tools/metrics/histograms/metadata/web_audio/histograms.xml

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<!--
This file is used to generate a comprehensive list of WebAudio histograms
along with a detailed description for each histogram.

For best practices on writing histogram descriptions, see
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md

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<histogram-configuration>

<histograms>

<histogram name="WebAudio.AudioBuffer.Length" units="frames"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The length (in frames) requested by createBuffer(). Recorded for every call
    to createBuffer(). Probably many (tens or hundreds) per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioBuffer.NumberOfChannels" units="units"
    expires_after="2022-04-17">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The number of channels requested by createBuffer(). Recorded for every call
    to createBuffer(). Probably many (tens or hundreds) per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioBuffer.SampleRate384kHz" units="Hz"
    expires_after="2022-06-26">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The sample rate (in Hz) requested by createBuffer(). Recorded for every call
    to createBuffer(). Probably many (tens or hundreds) per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioBuffer.SampleRateRatio384kHz" units="units"
    expires_after="2022-06-26">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The ratio of the buffer sample rate from createBuffer() to the context
    sample rate. This indicates if the buffer needs to be resampled. Recorded
    for every call to createBuffer(). Probably many (tens or hundreds) per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContext.CreateTime" units="ms"
    expires_after="2022-08-12">
  <owner>hongchan@chromium.org</owner>
  <owner>cduvall@chromium.org</owner>
  <summary>
    Measures the time it takes to create the AudioContext object. This is
    recorded every time an AudioContext is successfully created.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContext.HardwareSampleRate" units="Hz"
    expires_after="2022-06-19">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The hardware sample rate (in Hz) used by an AudioContext. Recorded for every
    WebAudio AudioContext that is created; probably only one or two per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContext.latencyHintCategory" units="units"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    If provided, the latencyHint option category of &quot;interactive&quot;,
    &quot;balanced&quot;, &quot;playback&quot;, or &quot;exact&quot;, in that
    order where &quot;exact&quot; means an explicit floating point value was
    provided. Recorded for every AudioContext that is constructed with a
    latencyHint.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContext.latencyHintMilliSeconds" units="ms"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    If the latencyHint is provided and is a floating-point number, the value in
    milliseconds is recorded. This is recorded for every AudioContext that is
    constructed with a floating-point latencyHint value.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContext.MaxChannelsAvailable" units="units"
    expires_after="2022-06-12">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The maximum number of (hardware) channels available in an AudioContext.
    Recorded for every WebAudio AudioContext that is created; probably only one
    or two per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContextOptions.sampleRate" units="Hz"
    expires_after="2022-06-26">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The sample rate requested by developer to be used as the sample rate when
    constructing an AudioContext with an AudioContextOptions dictionary. This is
    recorded for each AudioContext created, probably just one or two per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioContextOptions.sampleRateRatio" units="units"
    expires_after="2022-07-03">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The ratio of the user-selected sample rate to the hardware sample rate of an
    AudioContext. The ratio is represented as a percentage. This is recorded for
    each AudioContext created, probably just one or two per page.
  </summary>
</histogram>

<histogram name="WebAudio.AudioDestination.CallbackBufferSize" units="units"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The callback buffer size (in audio frames) for WebAudio rendering between
    the WebAudio graph and the audio device thread. This can differ from the
    value recommended by the audio hardware due to internal constraints in
    WebAudio. Recorded for every WebAudio AudioContext that is created.
  </summary>
</histogram>

<histogram name="WebAudio.AudioDestination.HardwareBufferSize" units="units"
    expires_after="2022-07-11">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The buffer size (in audio frames) for WebAudio rendering recommended by the
    audio hardware. Recorded for every WebAudio AudioContext that is created.
  </summary>
</histogram>

<histogram name="WebAudio.Autoplay" enum="WebAudioAutoplayStatus"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The autoplay status of an AudioContext when destroyed. This include all
    types of frames. In order to know the value only for main frames, the
    .CrossOrigin values can be substracted.
  </summary>
</histogram>

<histogram name="WebAudio.Autoplay.CrossOrigin" enum="WebAudioAutoplayStatus"
    expires_after="2022-04-24">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The autoplay status of an AudioContext when destroyed in a cross-origin
    frame.
  </summary>
</histogram>

