Why would a 2K version be larger than 4K?

[DCP-Junkie]

Good afternoon. I just built both a 2K and a 4K DCP from the same 4K file. To make sure that was the only difference, I set up the 2K version first and then copied that entire folder, went into the program for the copied folder and then changed the Resolution to 4K and left all other settings as they were. I then built both, one after another. The 2K version came out about 2GB larger (118GB total). Does this sound right? I did load both up in the player and both play and the dimensions look correct on each. Did I do something wrong here?

[Carsten]

2GB for a 118GB total filesize - I wouldn't find that unusual. You spec a compression bit rate, so, it is normal that, given a fixed bit rate, that the two versions come out very close in file size.

Can you have a look at the actual size of the resulting video MXF file?

[DCP-Junkie]

I looked at the sizes of the .mxf files and here are the results:

2K - 113.16GB
4K - 111.06GB

It just seems very strange that a 4K file would be smaller 2K. I would think it would have to be larger.

Thank you in advance for your help.

[Carsten]

You could have it larger if you configured a higher compression bitrate for 4k.

[DCP-Junkie]

I used the same copression bit rate on both of them at 150 M/bits which is where I typically build all of my content. Is there anything else, short of building them both again? Could it have something to do with the fact that I set up the 2K DCP and then made a complete copy of that folder and just changed the DCP output to 4K?

[Carsten]

No, it is just normal that if you leave the compression bitrate the same, that both video MXFs come out very close to each other both for 2k and 4k. These compressors allow for a bit of variance, at 2GB, you are in the range of 1%.

You could safely raise the compression bitrate to 200MBit/s if storage space is not an issue for you.

[DCP-Junkie]

Thank you for your help, I really appreciate it. I guess this brings up another question though. Should I be exporting at 200 M/bits? Are there projectors that won't be able to play it?

Thanks,

[Carsten]

The official limit for standard DCPs is 250MBit/s. Some older units have trouble with DCPs approaching that rate. 200MBit/s is safe and easy to remember.


- Carsten

[DCP-Junkie]

Thank you very much for your help once again.