Monday, November 14, 2011

j2k 2.6

The last release of j2k added support for Digital Cinema files, but I've since received some user feedback asking for more control over DCI bit rate. Ask and ye shall receive:


The controls are modeled after those found in OpenDCP. It defaults to a megabits per second model, but you can also specify a per-frame size in kilobytes if you prefer. The slider tops out at the DCI spec maximum, but you can enter a higher number in the text field if you wish.

As usual, j2k is free. Enjoy!

10 comments:

Fist Jab said...

Hello,

Thanks for making this plug-in available for free. In AE CS5, I can only choose "DCDM X'Y'Z' (Gamma 2.6) 5900K by Adobe)" and not "DCDM X'Y'Z' (Gamma 2.6) Neutral at D55 (by Adobe)" like you list in the j2k manual. Is this the same thing?

When using "DCDM X'Y'Z' (Gamma 2.6) 5900K by Adobe)" to export a JPEG2000 sequence, all the images look less saturated and a slightly different hue than a frame from the original source footage. Any idea why? Thanks!

Brendan said...

Hmm, I've heard some conflicting reports on this. I have both on my system, probably acquired from various different After Effects installs. The "5900K" profile is newer, so maybe Adobe found some issues with the original "Neutral at D55"? You're probably fine using that one, but I'll ask around some more.

It is normal and correct for the DCI images created using that profile to look less saturated when you read them back in. The reason is that DCI (a .j2c stream) does not store profiles, so the pixels are being interpreted sRGB. You should re-assign the XYZ profile to the footage, and then it will appear as you expect it to.

larsborg said...

Which one to use, depends on what color temperature you want for your creative whites.
Many movies are mastered for around 5900 K.
Some studios master to 6500 K, which is same color temp as HD TV. (Sorry, we didn't make such a profile).
OK, I must admit I cannot recall why we made the first one D55.

Brendan said...

Thanks for enlightening us, Lars! I'll update the j2k manual to recommend the newer profile.

RadoM said...

Hello,
Even if I set slider on max bit rate of 250 Mbit/sec output files are smaller than those created from the same source (with openjpeg) Visual quality is also lower than openjpeg. IS something wrong with my settings or this is maximum performance of j2k plugin. Which is true it's faster than openjpeg but in digital cinema quality is main issue because you project on big screen and everything is essential. One more time I set slider with the maximum of 250 Mbit/sec.

Brendan said...

Hi RandoM, could you please email me some examples and describe your steps in more detail, including which application you're using on which platform? When I set the data rate to 250 Mb/sec, the results are very close to the original file, as I'd expect.

Anonymous said...

Hi Brendan.
Congratulations for your plug in.
I have encoded an entire movie and watched it at a large comercial cinema and I could not find anything to complain about. It was a s16 transfer and on screen it looked like a 35mm projection without jitter.
Bit rate was set at 190mbps.

Anonymous said...

I forgot to mention.
If I enable "use opengl" in ae render settings, the output files come always at about 500k each, regardless of the bit rate set in j2k. Could you comment on this?
Pepo

Brendan said...

Glad to hear it worked well for your movie!

If you use the OpenGL renderer, you will often find that the resulting image is significantly softer. Compare renders of a lossless format like TIFF or PNG to see what's happening when you switch OpenGL on and off.

This softening means that JPEG 2000 can compress the image completely with only 500k instead of whatever amount you specified. The data rate is an upper limit. If you compress an all-black frame, you'll find that the output files would be REALLY small.

But I'm guessing you don't actually want that reduction in quality, so you'll probably want to keep the OpenGL renderer off.

Brendan

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