Billups article clarification? at DVinfo.net

Ken Hodson · December 1st, 2006, 12:59 AM

I was reading an article called "Scott Billups Tests Canon XL H1" from a competing site, so I don't want to provide a link.
In this article there is this quote which I do not understand, as well as never read any where before.

"The XL H1’s true 25Mbps segmented-frame signal packs 50 Mbps into each frame on tape while the SDI signal is a whopping 1.2Gbps."

50 Mbps huh?

Chris Hurd · December 1st, 2006, 07:53 AM

No problem with the link -- it's http://www.digitalvideoediting.com/a...e.jsp?id=43573

Billups wrote that article back when Canon USA was still in the "we will neither confirm nor deny" stage regarding Frame mode and how it works, so everything written about it back then (the article is from May 2006) was at best merely well-intentioned speculation.

Barry Green · December 1st, 2006, 10:43 AM

Obviously it's not phrased properly; of course there's not 50 megabits of information in each frame on tape.

Two ways you could look at it -- if we're talking about how much room each frame takes up on tape, you could simplify it by saying each frame is about 1 megabit, but that wouldn't be accurate because of the long-GOP nature of the encoding; the first frame in the group might take up substantially more space and then every following frame of the group takes up substantially less space.

The other way to look at it is, he might have been saying "since the HD-SDI signal is 1.2 gigabits per second, and there are 24 frames per second, each frame holds 1200/24 = 50 megabits of raw uncompressed information.

But I don't know why he would bother trying to spell that out, because it's completely irrelevant when it comes to what's on the tape. On the tape, each frame averages out to be about one megabit, not 50.

December 1st, 2006, 12:59 AM	#1
Ken Hodson Trustee Join Date: Aug 2003 Location: Vancouver BC Canada Posts: 1,315	Billups article clarification? I was reading an article called "Scott Billups Tests Canon XL H1" from a competing site, so I don't want to provide a link. In this article there is this quote which I do not understand, as well as never read any where before. "The XL H1’s true 25Mbps segmented-frame signal packs 50 Mbps into each frame on tape while the SDI signal is a whopping 1.2Gbps." 50 Mbps huh? __________________ Damnit Jim, I'm a film maker not a sysytems tech.

December 1st, 2006, 07:53 AM	#2
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	No problem with the link -- it's http://www.digitalvideoediting.com/a...e.jsp?id=43573 Billups wrote that article back when Canon USA was still in the "we will neither confirm nor deny" stage regarding Frame mode and how it works, so everything written about it back then (the article is from May 2006) was at best merely well-intentioned speculation. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

December 1st, 2006, 10:43 AM	#3
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	Obviously it's not phrased properly; of course there's not 50 megabits of information in each frame on tape. Two ways you could look at it -- if we're talking about how much room each frame takes up on tape, you could simplify it by saying each frame is about 1 megabit, but that wouldn't be accurate because of the long-GOP nature of the encoding; the first frame in the group might take up substantially more space and then every following frame of the group takes up substantially less space. The other way to look at it is, he might have been saying "since the HD-SDI signal is 1.2 gigabits per second, and there are 24 frames per second, each frame holds 1200/24 = 50 megabits of raw uncompressed information. But I don't know why he would bother trying to spell that out, because it's completely irrelevant when it comes to what's on the tape. On the tape, each frame averages out to be about one megabit, not 50.