Pre-call tests

In video calling scenarios that demand high communication quality, pre-call detection helps identify and troubleshoot issues beforehand, ensuring seamless real-time interaction.

This page shows you how to use Video SDK to run pre-call tests to identify and troubleshoot communication quality issues in your app.

Pre-call testing typically covers two aspects:

• Equipment quality test

  To test whether the local microphone, speaker, and camera are working properly, you run an echo test. The basic process of conducting an echo test is as follows:

  

• Network quality analysis

  The quality of the last mile network affects the smoothness and clarity of the audio and video that the user sends and receives. Last mile refers to the last leg of communication network between the edge server of the SD-RTN and the end-user devices. Network quality analysis enables you to get feedback on the available bandwidth, packet loss rate, network jitter, and round-trip delay of the upstream and downstream last-mile networks. The following figure shows the basic process of running a last-mile probe test.

  

information

Best practice is to run the device test first and then perform a network test.

Ensure that you have implemented the SDK quickstart project and that your app has obtained permissions to use the relevant devices.

This section shows you how to implement pre-call testing in your project.

The SDK provides the startEchoTest method to test the network connection and whether the audio and video devices are working properly. Refer to the following steps to implement the device quality test:

1. Before joining a channel, call startEchoTest. Specify the intervalInSeconds parameter to set the delay time for the echo test. The value range is 2-10 seconds and the default value is 10.

2. After starting the test, speak into the microphone. The user's audio is played back after a short delay. If the playback is normal, it means that the user's devices and upstream and downstream network are working normally.

3. To stop the test, call stopEchoTest, and then call joinChannel to join a channel.

To implement running an echo test in your app, refer to the following code:

// Start the echo test

// Only a host can call startEchoTest

await _engine.startEchoTest();

// Wait and check if you can hear voice playback

// Stop the echo test

// Call stopEchoTest to end the echo test. Until you call stopEchoTest, you cannot start another test or join a channel.

await _engine.stopEchoTest();

To test whether a local audio recording device, such as a microphone, is working properly, refer to the following steps.

1. Call startRecordingDeviceTest and set the indicationInterval parameter to the time interval after which the callback is triggered.

2. After starting the test, speak into the microphone. The SDK reports uid = 0, and the volume information of the device in the onAudioVolumeIndication callback.

3. When you are done testing, call stopRecordingDeviceTest to stop the test.

Information

Best practice is to set the indicationInterval parameter to more than 200 milliseconds and not less than 10 milliseconds, otherwise the onAudioVolumeIndication callback may not be received.

To implement running a recording device test in your app, refer to the following code:

// Select an audio capture device

await _audioDeviceManager.setRecordingDevice(deviceId);

// Implement the audio volume indication callback

onAudioVolumeIndication: (RtcConnection connection,

List<AudioVolumeInfo> speakers, int speakerNumber, int totalVolume) {

logSink.log('[onAudioVolumeIndication] speakers: ${speakers.toString()}, speakerNumber: $speakerNumber, totalVolume: $totalVolume');

},

// Start audio capture device test

await _audioDeviceManager.startRecordingDeviceTest(1000);

// Stop audio capture device test

await _audioDeviceManager.stopRecordingDeviceTest();

To test that the local audio playback device is working properly, refer to the following steps:

1. Call startPlaybackDeviceTest and set the audioFileName parameter to the absolute path of the audio file to be played.

2. If the user hears the audio, the playback device is working properly. The SDK triggers the onAudioVolumeIndication callback to report uid = 1 and the volume information of the playback device.

3. When you are done testing, call stopPlaybackDeviceTest to stop the test.

To implement running a playback device test in your app, refer to the following code:

// Select an audio playback device

await _audioDeviceManager.setPlaybackDevice(_selectedPlaybackDeviceId);

// Specify the absolute path of the audio file to start the playback device test

await _audioDeviceManager.startPlaybackDeviceTest(filePath);

// Stopping the audio playback device test

await _audioDeviceManager.stopPlaybackDeviceTest();

To test if the local audio device loop is working properly, refer to the following steps:

1. Call startAudioDeviceLoopbackTest and set the indicationInterval parameter to the time interval after which the callback is triggered.

