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Post By
Henrique Ferreira

In Reply To
Reverend Meteor

Subj: Re: Meteor has a dumb question...
Posted: Wed Jan 09, 2008 at 08:28:13 am EST
Reply Subj: Re: Meteor has a dumb question...
Posted: Tue Jan 08, 2008 at 06:02:46 pm EST

Previous Post

> > Ok on to my dumb question. The Blu-Ray discs are about 25 GB right? Does that I can put 25 GB of movie files on one disc or is it still going to be about 2+ hours of video that the disc can contain? If a disc could contain 25 GB of video I would be impressed.
>
> Single layer is 25GB, dual layer is 50GB.
>
> As for what the disks can hold, they can hold 25GB (or 50) of data, in whatever format it comes, be it a few hours of video at 1080p resolution at 40 Mbps, plus audio tracks with several channels, or 25GB (or 50) worth of data files in any formats. It's just like a DVD, only with a lot more room for storage.

Ok the reason I asked was because I saw this on wikipedia:

The choice of codecs affects the producer's licensing/royalty costs, as well as the title's maximum runtime, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more advanced video codecs (VC-1 and H.264) typically achieve a video runtime twice that of MPEG-2, with comparable quality.

So I wasn't sure if that meant the codec limited how much the disc could hold to a couple hours or something else.

> Ok the reason I asked was because I saw this on wikipedia:
>
> The choice of codecs affects the producer's licensing/royalty costs, as well as the title's maximum runtime, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more advanced video codecs (VC-1 and H.264) typically achieve a video runtime twice that of MPEG-2, with comparable quality.
>
> So I wasn't sure if that meant the codec limited how much the disc could hold to a couple hours or something else.

Yeah, the codec limits it, just like on DVD. You can encode 12 42-minute episodes of a given show on XviD (roughly 8 hours worth of video), at a 800~1100Kbps video rate and 125Kbps MP3 sound rate, and you'll have twelve ~350MB files, which fit on a (single-layer) DVD, but can only be played on a PC or on a DivX player.

Or you can encode 150 minutes of video at 3837Kbps in MPEG-2 with audio at 224Kbps audio and it'll fit on a (single-layer) DVD - on DVD Video format, which will play in any DVD player.

H264 compression, for those who know how to work with it, is great because at a similar bitrate than the XviD above it has much better quality, and at a smaller bitrate, it can still achieve at least the same, if not better, quality. Of course, other problems regarding the encoding arise, making it harder to work with for some kinds of videos, but that's neither here nor there (and I'm not informed the least to elaborate on that).

Suffice to say, the choice of the codecs with which the video is encoded has affected the DVD just like it will affect the BRD. Think of the BRD as a 25GB (or 50) DVD. From a DVD to a BRD (with the same number of layers) you can roughly multiply the hours of video 6 times at the same quality, increase the quality 6-fold, or any of the variants in-between (any mix of adding more video and increasing the overall quality).

Henrique Ferreira




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