Does a 2.3X:1 movie need less bitrate than a 1.78:1 movie?

[MisterFantastic]

Simple question that I've been wondering, does a movie that's matted with black bars (ie a 4:3 movie, or a 2.35:1 movie) need a substantial amount less bitrate than say a transfer of the same content, but at 1.78:1 (fullscreen)? The reasoning behind this would be that since the black bar mattes are always constant, the codec would need less space than something that fills the full 1920x1080 frame with information.
Would the difference in necessary bitrate be negligible, or would substantial?

[42041]

Yes. Black bars take nothing to encode (with the exception where the black bar cuts through the middle of a macroblock, which can actually be rather bad for compressibility there). So, assuming equal per-pixel compressibility, a scope film needs 74% the bitrate for the same compression quality.

[J-Mart]

Since a lot scope films are action films, I would assume they still need a higher bitrate due to the increased action anyway. But I'm sure a 2.40:1 drama could get away with a lower bitrate than a 1.78:1 drama, but I would rather they not try to find out.

That's what I think at least.

[oddbox83]

Technically, yes. In reality though, it depends more on how much movement or grain is having to be encoded. Techniscope 2.35:1 for example is going to need more bitrate than nice clean 4 or 3-perf 35mm at 1.85:1.

[I KEEL YOU]

Yes. A 1.78:1 movie is a full 1920 x 1080 frame whereas the 2.35:1 one is around 1920 x 700-800.

But it mostly depends on the encoding, how detailed the source is and the pace and camera movements of the movie itself. For example, 2001: A Space Odyssey only has a bit rate of 13 something mbps. At first glance that might seem very little, but when you take into account the blank screens of the overture and the intermission and the slow pace of the movie that doesn't vary a great deal from frame to frame, it's not as low as it might seem.

[42041]

Originally Posted by I KEEL YOU

But it mostly depends on the encoding, how detailed the source is and the pace and camera movements of the movie itself ... At first glance that might seem very little, but when you take into account the blank screens of the overture and the intermission and the slow pace of the movie that doesn't vary a great deal from frame to frame, it's not as low as it might seem.

Camera movement actually doesn't matter that much - it's relatively simple, predictable motion. Like oddbox83 suggested, grain/noise is far and away the biggest factor in compressibility over an entire film. Grainy/noisy films can require many times the bitrate for the same level of fidelity to the source as computer animation or clean digital footage, unless it's constantly loaded with complex motion like roiling water, crowds of people, rain/snow, etc.