static getCorrectAudioCodecs(codecs, mimeType) {
    // According to RFC 6381 section 3.3, 'fLaC' is actually the correct
    // codec string. We still need to map it to 'flac', as some browsers
    // currently don't support 'fLaC', while 'flac' is supported by most
    // major browsers.
    // See https://bugs.chromium.org/p/chromium/issues/detail?id=1422728
    const device = shaka.device.DeviceFactory.getDevice();
    const webkit = shaka.device.IDevice.BrowserEngine.WEBKIT;
    if (codecs.toLowerCase() == 'flac') {
      if (device.getBrowserEngine() != webkit) {
        return 'flac';
      } else {
        return 'fLaC';
      }
    }

    // The same is true for 'Opus'.
    if (codecs.toLowerCase() === 'opus') {
      if (device.getBrowserEngine() != webkit) {
        return 'opus';
      } else {
        if (shaka.util.MimeUtils.getContainerType(mimeType) == 'mp4') {
          return 'Opus';
        } else {
          return 'opus';
        }
      }
    }

    if (codecs.toLowerCase() == 'ac-3' && device.requiresEC3InitSegments()) {
      return 'ec-3';
    }

    return codecs;
  }
Generates the correct audio codec for MediaDecodingConfiguration and
for MediaSource.isTypeSupported.
@param {string} codecs
@param {string} mimeType
@return {string}