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Old November 19th, 2007, 11:48 AM   #1
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Number of iframes different in 24p?

I cannot find my original source (late night surfing, I'm afraid) but I believe I read somewhere that the EX generates more iframes (or was it only iframes) when shooting at the 24fps rate.

If so it would end any reservations about the MPEG long GOP issue. Does anyone have any information about this or I am just projecting?
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Old November 19th, 2007, 11:55 AM   #2
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It's long GOP and it looks great, especially at 35 mb!
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Old November 19th, 2007, 12:47 PM   #3
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Quote:
Originally Posted by Jim McQuaid View Post
I cannot find my original source (late night surfing, I'm afraid) but I believe I read somewhere that the EX generates more iframes (or was it only iframes) when shooting at the 24fps rate.

If so it would end any reservations about the MPEG long GOP issue. Does anyone have any information about this or I am just projecting?
In 25p, the GOP is 12-frames long; I guess 24p is not different.
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Old November 19th, 2007, 01:16 PM   #4
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Are you talking 1080p or 720p?

with 720p 24p the bitrate is virtually already as good as I frame only because there are 2.5 less frames to encode then 60p.

If you are talking 1080p then I don't know. Be carefull however the more I frames you add in the harder it gets to compress at lower bitrates. If you add too many I frames the compression quality could actually look worse.

The other thing to think about is that even with a GOP of 12 that still only equals 2 I frames per second of video. The same as if you used a 15 GOP with 30p. It's all about the ratio of I frames per the rate of the video. If you could have video at 6p you could have a GOP length of only 3 frames but that would still result in only 2 I frames per second.
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