Cepstral voice quality not good

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Asterisk Users 5 Comments

Hello list,

I have been using Cepstral’s 8KHz voices for my text-to-speech service for
some time now, and have been noticing that the voice quality is really poor,
doesn’t matter what phrase I give it to convert. None of the other 8KHz
voices I have ever used were this bad. It doesn’t seem good enough system to
be used in a commercial system. Is there any better quality text-to-voice
engine?

Zeeshan A Zakaria

5 thoughts on - Cepstral voice quality not good

  • I am using app_swift.

    As a side note, demo on their website also generates sounds which at places
    sounds like robotic.

    Zeeshan A Zakaria

  • Actually it is bad only when received on cell phones. Today I listened to
    the same voices on a Cisco 7942 and they were great. I actually enjoyed
    listening to them. Not bad on X-Lite either. Previously I was mostly
    listening to them only through cell phones. So it means it is because of the
    transcodings at cell phone providers’ ends. Bad though because many
    customers use cell phones exclusively. Maybe if I convert them to gsm format
    before playing, they’ll play better, but will add delay and additional
    processing because they are converted and played in real time.

    Zeeshan A Zakaria

  • One thing you’ll want to keep in mind is that app_swift currently outputs 8khz ulaw only, unless you’ve changed it in the source.

    There are other things such as buffers that also effect call quality with app_swift.

  • I fiddled with the demo version of swift a year or so ago and I had better
    sound quality if I used the non-8khz versions and had app_swift or asterisk
    convert it for me (not sure, giving app_swift a regular version seemed to
    JustWork(tm)