[pulseaudio-discuss] Underrunning null sink

[Travis Brown]

Hi,

  I am using Pulseaudio to send data from an application to 3 different outputs simultaneously: HDMI, analog output and a G.722 RTP stream.   To accomplish this, I set up a null sink call g722 using the following setting in be default.pa:

    load-module module-null-sink sink_name=g722 sink_properties=device.description=“g722”
    load-module module-combine-sink sink_name=combined slaves=alsa_output.pci-0000_00_03.0.hdmi-stereo-extra1,alsa_output.pci-0000_00_1b.0.analog-stereo,g722

 It actually works pretty great.  I use ffmpeg to pull data from the g722 monitor and transcode it and send it out via multicast to the phones/speakers.  

    /usr/bin/ffmpeg -re -f pulse -i g722.monitor -filter_complex aresample=16000,asetnsamples=n=160 -vn -ac 1 -acodec g722 -f rtp udp://224.0.2.60:50000 <udp://224.0.2.60:50000>

 The issue I am having is that ffmpeg underruns most of the time UNTIL I start pavucontrol.  Starting pavucontrol makes things behave beautifully.  ffmpeg gets a constant stream of data and the audio sounds great.  What I cannot figure out is what pavucontrol is doing to make things better.  It must be setting up something for the VU meters, but I am not sure that would actually improve things, or why it would.  

Thanks,
Travis

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