Timing a voice speed

Because of the natural variation between voices, each available voice speaks at slightly different speeds. For instance, with US English voices, Ivy and Joanna are slightly faster than Matthew, and considerably faster than Joey. Since there is so much variation between voices, there is no standard speed (words per minute) available for Amazon Polly voices. However, you can find how long it takes for your voice to say the selected text using Speech Marks.

To time the length of a spoken text passage

1. Open the AWS CLI.

2. Run the following code, filling in as needed.

        aws polly synthesize-speech \
             --language-code optional language code if needed
             --output-format json \
             --voice-id [name of desired voice] \
             --text '[desired text]' \
             --speech-mark-types='["viseme"]' \
             LengthOfText.txt

3. Open LengthOfText.txt.

If the text were "Mary had a little lamb," the last few lines returned by Amazon Polly would be:

     {"time":882,"type":"viseme","value":"t"}
     {"time":964,"type":"viseme","value":"a"}
     {"time":1082,"type":"viseme","value":"p"}

The last viseme, essentially the sound for the final letters in "lamb" starts 1082 milliseconds after the beginning of the speech. While this is not exactly the length of the audio, it's close and can serve as the basis for comparison between voices.