Allow creation of output endpoints with channel index masks

            // check that channelMask is the "canonical" one we expect for the channelCount.

            return channelMask == audio_channel_out_mask_from_count(channelCount);

            }

        case AUDIO_CHANNEL_REPRESENTATION_INDEX:

            if (kEnableExtendedChannels) {

                const uint32_t channelCount = audio_channel_count_from_out_mask(channelMask);

                if (channelCount >= FCC_2 // mono is not supported at this time

                        && channelCount <= AudioMixer::MAX_NUM_CHANNELS) {

                    return true;

                }

            }

            return false;

        default:

            return false;

        }