Some new notes about AppleTV

Another braindump so I can actually put in public what I’ve been doing in my spare time lately, given that most likely a lot of that won’t continue in the next months, as I’m trying to find more stable, solid jobs than what I’ve been doing as of lately.

If you follow me for a long time you might remember that a few years ago I bought an AppleTV (don’t laugh) for two main reasons: because I actually wanted something in my bedroom to watch Anime and listen to music and was curious about the implementation of it from a multimedia geek point of view. Now, a lot of what I have seen with the AppleTV is negative, and I’m pretty sure Apple noticed it just as well as I have. Indeed they learn from a lot of their previous mistakes with the release of the new AppleTV. Some of the “mistakes they learnt from” would probably not be shared by Free Software activists and hackers, as they were designed to keep people out of their platform, but that’s beside the point now.

The obvious problems (bulkiness, heat, power) were mostly fixed in hardware by moving from a mobile i686-class CPU to an ARM-based embedded system; the main way around their locks (the fact that the USB port is a standard host one, not a gadget one, and it only gets disabled by the lack of the Darwin kernel driver for USB) is also dropped, but only to be replaced with the same jailbreak situation they ahve on iPhone and other devices. So basically while they tried to make things lot more difficult, the result is simply that they hacked it in a different way. While it definitely looks sleeker to keep near your TV, I’m not sure I would have bought it if it was released the first time around this way.

At any rate, the one I have here is in its last months, and as soon as I can find something that fits into its space and on which I can run XBMC (fetching videos out of a Samba share on Yamato), I’ll probably simply get rid of it, or sell it to some poor fellow who can’t be bothered with getting something trickier but more useful. But while I want the device to actually accept the data as I have it already for what concerns Anime and TV series (assuming I can’t get them under decent terms legally), some months ago I decided that at least the music can bend over to the Apple formats — for the simple reason that they are quite reasonable, as long as I can play them just fine in Europe.

Beside a number of original music CDs (Metal music isn’t really flattered by the compression most online music stores apply!), I also have (fewer) music DVDs with videos and concerts; plus I sometime “procure” myself Japanese music videos that haven’t been published in the western world (I’m pretty much a lover of the genre, but they don’t make it too easy to get much of it here; I have almost all of Hikaru Utada’s discography in original forms though). For the formers, Handbrake (on OS X) did a pretty good job, but for the new music videos, which are usually in High Definition, it did a pretty bad job.

Let’s cue back FFmpeg, which, since last time I ranted actually gained a support for the mov/mp4 format that is finally able to keep up with Apple (I have reported some of the problems about it myself, so while I didn’t have a direct bearing in getting it to work, I can say that at least I feel more confident of what it does now). To be honest, I have tried doing the conversion with FFmpeg a few times already; main problem was to find a proper preset for x264 that didn’t enable features that AppleTV failed to work with (funnily enough, since Handbrake also uses x264, I know that sometimes even though iTunes does allow the files to be copied over the AppleTV, they don’t play straight). Well, this time I was able to find the correct preset on the AwkwardTV wiki so after saving it to ~/.ffmpeg/libx264-appletv.ffpreset the conversion process seemed almost immediate.

A few tests afterward, I can tell it’s neither immediate in procedure, nor in time required to complete. First of all, iTunes enforces a frame size limits on the file; while this is never a problem for content in standard definition, like the stuff I ripped from my DVDs, this can be a problem with High-Definition content. So I wrote a simple script (that I have pasted online earlier tonight but I’ll publish once polished a bit more) that through ffprobe, grep and awk could maintain the correct aspect ratio of the original file but resize it to a frame size that AppleTV is compatible with (720p maximum). This worked file for a few videoclips, but then it started to fail again.

Turns out, 1280×720 which is the 720p “HD Ready” resolution, is too much for AppleTV. Indeed, if you use those parameters to encode a video, iTunes will refuse to sync it over to the device. A quick check around pointed me at a possible reasoning/solution. Turns out that while all the video files have a Source Aspect-Ratio of 16:9, their Pixel Aspect-Ratio is sometimes 1:1, sometimes 4:3 (see Wikipedia’s Anamorphic Widescreen article for the details and links to the description of SAR and PAR). While Bluray and most other Full HD systems are designed to work fine with a 1:1 PAR (non-anamorphic), AppleTV doesn’t, probably because it’s just HD Ready.

So a quick way to get the AppleTV to accept the content is simply to scale it back to anamorphic widescreen, and you’re done. Unfortunately that doesn’t seem to cut it just yet; I have at least one video that doesn’t work even though the size is the same as before. Plus another has 5.1 (6-channels) audio, and FFmpeg seems to be unable to scale it back to stereo (from and to AAC).