IPB vs ALL-I Encoding.
 

I have been shooting HD video with the 7D and just got a 5D3, I haven't shot with it yet, I decided to actually read the manual.

The manual doesn't get into much detail about the differences between the two types of encoding. With the 7D I use MPEG StreamClip to convert the clips to ProResLT, so editing has never really been an issue. Is there a noticeable improvement in image quality to justify the extra file size?

Any other benefits to using ALL-I?

Thanks

~chuck

Re: IPB vs ALL-I Encoding.
 

Almost a hundred people have read this post with no response.

Is this a stupid question? Has it been answered so many times that I should not have to ask it? Nobody Shooting video with the 5D3? Is the DSLR Video revolution is over?

Re: IPB vs ALL-I Encoding.
 

ALL-I is basically intra frame compression. This means each frame is encoded not as a group of pictures (GOP) but a whole picture for each frame.

In high motion scenarios, ALL-I is very important as using IPB means you're estimating picture information from 1 complete picture every 12 or 15 frames based on the motion in the picture.

The trade-off is that ALL-I at lower bitrates may look worse than IPB or Long-GOP. 100Mbps is usually the sweet spot for H.264 based Intra frame encoding. (which is what AVC-Intra from Panasonic uses)

If you do any high motion video, you will really benefit from ALL-I.

Re: IPB vs ALL-I Encoding.
 

It is also much less processor intensive to edit.

Re: IPB vs ALL-I Encoding.
 

I did not reply because I'm not very knowledgeable about the subject. I use All-I because the manual recommends it. I do notice the files take up more room than when I used to use the same card in the 5D MK ll.

I wasn't aware I was supposed to post replies to every thread I read, even if I have nothing to contribute. I'll try to be less of a deadbeat in the future, I promise.

Re: IPB vs ALL-I Encoding.
 

Thanks for asking. This is a question I've been wanting to know the answer to as well.

Chris thank you for your great response.

Re: IPB vs ALL-I Encoding.
 

Now we're cooking with gas. Thanks for the replies.

I shot a little last night and encoded ALL-I to ProRes LT with MPEG streamclip. One of the clips was actually smaller when encoded to ProRes LT so I'm guessing that would have something to do with VBR H264.

Is there a difference in bit rate between the All-I and IPB? Since the camera can now record the increased bit rate for All-I is the bit rate greater for the IPB? If I'm not shooting things with lots of motion would/could IPB be better?

The only way to figure this out is to shoot a lot with both in different scenarios to see which performs better but I thought it might be a good idea to start a thread to discuss this because I don't think its obvious and maybe someone had actually shot some tests they would be willing to share with us.

Charles, I've been doing this for quite a while and try to answer or share my experiences as much as I can. The more I do this the more I realize how much more I have to learn. I don't think people who ask more questions than they answer are "deadbeats" nor do I think that of people who don't answer every question they read, but when the 7D came out this forum was a lot more fun and useful. I guess for a brief time we were all kind of new to DSLR video.

Re: IPB vs ALL-I Encoding.
 

Time for a little theory...

As mentioned above, I-frame only means that each frame is complete. It is compressed, yes, but without referring to other frames. The only compression occurs within the frame. Typically, this means it is better for editing natively, and should have a higher bitrate. It will take more storage. It *should* show fewer compression artifacts.

P-frames refer to previous frames, and therefore can be more highly compressed.

B-frames refer to previous and following frames, and can be still more highly compressed.

When we look at the results, the most important question is: Are my IPB files showing compression artifacts? If so, are my IP files? If so, are my I-only files?

Second, is my editor decoding these quickly enough so I can have a good editing experience? This doesn't really matter if you're transcoding to an editing codec like ProRes, as the original poster is.

Third, am I having any media problems? Running out of space? Cards fast enough to record I-only without dropping frames?

What is "best performance"? If it's only about image quality, then most I-frame implementations, if they have enough bitrate, should be "better" than most IP or IPB encodes. If you have good media and lots of it, why not record all I-only?

On the other hand, if you never see compression artifacts with IPB or IP files, good enough is good enough, isn't it? You do need to also think about IP and IPB performance on heavy grading, chromakey, or other filters that might see visual data invisible to the eye.

This is all theoretical, because actual performance really depends on the specific implementation of these encodes.

Re: IPB vs ALL-I Encoding.
 

I've been shooting ALL-i. Works great. Looks awesome, especially in 720p (doesn't break up in fast movement at all)

Re: IPB vs ALL-I Encoding.
 

I have shot music videos using IPB and results are just fine. If you're transcoding before you edit, I would recommend sticking with IPB... if you want to edit the native h.264 content, All-I may be something to think about.

As said before, for fast moving shots All-I would be a consideration... but for the most part you'll just wind up with larger files and fill your memory cards faster.

If you like to zoom your footage up to analyze pixels, or compare specs you may see a difference. But looking at the screen the way your audience/client sees it, I don't see the benefits to using it

Re: IPB vs ALL-I Encoding.
 

IPB is about 30Mbps while ALL-I is about 90Mbps so you fill up the cards 3X as fast i.e. 4 min per GB versus 80 seconds per GB. For our use (mostly weddings) I see no discernible difference in video quality between IPB & ALL-I so we use IPB. We edit in Premiere Pro which handles it fine without transcoding.

Re: IPB vs ALL-I Encoding.
 

Exactly Nigel... if you can't see the difference, the specs don't mean much. At least to me...

Re: IPB vs ALL-I Encoding.
 

I use the IPB all the time for wedding footages. Less space eating up and no difference in quality as well.