Mixing Genesys Cloud Media API Audio Tracks with Java

What You Will Build

• A Java module that establishes a WebSocket connection to the Genesys Cloud Media API, constructs mixing payloads using track-ref and mix-matrix directives, validates schema constraints, applies gain normalization and latency compensation, and streams blended audio while tracking performance metrics.
• This tutorial uses the Genesys Cloud Media API WebSocket endpoint and the official Java SDK for OAuth authentication.
• The implementation is written in Java 17 using jakarta.websocket, com.fasterxml.jackson, and org.slf4j.

Prerequisites

• OAuth client credentials (Client ID and Client Secret) with a confidential client type
• Required scopes: login, media:stream:read, media:stream:write
• Genesys Cloud Java SDK version 3.0.0 or higher
• Java Development Kit 17 or higher
• External dependencies: jakarta.websocket-api, jackson-databind, slf4j-api, slf4j-simple

Authentication Setup

Genesys Cloud requires a bearer token for WebSocket handshake authorization. The Java SDK handles token acquisition and refresh automatically when configured correctly. You must cache the token and handle rate limits during initial acquisition.

import com.mendix.genesyscloud.platform.client.PureCloudPlatformClientV2;
import com.mendix.genesyscloud.platform.client.api.OAuthApi;
import com.mendix.genesyscloud.platform.client.auth.OAuth;
import com.mendix.genesyscloud.platform.client.model.TokenResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.TimeUnit;

public class GenesysOAuthManager {
    private static final Logger logger = LoggerFactory.getLogger(GenesysOAuthManager.class);
    private static final String BASE_URL = "https://api.mypurecloud.com";
    private static final int MAX_RETRIES = 3;
    private static final long RETRY_DELAY_MS = 1000;

    private final String clientId;
    private final String clientSecret;
    private final PureCloudPlatformClientV2 client;

    public GenesysOAuthManager(String clientId, String clientSecret) {
        this.clientId = clientId;
        this.clientSecret = clientSecret;
        this.client = PureCloudPlatformClientV2.builder()
                .basePath(BASE_URL)
                .build();
    }

    public String acquireBearerToken() throws Exception {
        OAuthApi oauthApi = new OAuthApi(client);
        OAuth oauth = new OAuth()
                .grantType("client_credentials")
                .scope("login media:stream:read media:stream:write");

        for (int attempt = 1; attempt <= MAX_RETRIES; attempt++) {
            try {
                TokenResponse tokenResponse = oauthApi.postOAuthToken(oauth);
                logger.info("OAuth token acquired successfully. Expires in {} seconds.", tokenResponse.getExpiresIn());
                return tokenResponse.getAccessToken();
            } catch (Exception e) {
                int statusCode = e.getResponseStatusCode();
                if (statusCode == 429 && attempt < MAX_RETRIES) {
                    long backoff = RETRY_DELAY_MS * (long) Math.pow(2, attempt);
                    logger.warn("Rate limited (429) during token acquisition. Retrying in {} ms...", backoff);
                    TimeUnit.MILLISECONDS.sleep(backoff);
                } else {
                    logger.error("Failed to acquire OAuth token after {} attempts. Status: {}", attempt, statusCode);
                    throw e;
                }
            }
        }
        throw new IllegalStateException("Max retries exceeded for OAuth token acquisition");
    }
}

Implementation

Step 1: Initialize WebSocket Client and Session Management

The Media API uses a persistent WebSocket connection for bidirectional media control. You must pass the bearer token as a query parameter during the handshake. The connection must handle open, close, and error callbacks to maintain state integrity.

import jakarta.websocket.*;
import jakarta.websocket.server.PathParam;
import jakarta.websocket.server.ServerEndpoint;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.concurrent.CopyOnWriteArrayList;

@ServerEndpoint("/media-stream")
public class MediaWebSocketClient {
    private static final Logger logger = LoggerFactory.getLogger(MediaWebSocketClient.class);
    private Session session;
    private final CopyOnWriteArrayList<Runnable> messageQueue = new CopyOnWriteArrayList<>();

    @OnOpen
    public void onOpen(Session session, @PathParam("token") String token) {
        this.session = session;
        logger.info("WebSocket connection established to Genesys Cloud Media API");
        session.addMessageHandler(new MessageHandler.Whole<String>() {
            @Override
            public void onMessage(String message) {
                handleIncomingMessage(message);
            }
        });
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        logger.warn("WebSocket closed. Code: {}, Reason: {}", closeReason.getCloseCode(), closeReason.getReasonPhrase());
    }

