4 ms·

> Is the whole thing just so that the file is DRM-ed to hard that nothing else except expensive equipment can play it? Could be the case. However, one of the q

> Is the whole thing just so that the file is DRM-ed to hard that nothing else except expensive equipment can play it? Could be the case. However, one of the quirks about Digital Cinema Packages (DCPs) is that they don’t use video codecs like H.264/AVC or H.265/HEVC. Instead, to maintain maximum quality, every single frame is individually compressed and stored with JPEG 2000, and they are played through like a slideshow, just at 24 frames per second. Needless to say this adds compute and especially storage concerns. Storing every frame of a movie individually quickly hits hundreds of gigabytes if not terabytes; and you need to decode and have every frame ready in less than 41 milliseconds, which is shockingly difficult even on high-end hardware. Even a modern Core i9 would have to be parallel and have multiple frames ready at a time because doing it a single frame at a time would be too slow (and thus, most projectors almost certainly use custom chips or FPGA-based decoders but that's really, really expensive). Do I need to mention read speeds and network traffic? If every frame is, say, just 5MB, that is over 960 Megabits per second, saturating a Gigabit link. Another thing to consider is the multitude of speakers. Dolby Atmos is object-based, meaning there aren’t specific audio streams for specific speakers like in the past. Every speaker’s location is individually stored in the playback device varying between theaters, and the sound is calculated and mixed for that specific theater’s audio setup at the time the movie is played. When you are calculating audio in real-time for 30 or more speakers, the compute costs add up, potentially into custom hardware / FPGA territory. Also that "saturating a Gigabit connection" doesn't include the amount of data that the audio uses, and considering it's 24-bit PCM without any compression for dozens of streams for the objects, that's also pretty substantial. Just 2 streams of 16-bit PCM for ~70 minutes on a CD takes about 700MB. So, just for one movie, with every frame taking 5MB (possibly more or less, we don't know how big they actually are) and audio taking whatever it takes, you would need a 2.5Gig Ethernet link to be safe, and storage that can deliver that (which is also why an external hard drive is out of the question for actual playback, only very recently do we have built-in NVMe SSDs that can deliver that kind of speed, but we still don't have any external SSDs that can deliver anywhere close; it just has to be RAID on multiple storage devices). Now consider what you need for a theater with 12-20 screens at a time. The storage amount and speed requirements is substantial. Now consider this has been standard for over a decade and think about how expensive this would've been to implement in, say, 2013. Oh, and that storage had better not fail, ever, or your entire theater is down, and there's a lot of refund requests and unsold tickets until it's running again.

csnover 4y ago
I was curious about this so I did a little research. > you need to decode and have every frame ready in less than 41 milliseconds, which is shockingly difficult even on high-end hardware There appear to be multiple high-speed JP2K decoders on the market; Comprimato[0] include a calculator for their product and it claims that a $240 GPU from 2016 can decode 4k 4:4:4 at 72fps. > Do I need to mention read speeds and network traffic? If every frame is, say, just 5MB, that is over 960 Megabits per second, saturating a Gigabit link. According to Wikipedia, the DCP standard has a maximum bit rate for picture of 250Mbit/s[1]. My $60 home internet connection could stream that at almost 2x realtime. > When you are calculating audio in real-time for 30 or more speakers, the compute costs add up, potentially into custom hardware / FPGA territory. Dolby offer a software version of Atmos for soundtrack mastering that runs on a Mac Mini[2]. Real-time 128-channel object mixing was possible using consumer-grade hardware as early as EAX 5.0 in 2005[3], but Atmos does not need to be rendered in real time at a cinema, it can be done in advance and then during playback those pre-rendered PCM streams would be used which is a trivial amount of data to handle (under 20Mbit/s for a full 64-speaker array). [0] https://comprimato.com/products/comprimato-jpeg2000/ https://comprimato.com/products/comprimato-jpeg2000/ [1] https://en.wikipedia.org/wiki/Digital_Cinema_Package#Picture_MXF_files https://en.wikipedia.org/wiki/Digital_Cinema_Package#Picture... [2] https://professionalsupport.dolby.com/s/article/What-are-the-current-computer-OS-and-I-O-configurations-for-running-the-Dolby-Atmos-Renderer-on-a-dedicated-Workstation https://professionalsupport.dolby.com/s/article/What-are-the... [3] https://en.wikipedia.org/wiki/Environmental_Audio_Extensions#EAX_5.0 https://en.wikipedia.org/wiki/Environmental_Audio_Extensions...
- gjsman-1000 4y ago
  > There appear to be multiple high-speed JP2K decoders on the market; Comprimato[0] include a calculator for their product and it claims that a $240 GPU from 2016 can decode 4k 4:4:4 at 72fps. Interesting, that's a lot better. This is my source for my numbers: https://www.fastcompression.com/benchmarks/decoder-benchmarks-j2k.htm https://www.fastcompression.com/benchmarks/decoder-benchmark... A GPU helps for sure, a CPU alone is pretty bad. > According to Wikipedia, the DCP standard has a maximum bit rate for picture of 250Mbit/s.[1] I'm really surprised, I would not have thought that a 4K frame at a theatrical quality level would fit into about 1.3MB. But maybe that's why they chose JPEG 2000. > Dolby offer a software version of Atmos for soundtrack mastering that runs on a Mac Mini[2]. 128-channel object mixing was possible using consumer-grade hardware as early as EAX 5.0 in 2005[3]. That's not quite true because Dolby Atmos came out in 2012, not 2005. As for theatrical hardware, even though I'm not sure why it is so expensive, look at the Dolby CP850. It's a 64-channel object mixer for theaters and it costs about $8,000 (or $18,000, depending on where you shop and who you trust on the subject). As far as I know, EAX is not even a true surround sound encoding technology in the first place, and was a much more primitive system only for video games that is not directly comparable. I suspect part of the cost is all of the outputs, and also because Dolby has been clear that they make their money (patent licensing) on playback equipment, not production equipment. I can't find the specific webpage, but it's no secret in the industry Dolby charges much more on licensing for devices with lots of outputs.

