Picture: 
Sound: Extras:
Movie: Picture: Sound: Extras:
But despite this, the Blu-ray version is a must-have for those who love Zeppelin's music. It isn't because the picture, which is variable (big chunks are quite out of focus), but because of the excellent sound.
My old DVD version carried two channel Dolby Digital @ 192kbps. In 2007 (around the time of the Blu-ray release in the US) there was a deluxe two disc DVD version with the sound remastered into DTS 5.1, supervised by Jimmy Page. But the main audio track in this version employs Dolby TrueHD 5.1 at 16 bits, 48kHz. The lossless compression means that the bitrate is variable, according to the demands of the moment. It averages 2,088kbps, which is towards the top of the range for 16 bit, 48kHz Dolby TrueHD movies.
A high average bitrate can be caused by several things, and not necessarily higher quality. More use of the surround channels uses up bits, as does high average levels of sound, as does audio that is relatively unpredictable (such as random noise or transients). In this case it is the high average level of the sound and the fairly extensive bleed into the surround field that generates the high figure. If there is significant levels of noise, it is lost under the sound.
This track was also reported by my Yamaha home theatre receiver to actually have 6.1 channel EX encoding. That is, a surround centre channel is embedded into the regular surround channels and can be extracted for their use by modern decoders.
The result was excellent for the most part. On some tracks Plant's vocals were a touch quiet, but were brought out simply by turning up the volume to lift the level of the whole thing. Jones' keyboard intro on the 'No Quarter' was a little crunchy, but it sounded like he had bumped up some setting on the keyboard to give it some bite, rather than a particular distortion problem. The standouts were Page's guitar and Bonham's drums, both rendered with excellent clarity and articulation.
The surround channels were used primarily for ambience and crowd noise, except for a couple of discordant mix effects.
The TrueHD track has a core of Dolby Digital 5.1 with the maximum bitrate of 640kbps. This is duplicated with a standalone Dolby Digital 5.1 640kbps audio track to which the disc defaults, so be ready to flick over. The music proper doesn't start for 12 minutes, so you have plenty of time.
(Australian rating); Region Free
At the top of each is the full frame (suitably shrunk down) used in the comparison, with a 250 pixel wide detail from the frame underneath. The left side is from the PAL DVD. The image was captured digitally from the disc, scaled up from its native 720 by 576 pixel resolution to 1,024 by 576 (to present in the correct aspect ratio) by the application. I then scaled it, in order for it to be comparable to the Blu-ray version, to 1,920 by 1,080 pixels.
The detail is from that last scaled version, and has not been rescaled again. The right side is from the Australian Blu-ray. This has not been scaled at all. Different applications were used to capture the two frames, so some caution should be exercised in judging colour and brightness.
For visitors from NTSC lands, generally the PAL DVD is just a touch sharper than the NTSC DVD.
