dvb-fe-tool is a tool for monitoring and manipulating the front-end of the DVB device, e.g. selecting DVB-T/DVB-T2/DVB-C mode if applicable, and checking the low-level modulation parameters.
MPEG4 hardware decoding is done later, outside the front-end component, after the DVB transport stream (TS) is demultiplexed to select a particular program stream (PS) and the video stream (video PES) within it. Once the demultiplexer has picked out the desired MPEG4 video stream from within the transport stream, it can be fed to the hardware decoder, if one is available.
You should check if any
/dev/dvb/adapter*/video* devices exist - if not, then your DVB adapter has no hardware MPEG decoding capabilities at all. On typical PCs, the MPEG4 hardware decoding features would more commonly be found within the GPU, so having them in the DVB tuner would usually be useless duplication of functionality.
Also, moving the more compact MPEG4 datastream to the GPU for display takes far less system bus bandwidth than transferring the fully decoded bitmap images.