Wednesday, April 25, 2007

CineForm 444 vs HDCAM-SR revisited

During NAB, I had an honored visitor to the CineForm booth, Hugo Gaggiono, CTO of Sony's Broadcast Production System Division. Unfortunately, I was not there to meet him, so he spent time with Jeff Youel of Wafian discussing our recent test with HDCAM-SR, and how we were able to achieve the results we did (the reason for his visit.) I later tried to follow up with Hugo at the Sony booth, but I had no luck with paging him. Pity, as I now had data as to why CineForm did so well against his format.

That same day, I answered the challenge for an outsider (Russell Branch of InnoMedia Systems Ltd.) to evaluate the test materials comparing CineForm to HDCAM-SR. Russell had been following the discussion on the Cinematographer's Mailing List (CML) regarding this experiment, and kindly offered to perform the quality measuring tests himself. It's likely Russell had access to the OmniTech picture quality anaylsis device, and along with some help from the OmniTech guys we ran a DVD full of frames through their analysis. Their conclusion was very similar to our own, and it also showed the HDCAM-SR doing worse on the StEM, just as we had found. The main difference in this test (other than the OmniTech being much faster than my own analysis), was that the OmniTech device could show us why SR's quality dropped for StEM footage.

Often for testing CineForm I would gain up the difference (between compressed and the source) to show what has changed during the encoding. This photo is the OmniTech showing that very difference, subtracting the CineForm compressed images from the uncompressed source, revealing an effectively grey frame (no significant differences.) However, I never did this test with HDCAM-SR; after all, I can't fix any issues I might find, so the test never occurred to me. The OmniTech operator had no such issues; he didn't know what compression he was testing and was therefore completely unbiased (sorry, I didn't write down his name.) When he flipped on the differencing, there was a distinct image within the frame -- he even suspected it was HDCAM-SR based on the images revealed in the differencing. The brighter image parts of the display, indicating a larger encoding error, were the black regions of the source image. It turns out the Sony deck will not encode the very lowest values of black. I must quickly note that a standard broadcast signal will not contain these black levels and the Viper footage didn't either, and that is why SR is closer to the CineForm quality for the live footage. This black level issue will only come up for content meant for theatrical presentation--a film-out master, just like the StEM footage if designed to stress test. Now the amount of black truncation is not huge, but enough to explain the 2-3 dB drop in measured quality performance. Can anyone tell me why the whole 0 to 1023 range isn't recorded when the same range is valid over HDSDI/dual link?

While the original tests are valid, if we accounted for HDCAM-SR black levels by limiting the range of the source material, the difference would be less significant. Our original goal for these tests was to prove a software wavelet compressor can be as good as the best and most widely accepting compression solution. This we have achieved. But I will also acknowledge that with the two formats so close in quality, there will be some sequences that will favor SR over CineForm. I leave it up to others to find those sequences for their own comparisons. ;)

update April 30, 2007: I was just informed that it is a dual link HDSDI, not HDCAM-SR, that limits the valid range to only 4-1019. As we were only testing a file based workflow with CineForm 444, I re-ran the PSNR analysis only using the 4-1019 data range by clamping the extreme values. Surprisingly I found the PSNR numbers for SR only moved up a very small amount, far less than the 2-3dB I had predicted. The highly detailed StEM footage does seem to favor CineForm, likely due to our VBR nature versus the SR's CBR design, and the black levels where just a red herring.

update May 12, 2007: I have recently learned that the OminTek operator was Mike Hodson, the company founder and designer of the OmniTek PQA. So the testing was in very good hands.

Thursday, April 19, 2007

NAB Stuff -- CML Party

I'm back from NAB with a lot of exciting work to do -- funny how we are so busy to prepare for this show, only to have a brand new list of tasks to complete immediately after it. I skipped the last day, which is typically quieter, to get a head start on my to-do list. The show was exhausting as usual, but all indications are a very positive experience for CineForm and out booth partners (Wafian & Silicon Imaging.) The important thing was I was there long enough to attend the CML party.

This party is a geekfest of cameras in a shootout, plus beer and pizza. Thanks are well-deserved to Scott Billups and Geoff Boyle for organizing the event. There were cameras from Panavision, Sony,Panasonic, Silicon Imaging, Phantom & Canon (HV20 -- no joke was in the shoot-out vs a Phantom 65 and Genesis.) Capture gear was provided by Rave HD, Wafian and Codex. Pictures tell a lot.

Sunday, April 15, 2007

Apple catching on, proves CineForm right.

Several years ago, CineForm attempted to sell Apple on the idea of a digital intermediate codec for professional post. Unfortunately, back then they still had their heads stuck firmly in the DV sand, and believed DVCPRO-HD would be sufficient, which everyone today knows it isn't. With the announcement of Apple ProRes 422, it seems the CineForm message has finally taken some hold, but it seems only as far as offering an equivalent to Avid's DNxHD (good for CineForm.) It seems to be a DCT codec with nearly identical data rates to the Avid codec, 1080p24 is quoted at 22 MB/s or 176Mb/s (same as Avid.) It might be wishful thinking if the Apple codec is a CBR design like Avid's; I guess we will have to wait and see. Funny thing, with all our recent work on a 4:4:4 codec, it's like we knew this was coming. :)

Thursday, April 12, 2007

First new SI-2K and SI-2K Mini images.