csnover 4y ago

I was curious about this so I did a little research. > you need to decode and have every frame ready in less than 41 milliseconds, which is shockingly difficult even on high-end hardware There appear to be multiple high-speed JP2K decoders on the market; Comprimato[0] include a calculator for their product and it claims that a $240 GPU from 2016 can decode 4k 4:4:4 at 72fps. > Do I need to mention read speeds and network traffic? If every frame is, say, just 5MB, that is over 960 Megabits per second, saturating a Gigabit link. According to Wikipedia, the DCP standard has a maximum bit rate for picture of 250Mbit/s[1]. My $60 home internet connection could stream that at almost 2x realtime. > When you are calculating audio in real-time for 30 or more speakers, the compute costs add up, potentially into custom hardware / FPGA territory. Dolby offer a software version of Atmos for soundtrack mastering that runs on a Mac Mini[2]. Real-time 128-channel object mixing was possible using consumer-grade hardware as early as EAX 5.0 in 2005[3], but Atmos does not need to be rendered in real time at a cinema, it can be done in advance and then during playback those pre-rendered PCM streams would be used which is a trivial amount of data to handle (under 20Mbit/s for a full 64-speaker array). [0] https://comprimato.com/products/comprimato-jpeg2000/ https://comprimato.com/products/comprimato-jpeg2000/ [1] https://en.wikipedia.org/wiki/Digital_Cinema_Package#Picture_MXF_files https://en.wikipedia.org/wiki/Digital_Cinema_Package#Picture... [2] https://professionalsupport.dolby.com/s/article/What-are-the-current-computer-OS-and-I-O-configurations-for-running-the-Dolby-Atmos-Renderer-on-a-dedicated-Workstation https://professionalsupport.dolby.com/s/article/What-are-the... [3] https://en.wikipedia.org/wiki/Environmental_Audio_Extensions#EAX_5.0 https://en.wikipedia.org/wiki/Environmental_Audio_Extensions...

gjsman-1000 4y ago
> There appear to be multiple high-speed JP2K decoders on the market; Comprimato[0] include a calculator for their product and it claims that a $240 GPU from 2016 can decode 4k 4:4:4 at 72fps. Interesting, that's a lot better. This is my source for my numbers: https://www.fastcompression.com/benchmarks/decoder-benchmarks-j2k.htm https://www.fastcompression.com/benchmarks/decoder-benchmark... A GPU helps for sure, a CPU alone is pretty bad. > According to Wikipedia, the DCP standard has a maximum bit rate for picture of 250Mbit/s.[1] I'm really surprised, I would not have thought that a 4K frame at a theatrical quality level would fit into about 1.3MB. But maybe that's why they chose JPEG 2000. > Dolby offer a software version of Atmos for soundtrack mastering that runs on a Mac Mini[2]. 128-channel object mixing was possible using consumer-grade hardware as early as EAX 5.0 in 2005[3]. That's not quite true because Dolby Atmos came out in 2012, not 2005. As for theatrical hardware, even though I'm not sure why it is so expensive, look at the Dolby CP850. It's a 64-channel object mixer for theaters and it costs about $8,000 (or $18,000, depending on where you shop and who you trust on the subject). As far as I know, EAX is not even a true surround sound encoding technology in the first place, and was a much more primitive system only for video games that is not directly comparable. I suspect part of the cost is all of the outputs, and also because Dolby has been clear that they make their money (patent licensing) on playback equipment, not production equipment. I can't find the specific webpage, but it's no secret in the industry Dolby charges much more on licensing for devices with lots of outputs.