Does Goertzel algorithm works over analog signal?

My SIP phone is getting a tone(ringback) in regular rtp packet in PCMU payload (not using the rfc 2833 supported payload formats). To detect if tone or spee开发者_开发技巧ch is present in rtp data Goertzel algorithm should be used. I am new to this domain and not able to understand how to provide input from received rtp packet to Goertzel algo? or does this algo takes analog signal as input?

Decode the PCMU to signed 16-bit linear PCM and pass each packet to the Goertzel algorithm.

Depending on the library you are using you may need to convert to unsigned or perhaps even float, but signed 16-bit is most likely.

Standard code to convert to signed 16-bit linear PCM can be found here.