Mastering 24p DVDs from HD using Premiere Pro.

24p DVD mastering.

First some basics, there is no true 24p mode on standard DVD, there are is only 60i encoding (and 50i for PAL.)  So all those film source are encode to DVD by adding 3:2 pulldown (or 2:2 for PAL with a 4% speed up for 24p sources.)  How this pulldown is added impacts how well your DVD presents on today's common progressive displays. 

Adding 3:2 pulldown for NTSC DVD creation has been has been tricky, seemingly there are lots of dead ends (like using Encore to encode directly to 24p -- this should work, I have made several blurry DVDs trying to use it.)  This is one of the most common support questions.  McCarthyTech has a good blog post on using AE to manually insert pulldown before encoding as 60i, and this will work everytime.  It was his post that has prompted this one, as there is an even simpler way using Premiere CS3+ directly, and if you are careful it can be even better for final presentation.  McCarthyTech's technique can be improved if we trust the MPEG2 encoder can to add the pulldown using repeat flags.  Fortunately this works correctly using the 23.976p encode mode within Premiere's Adobe Media Encoder (MPEG2-DVD preset), now we just have to watch out for other Premiere limitations.  

The advantage of pulldown that uses the MPEG2's repeat flags, this can help with quality as only fields used to construct the 24p signal are compressed, the repeat flag pad the data out to 60i. This flags also help progressive scan DVD players reconstruct the correct 24p signal more reliably. The manually created pulldown in AE works for most situations as many DVD players can use the data-rate pattern to guess the pulldown, but it is not always extracted correctly (seen as a weave pattern during motion.)  Of course there is no issue for non-progressive outputs where the display is reasonable for pulldown detection (if needed.)

The way I produced several 24p DVDs in the last weeks is to export out of Premiere as a 1920×1080 24p (23.976) master CineForm AVI, then I used VirtualDub and scale using Lanzcos 3 filter to 720×480 and export out to CineForm 444 SD.  Load the SD clip back into Premiere SD 24p preset, interpret footage back to 16×9, and export with Adobe Media Encoder to MPEG2-DVD 24p. Encore will take this file without further transcoding.  Now that seems to be an odd path and it is, plus using VirtualDub is unnecessary, but the export to 1920x1080 master first is a very important step. 

I first made the mistake of exporting my 1080p timeline directly to MPEG2-DVD, and it looks horrible.  I've made this mistake before, as you simply expect it to work (never has in Premiere up to the tested PPro v3.2), but here why it doesn't always do what you want.  When you add any spatial distorting filter (motion, blurs and sharpens, etc), you see the results previewed at 1080p, any scaling for your preview display is applied after the filter operations -- so you adjust you filter so they look correct on a 1080p source.   We you use the Adobe Media Encoder, the scaling is applied first, before any of your filters -- as a result your output doesn't look like you previewed -- spatial filter are around 2.5 times stronger than you intended.   In one of my recent projects, I was using the additional resolution of the 1080p source to reframe for a nicer DVD output, see below how much it matters in what order of operations that scale occurs (see below.)

The image on the left is soft and badly aliased, and it looks far worse in motion.  Simply exporting the timeline to 1080p first, then using that new file to export to DVD solves the problem, without ever leaving Premiere.  The VirtualDub step in my above technique can be as simply skipped, as loading the exported 1080p AVI into Premiere will use the CineForm importer's own Lanzcos 3 scaler for exactly the same results, much faster and more convient.  

What, no more Aspect HD?

After 5 years we are now retiring Aspect HD, and I say Yah!!!! David Taylor, CineForm's CEO, has post as to why on DVInfo.net, but I like this change as we no longer need to remove key features from Prospect HD to make Aspect HD (that is how it is built.) This will streamline development and testing, plus slicing off all the really good stuff always bothered me. We will still have entry level products in the NEO line (more news to come,) but today's customers are increasingly purchasing their first CineForm product at the Prospect HD level (some going directly to P4K as Red users really need a workflow.) Recently Aspect was falling into no man's land, too pricey for the hobbiest and too feature limited for many professionals. The Prospect product line now starts at $749, lowering the entry point for professionals and existing Aspect users can product jump for $199 (only around $50 more than typical upgrade between AHD versions.) This upgrade will also include the upcoming CS4 version of PHD.

Aspect and Prospect a short History.

