All-I vs IPB – What do they mean?

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The Canon 5d Mark III lists the options of All-I and IPB in the movie recording size menu so I dug around to find what these two options mean. All-I and IPB are different methods of compression, but both are still h.264 videos with a .mov output.

IPB Compression

IPB is interframe compression and balances good image quality with a reduced overall file size. IPB is an option for Canon’s 5D Mark III and EOS-1D X (as of March 2012).

With this video compression, not all frames are kept and individually compressed. Instead, one key frame (or interframe) per every half second, for example, would be kept in full. For the other frames between key frames, the compression system just maintains the visible changes and uses the previous key frame to guess what the missing data is. The B in IPB stands for Bidirectional compression because this compression system looks at the previous key frame AND the following key frame to extrapolate the missing data. However, this compression method only allows in camera editing for one second increments. Further, frame by frame editing on the computer results in slightly lower image quality.

IPB compression is useful when long continuous recording is necessary but tight frame by frame editing is not required in post production. With IPB compression, a 4GB file would be roughly equivalent to 14 minutes of continuous recording at 1920 x 1080.


All-I Compression

All-I uses an intraframe method of compression. This method treats each captured frame as key frames and compresses them. As such this compression method generates a higher quality and the capability to edit frame by frame. Because it retains so much more data, this compression method generates file sizes about 3 times larger than those with the IPB method. A 4GB file with ALL-I compression would generally only be 4.5 to 5 minutes of continuous video at full HD 1920 x 1080.

All-I would be ideal for short clips that need tight editing.

8 comments for “All-I vs IPB – What do they mean?

  1. April 8, 2014 at 3:58 pm

    thanks much, this is a very helpful explanation.

  2. Jose Acosta
    September 6, 2014 at 1:27 am

    Thanks for the excellent explanation of the difference between these two types of video compression.

    Is it correct to state that the critical user will not see a difference in the two compression methods that come out of the camera? i.e. Are the differences only noticeable when editing?

    What are some examples of clips that would benefit from the frame-by-frame editing quality of All-I compression?

  3. John Versteege
    September 10, 2014 at 5:32 am

    Just found your website. I have learned already a whole lot and have been
    perusing for only 10 minutes. I feel like a kid in a toy store… Not afraid to ask…:-)
    Thank you for your approach. You are reaching the keen folks.

  4. Mau Perez
    November 29, 2014 at 6:31 pm

    Thank you very much for the information. 🙂

  5. January 1, 2015 at 4:23 am

    This is one of the most easy to understand posts on video compression. I would certainly experiment with both formats and test the final results.

  6. Singh
    January 7, 2015 at 6:58 am

    Very well put, that explains the concept effectively. Thank you for this.

  7. February 4, 2015 at 3:57 pm

    Great explanation. Thank you!

  8. Tolonge
    March 20, 2015 at 9:20 pm

    I’ve learned a lot, many thanks.

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