Why faster-whisper use only a small portion of available cpu time

[marczz]

I tested whisper and faster-whisper, as I have only an intel i7 processor with 16G ram , and no CPU.

Both whisper and faster-whisper are very slow:

• for medium model 10mn of audio take around 100mn Real, and 100mn user+sys for whisper, and 15mn for faster-whisper.
• With the small model I get 35mn Real for both whisper and faster-whisper and 17mn user+sys with whisper
  and 5:30 with faster-faster.

1. It is strange that faster-whisper is quicker for cpu time but the real time is unchanged.
2. Even if I use 8 threads (the number of cores) the cpu use stay very low, my load average is between 0.2 and 0.3
3. threading does not give any gain.

The threads are not blocking on io iotop don't show any overload.

My command line is:

whisper-ctranslate2 --compute_type int8 --threads 8 --language en\
   --model medium audio.wav

What wrong have i done? What is you experience with cpu only processing?