Nonlinear editing software and hardware vendors for years have understood the advantages of intermediate codecs. Early NLEs were largely restricted to offline editing, a sensible and necessary approach since the compressed M-JPEG video looked much worse than source tapes. But once NLEs started capturing at 3:1 and 2:1 compression, the M-JPEG video on NLE hard drives looked good enough to deliver. M-JPEG became the intermediate between source formats like Betacam SP and delivery formats such as Betacam SP, Digital Betacam, Cinepak, or MPEG-2.
As computers and drives got faster and cheaper, uncompressed capture and editing became common on SD NLE systems. 10-bit SD’s relatively modest 200 Mbps per-stream data rate means a few thousand dollars builds an NLE that easily pushes several streams of uncompressed video.
HD post is a different story. While a couple grand buys a card that captures 10-bit 1080p video, storage for uncompressed HD remains expensive, especially if you want the data security of a RAID 3 or RAID 5 system.
At around 1.3 Gbps and 500 GB per hour per stream, storing a few hours of uncompressed 10-bit 1080 HD will set me back $6,000 to $15,000, depending on the quality and redundancy risks I’m willing to accept. With HD, I’m much less willing to accept much risk; I don’t want to have to rent an HD VTR just to replace what my drives lost, and I can’t afford to miss an HD deadline.
Video Format
Mb/sec
GB/hr
The data-rate gap between compressed and uncompressed HD formats leaves plenty of room for a gentle intermediate post codec.
HDV (NTSC 1080i 29.97)
25
14
DV25 (NTSC, 29.97 fps)
25
14
DVCPRO50 (NTSC, 29.97 fps)
58
27
DVCPRO HD 720p (8-bit 60 fps)
115
53
HDCAM 1080i (8-bit 29.97 fps)
135
61
Uncompressed SD 10-bit (NTSC, 29.97 fps)
224
101
Uncompressed 720p 8-bit (60 fps)
885
399
Uncompressed 1080 10-bit (29.97 fps)
1330
597
Uncompressed 1080p 10-bit (RGB 24 fps)
1999
717
Getting the Most for My Money
The answer is out there, but it took me a while to see it. Vendors realized that, just as with analog tape, transcoding isn’t inherently bad. Bad transcoding is bad, good transcoding is good. When Avid first showed me DNxHD, their intermediate codecs for HD material, I saw that multiple processing generations didn’t impart any easily visible difference between DNxHD and HDCAM source. I understood the benefit, but I didn’t fully get it. Same with CineForm’s CFHD codec: Dandy results, but I was still planning on working with uncompressed HD.
Then I went shopping for HD storage. The cost of an array with the performance I needed for uncompressed HD brought me some clarity. When it’s my money, I don’t think, "Well, it’s only an extra six to ten thousand dollars." I ask, "How can I better spend my money?"
I could just go back to an offline-online workflow, and I plan to for certain projects this year. But I want to finish some HD projects in house, and intermediate codecs let me do that.
If an intermediate codec keeps the data rate around 200 Mbps, then I can use less-expensive storage and still work with finishing-quality material. Or I can gain the security of a RAID 3 or 5 system and not worry about the performance hit compared to RAID 0. Even though this is a real $10,000 issue for me, this isn’t about saving money. It’s about spending wisely. The money I save on storage I can spend on a better lens, camera or crew. Working with compressed HD in post can result in visually improved production values.
There are other intermediate codecs besides those from Avid and Cineform. Some editors use the DVCPRO HD codec in Final Cut Pro as an intermediate. Some use AJA’s Qrez. Apple released their Apple Intermediate Codec (AIC) for use with HDV in Final Cut Express and iMovie HD. I hope we’ll see more HD intermediate codecs at NAB this year.
My NAB 2005
I used to assume that compressed HD acquisition and uncompressed HD post was the way to go. But this year at NAB, I’ll take a close look at uncompressed acquisition (Kinetta and Viper cameras, HDCAM SR and hopefully more) and compressed post.
Not that I’ll abandon compressed acquisition. Or compressed delivery. At NAB I’ll be spending a lot of time at all the camera exhibits. And I’ll be looking at H.264, VC-1 (aka Windows Media 9) and their ilk closely. Compression is something I can live with, but I want to choose where in my pipeline I use it.
Of course, exhibitors at NAB have a habit of revealing products that drastically change my shopping list. So I really don’t know what I want before NAB and what I want at NAB, which often don’t end up being the same thing. But that’s why I go. See you there.
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