Playing 5.1 audio from a MacBook

This Much I Know – » 5.1 surround sound playback on Mac (and maybe Apple TV)

QuickTime doesn’t come with an [tag]AC-3[/tag] codec by default. There is an open-source QuickTime component available, called A52Codec, which enables QuickTime to open, import and export AC-3 audio. (It does this using a free AC-3 library called liba52.) A52Codec provides some form of support for working with AC-3 under QuickTime, at least for file conversion and export. What the A52Codec can’t do, however, is to enable applications to stream encoded AC-3 data straight to the optical output on the Mac.

Apple’s DVD Player application – included for free on every Mac – can play the 5.1 AC-3 audio from a physical DVD directly through the optical output of your Mac. DVD Player does this by streaming the encoded AC-3 straight from the DVD to the optical out, bypassing QuickTime. Some other players – notably VLC (which also uses liba52) – will stream AC-3 straight to your optical output, too. But any application which uses QuickTime for its audio playback – and this includes Front Row, iTunes, and QuickTime Player – works by first decoding audio into its discrete channels, before outputting it to your system audio device. The AC-3 encoding is lost in the process. So if you want a Mac Mini and Front Row to run your home theatre, with 5.1 sound from third-party movie files, then it’s not so easy.

Bluray has won, now what?

I’ve paid no attention to home theaters for the last four years (really!) because there has been a major format war between HD DVD and Blu Ray and more over I can’t imagine throwing away the gigantic 200 kg 72″ rear projection TV monster I have, but with HD DVD dying this February and so many plasma’s coming out, its time to see what the story is. Here is the scoop:

* This old Mitsubishi 72″ rear projection actually doesn’t look too bad. It produces 1080i60 (that’s 1080 lines vertical, interlaced at 60 frames per second. Confused yet?). It also handles 480p30 (which is 480 lines progressive at 30 frames per second). It is amazing, but even though acquired either years ago, that’s really not all that bad. Today’s flat screens can handle 1080p30 which it turns out is essentially identical to 1080i60 in bandwidth).
* It only has component inputs which means it uses three wires rather than the new HDMI (HDMI gloms it all together and also adds audio while DVI used by computers is similar but doesn’t carry audio). All Blu Ray players have component output. Right now, the Comcast HD DVR for instance products full 1080i60 and also Dolby 5.1 via optical output, so the Mitsubishi is actually well matched to this.
* There is a scary set of “flags”: (that no one uses today) that tells the Blu Ray player not to send 1080i60 signals to “component outputs”: But no discs today actually implement it.

The net of it is that in order to upgrade to Blu Ray, it looks like it will work out OK mainly because all the source material produced by Hollywood is in 1080p24 form right now. When they send things out as 1080p60, so double the frame rates, then that year 2000 RPTV is obsolete. Whew!

OTOH, will you really see a difference with “Blu Ray”: most good DVD players that are stuck with 480i60 and actually doing upconverts to 480p30, so it doesn’t look all the bad. While that doesn’t sound like it, it turns out that in terms of resolution 480p30 is like getting 960i60 so it is pretty close to 1080i60. Net, net, it isn’t clear how much better the picture is. The key again is that source material is actually in 1080p24, so that is the best you can see in the end.

There are many “comparisons”: that show how much better 1080p images are as single images. I actually find these pretty strange since they really aren’t right. If you show a 1080p image as a single frame you will get double the resolution so it will look better as iLounge shows. This is because the 1080i image is actually done as two fields of 540 lines that come out twice as fast. If you do that math, it is better clear that 1080p24 source material has to look more or less the same at 1080p30 or 1080i60. If there is ever 1080p60 film from Hollywood, then everyone needs new televisions. Even some new films like “Star Wars”: was shot in 1080p60, these have not yet seen the light of day and most traditional films were done 24fps.

Even in digital movie theaters (drool, drool), the standard formats are 1080p24, 2160p24 (whoohoo!) and 1080p48.