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T2i frame dropping?


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#1 Cristian Carceller

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Posted 09 November 2010 - 01:55 AM

So I have just got off of a shoot with the t2i. But when I brought the footage to the computer, I saw that random " glitching lines" would appear mainy with zoom and pulling focus
I recorded on a sandisk class 10 8gb card. The card was full at the end. Is this why. Also the footage was played straight off the computer, hasn't gone through my workflow with m peg stream clip. I think this problem is dropping frames l? Is this happening to anyone else? I might get the 16gb for the problem or is it a waste of money?
Please let me know because I have to shoot again this Saturday but I do not want to run into this problem
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#2 Cristian Carceller

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Posted 09 November 2010 - 01:59 AM

Should I just upgrade to compact flash cards?
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#3 Cristian Carceller

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Posted 09 November 2010 - 02:15 AM

Nvm, t2i's don't support cf cards
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#4 Phil Rhodes

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Posted 09 November 2010 - 02:58 AM

You need to extract some stills and post them here or it's difficult to be specific.

P
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#5 Saul Rodgar

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Posted 09 November 2010 - 04:49 AM

I have noticed dropped frames on footage from 5Ds and other DSLRs' too. Like frames missing every so often, most noticeable on footage of slow and continuously moving things like smoke. Or it happens when the camera moves too fast, long-GOP compression style, which h264 as a codec uses, if in a combination of intraframe and interframe compression. This unlike older, less advanced long-GOP codecs such as HDV, say, which only uses interframe compression, but which is widely known to cause dropped frames during fast moving pans, etc. Advanced h264-based codecs like AVC Intra are better at handling this type of video dropouts, because they have been designed from the ground up for serious motion picture production, see below.

Compounding the h264 long-GOP issues, and because all this information needs to be encoded real time on the camera- which is very processing intensive- I think some of it also has to do with the fact that because most HDSLRs were never intended to be used a serious motion picture production cameras, when the camera's circuitry can't handle the processing crunch, it just drops frames. I have not tried comparing side-by-side cameras with double DGIC 4 processor to single processor ones tho. And it could be individual camera issues, and not inherent to the codecs or the number of processors they possess. But I sort of doubt that is the case.

Still, for the relatively high quality image one gets for the price and portability of today's HDSLRs, one's got to take the good with the bad. And there is no such thing as a perfect film or video format or video codec either . . . ;)

Edited by Saul Rodgar, 09 November 2010 - 04:51 AM.

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#6 Saul Rodgar

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Posted 09 November 2010 - 05:08 AM

My mistake, h264 is not long-GOP, but its problems can be attributed rather to its slice encoding protocol.
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#7 Phil Rhodes

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Posted 09 November 2010 - 06:38 AM

h264 is not long-GOP




Well, usually it is - the most common applications of h.264 are things like Youtube and Vimeo and Quicktime movie trailers, all of which use the technique.


AVC Intra is a variant of h.264 that simply doesn't use B or P frames. Some cameras, such as the Panasonic GH1, do not use B (bidirectionally-predicted) frames in order to simplify the task of encoding, although this does quite adversely affect both objective SNR and perceived image quality. The GH2 apparently uses both B and P frames.


The only other DSLRs that don't use long-GOP encoding are those capable of MJPEG recording, such as the Nikon range; MJPEG is intrinsically I-frame only.


P
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