intraframe (ALL-I) and interframe (IPB)??

Discussion in 'Canon DSLRs' started by Jason McDonald, Mar 2, 2012.

  1. Jason McDonald Chatty!

    This may sound like a noob question, and please point me in the right direction for how all the codecs work, but how exactly is this intraframe (ALL-I) and interframe (IPB) different (Or the same) as H.264.

    I've always wondered how video codecs work, what is best for web and what is best for TV and how to get the best in your end product.

    For photography, I shoot RAW because it retains all the data. It's not hard to capture RAW but I'm assuming it is with video. Anyways, maybe the pros can chime in...
  2. Archie Campbell Chatty!

    Intraframe and interframe are essentially different ways of compressing the movie files but they are still h.264 videos in the .mov container.

    Intraframe compresses each frame basically separating each frame and compressing it individually.

    Interframe on the other hand creates an I frame (I think this is the right terminology) every set number of frames (for example 8) and then only records the data that changes in the next frames. For example if you were filming a locked off interview then only the persons mouth and body might be moving but the background would stay the same and therefore that data could just be used from the I frame and not need to be recorded for the next few frames.

    A very basic explanation and I would be interested to know how someone can expand on this.
  3. Samuel Hurtado Chatty!

    the explanaition above is correct
    I'll add that I'm not sure all-I will deliver better quality: if it's still 8-bit 4:2:0, at 3 times the bitrate, it may be just more editor-friendly, not higher quality
    we'll see...

    edit: and also, if anybody wants more in-depth information:
  4. Archie Campbell Chatty!

    Hopefully it would be 4:2:2 colour spacing.

    Surely 3 times the bitrate means 3 times the quality and detail in the footage? I think until we see what sort of bit rate it can output it doesn't seemed to have moved that far in the 3+ years since the 5dii
  5. Samuel Hurtado Chatty!

    33 mbps interframe can look a lot better than 100 mbps intraframe in terms of detail and compression artifacts; or not; we'll have to wait and see the actual footage

    intraframe usually has the advantage that, because of how it works, it can look more organic
    but it usually requires higher bitrate for the same quality

    also, the 5D2 and its brothers are 50 Mbps, but very inefficient, quality is not any better than other implementations of H.264 at about half the bitrate
  6. Jannik Weber I'm new!

    Does anybody know (or guess, calculate) how high the data rate is? Respectively how many minutes I can record on a 32Gig with all-i? I think there will be a lot less minutes then with IPB?
  7. Samuel Hurtado Chatty!

    All-I is 91 Mbps, 680 MB/min, 47 min in a 32GB card
    IPB is 33 Mbps, 250 MB/min, 128 min in a 32GB card
    Jannik Weber likes this.
  8. Jannik Weber I'm new!

    Thank you Samuel! Then I have to change to 32GB cards...
  9. Donald Ong Chatty!

    Wow. How's the quality from IPB, then? ALL-I seems abit too big to be practical as i'll be recording events and having to change cards every 50mins is a pain. Is IPB acceptable? as long as its close to the old 5d2 or 7d then its fine. Just wnt to know if its still decent. ALL-I seems too big to be of practical event use.... of course for narrative stuff I'll use ALL-I, but for events, definitely IPB if its still decent.
  10. Samuel Hurtado Chatty!

  11. Donald Ong Chatty!

    ah ok. Btw, is the SD card slot a viable option or is it just there for lower res picture/lower res stuff? or is it actually a viable alternative to CFs? large CF cards are expensive as hell. :(
  12. Samuel Hurtado Chatty!

    IPB has a lower bitrate than the old codec, and my cheap Transcend class 10 SDHC cards work great with my T2i, so for that it's definitely ok

    for all-I, these may or may not work: 91 Mbps is just above the class 10 specification (80 Mbps sustained write speed), so some class 10 cards won't work
    some should (those expensive Sandisk one definitely should), but we'll have to wait and see
  13. Donald Ong Chatty!

    Hope the quality isn't too shabby. But then again, with the reduced moire and down scailing, it should look better than the other canons even at a lower bitrate...i hope
  14. Sarah Nichols Chatty!

    So essentially what we should say is if anybody wants to record ALL-I, get ready to spend around £80 per 40mins of video on a SanDisk Extreme Pro 32GB SDHC Card as this writes above 90Mbps and this is the speed that Canon recommends?
  15. Samuel Hurtado Chatty!

    I think you're mixing bits and bytes: you don't need a 90 MB/s card for 90 Mbps footage!
    class 10 is >10 MB/s sustained write - that is 80 Mbps - most class 10 cards will work with all-I, but some won't
  16. Donald Ong Chatty!

    Haha yes. I'd have to say. The guy who came up with bits and bytes ought to be shot. Bloody imbecile. Couldn't they have less confusing units?
  17. Sarah Nichols Chatty!

    Would you say the IPB is better quality than the ALL-I as I have not seen any comparisons and it does not seem to be discussed as much as I thought it would be.
  18. John Schultz I'm new!

  19. Donald Ong Chatty!

  20. John Schultz I'm new!

    IPB can look soft without post processing, however it's the highest quality in terms of real detail and low noise. If the customer can sharpen and add noise/grain in post, that would look the best. Otherwise, ALL-I with in-camera sharpening looks fine to many people. The noise also helps with perceived detail/texture. Experiment with in-camera sharpening to get an acceptable look.

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