Things have changed a lot over at Silicon Imaging, check out the new body and styling of the SI-2K as designed by P+S Technik. See their press releases regard their partnership with P+S Technik and integrated Iridas SpeedGrade system.

Even the Mini's styling got an overhaul, but that interchange P+S Technik lens mount is sweet. With adaptors you can place lens of these types : PL, B4, Nikon F, Canon EF, Panavision PV, C mount, and some I haven't heard of.

Mini with a PL lens
Mini with a B4 lens

Tuesday, April 10, 2007

AVCHD support

Switching gears from proving 4K and 2K are effectively the same, to something totally consumer -- AVCHD. This entry level HD acquisition format as been troubling editors/hobbiest for a while now. You may have thought M2T (HDV) was hard to edit, but try working with AVCHD, the MPEG4 long GOP hardly even plays on most PCs. We know AVCHD to CineForm file conversion was going to the best way to edit this stuff, it just a matter of finding a suitable decoder. After 4+ months of searching and trying to license components from companies that will not return any calls, I just found a new decoder/player that works great with HDLink (included in all our PC tools.)

Now this player / AVC decoder is a little pricy at $50, but to make a $1000+ camera editable, it is an excellent deal. Here is the link : Player + AVC Plugin. (You need both the player and AVC PlugIn.) If even works with the demo version (which adds a small logo) and with our trial version (which doesn't add any logos.)

Once installed you can use the current HDLink to create CineForm AVIs with small trick -- rename the AVCHD files from *.m2ts to *.avchd (or something random.) HDLink mistakes the M2TS for a regular M2T file otherwise, we will fix this in the next release. In the meantime you can edit your AVCHD footage in real-time without issue now.

Update 07/07/07:All our products now support *.m2ts files, however you still need a valid AVDHD decoder to do the file conversions. You can test if you have the right decoders install by trying to play the *.m2ts files in window media player (when that works the CineForm conversion will work.)

Please also see CineForm's tech. note.

Saturday, April 07, 2007

Myth-busting : 4K vs 2K

I've be recently watching a few episodes of Mythbusters after my father said it was fun, and it is. So I figure that's what I been trying to do here, bust the myths like compression can't be used in post, or in this post measure the real difference between 4K and 2K aquisition; I just don't get to blow anything up.

This is not an blind image comparison test like I've done previously, after all we know 4K is better than 2K -- right? Instead I will investigate how much better 4K is than 2K under normal export scenarios. This is not so much a SI-2K vs Red One comparison, rather it is practical look at what happens when mixing camera sources or mixing shooting modes from one camera (all these bayer cameras tend to shot at a lower resolution when overcranked.) Also for anyone shooting with B4 or 16mm lens, you are only going to get 2K or maybe just 1080p, so it will be good to know what you are missing out on. For those who question my bias, yes we have licensed CineForm RAW compression (non-exclusively) to Silicon Imaging for their SI-2K camera, however CineForm is marketing our solution to all RAW shooters from Arri D20, Dalsa Origin and Red One users. We hope to benefit no matter what resolution you shot with.

Let's be real here, for today's delivery format will not have people finishing their productions at 4K (I doubt even 1% of 4K acquisitions will be finished at 4K 4:4:4), for those getting a filmout, they are typically done at 2K, even digital mastering for D-cinema is mostly 2K or 1080p for most E-Cinema and HD masters. So the 4K image is primarily going to buy you some flexibility for re-framing, the over-sampling will help clean up noisy sources, and ease pulling of keys, certainly a good thing. But assuming you have lit your project well and framed correctly in camera, how much difference is visible between shooting 4K vs 2k?

For this test I have a 4K sequence from a Dalsa Origin (4096x2048), I could do the same from any of the high resolution sources like Red One or Arri D20. To simulate the same sequence shot at 2K RAW took a little work. The original 4K RAW frame was compressed into a CineForm RAW AVI, this AVI was loaded into AfterEffects (the CineForm compression stage was needed as AfterEffect will not load the RAW DPX file from Dalsa, but as the compression is very light, this will not impact anything.) The AVI was placed into a 4K composite, in which I added a blur filter to simulate the effect of a optical low pass filter (OLPF,) which would be used on any decent bayer camera. Working out the amount of blur was tricky, more on that later. The 4K After Effects composite with the blur was then exported as a 2K DPX (RGB 4:4:4) sequence. As RAW bayer only has one chroma sample per pixel, not three like 4:4:4, this DPX sequence was then sub-sampled into a 2K RAW sequence (one third the size.) This new RAW sequence was encoded into a 2K CineForm RAW file, nearly a quarter the size of the original CineForm RAW 4K AVI (only 10MBytes/s.) The next step was to place both the original CineForm RAW 4K sequence and the derived 2K RAW sequence into a 2048x1024 project running Prospect 2K under Adobe Premiere. You will be able to see timeline playback and mixing of 4K and 2K in real-time at our NAB booth (SL7826) on mid-range PCs (any modern core dual Intel system.) I set the demosaicing quality to the best and then visually compared the look of 4K vs 2K. Oopss, something wasn't right.