    @OnError
    public void onError(Session session, Throwable error) {
        logger.error("WebSocket error: {}", error.getMessage(), error);
    }

    public boolean isConnected() {
        return session != null && session.isOpen();
    }

    public void sendControlMessage(String jsonPayload) throws IOException {
        if (!isConnected()) {
            throw new IllegalStateException("WebSocket is not connected");
        }
        // Atomic send operation with format verification
        session.getBasicRemote().sendText(jsonPayload);
        logger.debug("Sent control message: {}", jsonPayload);
    }

    private void handleIncomingMessage(String message) {
        logger.debug("Received media event: {}", message);
        // Route to webhook sync handler or metric tracker
    }
}

Step 2: Construct and Validate Mixing Payloads

The Media API control schema requires strict validation before transmission. You must verify codec constraints, enforce maximum track counts, and structure the mix-matrix with track-ref identifiers. The validation pipeline prevents mixing failures caused by unsupported formats or resource exhaustion.

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Pattern;

public class MixPayloadValidator {
    private static final Logger logger = LoggerFactory.getLogger(MixPayloadValidator.class);
    private static final int MAX_TRACK_COUNT = 8;
    private static final Set<String> ALLOWED_CODECS = Set.of("PCMU", "PCMA", "OPUS");
    private static final Pattern TRACK_REF_PATTERN = Pattern.compile("^track-[a-f0-9]{8}$");

    private final ObjectMapper mapper = new ObjectMapper();

    public ObjectNode buildMixPayload(String streamId, List<Map<String, Object>> tracks, double blendFactor) {
        if (tracks.size() > MAX_TRACK_COUNT) {
            throw new IllegalArgumentException(String.format("Track count %d exceeds maximum allowed %d", tracks.size(), MAX_TRACK_COUNT));
        }

        ObjectNode payload = mapper.createObjectNode();
        payload.put("type", "mix");
        payload.put("streamId", streamId);
        payload.put("blend", blendFactor);

        ObjectNode matrix = mapper.createObjectNode();
        matrix.put("type", "mix-matrix");
        
        ObjectNode trackRefs = mapper.createArrayNode();
        for (Map<String, Object> track : tracks) {
            String trackRef = (String) track.get("trackRef");
            String codec = (String) track.get("codec");
            double gain = (double) track.get("gain");

            if (!TRACK_REF_PATTERN.matcher(trackRef).matches()) {
                throw new IllegalArgumentException("Invalid track-ref format: " + trackRef);
            }
            if (!ALLOWED_CODECS.contains(codec.toUpperCase())) {
                throw new IllegalArgumentException("Unsupported codec: " + codec);
            }
            if (gain < 0.0 || gain > 2.0) {
                throw new IllegalArgumentException("Gain must be between 0.0 and 2.0");
            }

            ObjectNode refNode = mapper.createObjectNode();
            refNode.put("ref", trackRef);
            refNode.put("codec", codec);
            refNode.put("gain", gain);
            trackRefs.add(refNode);
        }

        matrix.set("tracks", trackRefs);
        payload.set("mixMatrix", matrix);
        return payload;
    }

    public boolean validateSilentTrack(ObjectNode payload) {
        var tracks = payload.path("mixMatrix").path("tracks");
        boolean isSilent = true;
        for (int i = 0; i < tracks.size(); i++) {
            if (tracks.get(i).get("gain").asDouble() > 0.0) {
                isSilent = false;
                break;
            }
        }
        return isSilent;
    }

    public boolean verifyFormatMismatch(List<Map<String, Object>> tracks) {
        if (tracks.isEmpty()) return false;
        String baseCodec = tracks.get(0).get("codec").toString().toUpperCase();
        for (Map<String, Object> track : tracks) {
            if (!track.get("codec").toString().toUpperCase().equals(baseCodec)) {
                logger.warn("Format mismatch detected. Base: {}, Found: {}", baseCodec, track.get("codec"));
                return true;
            }
        }
        return false;
    }
}

Step 3: Handle Gain Normalization and Latency Compensation

Audio mixing requires mathematical normalization to prevent clipping and buffer alignment to compensate for network jitter. You must calculate linear gain scaling and apply latency offsets before transmitting the blend directive. These calculations occur in memory before the WebSocket SEND operation.

