Crops out a 93 pixel lower band:
ffmpeg -i 4.mp4 -filter_complex "[0:v]crop=in_w:in_h-93:0:0[cropped]" -map "[cropped]" 4a.mp4
Crops out a 34 pixel lower band:
convert 5.jpg -gravity South -chop 0x34 5a.jpg
Cuts out the last N seconds. -t needs to be the total length of the video, you must have to know the video length (in seconds) and specify the t parameter with the right value.
ffmpeg -i setup.mp4 -t 233 -c copy output.mp4
So, let's pretend you are running a medical center, maybe a pizza place or any business that requires attending customers by the phone and walk-ins at the same time. It is obvious that you need at least one person not talking on the phone. It is also obvious that you need a call center queue for those customers on the phone.
First of all, a Call Center is a very specific use case of a FIFO queue. Any respectable call center business must have some kind of implementation for their own use or their users.
People do not like to wait while listening to your music on hold; also people waiting in the queue are costing money (many carriers bill incoming calls). Depending on the nature of your business, people could switch to another business or just wait. Because of this, it is very common these days that call centers to offer a call-back feature. A call center feature is the one that allows users to hang out without losing its turn in the queue. When it is their turn (or about to be their turn), the system callbacks them.