Apparently this is a big deal. B frame is only used on high end pro camcorders..? And I guess this is a big thing and has the Canon 7d videophiles in a big buzz. Can anyone expand on. This?
Nikon D7k 1080p video in..... B frame?
(10 posts) (10 voices)-
Posted 2 years ago #
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Yes - what is B frame?
Posted 2 years ago # -
It comes after A frame and before C frame… lol
Posted 2 years ago # -
"# B‑frames can use both previous and forward frames for data reference to get the highest amount of data compression."
For more info: http://en.wikipedia.org/wiki/Video_compression_picture_types
To sum it up, it is a very good video compression method, at least from my understanding of the article.
Posted 2 years ago # -
I have a limited knowledge of such things and while it is beneficial and semi-bad for Canon, the D7000s bitrate sort of brings it down to an "eh" level.
Since Canon's all do IP but at a higher bit rate they will win when the D7000 is recording anything fast moving however if they are both recording something semi-static the D7000's video will match the Canon's even at a smaller bit rate.
If that makes any sense to anyone, not even I understand if what I said is correct.
I need more sleep.
Posted 2 years ago # -
krevlingoodspeed said:
I have a limited knowledge of such things and while it is beneficial and semi-bad for Canon, the D7000s bitrate sort of brings it down to an "eh" level.Since Canon's all do IP but at a higher bit rate they will win when the D7000 is recording anything fast moving however if they are both recording something semi-static the D7000's video will match the Canon's even at a smaller bit rate.
One can not so simplistically compare the bitrate of a stream with bidirectional frames to one without and pull meaningful quality comparisons from it.
One needs to take a great deal of caution when drawing quality assumptions from bitrate in general. In any perceptual encoding process the "maturity" of the encoder is paramount, as implementation is very complex and not set in stone by the MPEG standards. For example: LAME (MP3) can typically achieve perceptual transparency around 200kbps VBR whereas the Blade and Xing encoders struggle to at 320.
In other words, all speculation on video quality before comparing apples to apples is masturbation at best.
Posted 2 years ago # -
Testing123 is right.
However, B framing is better than Canon's method of framing, which just compresses each frame internally. This cannot be disputed. It is a superior compression technique that achieves smaller files at the same quality or the same size files at a superior quality.
Nikon appears to have gone with smaller files at similar quality. Online comparisons of the 60D / T2i and the D7000 are virtually indistinguishable, but Nikon's files are 1/2 the size of Canon's video files (approximately 170MB/minute compared to 330MB/minute for Canon).
I had a T2i and one of the reasons I sold it to get a D7000 was that I was sick of filling my memory cards up with just the tiniest bit of video. It is ridiculous. Then you have to deal with storing it.
The D7000 shoots 720p at 24p or 30p, which is great for me. With the T2i you are forced to do 720p at 50p/60p, which means you are stuck with effectively twice as much data. That might be nice in some situations but it means 720p has the exact same bitrate as 1080p on a T2i(it has twice the pixels, but half the frame rate = same amount of data). The best scenario would be able to choose between 24/30p and 50p/60p at either resolution, but if I'm going to be forced to pick one I'll take 24/30p. I'm shooting home / vacation videos, not a blockbuster cinema, which shoots at 24p anyway. At 720p*24p, you are down to 1/4 of the T2i's bitrate. That's a significant difference in file output size. I might actually enjoy shooting video instead of stressing at how quickly my memory card is filling up.
The one down side is that B framing takes more processing power to achieve, but apparently the Expeed2 is up to the task. It is highly likely that Nikon choose, in addition to using a better compression algorithm, to increase the compression above and beyond the T2i, which means that the video quality will not be as nice. However, what I have seen leads me to believe this trade-off for dramatically smaller sizes was worth it.
Posted 2 years ago # -
All else being equal, interframe IBP compression should be superior to intraframe compression. I assume the AVCHD CODEC employed by the Nikon D7000 is a form of long-GOP interframe compression. I wasn't aware that the Canon CODEC was intraframe only. Anyone know the size of both Nikon's and Canon's GOPs?
Posted 2 years ago # -
Did you hear that? That was my head exploding at the alphabet soup of complex algorithms used for recording video on a digital photography camera. ( JK I appreciate the info)
Posted 2 years ago # -
studio460 said:
All else being equal, interframe IBP compression should be superior to intraframe compression. I assume the AVCHD CODEC employed by the Nikon D7000 is a form of long-GOP interframe compression. I wasn't aware that the Canon CODEC was intraframe only. Anyone know the size of both Nikon's and Canon's GOPs?oh Studio, I am so positive you said something here, but I haven't the slightest idea of what it was.
Posted 2 years ago #
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