IPB vs ALL-I doubts

[Rafael Lopes]

Ok, so I was checking out the Canon 6D manual and I´ve read that shooting 1920, 24p IPB you can get around 1h of shooting, whereas with 1920, 24p ALL-I you get ONLY around 20min. The manual says ALL-I is "more suited for editing". Is this really true? I´ve read on dpreview that the reviewers could not tell the difference. I´d really like to know if anyone cared to do some side by side comparison and came to practical conclusions.

[Evan Donn]

Couldn't tell the difference in quality, or in editing? I think they're probably a wash in terms of quality - each has it's own shortcomings. The main difference is that IPB requires more processing power to decode, so ALL-I will let a slower processor playback and edit more easily. The thing is now a lot of editing systems leverage the GPU to decode AVCHD, so you may not see much performance difference at all on a system with a sufficiently fast GPU. In that case it's likely to become more apparent in situations where you are trying to play back multiple simultaneous streams that all need to be decoded at once.

[Rafael Lopes]

Could not tell the difference in image quality. Did you try both ways? Does it bring any benefits shooting ALL-I , like it doesn´t degrate as fast when color correcting?

BTW, what does the MarkII use?

[Evan Donn]

MarkII is IPB. I don't think ALL-I brings any real image quality improvement, either in capture or post. It's basically the same codec, just used in a way that is less efficient but also less computationally intensive to decode. Because it's less efficient it has to run at a much higher data rate to keep the image quality on par with IPB. In fact there may be situations where it's slightly worse than IPB due to it's lower efficiency, i.e. high-detail combined with high motion. If the post production playback performance isn't of benefit to you then I don't think there's much reason to use ALL-I.

[Jon Fairhurst]

In theory, ALL-I is better for fast motion scenes, but the advantage might be small in reality. Between rolling shutter and lower overall efficiency, ALL-I might not buy you much for high-motion scenes.

That said, for high-motion, handheld work, I'd probably choose ALL-I. I like "theory".

For instance, in theory, I have a 5D3. In reality, I only have a 5D2. :)

[Charles Newcomb]

Originally Posted by Evan Donn

MarkII is IPB. I don't think ALL-I brings any real image quality improvement, either in capture or post. It's basically the same codec, just used in a way that is less efficient but also less computationally intensive to decode.

Interesting. Because of this thread I went into a documentary I've been working on. Half was shot with the MK2, half with the MK3. Because Canon recommended it, I shot the MK3 footage in All-I. But when I look at the footage in FCPX, I see absolutely no difference between the MK2 & MK3 quality or playback speed.

Now I'm wondering why I shoot everything in ALL-I.

[Taky Cheung]

Visually there aren't much difference. IPB is more compressed with interframes compression, long GOP (group of picture). All-I means all I-Frame only which makes scrubbing and playback a lot faster.

The day I do Same Day Edit at weddings, I will do All-I because I can edit faster with a regularly laptop.

[Jad Meouchy]

I did some really basic side-by-side testing at 50mbps (6D) and couldn't perceive a difference, though the IPB actually seemed to hold up better when pushing the color. Like others have said, ALL-I is made for easier/faster editing at the expense of file size and codec efficiency. Given the same bitrate, IPB should and does look better.