intra-frame compression Vs interframe compression? how do they help movie rec.?

[ssrdd]

As we have seen the new flag-ship 1D-X, it has these two optional video recording compressions.
how do they really improve the image cadency and resolution? i read in articles since last night how do they really help in editing room?

thank u for u r valuable time,
shiva.

 

[akiskev]

As we have seen the new flag-ship 1D-X, it has these two optional video recording compressions.
how do they really improve the image cadency and resolution? i read in articles since last night how do they really help in editing room?

thank u for u r valuable time,
shiva.

One thing I know for sure is that a video with only I frames, is very easy to decode and process.
IPB offers better compression but is more cpu intensive.This happens because way more calculations are needed to be done to decode P and B frames(compared to I frames).

Another thing I would like to discuss is that I frames in h264 encoding do not offer some big improvement (quality or compression wise) over I frames produced with mpeg4 or mpeg2. h264 is all about P and B frames. If you take P and B out of the equation, then you end up doing the same thing with a very old codec.
With a video with I frames only, you will need way more bitrate to have the same image quality you 'd have with an IPB video.
Surely if the bitrate is very very high, the image quality will be great. The way I see it, this I-only video mode is a move towards raw video.

 

[NormanBates]

IPB uses a lot of math to achieve a very similar (but not quite equal) image quality with much lower bitrate

therefore, for watching, IPB is great

but for recording and for editing, intra is a lot better:
* much faster to edit and work with (not really an issue if you use premiere CS5 with CUDA acceleration; but even then, for after effects it makes a difference)
* more headroom to tweak in post: with IPB you're throwing some information away; it's the kind of information that your eyes just can't see; but if you want to color grade that footage heavily, those small differences will stand up

so: if you're using a serious workflow, intra is awesome; if you're shooting footage and posting it directly on the internet, IPB is just as good

(in any case: with high enough bitrate, IPB can be just as good as intra; but then it has no advantage over intra, and is more difficult to decode)

 

[akiskev]

(in any case: with high enough bitrate, IPB can be just as good as intra; but then it has no advantage over intra, and is more difficult to decode)

I agree with your post except this part. I think it's the other way around. In low bitrates IPB has the advantage over I-only encoding, but in high enough bitrates intra "catches up".

 

[NormanBates]

at any given bitrate, IPB can always deliver better image quality (it does the same, with less restrictions, so it has to throw away less info); but once the bitrate is high enough, the difference is very small, and IPB becomes too complex to encode and decode, whereas intra remains useable

"the intra advantage" is that it is less complex, and given enough bitrate it doesn't need to throw away a lot of information

in any case, in relation to the 1DX, there is a lot of conflicting information regarding codec and bitrate

mainly, we have two different bits of information regarding codec and bitrate:
* first, dpreview said: “a 16Gb card will hold around 6 minutes of footage” which means 350Mbps
http://www.dpreview.com/articles/5149972341/canon-eos-1d-x-overview
* now, canon professional network says: “When filming with ALL-I, file sizes will be around three times larger than with IPB”
http://wideopencamera.com/just-the-cut/canon-1d-x-what-the-compression/
only one way to make those match: in the dpreview thing 16Gb actually means gigabits, IPB is 17Mbps, and all-I is 50Mbps
but who uses gigabits to talk about SD card capacity? and who is still using 2GB cards?
if this is right, it means 8 bit, and probably 4:2:0 too
let’s wait and see, but it could be very disappointing