Pixel shift technology re Canon Pro Camcorder XH-A1 and XF -305

[Brian Louis]

[Bob Dix] “Apart from blu-ray , is there any way to get your edited video on to a TV except by Pro tape ?”
When you say “a TV” are you refering to viewing it on a TV or for Broadcast??

[Bob Dix]

Hi Brian,
Either way , we go to a TV via blu-ray and tape HDMI now, are there any alternatives ?
But, do you know anything about Canon’s pixel shift technology and how do you get an edited project from a HDD camcorder direct to a TV ? Or can you Export direct into Memory CF or SD card in a XH -A1 Camcorder ?

Freelance Imaging & Video
AUSTRALIA

[Brian Louis]

I usually save edited files to Harddisk for archiving and previewing via a Harddrive docking station and a WesternDigital HD player($100us), I don’t bother saving back to CF/SD as harddrives are much cheaper per gig than cards.

This link refers to pixel shifting and reasons for it, usually to increase apparent resolution.
https://en.wikipedia.org/wiki/Three-CCD_camera

[Bob Dix]

Thanks, Brian, good idea.

Anything on Canon’s Pixel shift technology ?

Freelance Imaging & Video
AUSTRALIA

[Bob Dix]

Sorry,
I did not see the link you gave me . It does not appear to have anything to do with “stretching the pixels” from 1440 x1080 to 1920 x 1080i in a single CMOS rated 1920 x 1080p which imports to Premiere Pro as 1440 x 1080i and then miraculously appears as 1920 x 1080i when played from a tape via HDMI to a TV ?

Freelance Imaging & Video
AUSTRALIA

[Brian Louis]

[Bob Dix] “a single CMOS rated 1920 x 1080p which imports to Premiere Pro as 1440 x 1080i and then miraculously appears as 1920 x 1080i when played from a tape via HDMI to a TV ?”

Hi Bob:
There is a bit of signal processing magic at work, if you take the output of the 1920×1080 image sensor at 4:2:2 there isn’t enough bandwidth to fit it on a 25Mbps DV style tape, so image signal processing reduces the pixel count to 1440 horizontal which is anamorphic, this reduces the horiz pixel by almost a third, Quadratic manipulation reduces the color space from 4:2:2 to 4:2:0 which is another form of compression, the resulting video is further compressed by a Mpeg2 algorithm to give you 1440×1080 4:2:0 MTS video which will fit into the bandwidth of a dv style tape, when captured via firewire from tape you end up with 1440×1080 which a program like premiere stretchs the anamorphic video to fit the 16:9 frame. if tape captured via HDMI it can be either 1440 or upscaled 1920 depending on the cam or the tv which will do the proper scaling when it detects the video format.

[Bob Dix]

That is the explanation that makes sense.

Thanks,
Bob

Freelance Imaging & Video
AUSTRALIA

[Michael Galvan]

Well one thing to keep in mind too is although the XHA1 sensor system uses pixel shift, what is recorded to tape doesn’t take advantage of it. The resolution of the sensors natively is already whats recorded to tape. 1:1.

It is only the XH G1(s) or the XL H1(s) that can take advantage of the pixel shift because they have HD-SDI ports that can record the live signal precompression. And in this case, the pixel shift is increasing the resolution and such is recorded, as long as its being recorded to a proper codec that retains it (like using a Nanoflash).

I currently have the XLH1s/Nanoflash combination and can easily see the resolution increase from the Nanoflash recorded files vs. what is recorded to tape.

Hope this helps!

[Bob Dix]

Hi Michael,

That is interesting because Canon state that the tapes recorded in HDV standard with the Canon LX H1,XH G1 or XH A1 can be played back on their HV20/30/40 and when played back on a Full HD Video Monitor the result is impressive in fact equivalent to blu ray or may be on a good day shooting better ? Even the output from a Canon 5D mark II at 1920 x 1080p to a HV40 reduced to 1440 x 1080i looks pretty good, via Premiere Pro.
The XLH 1 as a camera is lens superior etc in many ways, but, the HV40 does a very good job as a VTR

Freelance Imaging & Video
AUSTRALIA

[Michael Galvan]

Hi Bob,

Yes, certainly the images from tape are very good indeed!

But if you are looking at how the pixel shift technology in the XH/XL cameras affects the image, you really won’t see it from the tape as the sensors resolution are a 1:1 match to what is recorded to tape.

You can only take advantage of the increased resolution from the pixel shift from the Canon XLH1(s) or XHG1(s) by recording from the HD-SDI to a full raster codec.

It is explained more in detail in this whitepaper from Alan Roberts, who does these assessments for the BBC.

https://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP034_ADD25-Canon-XHG1.pdf

He measured full resolution 1920×1080 from the HD-SDI port from the XHG1 and about 1000 lines.

I see the same thing with my XLH1s/Nano combo. Hope this helps!