Assertion `pcm' failed.

[flatsiedatsie]

I have some users of the Voco add-on for the Mozilla WebThings Gateway, which uses NanoTTS, which are reporting a PCM error that I am unable to reproduce on my own Pi 4.

2020-05-06 21:27:36.677 ERROR : voco: error: opening pcm device failed No such file or directory
2020-05-06 21:27:36.679 ERROR : voco: nanotts: pcm.c:736: snd_pcm_stream: Assertion `pcm' failed.

(note the two different quotation marks by the way)

This is on a Pi 4. Perhaps they are using USB audio output hardware.

This is the code that calls NanoTTS:

    def speak(self, voice_message="",site_id="default"):
        try:
            # TODO add an environment variable here to set alsa to the USB output device?
            
            
            my_env = os.environ.copy()
            my_env["ALSA_CARD"] = str(self.playback_card_id)
            
            ps = subprocess.Popen(('echo', str(voice_message)), stdout=subprocess.PIPE)
            output = subprocess.check_output((str(os.path.join(self.snips_path,'nanotts')), '-l',str(os.path.join(self.snips_path,'lang')),'-v',str(self.voice),'--speed','0.9','--pitch','1.2','-p'), stdin=ps.stdout, env=my_env)
            ps.wait()
            
        except Exception as ex:
            print("Error speaking: " + str(ex))

So it could be that they are using USB audio output devices, and the environment variables aren't set properly for that case.

I noticed there was a way of compiling NanoTTS without ALSA. Would that perhaps make it more universal/robust/agnostic?

[zen2]

Late answer but I let it for other ones that get the same issue.
Your problem is an alsa problem: alsa try to use the PCM device of your first sound card and your usb one is not the first one.
You can list your sound cards:

$ cat /proc/asound/cards
 0 [Loopback       ]: Loopback - Loopback
                      Loopback 1
 1 [NVidia         ]: HDA-Intel - HDA NVidia
                      HDA NVidia at 0xf6080000 irq 165
 2 [STX            ]: AV200 - Xonar STX
                      Asus Virtuoso 100 at 0xe000, irq 24

You need to pick up the sound card name you want to use that is between bracket or the card number before bracket.
Then configure it with either:

• /etc/asound.conf (system level config file)
• ~/.asoundrc (user level config file)

For exemple for the STX card listed previously:

pcm.!default {
    type plug
    slave.pcm "duplex"
    slave.rate 48000
}

pcm.duplex {
    type asym
    playback.pcm "dmix:CARD=STX"
    capture.pcm  "dsnoop:CARD=STX"
}

If you prefer or need the card number instead of sound card name, you can replace STX by the number.
That can be needed if you got several cards with the same name.