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.