On Apr 21, 2008, at 9:35 PM, Frank Bulk - iNAME wrote:
I've found it interesting that those who do Internet TV (re)define HD in a way that no one would consider HD anymore except the provider. =)
The FCC did not appear to set a bit rate specification for HD Television. The ATSC standard (A-53 part 4) specifies aspect ratios and pixel formats and frame rates, but not bit rates. So AFAICT, no redefinition is necessary. If you are doing (say) 720 x 1280 at 30 fps, you can call it HD, regardless of your bit rate. If you can find somewhere where the standard says otherwise, I would like to know about it.
In the news recently has been some complaints about Comcast's HD TV. Comcast has been (selectively) fitting 3 MPEG-2 HD streams in a 6 MHz carrier (38 Mbps = 12.6 Mbps) and customers aren't happy with that. I'm not sure how the average consumer will see 1.5 Mbps for HD video as sufficient unless it's QVGA.
Well, not with a 15+ year old standard like MPEG-2. (And, of course, HD is a set of pixel formats that specifically does not include QVGA.) I have had video professionals go "wow" at H.264 dual pass 720 p encodings at 2 Mbps, so it can be done. The real question is, how often do you see artifacts ? And, how much does the user care ? Modern encodings at these bit rates tend to provide very good encodings of static scenes. As the on-screen action increases, so does the likelihood of artifacts, so selection of bit rate depends I think on user expectations and the typical content being down. (As an aside, I see lots of artifacts on my at-home Cable HD, but I don't know their bandwidth allocation.) Regards Marshall
Frank
-----Original Message----- From: Alex Thurlow [mailto:alex@blastro.com] Sent: Monday, April 21, 2008 4:26 PM To: nanog@nanog.org Subject: Re: [Nanog] ATT VP: Internet to hit capacity by 2010
<snip>
I'm going to have to say that that's much higher than we're actually going to see. You have to remember that there's not a ton of compression going on in that. We're looking to start pushing HD video online, and our intial tests show that 1.5Mbps is plenty to push HD resolutions of video online. We won't necessarily be doing 60 fps or full quality audio, but "HD" doesn't actually define exactly what it's going to be.
Look at the HD offerings online today and I think you'll find that they're mostly 1-1.5 Mbps. TV will stay much higher quality than that, but if people are watching from their PCs, I think you'll see much more compression going on, given that the hardware processing it has a lot more horsepower.
-- Alex Thurlow Technical Director Blastro Networks
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