Thursday, July 26, 2007

Canon HV20 - 24p or not?

Yes, it is 24p.

Got that out of the way. It seems that there have been a bunch of forum threads attacking Canon, saying that this awesome little camera doesn't really shoot 24p. Not that misinformation is unusual for the internet, however, these posts often quote me or CineForm as backing this position. Neither myself nor CineForm support these posts or claims.

The problem arose when I did state that there can be a subtle issue for chroma keying when using any 4:2:0 24p signal encoded into 60i. Some users took that and ran with it. I had seen some of this in customer footage, nothing I have shot. I probably wouldn't have mentioned anything other that it is a another selling point to using the HDMI output from these new cameras (which is damn cool), and I'm a video geek. Since then I'm not even sure this issue exists outside of MPEG compression artifacts, as some more recent burrowed footage looks great. I have so little HV20 footage to work from that we shoot ourselves -- Canon, we need a camera longer than a few days -- I want one to take home :).

Basically, the 24p signal is good, and the CineForm pulldown from 1080i60 HDV tape works perfectly. That is my position.

Here is some 24P extracted footage from a friend's HV20 as she was documenting some behind the scenes footage for our 48 Hour Film Project shoot -- the camera pictured is a Silicon Imaging 2K. We intercut the HV20 footage into the credits of this movie and presented it at 1080p24 on a Sony 4K projector. The linked clip is a 110MB 1440x1080 CineForm AVI, so if you need a CineForm decoder for your PC (Mac version coming), you can download one for free from

P.S. Other HV20 misinformation : when recording the Canon HV20 to tape, the image is 1440x1080, that is the HDV standard used. It is not 1920x1080, you only get that out of the HDMI port, and even then the image is likely upsized from an internal 1440x1080 image (which is still very nice.) The 1920x1080 native image is only available in the still camera mode.

Wednesday, July 25, 2007

Digital Media Net interview

David Basulto of and now, did an interview with me a week or so back. This covers some of the basics of what CineForm is all about and what we are trying to achieve. You can listen to the full interview here: Unfortunately, the Skype recording of the interview mixed the two voices as if we were stepping on the end of each others sentences (we weren't.)

Friday, July 20, 2007

Mastering Digital Cinema

The crew at CineForm has been very busy over the last four days. As intended, we trans-coded and up-converted all the 48 Hour Film submissions for the San Diego division of this international film festival. We had a total of 47 entries (including our own) and nearly 47 different video formats, compressions types, frame rates, frame resolutions and aspect ratios. This was a bigger can of worms than I had predicted, as filmmakers/editors in a rush make a lot of mistakes. CineForm, as a major local sponsor, wanted all the films to look their best when output on the Sony 4K projector, yet the conditions of this competition--think Iron Chef for filmmakers--does conspire against our goals to make the pictures really pretty. That said, many of the pictures did look awesome, and basically every film was improved by our up-conversion, resulting in many happy filmmakers. The audiences cheered and clapped each time our tag was shown, but even more enthusiastically when shown the second time at the end of each night's screening (that felt nice.) Thank you Geoff Pepos of Rogue Arts for making our 15-second tag -- I hope to post that for others to see soon.

The project was presented by a portable Wafian DDR, the HR-F1. This makes a very nice playback server now that there is a play-list feature (that feature is still beta.) In each session, there were around 10 films, with 5-6 other reels for 48 Hour promotion materials and other sponsor advertisements. The Wafian box performed flawlessly.

Here is a cross section of the formats we had to deal with :

DV 60i, 24p, 24pA, mixed 24p/24pA/60i, in 4x3, 4x3 letter boxed, 16x9, mixed aspect ratio (some not intentional), wrapped in MOV or AVIs, recoded to H.264 (at the horror of 256mb/s). We had Apple Intermediate codec encodes as 30p (we said no to 30p as this was for a 24p presentation, yet we had 3-4 films submitted that way), we had a couple of ProRes movies, and range of 720p24 DVCPRO-HD materal, some coded at 60p . We had a surprising number of clips mastered at 24.000 and 30.000 fps -- how or why they did this, I have no idea -- the cameras were standard 23.976/29.97 shooters. Very little 1080p at 23.976, our presentation format, four at most (our own film being one of them.) That was picture data; audio was a whole new set of issues. Converting it all was actually a lot of fun.

We learned a lot during this process, and I expect there will be several enhancements made to our own products to ease the conversion for a wide range of source material. We actually produced code over these last few days to deal with pulldown and framing issues we saw.

Some take-aways for filmmakers entering these competitions:

1) Choose a video format before you start shooting and stick with it. And for 24p presentation don't mix 60i and 24p sources.
2) Don't letterbox a 16x9 movie into a 4x3 frame; that just wastes resolution -- I know some cameras force you to do it and this is actually recommended by the 48 Hour Film web site. This causes another issue in you have a 16x9 sources and render to 4x3, any re-frame (zooming into a shot) will make your letterboxing size change between scenes -- there were 2 or 3 films with that issue.
3) Stop the lens down, or use neutral density filters; many movies had large, clipped white regions that could have been avoided to achieve a more filmic look.
4) If you want a really dark look, still light your scene well and make your film dark in post; we saw lot of source compression artifacts in the shadows of dark films.
5) Basically for items 3-4 there is only a small range of light that works well for most low cost video cameras; try for the camera's sweet spot. That might mean you need to gel your windows for interior shoots.
6) Don't use heavy compression on your output, don't export to MPEG2, MPEG4 etc. for your deliverable -- use that for your YouTube uploads.
7) Shoot HD 24p if you can, as it looks great on the big screen.