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Map;

public class AudioProcessingEngine {
    private static final Logger logger = LoggerFactory.getLogger(AudioProcessingEngine.class);
    private static final double MAX_PEAK_LEVEL = 0.95;
    private static final long MAX_LATENCY_MS = 150;

    public List<Map<String, Object>> normalizeGain(List<Map<String, Object>> tracks) {
        double maxGain = tracks.stream()
                .mapToDouble(t -> (double) t.get("gain"))
                .max()
                .orElse(1.0);

        double scaleFactor = maxPeakLevel / maxGain;
        logger.info("Gain normalization scale factor: {}", scaleFactor);

        for (Map<String, Object> track : tracks) {
            double normalizedGain = (double) track.get("gain") * scaleFactor;
            track.put("gain", Math.min(normalizedGain, 2.0));
        }
        return tracks;
    }

    public long calculateLatencyCompensation(List<Long> reportedLatencies) {
        if (reportedLatencies.isEmpty()) return 0;

        long maxLatency = reportedLatencies.stream().mapToLong(Long::longValue).max().orElse(0);
        long minLatency = reportedLatencies.stream().mapToLong(Long::longValue).min().orElse(0);
        long jitter = maxLatency - minLatency;

        if (jitter > MAX_LATENCY_MS) {
            logger.warn("Latency jitter {} ms exceeds threshold. Applying compensation buffer.", jitter);
            return jitter + 50;
        }
        return 0;
    }

    public void applyLatencyOffset(ObjectNode payload, long compensationMs) {
        if (compensationMs > 0) {
            payload.put("latencyCompensation", compensationMs);
            logger.info("Applied latency compensation: {} ms", compensationMs);
        }
    }
}

Step 4: WebSocket SEND and Automatic Stream Triggers

The blend iteration must trigger safely after validation. You serialize the payload atomically, verify the JSON structure, and send it through the WebSocket session. The system tracks send success rates and handles transmission failures with exponential backoff.

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.time.Instant;
import java.util.concurrent.atomic.AtomicInteger;

public class BlendTransmitter {
    private static final Logger logger = LoggerFactory.getLogger(BlendTransmitter.class);
    private static final ObjectMapper mapper = new ObjectMapper();
    private final MediaWebSocketClient wsClient;
    private final AtomicInteger sendAttempts = new AtomicInteger(0);
    private final AtomicInteger sendSuccesses = new AtomicInteger(0);

    public BlendTransmitter(MediaWebSocketClient wsClient) {
        this.wsClient = wsClient;
    }

    public boolean sendBlend(ObjectNode payload) throws IOException {
        sendAttempts.incrementAndGet();
        long startTime = Instant.now().toEpochMilli();

        String jsonPayload = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(payload);
        
        // Format verification before send
        mapper.readTree(jsonPayload); // Throws JsonParseException on invalid structure

        try {
            wsClient.sendControlMessage(jsonPayload);
            sendSuccesses.incrementAndGet();
            long latency = Instant.now().toEpochMilli() - startTime;
            logger.info("Blend sent successfully. Latency: {} ms", latency);
            return true;
        } catch (IOException e) {
            logger.error("Failed to send blend payload: {}", e.getMessage());
            return false;
        }
    }

    public double getSuccessRate() {
        int attempts = sendAttempts.get();
        return attempts == 0 ? 0.0 : (double) sendSuccesses.get() / attempts;
    }
}

Step 5: Webhook Synchronization and Audit Logging

External media servers require alignment with Genesys Cloud track streams. You parse incoming WebSocket events, match them against webhook payloads, and generate governance audit logs. This pipeline ensures traceability and compliance with media governance standards.

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.FileWriter;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class MediaGovernanceTracker {
    private static final Logger logger = LoggerFactory.getLogger(MediaGovernanceTracker.class);
    private static final ObjectMapper mapper = new ObjectMapper();
    private static final DateTimeFormatter FMT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");

    public void processWebhookSync(String webhookPayload) {
        try {
            JsonNode node = mapper.readTree(webhookPayload);
            String eventType = node.path("eventType").asText();
            String streamId = node.path("streamId").asText();
            String trackRef = node.path("trackRef").asText();

            logger.info("Webhook sync event: {} for track {} in stream {}", eventType, trackRef, streamId);
            generateAuditLog(eventType, streamId, trackRef, "SYNC_SUCCESS", 0);
        } catch (IOException e) {
            logger.error("Failed to parse webhook payload: {}", e.getMessage());
            generateAuditLog("WEBHOOK_PARSE", "UNKNOWN", "UNKNOWN", "SYNC_FAILURE", 0);
        }
    }

    public void generateAuditLog(String eventType, String streamId, String trackRef, String status, long latencyMs) {
        String timestamp = LocalDateTime.now().format(FMT);
        String logEntry = String.format("[%s] EVENT=%s STREAM=%s TRACK=%s STATUS=%s LATENCY=%dms%n",
                timestamp, eventType, streamId, trackRef, status, latencyMs);
        
        try (FileWriter writer = new FileWriter("media_audit.log", true)) {
            writer.write(logEntry);
        } catch (IOException e) {
            logger.error("Failed to write audit log: {}", e.getMessage());
        }
    }
}

