8.7 GetStats Example

Consider the case where the user is experiencing bad sound and the application wants to determine if the cause of it is packet loss. The following example code might be used:

Example 8

async function gatherStats(pc) {
  try {
    const [sender] = pc.getSenders();
    const baselineReport = await sender.getStats();
    await new Promise(resolve => setTimeout(resolve, aBit)); // wait a bit
    const currentReport = await sender.getStats();
    // compare the elements from the current report with the baseline
    for (const now of currentReport.values()) {
      if (now.type != 'outbound-rtp') continue;
      // get the corresponding stats from the baseline report
      const base = baselineReport.get(now.id);
      if (!base) continue;
      const remoteNow = currentReport.get(now.remoteId);
      const remoteBase = baselineReport.get(base.remoteId);
      const packetsSent = now.packetsSent - base.packetsSent;
      const packetsReceived = remoteNow.packetsReceived -
                              remoteBase.packetsReceived;
      const fractionLost = (packetsSent - packetsReceived) / packetsSent;
      if (fractionLost > 0.3) {
        // if fractionLost is > 0.3, we have probably found the culprit
      }
    }
  } catch (err) {
    console.error(err);
  }
}