FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)

Started Sep 25, 2010 | Discussions
DLSRmovie
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FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
Sep 25, 2010

Just got a response from Nikon regarding how they compress their
h264 video.

Response (David D.) 09/24/2010 09:02 PM
HI

Thanks for the question. The D7000 uses B frames in it's H.264 encoded video. Thanks

-David

Thanks for using Nikon products!

Nikon Inc. (USA) Support / Service
http://support.nikontech.com

harri manni
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to DLSRmovie, Sep 25, 2010

Good or bad?!

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gaman
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to harri manni, Sep 25, 2010

harri manni wrote:

Good or bad?!

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Harri - My blog: flatulated.blogspot.com

Good for Nikon - bad for Canon

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gaman
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to gaman, Sep 25, 2010

Just to explain:

When "B" (bidirectional) frames are used, the compression engine is more efficient and gives better results, around 15/20%, at a given bit rate.

The new D7000 iseems to have a lower bit rate of 20Mbits compared to the 40Mbits of 7D and 550D (but Canon's didn't use B frames).

Does this mean we have to expect same - or better - quality than the other comparables DSLRs with higher bit rates?

I think we'll find an answer in the next days...

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MichaelIsGreat2
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to harri manni, Sep 25, 2010

Bad is probably the answer to whether B-frames are good or bad!

What are B-frames?
From Wikipedia:

The three major picture types used in the different video algorithms are I, P and B. They are different in the following characteristics:

  • I‑frames are the least compressible but don't require other video frames to decode.

  • P‑frames can use data from previous frames to decompress and are more compressible than I‑frames.

  • B‑frames can use both previous and forward frames for data reference to get the highest amount of data compression.

From this definition, I assume that, when the processor is not quick enough and/or when the data throughput is not quick enough, basically the cheapest solution is to use B frames and use slower processors and data lanes. The costlier solution would be to use a speedier processor and implement speedier data throughput.

I am no expert on this matter! Let others, more knowledgeable people, give their feedback on this matter so that my attempt to answer can be assessed for good. Thanks in advance, you knowledgeable guys on this matter.

Another question. Do the HD video on the Canon DSLR cameras use B frames? That is also another interesting question I would like to have an answer.

Having said that, HD video on the D7000 is focused on families and I guess that this implementation with B frames is sufficient to get the job done.

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goodgoings
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to MichaelIsGreat2, Sep 25, 2010

In my understanding B frames are good and it may hold up well against the Canon's less effective compression.

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gaman
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to MichaelIsGreat2, Sep 25, 2010

MichaelIsGreat2 wrote:

Bad is probably the answer to whether B-frames are good or bad!

What are B-frames?
From Wikipedia:

The three major picture types used in the different video algorithms are I, P and B. They are different in the following characteristics:

  • I‑frames are the least compressible but don't require other video frames to decode.

  • P‑frames can use data from previous frames to decompress and are more compressible than I‑frames.

  • B‑frames can use both previous and forward frames for data reference to get the highest amount of data compression.

From this definition, I assume that, when the processor is not quick enough and/or when the data throughput is not quick enough, basically the cheapest solution is to use B frames and use slower processors and data lanes. The costlier solution would be to use a speedier processor and implement speedier data throughput.

I am no expert on this matter! Let others, more knowledgeable people, give their feedback on this matter so that my attempt to answer can be assessed for good. Thanks in advance, you knowledgeable guys on this matter.

Another question. Do the HD video on the Canon DSLR cameras use B frames? That is also another interesting question I would like to have an answer.

Having said that, HD video on the D7000 is focused on families and I guess that this implementation with B frames is sufficient to get the job done.

AH.264 video sequences can be encoded using only the I frames (lower compression, higher bit rrate and image quality but bigger files), or using various combinations of B and P frames - added - to the I frames (B or P frames only, can't be used).

Tipically, most DSLRs use IP sequences for video encoding. Given the same bit rate, adding the B frames improve the overall efficience reducing visible artefacts at the same time.

Also, it means that the same quality of a IP sequence can be attained with fewer bits.

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powertoold
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to MichaelIsGreat2, Sep 25, 2010

You can also look at it the other way: more compression means better processor.

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gaman
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to powertoold, Sep 25, 2010

powertoold wrote:

You can also look at it the other way: more compression means better processor.

True (as long as the image quality is preserved).
Usually, B frames require codecs with more computational power.

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jonrobertp
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to gaman, Sep 26, 2010
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could care less how they do it. But does it really AF during vid shooting ????

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DLSRmovie
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to jonrobertp, Sep 26, 2010

It's true that it can never be 100% B-frame, b/c you still need some i-frames like
for the 1st frame since there wouldn't be a prior frame.

It seems like for interview type videos, B-frames would be very efficient, but if you
are recording in a situation where the subject is moving and/or the camera is
moving then B-frames would be inferior b/c the actual contents would be
approaching what i-frames do, which is record every frame every time.
And in the latter case, the Nikon is limited to half the bitrate of the Canon.

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Rexyinc
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to DLSRmovie, Oct 27, 2010

Where did we get with all this now?

Good ? Bad ? Better then canons version of compression?
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zm15
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to Rexyinc, Nov 19, 2010

B frames are a very good thing since they pull image information from the surrounding frames, thus you can keep more of the image intact instead of just the P data.

I pictures can contain only intra macroblocks
P pictures can contain either intra macroblocks or predicted macroblocks
B pictures can contain intra, predicted, or bi-predicted macroblocks

source: http://en.wikipedia.org/wiki/Video_compression_picture_types

So in summary, B frames are a good thing because they gather info from both directions to form the image.

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The Big One
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Re: FYI: Nikon D7000 uses B-frames for h264 encoding (just confirmed)
In reply to jonrobertp, Nov 19, 2010

jonrobertp wrote:

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could care less how they do it. But does it really AF during vid shooting ????

You mean the 7000? On paper, yes, but in real life I find it is not that great, and prefer manual focsusing. YMMV of course.

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