5MB/s?? at DVinfo.net

Rob deJong · December 27th, 2009, 01:49 PM

I do not understand the specs of the 7D. After all the positive info on image quality of 7D video, I cannot beleive the bitrate of 5 MB/s in the specs on Dpreview. What does this mean? It is much lower then most camcorders. Worse image quality?

Perrone Ford · December 27th, 2009, 01:52 PM

Umm, common mistake.

The "B" is capitalized. 5MBps = 40Mbps. Usually you see the Mbps listed for camcorders.

Mark Holmes · December 27th, 2009, 03:39 PM

Yep - it's easy to forget the bytes/bits thing...

Ian G. Thompson · December 27th, 2009, 05:12 PM

Yup....confusing. As much as I already know this I still get caught up in the confusion every now and then.

Pedanes Bol · December 27th, 2009, 08:21 PM

Quicktime inspector shows 48 mbits/s for the original 7D 1080/30p clips.

Ian G. Thompson · December 27th, 2009, 08:32 PM

Yup...that 48 megabits/s equals around 5.5 MB/s.

Keith Moreau · December 28th, 2009, 12:20 PM

Has anybody seen any codec related motion artifacts at this pretty high bitrate and theoretically good codec? I haven't noticed but I haven't been looking hard.

Perrone Ford · December 28th, 2009, 12:32 PM

Quote:

Originally Posted by Keith Moreau

Has anybody seen any codec related motion artifacts at this pretty high bitrate and theoretically good codec? I haven't noticed but I haven't been looking hard.

Many. And I've posted some here.

Liam Hall · December 28th, 2009, 12:43 PM

Quote:

Originally Posted by Keith Moreau

Has anybody seen any codec related motion artifacts at this pretty high bitrate and theoretically good codec? I haven't noticed but I haven't been looking hard.

Loads. Some shots have been totally unusable due to the failings of the codec. But at least I know what to avoid now:)

Jan Tervo · January 1st, 2010, 01:20 PM

Quote:

Originally Posted by Liam Hall

Loads. Some shots have been totally unusable due to the failings of the codec. But at least I know what to avoid now:)

Could you send some examples, please.

Kind regards,
jan

Barry Green · January 2nd, 2010, 04:48 PM

Quote:

Originally Posted by Keith Moreau

Has anybody seen any codec related motion artifacts at this pretty high bitrate and theoretically good codec? I haven't noticed but I haven't been looking hard.

Understand that while the bitrate is pretty high, and the codec is theoretically good, the particular implementation of the codec is simplistic, so the overall performance isn't nearly as good as you'd expect. Not all implementations of h.264 are equivalent. There are certain features or tools that the designers can choose to use or not use. On the 5D/7D, they chose not to use B-frames, and B-frames give the codec incredible efficiency. As a net result, 50mbps of h.264 on the 5D/7D isn't nearly as robust as the 21mbps PH mode of AVCHD h.264 is.

So -- to sum it up, the codec in the 7D is pretty good, but as for codec artifacting, it's probably only about HDV caliber when all is said and done.

December 27th, 2009, 01:49 PM	#1
Rob deJong Regular Crew Join Date: May 2009 Location: Saly Hungary Posts: 169	5MB/s?? I do not understand the specs of the 7D. After all the positive info on image quality of 7D video, I cannot beleive the bitrate of 5 MB/s in the specs on Dpreview. What does this mean? It is much lower then most camcorders. Worse image quality?

December 27th, 2009, 01:52 PM	#2
Perrone Ford Inner Circle Join Date: Nov 2006 Location: Tallahassee, FL Posts: 4,100	Umm, common mistake. The "B" is capitalized. 5MBps = 40Mbps. Usually you see the Mbps listed for camcorders. __________________ DVX100, PMW-EX1, Canon 550D, FigRig, Dell Octocore, Avid MC4/5, MB Looks, RedCineX, Matrox MX02 mini, GTech RAID, Edirol R-4, Senn. G2 Evo, Countryman, Moles and Lowels.

December 27th, 2009, 03:39 PM	#3
Mark Holmes Regular Crew Join Date: Mar 2004 Location: San Diego, California Posts: 119	Yep - it's easy to forget the bytes/bits thing... __________________ Mark Holmes www.daisy3pictures.com

December 27th, 2009, 05:12 PM	#4
Ian G. Thompson Major Player Join Date: Jan 2007 Location: Rockledge, Florida Posts: 351	Yup....confusing. As much as I already know this I still get caught up in the confusion every now and then.

December 27th, 2009, 08:21 PM	#5
Pedanes Bol Regular Crew Join Date: May 2007 Location: Boston MA Posts: 167	Quicktime inspector shows 48 mbits/s for the original 7D 1080/30p clips.

December 27th, 2009, 08:32 PM	#6
Ian G. Thompson Major Player Join Date: Jan 2007 Location: Rockledge, Florida Posts: 351	Yup...that 48 megabits/s equals around 5.5 MB/s.

December 28th, 2009, 12:20 PM	#7
Keith Moreau Major Player Join Date: Nov 2006 Location: Brisbane, California Posts: 530	Has anybody seen any codec related motion artifacts at this pretty high bitrate and theoretically good codec? I haven't noticed but I haven't been looking hard.