Recover 4:4:4 from 7Ds HDMI output

[Paul Frederick]

ProVideo Coalition.com: TecnoTur by Allan Tépper

Real interesting article! Claims that the 7D really only records a 1620x910 image that is upscaled to the card. What you see on the HDMI output is really what is recorded then it's upscaled and recorded to card.

[Ian G. Thompson]

Paul, as I mentioned to you that’s not what they are saying. Instead of trying to make sense out of this 3rd party article go to the Syndicate’s actual Web site and see what they have to say. But once again this is what I see:

“Due to the nature of the 7D HDMI output the actual usable resulting frame will be uncompressed 1620x910, but will be the same crop as the 1080p compressed material on the camera's memory card. In the top right corner there will also be a red dot that has to be removed in post by grabbing those pixels from the corresponding file on the camera's memory card. We're working on automating this process in future versions.”

They are not suggestion anywhere on their site that the actual resolution from the 7D is upsized from 1620x910. It’s how the picture looks in overlays….especially when using the EOS Utility software. They even mention Hudson’s hack and are hoping he is able to get the full 1920x1080…..that it shoots. With that particular comment they made…I am suspecting they are capturing the image somehow through the EOS utility software. I do it on my PC with the 7D…over USB…with screen capture software…and it’s all uncompressed….but with the focusing square in it. This is all ‘before” it hits the card. But I still have to upscale it to 1920x1080 from about 1620x910. I don’t know how they are making it 4:4:4 from 4:2:0 though.

Basically you are getting that smaller resolution because you are working with a window within a window. So, those guys really have not hacked the cam and they are still not capturing what the cam actually records. Their statement only suggests that they are capturing the same 16:9 SHAPE that you see on the card...not the resolution.

[David Chapman]

I get it (after reading from the source).

The article author should have said, "The uncompressed 1620x910 is the same pixel ratio as the 1920x1080 that is recorded to the card compressed and can be upscaled to match the true 1920x1080 size."

1620x910 x 15.6% = 1920x1080

The article makes it sound like "the same crop that is recorded to the card" being a cropped end result and not full HD. Gosh, Allen :-)

[Ian G. Thompson]

Ha...yeah David...it is a little misleading.

Whatever it is the Syndicate is doing to get 4:4:4 seems cool though. But for $300 USD I can live with the 4:2:2 that the HDMI puts out.

[Tim Kay]

Originally Posted by Ian G. Thompson

Ha...yeah David...it is a little misleading.

Whatever it is the Syndicate is doing to get 4:4:4 seems cool though. But for $300 USD I can live with the 4:2:2 that the HDMI puts out.

hmmm, and how does one do this ?

[Paul Frederick]

Ian,

Thanks for clearing that up! It was misleading. I agree $300 US is way to much to pay to check it out though.

[Ian G. Thompson]

Originally Posted by Andy Dufrain

hmmm, and how does one do this ?

He he...just waiting patiently for Mr. Hudson to do his "Magic"...Lantern.

You should still be able to grab a 4:2:2 image...but not at 1920x1080 and not without that irritating red dot in the upper right hand corner. The Syndicate got around that but using a piece of the compressed image...and ...kinda "pasted" it over. After that they did some kind of Mojo (with their software) to make it 4:4:4. You got me on that one.

Hey Paul...no problem. I'm still learning this stuff just like you..

[Robert Kennedy]

Could someone please reconstruct the 4:4:4 in my old VHS home videos?

I did my own quick test on the HDMI signal to be sure.. here's the link to the ProRes:

Comparison of HDMI vs. CF card from a Canon EOS 7D on Vimeo

Conclusion: In the current firmware, there is not a wealth of information in the HDMI feed that is "lost by the H.264" compression. Capturing the HDMI signal poses many problems with little benefit.

I've been looking for a <$2000 camera with a S35 or larger sensor, interchangeable lens mount, a live output of 1080/23.98p uncompressed 4:2:2 via HDMI (or HD-SDI). Sadly the 7D (which I happily own) does not fit that bill. 10-bits would be great too.

[Ian G. Thompson]

Just what do you really expect from HDMI output other than 4:2:2? Visually HDMI doesn't make that much of difference on any HDMI cam that I've seen. Start doing things like chroma keying and then you'll really start seeing the benefits.

By the way...I think it's the other way around...the compressed image actually looks more contrasty than the HDMI output (if ever so slightly).

[Robert Kennedy]

I observed a greater disparity in image quality when comparing the HDMI out of an HDV camcorder as I expected.

I got what I expected from my testing, not what I had hoped.