[asterisk-bugs] [JIRA] (ASTERISK-29793) adsi: CAS is malformed

[N A (JIRA)]

N A created ASTERISK-29793:
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             Summary: adsi: CAS is malformed
                 Key: ASTERISK-29793
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-29793
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Resources/res_adsi
    Affects Versions: 18.8.0
         Environment: PJSIP + Confbridge
            Reporter: N A
            Severity: Major


The CAS that res_adsi is generating seems to be malformed or non-compliant in some way. When I manually use PlayTones to produce a CAS in the dialplan, my CPE correctly responds to it with the DTMF "A" ACK. However, when using the native CAS in __adsi_transmit_messages, it does not work and my CPE does not recognize the CAS. As a result, GetCPEID() exits.

I can trick GetCPEID() by generating my own CAS before calling GetCPEID(), which makes the first CAS and response work, but subsequent CAS's generated by the application internally cannot be "propped up" in this manner.

As such, GetCPEID() will always fail and exit.

I have analyzed a few properties of the waveform and have concluded that the issue does not seem related to duration. A CAS of 80ms and 110ms both seem to work fine. The CAS generated by Asterisk seems to be about 100ms. The audio captured using MixMonitor doesn't seem to reflect volume adjustments, but the CAS generated by Asterisk is noticeably quieter than ones generated manually. 

FWIW, I cannot get the CAS to be recognized at all unless the endpoint is joined to it in a ConfBridge. I have dtmf_passthrough = yes, silence drop set to no, to maximize audio quality.

When analyzing the recordings using the Plot Spectrum feature in Audacity, the CAS generated by Asterisk internally seems a lot noisier than the purer CAS generated by PlayTones in the dialplan. Perhaps this is causing the CPE to not recognize it.



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