5+ years ago when Aspect HD was first released it retailed $1199, it was the only HDV professional product of its day for post. The only HDV camera at the time was the barely HD single chip 720p JVC HD10U, so Aspect HD took in only one camera format, 720p HDV and converted into an 8-bit AVI for much easier post within Premiere 6.5 (wow, we come so far since then.) Aspect HD was upgraded to Premiere Pro 1.0 and we soon added 1080i support as Sony FX1/Z1U was coming (we have a bread-boarded prototype of the Z1 in box at the office -- somewhere.) Then HDV exploded, many great cameras, and CineForm implemented the first HDV support for Adobe into Premiere 1.5.1, and Aspect HD prices fell and the sales volumes grew. Around the same time a Prospect HD beta version was used in the post of Dust to Glory, the first film sourced (and HDCAM, DV, etc.) theatrical release ever to have had an compressed online DI workflow. Support for more and more cameras where added, XDCAM-HD, P2, AVCHD, etc. While Aspect was growing beyond it HDV roots (bumping up against it 1440x1080 8-bit limits,) and Prospect was turning in the swiss army knife for all input types with the addition of DPX sequences, XDCAM-EX, Grass Valley Infinity, SI-2K, Red, Dalsa, Phantom all with HDSDI I/O. Over the years of Prospect, feature additions includes 10-bit, 12-bit, 4:4:4, alpha channels, RAW compression, Active Metadata and much more.  So today the Prospect line fits the role for today's indie professional, with so many input formats and many possible output types, it is nice to have an intermediate that handle yours resolution, bit-depth needs in real-time, without breaking the budget, your disk system, or the PC your are try run on. Aspect HD was being left behind when compared to Prospect, so I hope many Aspect users will make the jump to Prospect, as it is a big step up.

Bits of Fun

Here are a couple of videos internally created by CineForm engineers (plus friends) just for fun. The first is this year's entry to the 48 Hour Film Project. We drew the tough genre of "Holiday Film", so it is now seasonally appropriate (we created this one back in August.)



Competition requirements: a "Holiday Film" to be written, shoot, edited and delivered within 48 hours with these elements:
1) Character: Joe or Josie Beeble -- Construction Worker
2) Prop: Tweezers
3) Line of Dialog: Hey, have you heard the news?

The second is currently a finalist on www.recordtherush.com, which is a competition entry to help one of our engineers win an Audi S4. The entry is called Visceral Thirst, so please vote for Tim (he said I can have a drive if he wins.)

Both films where shot using an SI-2K Mini, although Tim used some Sony V1U footage (all the beautiful car shoots in Visceral Thirst are SI-2K,) and both where finished in tight time-frames using Prospect 4K and Active Metadata.

Intel Core i7 and CineForm

Wow! That was my immediate reaction when I first did a CineForm decoder performance test on the new Core-i7 processor. I've had access to these new Intel processors for a while now and I knew they where fast, I just didn't how fast. The system we very honored to have early access to was a Intel Core i7-965 Extreme Edition system (Nehalem architecture) running a 3.2Ghz quad core. When we first booted the system, we saw 8 CPUs within task manager, even though this is a quad core. These new chips have re-introduced the concept of Hyper Threading, each core can be setup as 2 virtual cores -- this means we will likely see 16 virtual CPUs in upcoming dual quad workstations. Nice! With so many virtual CPUs to run on, I knew we had to upgrade our decoder for better n-way threading (which the encoder already had.) This work I was most involved with over the last month, resulted a 50% boost in frame rate over our already fast decoder on Core-2 architecture dual-quads. Now it is time to test Core i7-965 .

In these tests I compared my beloved xw8600 HP workstation 3.16Ghz 8 core with 4GB RAM, running XP-Pro 4GB RAM, with a gaming configured desktop Core-i7 4 core running Vista 64 and 3GB RAM. No operations used GPU assistance.

Running with only half the number cores, this new processor nearly doubles the average performance of CineForm HD and 2K in 4:2:2, 4:4:4 and RAW formats, and even approaches real-time full resolution playback of 4K (a workstation class Core-i7 will be playing back 4K without issue from CineForm RAW or 4:4:4 encoded sources.) All this frame rate overhead greatly eases multiple stream processing and allows for huge efficiency increasing in batch processing of mezzanine and image archives. It also allows for much more Active Metadata (AM) processing through CDL style color databases, 3D LUT film looks and other yet to annouced AM features.

Intel and/or HP, when can I get my hands on an i7 dual Xeon? Please.

Where i7 didn't scale as well was with high quality 4K RAW demosaicing filters. Both the 4K R3D decodes and high quality debayer modes in CineForm RAW produce minimal speed-ups from 8-core Core2 to the 4-core i7 (still amazing considering the reduction in cores.) Looking at our own code, the demosaic has not used much of the SIMD (media) instruction set, nor is it particularly memory I/O limited, just lot of operations per pixel. It seems we do have room for more performance optimization in the demosaic.

