Quote:
Originally Posted by socalkev
MPEG4, especially when made with H.264, shows the same quality as MPEG2 at about a third or so of the bitrate. Quoting from the Apple web site,
Even with that, though, a 720p file has roughly 3 times the pixels of an NTSC DVD file. Apple's 720p trailers are usually 5000-6000, for example. |
imagine what happens when you try to cut the bit-rate down by a factor of 4 like Apple?s iTune HD rental service or you try to cut it down 10 times like some websites. Granted the usage of higher-end codecs like H.264/MPEG4-AVC or VC-1 can lessen the losses in quality, but no compression technology in the world can handle fast changing video with low bit-rates without severe degradation. People often hear MPEG-4 and the knee-jerk reaction is that it?s automatically better than MPEG-2 because they see a bigger number but that?s only true if it?s at or almost the same bit-rate.
In light of the fact that 8 mbps 1280×1080 video gets you sued, you have to wonder what Steve Jobs is thinking when he says Blu-ray and HD DVD will get killed by download services such as his newly launched 4 mbps 720p ?HD? iTunes movie rental service. I guess if consumers believe the lie that you can do HD with these low bit-rate downloads, then Steve might be right. But with cheap 42 inch 1920×1080 full 1080p LCD and Plasma panels coming out spring this year at less than $1400, consumers are going to be in for a surprise when they see the difference between the free stuff coming over the airwaves versus the crap they actually pay for coming from Satellite and download services.
Video quality reference table from best to worst:
Source/service CODEC Resolution Bit-rate
Blu-ray H.264 or MPEG2 1920×1080 1080i/p 40
Xbox Live Video VC-1 1280×720 720p 6.8
DVD MPEG2 720×480 480i * 8
Apple iTunes QuickTime/H.264 1280×720 720p 4
Web ?HD? downloads H.264 1280×720 720p 1.5
* Can up-scale well up to 1080i or 1080p because of reasonable bit-rate.