<histogram name="WebAudio.Autoplay.UnlockType"
    enum="WebAudioAutoplayUnlockType" expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    Records how an AudioContext was unlocked (if it was). This is recorded when
    the AudioContext is destroyed.
  </summary>
</histogram>

<histogram name="WebAudio.BiquadFilter.Type" enum="BiquadFilterType"
    expires_after="2022-05-01">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The type of the BiquadFilterNode. Recorded each time the type is set. This
    recorded once (to lowpass) when a biquad filter is created and also recorded
    whenever the filter type changes due to user action or programatically. It
    is unlikely the type will change more than once.
  </summary>
</histogram>

<histogram name="WebAudio.ConvolverNode.ImpulseResponseLength" units="ms"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The duration in millisec of impulse responses for a ConvolverNode. Recorded
    each time the impulse response is set for a ConvolverNode.
  </summary>
</histogram>

<histogram name="WebAudio.IIRFilterNode.Order" units="units"
    expires_after="2022-06-30">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The order of the WebAudio IIRFilterNode. The order is one less than the
    number of feedback coefficients used in the denominator of the IIRFilter
    transfer function. Recorded each time an IIRFilter is constructed.
  </summary>
</histogram>

<histogram name="WebAudio.OfflineAudioContext.ChannelCount" units="units"
    expires_after="2022-06-30">
  <obsolete>
    Removed 2021-01-12. See crbug.com/1165240.
  </obsolete>
  <owner>hongchan@chromium.org</owner>
  <summary>
    The number of channels specified for the offline audio context. Recorded for
    every offline context created. Probably only a few per page, but could be
    potentially much more (thousands).
  </summary>
</histogram>

<histogram name="WebAudio.OfflineAudioContext.CreateTime" units="ms"
    expires_after="2022-08-12">
  <owner>hongchan@chromium.org</owner>
  <owner>cduvall@chromium.org</owner>
  <summary>
    Measures the time it takes to create the OfflineAudioContext object. This is
    recorded every time an OfflineAudioContext is successfully created.
  </summary>
</histogram>

<histogram name="WebAudio.OfflineAudioContext.Length" units="frames"
    expires_after="2021-05-23">
  <obsolete>
    Removed 2021-01-12. See crbug.com/1165240.
  </obsolete>
  <owner>hongchan@chromium.org</owner>
  <summary>
    The length (in frames) specified for the offline audio context. Recorded for
    every offline context created. Probably only a few per page, but could be
    potentially much more (thousands).
  </summary>
</histogram>

<histogram name="WebAudio.OfflineAudioContext.SampleRate384kHz" units="Hz"
    expires_after="2021-02-18">
  <obsolete>
    Removed 2021-01-12. See crbug.com/1165240.
  </obsolete>
  <owner>hongchan@chromium.org</owner>
  <summary>
    The sample rate (in Hz) specified for the offline audio context. Recorded
    for every offline context created. Probably only a few per page, but could
    be potentially much more (thousands).
  </summary>
</histogram>

<histogram name="WebAudio.PannerNode.PanningModel" enum="PanningModelType"
    expires_after="2022-04-24">
  <owner>hongchan@chromium.org</owner>
  <summary>
    The panning model for the PannerNode. Recorded once with the default value
    at creation and once again whenver it is changed. Once changed, it is
    unlikely to be changed again. If there are any PannerNodes created at all,
    then there is probably one for each source (AudioBufferSourceNode,
    OscillatorNode, or other source).
  </summary>
</histogram>

<histogram name="WebAudio.PushPullFIFO.UnderflowGlitches" enum="Boolean"
    expires_after="2022-06-26">
  <owner>hongchan@chromium.org</owner>
  <summary>
    Captures if WebAudio caused glitches or not due to the FIFO underflow. It is
    recorded when PushPullFIFO is destroyed. (e.g. navigating away from the
    page.)
  </summary>
</histogram>

<histogram name="WebAudio.PushPullFIFO.UnderflowPercentage" units="%"
    expires_after="2022-04-17">
  <owner>hongchan@chromium.org</owner>
  <summary>
    Percentage of FIFO underflow happened due to the the missed deadline of
    WebAudio rendering engine. It is recorded when PushPullFIFO is destroyed.
    (e.g. navigating away from the page.)
  </summary>
</histogram>

</histograms>

</histogram-configuration>