Blu-ray Reviews: The Sound of High Definition

Basically, by setting a Blu-ray player to the task of trying to decode the content of these tracks, I can determine whether it is actually capable of handling a full Dolby Digital Plus or Dolby TrueHD audio track, or merely the standard Dolby Digital core contained within it. By having this contents listing here I can relax about the scrap of paper I previously had this information recorded on.

Incidentally, if you're sharp eyed, you may notice that Titles 18, 19 and 20 have slighty different video standards. 18 and 19 I've put down at 1080i60, while 20 I've put down at 1080p60. In 18 and 19 there is a repeated sequence of three clean frames, then two interlaced, then three clean and so on. In 20 the sequence is thus: A B C D D E F G H H. In other words, there are four clean frames and then the fourth frame is repeated. Why is this? Who knows. Why the difference with Title 18 which, graphically, is virtually identical except for this cadence difference? Who knows.

There is some interesting bass -- random noise I think, but perhaps intentional -- with significant output as low as 11.7 hertz on this disc as well. More on this here.

UPDATED 16 March 2009: I have corrected a couple of minor errors in the table below, and added bitrates for the Dolby TrueHD tracks. These are derived from the excellent BDInfo tool (version 0.5.2). So also are the bit-depths (16 or 24 bits) for the Dolby TrueHD tracks.

Cinema Squid, the creator of BDInfo, rightly points out that the bitrate for lossless audio tracks like Dolby TrueHD and DTS-HD Master Audio has no relationship whatsoever to the fidelity with which they capture the audio tracks. I, like he, simply enjoy having extra information available. But it does also tell you something, which Mr Squid also points out: 'it's just an indicator of the compressability of the source'. Why can some sources be more highly compressed than others?

It could be a coincidence in the way the algorithm analyses the particular audio tracks. But mostly it has to do with the number of levels and the number of channels employed. If a 5.1 channel sound track just bleeds a little audio to the surround channels from time to time, you're going to get a good level of compression (compared to the original 5.1 channel PCM). A busy sound track employing all the channels most of the time will give much lower compressibility.

By golly, you could almost come up with a 'surround utilisation' metric. But that will require more thought.