![]() Learning from real-world examples # Example 1: Render tasks going beyond render budget # The two screenshots above are great examples of the ideal tracing data. In both cases, the ideal tracing data is characterized by well-aligned audio device callback invocations and render tasks being completed well within the given render budget. Both cases lead to glitches in the audio stream. The common irregularity here is a big block caused by the garbage collection or missed render deadlines. This thread is currently not a real-time priority one. When the worklet is activated all the web audio operations are rendered by the AudioWorklet thread. In Worklet Mode, which is characterized by one thread jump from AudioOutputDevice to the AudioWorklet thread, you should see well-aligned traces in two thread lanes as shown below. See the following Chromium issues for more details: #825823, #864463. The combination of Linux and Pulse Audio is known to have this problem. If you see irregularity from the trace data in this lane, it means the callback timing from the device may be jittery. The AudioOutputDevice is a real-time priority thread originating from the browser's Audio Service that is driven by the audio hardware clock. In operating system mode, the AudioOutputDevice thread runs all the web audio code. Each mode uses a different threading model, so the tracing results also differ. The renderer has two different render modes: Operating system mode and Worklet mode. The tracing data visualizes how Chrome's web audio engine renders the audio. The tracing tab will visualize the result. When you have enough trace data, go back to the tracing tab and press Stop. Go back to your application tab and redo the steps that triggered the issue. dionode (if you need the detailed trace for each AudioNode).audio-worklet (if you're interested in where the AudioWorklet thread starts).In the Disabled by Default Categories section, select the following: v8.execute (if you're interested in AudioWorklet JS code performance).In the Record Categories section, select the following: Press the None buttons on both the Record Categories and Disabled by Default Categories sections. Press the Record button and select Manually select settings. Open another tab and go to about://tracing. Open your application (web page) on a tab. Once you have the browser ready, follow the steps below: ![]() Alternatively you can either launch a new instance of Chrome or use other builds from different release channels (e.g. The instructions below written are for Chrome 80 and later.įor best results, close all other tabs and windows, and disable extensions. Use about://tracing # How to capture tracing data # If the capacity goes near 100 percent, that means your app is likely to produce glitches because the renderer is failing to finish the work in the given budget. With this extension, you can monitor a running estimate of render capacity, which indicates how the web audio renderer performs over a given render budget (e.g. The Web Audio DevTools extension can help you by visualizing the graph. It is never easy, and it becomes more difficult when you have a bigger audio graph. Then it’s time for debugging by listening. (The Web Audio API doesn’t have features for node/graph introspection.) Some changes happen in your graph and now you hear silence. ![]() The audio graph, a network of AudioNode objects to generate and synthesize an audio stream, often gets complex but the graph topology is opaque by design. When you want to visualize the audio graph and monitor how the audio renderer performs in real time. When do you use Web Audio DevTools extension? # The general instructions for tracing are available here. This information is useful for understanding an underlying problem, so Chromium engineers will often ask it especially when the local reproduction is not feasible. It usually shows missed audio callback deadlines or big garbage collection that might cause unexpected audio glitches.
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