. My eldest, 12, jumped right on Facebook, and trust me, she didn’t want me hanging out and watching her. Both of them looked up periodically and asked, “Don’t you just love it, Daddy?” “Maybe if I get a chance to actually use it,” I thought but, tactfully, didn’t state.
My wife, who’s suddenly (and thankfully) connecting to her frugal side, looked it over for about 10 minutes, and asked “What do I need this for? I still need my laptop for writing and updating my website, and I still need my cell phone for calls. It’s too big to be a music player. Who’s going to buy this thing?”
As for me, I have multiple impressions. As a longtime technology guy, I hated that I had to plug into iTunes before even using the iPad; it felt like a velvet chain tying me to Apple. While I recognize that iTunes has been a fantastic tool for many folks who are less computer-literate than me, I chafe at having to work through iTunes to get podcasts and other content onto my iPod. I’d rather simply drag and drop via Finder or Windows Explorer. That said, there are some nice touches, such as the ability to automatically resample all the pictures in your collection before transfer to save space on the iPad.
My second impression was as a content producer. As you’ve undoubtedly heard, the iPad isn’t a device for content production; there are few tools, and the typing, while probably best-in-category for a touchscreen, is still miles behind even the lowliest netbook keyboard. If I have a column to write on a plane, I’ll bring my netbook.
My final impression came as I sat with my 12-year-old before bed, when she discovered the pictures I transferred over and started scrolling through them. In this role, the iPad has no equal. You can scroll through at any pace, choose pictures with a touch of the finger, and zoom in and out with simple pinch controls. Then it struck me that the ideal use for the iPad would be as a demo platform for videographers and photographers. Say you meet potential clients at a restaurant or at their office. Sure, you could carry a notebook, but that takes 3 minutes to boot, and it’s invariably awkward to carry and set up. The iPad turns on instantly, the screen looks great, and navigation is touchscreen-simple. If you’re looking for a device to unobtrusively show off your work demo reels, this is it.
This leads us back to encoding for the iPad. Before choosing a definitive set of encoding parameters, let’s discuss some interesting data points. First, while the iPad can play 720p video encoded in H.264 format (Main Profile, Level 3.1), it automatically shrinks the video to fit the 1024x768 screen, with black bars atop and below the 720p video. If you choose a video in iTunes and click Advanced > Create iPad or AppleTV version, iTunes converts the video to 960x540 at about 3.75Mbps. If I were creating video for transferring over to an iPad via cable—say, a demo reel or the first draft of a wedding video—I would use those specs.
Second, though Wi-Fi has wonderfully high maximum connection speeds (such as 54Mbps), during my tests, the iPad was located right next to the wireless router, and I pulled a maximum of 856Kbps, with other readings (using CNET’s connection speed test) as low as 130Kbps; it averaged in the 600Kbps range. If you’re encoding video for real-time delivery from the web to the iPad via Wi-Fi, a 600Kbps target sounds about right.
Interestingly, Apple has released some very detailed recommendations that you can find here. For Wi-Fi delivery, the document recommends 640x360 resolution at data rates ranging from 640Kbps to 1.24Mbps, with 40Kbps audio at 22.05 sample rate, presumably mono, though that’s not stated. Note, however, that these recommendations are for HTTP live streaming, which means that if the iPad can’t sustain the throughput at the higher rates, it will automatically drop down to a lower rate. If you’re producing only a single stream, I’d encode at a max of about 800Kbps, which should provide plenty of quality at a stream that the iPad can retrieve and play in real time.
Jan Ozer (jan at doceo.com) is a frequent contributor to industry magazines and websites on digital video-related topics. He is chief instructor at StreamingLearningCenter.com.