This was an awesome experience and I hope we get the opportunity again.

Thursday, July 12, 2007

24p is in most cases 23.98, or 23.976 or 24000/1001 fps.

Sorry for the weird title, but I have just received that question twice in ten minutes from 48 Hour Film Project contestants. In my last post, I said we are presenting in 1080p24, and we would prefer 24p submissions. The problem is 24.000p is likely not available on 98% of the cameras being entered into the competition (the 2% that can shoot 24.000p are the two Silicon Imaging cameras used by our team -- unless some of the Red guys are entering with a prototype--that would be fun.) The rest shoot what is commonly called 23.98, but I prefer 23.976 (it matters sometimes in AE), but it is really 24000 divided 1001 frames per second or 23.9760239760... So when I said 24p, I really mean 23.976...p -- sorry for the confusion. Even our SI-2K cameras are set to 23.976. 23.976 is the new 24p. Now if you can shoot or edit 24.000, that is fine, too; just never mix 23.976 and 24.0; you get this nasty frame ghosting due to the frame blending in most NLEs. In our more recent software, we pop-up a warning when you add 24.0 to 23.976 timeline (or vice versa.) So if you have a 24.0 camera with a 24.0 timeline, we will re-master it to 23.976 for projection.

Why this weird number : 23.976 (and its direct cousin 29.97?) It goes back to when someone thought it was a good idea to add color to television. They needed to shift the frame-rate slightly so the new "NTSC" color sub-carrier didn't freak out the existing black and white TVs. Now we are stuck with it, and it still works on your mid-century B/W set (but where is the HDMI connector?)

Monday, July 02, 2007

Mastering your short for theatrical presentation.

While this post is aimed squarely at those doing films in the San Diego division of the 48 hour Film Project (yes, many of my posts will be on this topic for a while), I hope this information is general enough for anyone producing a short/feature for HD presentation.

As CineForm will be re-mastering all 50 films for their theatrical presentation starting two days later, we had to determine the best way to handle the range of input formats without degrading the overall presentation quality. Years of seeing my own HD work crushed to letterboxed SD drove this years CineForm involvement. While projecting HD as HD and SD and SD is simple enough, we found in our theater tests that the projector format-switching introduces unwanted garbage on the screen as the projector re-syncs -- one of the projectors even required realigning the display after each format switch (although not the Sony 4k.) With common format ranging form SD 60i, SD 24p, 720p, 1080i60 and 1080p24, we were in for a lot of projector switching. For this reason, we are re-mastering all submissions to 1920x1080 and projecting at 24 frames per second, i.e. more work for CineForm.

As 24p is not perfect, it is a good idea for filmmakers to consider its minor limitations. It is best to avoid excessive camera motion, particularly if you are shooting 60i SD or HDV, which is more forgiving of camera movement. In most situations, cameras on tripods or with slow camera movements typically translate better to the big screen. Also, as the presentation is 16x9 wide-screen, use it if your camera supports this mode. If you are using letterbox on a 4x3 camera, we will scale the active picture to fill the screen. Full screen 4x3 shorts will be kept in their original format; the source aspect ratio will be preserved for all content.

Clearly, 24p sources work the best; however, converting 60i to 24p is not too difficult to achieve nice results. However, 30p or "frame mode" common on many cameras should be avoided, as that doesn't convert to 24p well.

Most of the above advice is pretty straight forward and standard, but then I considered the number for very nice 24p sources (like Sony's V1U and Canon's HV20) that are not supported within popular NLEs (e.g. Apple FCP.) 24p editing on a 60i timeline is far more common than it should be, and just like interlace video, it should be outlawed. :) The issue is that each 24p clip on a 60i timeline will not have the same "cadence;" with each cut potentially making sequences with half frame lengths, making a good 24p master is nearly impossible, and that is not even considering what happens with dissolves. Clearly, if you can edit 24p on a 24p timeline, do it! Fortunately, CineForm customers don't have this issue, but I couldn't recommend that all filmmakers learn new software for this project. So at first I though we couldn't support bad cadence 24p (in 60i), particularly with a very short time-frame to remaster so many films, but then I saw it as an opportunity to upgrade our internal 60i to 24p algorithms to handle this craziness. That is what I've been working on this weekend, and the San Diego audience will see it in action in two weeks and see that it works pretty well.

So, in order of preference :
* shoot HD 24p edit in 24p (render out as 24p or as 24p with pulldown.)
* shoot HD 24p edit in 60i (render out as 60i)
* shoot HD 60i
* shoot DV 24pA edit in 24pA (render as DV 24pA)
* shoot DV 24p edit in 60i (render as DV 60i)
* shoot DV standard 60i edit in 60i

Please avoid 30p/60p (of course these are fine for slow-motion, but speed change them to 24p.)

Have I missed anything? Please ask any questions in the comments section.