Canon XL-H1s - digging in to the minutia...
by Devin Rice on Aug 2, 2010 at 7:44:56 pm
Salutes all. First, a big thanks to folks who've posted tons of valuable info on Creative Cow forums. It's been a great resource. (Someday I'll have some actual wisdom to be able to share on these forums myself!)
In the mean time, here's a couple of questions about my new Canon XL-H1s.
Typically I record to a Firestore FS-H200 Pro recorder and pop a tape into the camera just for a backup. I've never had to use the tape for source as the Firestore's been working very nicely, (but it sure is good piece of mind to have a backup!).
Currently I'm in pre-production for an (extremely) low budget sci-fi feature and thinking of using the Canon as a B camera for some FX scenes to get a second angle per take. So, we're delving into the SDI output feature on the XL-H1s.
According to the manual the camera shoots 1080/60i and 1080/24p, 30p native). Tests we conducted by connecting the camera SDI out directly to the SDI in on an AJA Kona card showed the camera output was interlaced whether the camera was set to 60, 30 or 24 fps. Further research into the manual revealed that the camera actually down-converts the SDI output to 60i regardless of the frame rate setting and only the HDV/DV terminal (firewire 400 connector) receives the 30 or 24 progressive video (which would be the compressed signal). (Then there's the issue that the FS H200 only records 50i or 60i at 1080, so then what actually would capture the 1080/30p or 24p video from the HDV/DV terminal?).
So, even though the camera outputs a native 1080/30p and 1080/24p, this output is not available through the SDI out? If the camera really records 30 frames progressively with 1080 lines, why wouldn't you be able to capture this through the SDI out? Seems odd to me. Am I missing something here?
By the way, we did an A-B comparison between the uncompressed SDI 1080i footage and the 1440 x 1080 (quicktime) footage captured to the Firestore. There is, as you might expect, a definite quality difference between the two, (the SDI footage obviously having a lot more detail.).
After reading volumes of specs and theory it was great to actually see the difference with our own eyes!
Here is some information which I quote from a review of the camera on Millimeter Magasine:
At any rate, what comes out of the HD-SDI spigot is always uncompressed 1080/60i. Newly minted synthetic progressive frames must therefore be segmented into halves in order to fit the 60i cadence. For instance in 30PsF (progressive segmented frames/second), a progressive frame's odd lines are first output, then even lines, amounting to 60 half-frames per second, all of which are reassembled into intact progressive scans upon playback. This introduces the unique irony that 30F, which began life interlaced at 60i, is output as 30PsF at 60i.
24F comes out the HD-SDI spigot as 24PsF, with 2:3 pulldown added to pad 48 half-frames into a total of 60 segments. Downstream devices like NLEs that recognize segmented progressive frames and 24p repeat flags will readily ingest Canon's PsF stream and restore either 30F or 24F “progressive” frames upon playback.
Re: Canon XL-H1s - digging in to the minutia... by Devin Rice on Nov 12, 2010 at 2:25:19 am
Seems like we're (once again) caught in the marketing spin that camera manufacturers and sellers are desperately throwing out to disguise the fact that none of these cameras have quite arrived at what we're all waiting for: true high-definition video. 12-15 years ago we were all in a dither about what was "broadcast quality" video. Was it Beta SP? Was it Digi-beta? Truth is, they were broadcasting all kinds of video resolutions from cameras with all kinds of specs/limitations. Now, in the dawn of HD TV, everyone is prematurely claiming to have achieved "true HD", but when really pressed to the wall, no-one, (at least in my research in the under-$20k-camera range), seems to be able to actually produce an uncompressed 1920 by 1080 native progressive output at 30 frames per second. (Someone please correct me if I've missed a camera out there that actually will!)
And spin doctors can get away with this because like "broadcast quality", "HD" isn't an exact standard with rigid specifications. At least it doesn't seem to be if you read the hyperbole dished out by camera makers and sellers.
I know it will come, and it will be soon. Everyone's racing towards the finish line. I just wish folks would be a little more honest before their camera actually arrives there.