The CPU is not a primary concern. Usually the camera is limited by the bandwidth it is connected to RAM, leading to a max number of raw frames that can be taken per second.
Yes, and another issue is how fast can you save the image. The eMMC 5.0 storage used by the Librem 5 won’t be nearly as fast as the UFS 3.0 storage used by the flagships. Where the SoC is important is when we are talking about the fancy image processing that paper describes. If it takes the SoC 30 seconds to process the image, then it isn’t usable.
Looking through the spec sheet on the i.MX 8M Quad, I’m not very optimistic. It doesn’t have a dedicated digital signal processor or image signal processor, like Snapdragon processors. It also doesn’t list how many megapixels are supported in a camera like Snapdragon does. The i.MX 8M seems to be designed for video streaming, but not for the kind of image processing done by a comparable Snapdragon. In terms of its CPU, the iMX 8M Quad is basically the equivalent to the Snapdragon 425 released in Q3 2016, but it does not seem to have the same image processing capabilities.
It seems like all the open source implementations use OmniVision image sensors, and those range in resolution up to 32 megapixels. Fairphone offers a camera module with the OmniVision OV12870 with 12 MP, so hopefully we will get something similar in the Librem 5, but the Snapdragon 800 in the Fairphone 2 is capable of processing 12MP images, and I’m not sure that the i.MX 8M Quad can do that.
Oh well, I’m still going to have a blast playing with the Librem 5. It looks like it will have enough processing power to run a full Linux desktop on an external monitor, which is the most important thing in my opinion. What worries me is whether we will have better processors from NXP in the future. NXP might decide to not design anything better than the i.MX 8M mini, since that is all that the automotive market needs, and we don’t really have any other options. Maybe RISC-V will eventually provide an alternative, but it looks like that is at least 5 years in the future.