3 ms·

Is there a reason h264 wasn't used? It has been widely available since at least 2006 and supports all kinds of resolutions, etc.

Isthatablackgsd 5y ago
I believe it is something to do with bit depths. JPEG2000 can support up to 16-bits whereas H264 only can support up to 10-bits. So using H264 8/10-bits could produce noticeable artifacts when it is being used in a big screen. So using JPEG2000 will alleviate the artifacts since it have higher bit depth as it have extra space for more information to fit in. Here another article [1] I found recently that discussed why Movie theaters use JPEG2000 over popular video format. [1] https://www.design-reuse.com/articles/4595/digital-cinema-reels-from-motion-jpeg2000-advances.html https://www.design-reuse.com/articles/4595/digital-cinema-re...
__david__ 5y ago
jpeg2000 has a number of positive traits: * The industry doesn't want you to see compression artifacts, ever. Digital Cinema has no inter-frame compression, it's encoded as a series of individual jpeg2k images at a pretty reasonable quality. * If one frame has a glitch, the glitch doesn't propagate over a bunch of frames the way x264 style compression does. * jpeg2k at too-low a quality doesn't have jpeg/mpeg style square artifacts—instead certain parts of the picture will look slightly blurrier. * jpeg2k has an interesting property where a 4k image can be encoded (with the proper parameters) such that when decoding you can stop at some point midway through a single frames data and have the equivalent encoded 2k image. Which means you can encode for 4k and ship it to theaters that only have 2k projectors (and that 2k hardware isn't required to render to a 4k framebuffer and then downsample). * Since it's more modern than jpeg was (and dcinema was standardized before something like webp came along), it has a lower bytes/quality ratio than jpeg. IE, to achieve equivalent quality image from jpeg you'd need a lot more data. * Support for deeper color depths and a much wider gamut. This is of course limited by what a projector can recreate, but they didn't want to limit to rec 709 or something. They didn't care about patent encumbrance because they didn't need push this out the consumers—the jpeg2k patent stuff only affects the decoders and encoders, both of which are owned by people who can afford to pay.

Isthatablackgsd 5y ago

I believe it is something to do with bit depths. JPEG2000 can support up to 16-bits whereas H264 only can support up to 10-bits. So using H264 8/10-bits could produce noticeable artifacts when it is being used in a big screen. So using JPEG2000 will alleviate the artifacts since it have higher bit depth as it have extra space for more information to fit in. Here another article [1] I found recently that discussed why Movie theaters use JPEG2000 over popular video format. [1] https://www.design-reuse.com/articles/4595/digital-cinema-reels-from-motion-jpeg2000-advances.html https://www.design-reuse.com/articles/4595/digital-cinema-re...

__david__ 5y ago

jpeg2000 has a number of positive traits: * The industry doesn't want you to see compression artifacts, ever. Digital Cinema has no inter-frame compression, it's encoded as a series of individual jpeg2k images at a pretty reasonable quality. * If one frame has a glitch, the glitch doesn't propagate over a bunch of frames the way x264 style compression does. * jpeg2k at too-low a quality doesn't have jpeg/mpeg style square artifacts—instead certain parts of the picture will look slightly blurrier. * jpeg2k has an interesting property where a 4k image can be encoded (with the proper parameters) such that when decoding you can stop at some point midway through a single frames data and have the equivalent encoded 2k image. Which means you can encode for 4k and ship it to theaters that only have 2k projectors (and that 2k hardware isn't required to render to a 4k framebuffer and then downsample). * Since it's more modern than jpeg was (and dcinema was standardized before something like webp came along), it has a lower bytes/quality ratio than jpeg. IE, to achieve equivalent quality image from jpeg you'd need a lot more data. * Support for deeper color depths and a much wider gamut. This is of course limited by what a projector can recreate, but they didn't want to limit to rec 709 or something. They didn't care about patent encumbrance because they didn't need push this out the consumers—the jpeg2k patent stuff only affects the decoders and encoders, both of which are owned by people who can afford to pay.