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MillimeterEncoding for the Apple iPad, Part 1
Apr 20, 2010 12:00 PM, By Jan Ozer
Figure 1. A 720p video played on an Apple iPad is scaled down to 1024x576 with letterboxes on top and bottom.
If the Apple iPad had a tattoo, it would read, "Born to consume content." Love it or hate it, if you're a video producer on any platform, someone soon will be asking you to get your (and probably their) content onto the iPad. So that's what I'll cover over the next two issues of Final Cut Pro Insider. In this issue, I'll look at producing videos for uploading to iTunes or for personal consumption on your iPad. Next time, I'll discuss strategies for delivering via 3G and Wi-Fi. Let's jump in.
Producing for iTunes
There are three ways of transferring video to the iPad: the physical cable, Wi-Fi, and 3G, with the last unavailable until early May. If high-quality video is your goal, the best scenario is transferring the video to the iPad via direct cable, since bandwidth restrictions don't apply. This would be the case if you’re encoding your own demo materials for a pitch meeting or encoding HD content for upload to iTunes. In these instances, I'll assume that the video is targeted for full-screen playback on the iPad, as opposed to video in a window. That being the case, what encoding parameters should you use to produce your video?
Well, starting with resolution, if you're producing for double-duty viewing on both the iPad and general-purpose computers, 720p (1280x720) is a good choice, since it plays well on the iPad and is the overwhelming choice of producers distributing HD TV shows on iTunes. On the other hand, if you’re primarily producing podcasts for mobile viewing, you should consider at least three other options: two high resolution and one low resolution.
To understand why, remember that the iPad's screen is 1024x768. When playing 720p video, the iPad scales it down to 1024x576 and displays black bars on the top and bottom, so any horizontal pixels beyond the 1024 are essentially a waste. This is shown in Figure 1, a 720p podcast from the hit show Glee.
So the first option is encoding your videos at 1024x576, which has 36 percent fewer pixels than 720p, which should translate to identical quality at 64 percent of the file size, and 64 percent of the download time for files downloaded from iTunes. The second option is 960x540, which is the resolution that iTunes uses if you choose a video and click Advanced > Create iPad or AppleTV version.
The third option is 640x360, which came into the picture courtesy of an email I received from a buddy who went to NAB this year. A few days earlier, I had asked his advice about encoding for the iPad. Here's a message he sent from Vegas.
"We had a good meeting with some Apple folks today, including the technical marketing manager, Mac OS X - QuickTime. He pointed me to a new technical note that he just published on encoding content for distribution the iPhone and iPad.
"I remembered that you were looking for some recommendations here, and apparently he has done a lot of testing to come up with these best practices. He said the iPad scaler is so good that sending content at higher res than 640x360 just isn’t worth the bandwidth."
In addition to saving space and download time, a 640x360 video will also play in the iPhone and iPod touch, as well as many older iPods, as long as you encode using the Baseline profile. So this idea has some nice appeal.
Continue the discussion on “Crosstalk” the Millimeter Forum.