2. After starting the test, speak into the microphone. The microphone captures the sound and then plays it on the playback device. The SDK returns two onAudioVolumeIndication callbacks to report the volume information of the audio capture device with uid= 0, and the audio playback device with uid= 1, respectively.

3. When you are done testing, call stopAudioDeviceLoopbackTest to stop the recording device test.

Information

Best practice is to set the indicationInterval parameter to more than 200 milliseconds and not less than 10 milliseconds, otherwise the onAudioVolumeIndication callback may not be received.

To implement an audio loopback device test in your app, refer to the following code:

await _audioDeviceManager.startAudioDeviceLoopbackTest(1000);

await _audioDeviceManager.stopAudioDeviceLoopbackTest();

The SDK provides the startLastmileProbeTest method to probe the last-mile network quality before joining a channel. The method returns information about the network quality score and network statistics. Take the following steps to run a last-mile network quality probe test:

1. Before joining a channel or switching user roles, call startLastmileProbeTest to start the network test. Set the probe configuration and the expected maximum bitrate in LastmileProbeConfig.

2. After you start the test, the SDK triggers the following callbacks:

   • onLastmileQuality: This callback is triggered two seconds after startLastmileProbeTest is called. It provides feedback on the upstream and downstream network quality through a subjective quality score.

   • onLastmileProbeResult: This callback is triggered 30 seconds after startLastmileProbeTest is called. It returns objective real-time network statistics, including packetLossRate, network jitter, and availableBandwidth.

3. Call stopLastmileProbeTest to stop last-mile network testing.

To implement network quality testing in your app, refer to the following code:

// Configure a LastmileProbeConfig instance

LastmileProbeConfig config = const LastmileProbeConfig(

probeUplink: true, // Probe uplink network quality

probeDownlink: true, // Probe downlink network quality

expectedUplinkBitrate: 100000, // Desired maximum transmit bitrate in bps, in the range [100000,5000000].

expectedDownlinkBitrate: 100000, // Desired maximum receive bitrate in bps, in the range [100000,5000000].

);

// Start the probe test

await _engine.startLastmileProbeTest(config);

// Stop the probe test

await _engine.stopLastmileProbeTest();

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

If you encounter problems while running pre-call tests, first ensure that you have implemented the API calls properly. To troubleshoot device and network issues, refer to the following table:

Problem	Solution
Can't hear sound when testing audio devices.	Check that the recording device and the playback device are working properly, and are not occupied by other programs. Check that the network connection is normal.
Cannot see the screen when testing video devices.	Check that the video device is working properly and not occupied by other programs. Check whether the network connection is normal.
Poor uplink network quality detected (packet loss > 5%; network jitter > 100ms)	Check that the local network is working properly. Ensure that the bitrate of the published audio and video streams does not exceed the available uplink bandwidth by reducing the resolution or lowering the frame rate.
Poor downlink network quality detected (packet loss > 5%; network jitter > 100ms)	Check that the local network is working properly. Ensure that the total bandwidth of the local subscription does not exceed the available downstream bandwidth by: Reducing the number of subscribed audio and video streams on the receiving end or reducing the bitrate of published audio and video streams on the sending end. Enabling dual-stream mode on the sending side and requesting to receive small streams on the receiving side to reduce bandwidth consumption. Enabling the video stream fallback function or the multiple streams by priority fallback function at the receiving end.

• startRecordingDeviceTest
• stopRecordingDeviceTest
• startPlaybackDeviceTest
• stopPlaybackDeviceTest
• startAudioDeviceLoopbackTest
• stopAudioDeviceLoopbackTest
• startEchoTest
• stopEchoTest
• startLastmileProbeTest
• stopLastmileProbeTest
• onLastmileQuality
• onLastmileProbeResult