All the transcodes where performed using the CineForm R2CF utility that comes with our NEO 4K and Prospect 4K products. R2CF has a very efficient implementation of the R3DSDK, allowing for close to 100% CPU utilization. I have included the R3D to CineForm transcode times, as REDCODE is known to be a particularly compute heavy format. These times do also include time for a CineForm encode, but this only effects the FPS numbers by around 10% as our encoder is very fast (up to ten times faster than a R3D decode plus additional processing [adding curves and color space controls.]) I'm showing the combined numbers as that is the CineForm workflow for R3D, you do a R3D decode once to convert to CineForm, then work with (decoding multiple time) CineForm files for the extra speed and flexibility.

I expect another factor in the widening margins for the CineForm decode performance on the Core-i7, is we avoid arithmetic coding, which is tricky and compute intensive for CPUs (and nearly impossible for GPUs to do efficiently -- we are asked about GPU acceleration often.) CineForm codec was always designed for speed on Intel processors, where faster memory and faster media instructions almost directly relates to proved frame rates, as we have compute-lite entropy coding engine. While arithmetic coding would increase bit-efficiency maybe 5-10%, the performance gains of 4-6X by not using it, made the easy choice when we started this codec work 7 years ago (on 1.7GHz P4s using MMX -- the fastest we could get could only do NTSC/PAL SD in real-time.) Now someone needs to suggest a fun use of for Express files running at 450 frame per second.

2K is still compelling

On my drive into the office I'm often listening to media related podcasts like TWIM, Red Centre, and Filmspotting. Today's drive I was catching up on Filmspotting podcast episode #235, which opens with a nice review of Slumdog Millionaire, the latest feature from Danny Boyle (Trainspotting, 28 Days Later, Sunshine, etc.) Now I knew this was Silicon Imaging SI-2K project, shoot as CineForm RAW, but other than that I've been too busy to learn anything more about. Filmspotting is a film review show, so not a techno-geek-out fest like Red Centre or elements of TWIM, so you never hear them talk about cameras, but after raves for the story, acting, narrative structure, there where high praises for the cinematography, amazed that is was digitally acquired and the types of shots where able to get in India, commenting "you do not film in the streets of Mumbai...you are taking your life into your own hands, and they actually did." Clearly this points to the huge advantage of a 2K camera with a real 11 stops of dynamic range at the size of deck of tarot cards. Yet this is "only" a super-16mm equivalent sensor, proving again that making a film has very little to do with megapixels and sensor size. Now I'll have to see the film, as it is getting a 92% freshness rating over on rottentomatoes.com.

My Take on Red's Announcements

Very cool. The higher the bit-rates and the higher the resolution goes, the even greater need for high performance compressed digital immediate for post, mezzanine and long term archive, i.e. CineForm. And for anyone wishing to produce their own compressed RAW video cameras, Red and SI are not going to be in that business alone; CineForm RAW is ready when you are.

Anyone notice how the whole Red "Brain" line-up looks like chunker versions of Silicon Imaging dockable SI-2K Mini? Red continues to confirm SI's vision. :)

Even More Decode Speed

The last 2-3 weeks I found my time consumed with more decoder optimization. While the core of the CineForm codec has now been around for nearly 7 years, it enhancement has never stopped, whether we are adding new pixel formats, Active Metadata, improving quality or striving for more performance. Working on the codec core is more rewarding as an engineering success is not dependent on eccentricities the third party applications like Premiere or FCP, which like to get in the way.

The decoding engine has been threaded for 8 cores for some time, but it was only efficiently using about 3-4 cores. This inefficiency was not an issue for real-time playback as the codec was already very fast, faster than necessary for real-time multi-stream playback (even on dual core systems.) Each decoder during a transition or layered effect would happily use much of the available CPU. Better codec threading was needed for a new market the CineForm is finding itself in, file based film and television archives and mezzanine storage for HD distribution. These markets have been limited by the real-time nature of tape format like D5 and HDCAM SR. If you are going to switch to file based storage, no point in limiting yourself to 1:1 real-time, you want faster than real-time for batch processing and file format conversions wherever possible. This is one reason CineForm is displacing JPEG2000 for archives, is it just too slow for batch processing in software (typically much slower than real-time 1:1, i.e. slower than tape.)

While the current public beta is more efficiently threaded for up to 8 cores, up a 50% decoder speed-up for some sources, the in-house decoder (out soon) will support up to 32 cores, ready for those new Intel powered workstations with will have 6 and 8 cores per physical part coming very shortly.

Some performance numbers from my stock HP xw8600 8-core 3GHz workstation:
444 1080p 12-bit per channel StEM footage -- 64fps.
444 1080p 12-bit per channel Stereo (3D) -- 43fps per eye (86fps total throughput.)
RAW 4K 12-bit per channel with demosaic (no GPU acceleration) -- 22fps.
RAW 4K 12-bit per channel decoding at 2K (no GPU acceleration) -- 59fps.

All testing used Build 186 of Prospect 4K beta.