Help how to lower Mbps stream without too much CPU

[nightshadow36]

I am not sure if it is correct what I want to do.
Is there an option to lower the Mbps on a stream without using too much CPU, for example can I get a 4Mbps stream down to 2Mpbs without much CPU?
For example is transcoding the only option there are so many ways i am looking for the best without killing the CPU

Transcoding? Encoding? changing the format container? Lowering bitrate? Framerate? Transrate?
Do you know how to get 4Mbps down to 2Mbps without much CPU usage?

Sorry to ask TBS support. I have tried logging into mumudvb support forum but it does not work, I do not know who else to ask for the help.
Thank you.

I7 Quad core
1 x Ubuntu Server, Phoenix card reader, Oscam, Mumudvb
4 x tbs6985 tuners
FFserver FFmpeg - I can install if needed.
How to get 4Mpbs to 2Mbps without much CPU?
I have about 70 channels so this is why I am looking for an option that does not kill CPU
Regards.

[updatelee]

If its just one channel thats pretty easy, using the intel GPU (VA-API) you can transcode 4mbps to 2mbps with minimal cpu usage. transcoding 70x 4mbps feeds into 70x 2mbps feeds is going to be tough.

UDL