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Everyone was rejoicing when Blu Ray’s standard allowed manufacturers to include uncompressed sound on disks. Most certainly Blu Ray’s provide much improved sound but did you know that even DVDs allowed sound with more precision than some of today’s Blu Ray’s have? Let me explain…

Perceptual Coding

Perceptual coding in terms of audio and video means removal of information that cannot be perceived or distinguished by the human visual or auditory systems (your eyes and your ears). In even simpler terms, it is removal of stuff that you would not actually notice if it was removed. Why is this important? Well, it allows us to cram a 3 hour movie on a disk at a quality that would normally take about 25 Blu Ray disks.

If you have limited space or bandwidth, perceptual coding is ALWAYS going to give you better quality than lossless / uncompressed data. This is true for both video and audio. For example, if we were to take the data rate of uncompressed audio on Blu Ray today and we were to use perceptual coding using the same bitrate, we would be able to allocate more bits and more precision to data that we can actually perceive which would give higher perceived quality. In the same space, we could have movie soundtracks running at 96Khz sampling rate (96 samples a second) and 32bit precision of the individual samples, which would give audio a completely lifelike sound.

The Reality of Movie Soundtracks

Unfortunately, when it comes to movie soundtracks – unlike music – very few have been recorded and mixed at the higher sampling rate. This means that uncompressed sound at the current sampling rate (48Khz) and bit precision (16 to 24bits) is as good as it gets until studios decide otherwise. But it is good to know nevertheless that you don’t necessarily want lossless coding, especially when you have limited bandwidth. Lossy coding – if done correctly – will give better sound and picture at the same bandwidth.

While We Wait

While we wait, there are ways that sound can be much improved in a Home Cinema. I will be talking about these in the coming weeks.

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