I am trying to render a 20 second sample video using the Adobe Media Encoder 2015 CC Youtube 4k preset. The target and maximum bitrate displayed is both 40 but the output file ( if I right click and then properties ) only showed 16,000 kbps? Why isn't 40,000 kbps? I also tried using other presets and custom ones, whenever I put 16 bitrate the output file will only have 7,000kbps. Am I missing something? I wanted the bitrate of the video to be high like 45,000, I am using the same 20 second video in all my tests.
What is the content of the clip - motion video, or stills/graphics? If the latter, it will compress very well and maybe that is why the file is smaller.
The content is just a still 1920x1080 photo with a music and a visualizer (audio spectrum). The composition is 1920x1080 60fps. It's just a simple background with a music and I wanted it to be like about 50mb bitrate in 4k.
I think that explains it then - a still background will compress easily and the compressor it not going to use more data than needed to compress that frame at the desired quality. A still image can only look "so good" and increasing the bitrate won't make it look better.
EDIT: I should add that often times when setting up an encoder as VBR, it will ask for Min-Avg-Max values. However, the H.264 encoder only asks for Target and Max. That doesn't mean there isn't a lower figure it will use though. If you are encoding a black screen, or similarly simple content, it is not going to use Target to encode that. It will encode at a lower bit rate that suits the content. I believe if you select CBR, then you can dictate a Constant Bit Rate that will even apply to still frames. Give it a try if that is your goal.