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Thomas Morter-Laing
Data rate displayed?
on Jun 21, 2010 at 8:57:56 pm

Hope this isn't too basic, but can someone explain if HDV is recorded up to about 25mbps then why in the FCP browser list does it say "3.2 Mbps?" is that cos of how it's captured? In which case why then when I get info about the source footage it says the data rate is 25 (ish) Mbps? Also why is footage from an ikegami camerA got a higher data rate (3.6mbps) in FCP when it's only recording in SD? I appreciate HDV isn't the "best" HD but it's still surely better than that??? Cheers!

:D
Tom Morter-Laing
Certified Apple Product Proffessional, 2010
Production Assistant, Grace Productions
Degree; TV Production



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John Fishback
Re: Data rate displayed?
on Jun 21, 2010 at 9:13:00 pm

It may be a case of mega-bits vs. mega-bytes. There are 8 buts in a byte, so 3.2 mega-bytes/s = 8 x 3.2 = 25.6 mega-bits/sec.

John

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Thomas Morter-Laing
Re: Data rate displayed?
on Jun 21, 2010 at 9:36:42 pm

Ah good point lol, thanks for making me feel Stupid hehe! Why then is the (albeit very good) SD camera a higher bitrate than the HDV Z1?

:D
Tom Morter-Laing
Certified Apple Product Proffessional, 2010
Production Assistant, Grace Productions
Degree; TV Production



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cowcowcowcowcow
Alan Okey
Re: Data rate displayed?
on Jun 21, 2010 at 10:02:37 pm

[Thomas Morter-Laing] "Why then is the (albeit very good) SD camera a higher bitrate than the HDV Z1? "

You neglected to mention the codec that the SD camera is using.

Resolution and compression are two separate and unrelated specifications. Within each SD and HD format (SD, HD 720 and HD 1080), there exist many different compression schemes for recording. Panasonic's DVCPRO 50 is an SD format that records at 50 megabits per second vs. standard DV, which is 25 megabits per second, even though both are the same resolution. DVCPRO 50 has double the chroma sampling of standard NTSC-DV - 4:2:2 vs. 4:1:1.

HDV is a highly compressed HD format. So compressed, in fact, that it has the same bitrate as standard definition DV. This is possible via long-GOP MPEG-2 based compression, 4:2:0 chroma sampling and thin raster recording, which uses 1440x1080 anamorphic pixels vs. the square 1920x1080 pixels of uncompressed HD.


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