Real time factor
Encyclopedia
The real time factor (RTF) is a common metric of measuring the speed of an automatic speech recognition
system. It can also be used in other context where an audio or video signal is processed (usually automatically) at nearly constant rate (e.g. reading music from a CD).
to process an input of duration 
, the real time factor is defined as
.
If, for example, it takes 8 hours of computation time to process a recording of duration 2 hours, the real time factor is 4. When the real time factor is 1 or less than 1 , the processing is done in real time. It is a hardware-dependent value.
The accuracy of a speech recognition system, on the other hand, is measured with the word error rate
.
Speech recognition
Speech recognition converts spoken words to text. The term "voice recognition" is sometimes used to refer to recognition systems that must be trained to a particular speaker—as is the case for most desktop recognition software...
system. It can also be used in other context where an audio or video signal is processed (usually automatically) at nearly constant rate (e.g. reading music from a CD).
Definition
If it takes time to process an input of duration , the real time factor is defined as.If, for example, it takes 8 hours of computation time to process a recording of duration 2 hours, the real time factor is 4. When the real time factor is 1 or less than 1 , the processing is done in real time. It is a hardware-dependent value.
The accuracy of a speech recognition system, on the other hand, is measured with the word error rate
Word error rate
Word error rate is a common metric of the performance of a speech recognition or machine translation system.The general difficulty of measuring performance lies in the fact that the recognized word sequence can have a different length from the reference word sequence...
.