245 vs 250 MB/s encoding rate @ 25fps

[macuser]

Hello everyone !

At the moment I am working at the pre-process of a film festival, checking and inspecting all sorts of DCP's.

A few days ago I had a discussion with a company that produces and delivers DCP's. The topic is about encoding rates, some DCP's the company delivers gave hints with 'dcp_inspect' saying that the bit rate is above the recommandations 250 MB/s instead of 245 MB/s @25fps.

I confronted them with that and their answer was that the filmmaker can see the difference between 250 MB/sand 245 MB/s so they deliver the 25fps always with 250 MB/s only to avoid discussions with the filmmakers....

I would like to read your comments about this - is there any visible difference ? What are your points to this ? What would you answer to the producer ? What would you say to the filmmaker ?

Kind regards
Max

[carl]

Others will have more direct experience of this than me, but I would be extremely surprised if anybody can see the difference between 245MB/s and 250MB/s.

[Carsten]

No one can see that difference, not with JPEG2000 codec, and certainly not with any other codec.

A still very popular DCI compliant server crashes towards 250 MBit/s, even well below, depending on content. It is NOT a good idea to approach that limit. I have never seen commercial DCPs challenging it, and for a good reason. Explicit HFR DCPs are another story.


- Carsten