Minimal working frame rate for H264 codec When making a video from single image files whereas each image file should be visible for about one second, it does make sense to encode a video with an extremely low frame rate such as 1 frame per second. For this type of application, every frame rate greater than this would be a waste of resources.

I am wondering if the H264 codec (or any specific implementation, such as x264) itself has any lower limit for the frame rate below which it comes to technical problems or some kind of instabilities. In case there is no problem with encoding, can we expect video players to properly deal with such an unusual low frame rate?

Thanks for sharing your experience!
I'm not sure how it will behave at very low frame rates, but it is worth pointing out this would also limit your options on how and when you could change frames since they would have to follow on the clock cycles.  What is more likely to work in this case is a long keyframe interval.  The majority of frames in a compression like H.264 only store the changes from the previous frame.  In the case of a still image, the compression ratios will be huge because very little (no) change occurs between frames.  I'm not sure that you would really pick up enough of a savings from dropping the frame rate to be worth the loss of control over when you can make a change to the frame.

The best bet would be to try it with your media and see the results.  Compression is a highly content dependent thing and the best quality and compression for any particular clip is going to depend a lot on the nature of that clip, so trial is still the best way to test it out.