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ALSA Underruns and mp3 stream issues
  • I'm trying to track down the cause of occasional periods of silence that are happening with my Airtime installation. One thing I've picked up in the logs (ls_script.log) are these: "2013/11/07 19:13:05 [alsa_out(default):2] Underrun!" that seem to coincide with the start or end of every track. Is it something to worry about? Other threads mentioning it asked about whether the installation is a virtual server; it is a VM on an ESXi box, with two cores and 1GB of ram.

    I'm have ALSA output enabled, as well as one stream configured, connecting to the local icecast server. When I set the stream to mp3, CPU usage sits at 40%, when I disable it or set it to ogg, CPU usage sits at 17%. When the stream is disabled, the "Underrun!" messages stop.

    Changing from ALSA to OA drops liquidsoap cpu usage to 8%, but breaks it in VLC for some reason (large gaps) whether it's mp3 or ogg.

    So is there some issue with encoding streams in mp3, or are these unrelated symptoms?

    KERNEL_VERSION                 = 3.5.0-23-generic
    MACHINE_ARCHITECTURE           = x86_64
    TOTAL_MEMORY_MBYTES            = 1019080
    TOTAL_SWAP_MBYTES              = 1044476
    AIRTIME_VERSION                = 2.5.0
    OS                             = Ubuntu 12.04.3 LTS x86_64
    CPU                            = Intel(R) Xeon(R) CPU E5-2420 0 @ 1.90GHz
    WEB_SERVER                     = Apache/2.2.22 (Ubuntu)
    PLAYOUT_ENGINE_MEM_PERC        = 1.6%
    PLAYOUT_ENGINE_CPU_PERC        = 0.0%
    LIQUIDSOAP_PROCESS_ID          = 28974
    LIQUIDSOAP_MEM_PERC            = 3.2%
    LIQUIDSOAP_CPU_PERC            = 28.9%
    MEDIA_MONITOR_MEM_PERC         = 1.7%
    MEDIA_MONITOR_CPU_PERC         = 0.0%
    -- Your installation of Airtime looks OK!

    Post edited by Bob Smith at 2013-11-07 12:59:39
  • 3 Comments sorted by
  • Vote Up0Vote Down hoerichhoerich
    Posts: 627Member, Airtime Moderator
    Hi Bob,
    I experienced similar with my 2.5-version.
    See this comment http://forum.sourcefabric.org/discussion/comment/27084#Comment_27084
    I disabled stream 1, because I don't need it. But that's just working for me...
    Official Airtime Forum Manager
    Most of the time an issue is located between keyboard and chair.
  • Hi Hoerich,

    Did you also experience unusually high CPU usage with the mp3 stream enabled? If that's reproducible it might be worth a bug report.
  • Vote Up0Vote Down hoerichhoerich
    Posts: 627Member, Airtime Moderator
    I deactivated any streams for now. gotta check it this week.
    Official Airtime Forum Manager
    Most of the time an issue is located between keyboard and chair.