The first thing I noticed was there was some color fringing in the 2K image, which you don't see on a real 2K shoot, yet the 4k look great scaled to 2k within Premiere. It turns out my guess for the blur level to simulate the OLPF was wrong -- too little and you get image aliasing, too much you get a blurry image. So a went back to composite and produced a range of sequences with different OLPF strengths, to get an image that wasn't overly blurred or aliased, just like a correctly configured camera.

The results of my test sequence is shown in these frames:

The CineForm RAW 4K exported as 2048x1024 (click on image to see a 1:1 scale)

The CineForm RAW 2K simultation exported as 2048x1024 (click on image to see a 1:1 scale)

There is a mild softening in the 2K RAW source, the difference is not massive, my guess is about a 10% reduction in something (frequency response maybe, but I wasn't directly measuring this.) However this 2K image is unsharpened, showing signs of the OLPF, so the next image adds a little sharpening, just like a regular camera (quick and dirty -- I didn't spend much time on this.)

The 2K RAW sharpened export as 2048x1024 is starting to look much more like to 4K downscale. (click on image to see a 1:1 scale)

As expected 4K still has an edge, but for practical workflows it is not going to greatly impact the results for a typical shoot. There will be no issues in mixing 4K and 2K sequences with your projects, your audience will not be able to tell. This test also shows how well a bayer "raw" image can maintain the look of a 4:4:4 image at the same resolution. 4K RAW downscaled to 2K gives a very good 4:4:4 source, and 2K RAW does a pretty good job of maintaining the 4:4:4 quality. For those who are still budgetting for 4K masters and 4K projection, make sure your audience sits in the front few rows. :)

Tuesday, April 03, 2007

Iridas working with CineForm

We have been squeezing in some work for Iridas in this tight pre-NAB time frame. We weren't going to find the time for a related press release, but thankfully Iridas had the time.

Monday, April 02, 2007

Mastering to HDCAM-SR vs CineForm 444

HDCAM-SR has found its way into to very important parts of the market, on-set capturing and final mastering. The quality is very high so it is clearly suitable for both. In our previous tests we compared CineForm 444 and HDCAM-SR as an on-set recording format. In this test we compared the performance in mastering.

Our source material was 580 frames of the Magic Hour sequence from the Standard test Evaluation Material (StEM) which is used for DCI compliance testing. The footage is very demanding on compression, with a lot of film grain, complex motion and significant detail within each frame. We played an uncompressed 16x9 version out to the Sony SRW1 deck in 440 and 880Mb/s modes, and compared those to range of quality modes offered by the CineForm 444 codec. As the 880Mb/s mode is designed for two camera shooting or operating at 60p, it is really overkill for a single stream of 24p content, so we added CineForm Filmscan2 to the testing mix (our overkill mode.)

The graph says a lot (click to see a larger image):

The large swing in the SR PSNR quality measurements is true to the constant bit-rate codec design, all tape based or fixed rate codecs have this nature. Whereas the CineForm 444 variable bit-rate maintains a mostly constant quality. The 880 Mb/s mode didn't do as well as I expected; doubling the SR bit-rate didn't buy very much. The graphs below compares the 440 and 880 mode for their color channel performance:

The odd element is the red channel's performance in 880Mb/s mode, it should not should have been so much better than green or blue (first 200 frames.) It does in fact appear that the RGB channels are swapped, as if the dual link cables were interchanged for this test, yet they are fine for the 440Mb tests. I'm curious if anyone knows whether the SRW1 will even operate with the dual link cables reversed, or whether this a byproduct of using the 880 (HQ) mode on a single camera stream. We did perform the 880Mb/s test after all other camera and deck testing at 440Mb/s, so an error may have been made when configuring for this test.

The graphs comparing Filmscan1 and Filmscan2 (in keying modes) shows a predictable increase in PSNR quality over all channels equally.

At some point I would like to investigate the 880 mode again, mainly for curiosity, as it is not commonly used (only the SRW1 deck currently supports it.) The SRW1 is a mobile recorder, it is not used for mastering, all the studio decks only support 440Mb/s. At the standard rate of HDCAM-SR, CineForm 444 maintained a higher quality throughout the entire sequence, no mater which CineForm quality setting was selected during the test.

The implications are simple, the digital file based delivery of content is not compromising quality versus tape based mastering and delivery. An entire two hour feature can be mastered to a signal 350GB harddrive, for long term archive (long shelf life than tape), lossless duplication for storage redundancy and data migration, and simple delivery for film-out or mastering to other delivery formats (the drive will cost less than the tape(s).) Tape is still the dominate solution, but as the production world moves towards IT solutions, it is nice to know disk based compression can deliver the goods. For those uncompressed fans, the same feature would consume 1.7TBs, still do-able just less convenient.