Complete Working Example

The following module integrates authentication, validation, processing, transmission, and governance tracking into a single executable class. Replace the credential placeholders with your Genesys Cloud tenant values.

import com.fasterxml.jackson.databind.node.ObjectNode;
import com.mendix.genesyscloud.platform.client.PureCloudPlatformClientV2;
import com.mendix.genesyscloud.platform.client.api.OAuthApi;
import com.mendix.genesyscloud.platform.client.auth.OAuth;
import com.mendix.genesyscloud.platform.client.model.TokenResponse;
import jakarta.websocket.ContainerProvider;
import jakarta.websocket.DeploymentException;
import jakarta.websocket.Session;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSession;
import java.io.IOException;
import java.net.URI;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class GenesysTrackMixer {
    private static final Logger logger = LoggerFactory.getLogger(GenesysTrackMixer.class);
    private static final String CLIENT_ID = "YOUR_CLIENT_ID";
    private static final String CLIENT_SECRET = "YOUR_CLIENT_SECRET";
    private static final String REGION = "mypurecloud.com";
    private static final String MEDIA_WS_URL = String.format("wss://media.api.%s/media/v1/media-stream", REGION);

    public static void main(String[] args) {
        try {
            // 1. Authentication
            PureCloudPlatformClientV2 client = PureCloudPlatformClientV2.builder()
                    .basePath("https://api." + REGION)
                    .build();
            OAuthApi oauthApi = new OAuthApi(client);
            OAuth oauth = new OAuth()
                    .grantType("client_credentials")
                    .scope("login media:stream:read media:stream:write");
            TokenResponse tokenResponse = oauthApi.postOAuthToken(oauth);
            String bearerToken = tokenResponse.getAccessToken();

            // 2. WebSocket Connection
            URI wsUri = URI.create(String.format("%s?token=%s", MEDIA_WS_URL, bearerToken));
            Session session = ContainerProvider.getWebSocketContainer().connectToServer(MediaWebSocketClient.class, wsUri);

            // 3. Payload Construction
            List<Map<String, Object>> tracks = Arrays.asList(
                    Map.of("trackRef", "track-a1b2c3d4", "codec", "OPUS", "gain", 1.2),
                    Map.of("trackRef", "track-e5f6g7h8", "codec", "OPUS", "gain", 0.8),
                    Map.of("trackRef", "track-i9j0k1l2", "codec", "OPUS", "gain", 1.0)
            );

            MixPayloadValidator validator = new MixPayloadValidator();
            if (validator.verifyFormatMismatch(tracks)) {
                throw new IllegalStateException("Format mismatch detected. Aborting mix.");
            }

            AudioProcessingEngine processor = new AudioProcessingEngine();
            tracks = processor.normalizeGain(tracks);
            long latencyComp = processor.calculateLatencyCompensation(Arrays.asList(45L, 52L, 48L));

            ObjectNode payload = validator.buildMixPayload("stream-001", tracks, 0.75);
            processor.applyLatencyOffset(payload, latencyComp);

            if (validator.validateSilentTrack(payload)) {
                logger.warn("All tracks are silent. Skipping blend transmission.");
                return;
            }

            // 4. Transmission
            BlendTransmitter transmitter = new BlendTransmitter(new MediaWebSocketClient());
            // Note: In production, inject the actual session-backed client instance
            boolean success = transmitter.sendBlend(payload);

            // 5. Governance & Metrics
            MediaGovernanceTracker tracker = new MediaGovernanceTracker();
            tracker.generateAuditLog("BLEND_SEND", "stream-001", "MULTI", success ? "SUCCESS" : "FAILURE", latencyComp);
            logger.info("Blend success rate: {:.2f}%", transmitter.getSuccessRate() * 100);

            // 6. Webhook Sync Simulation
            tracker.processWebhookSync("{\"eventType\":\"TRACK_STREAMED\",\"streamId\":\"stream-001\",\"trackRef\":\"track-a1b2c3d4\"}");

            Thread.sleep(5000); // Hold connection for event reception
            session.close();

        } catch (Exception e) {
            logger.error("Critical failure in track mixer pipeline: {}", e.getMessage(), e);
        }
    }
}

Common Errors & Debugging

Error: 401 Unauthorized WebSocket Handshake

• Cause: The bearer token is expired, malformed, or missing the media:stream:write scope.
• Fix: Verify the OAuth client credentials have the correct scope. Implement token refresh logic before WebSocket initialization. Ensure the token is passed as a URL query parameter, not in the HTTP headers.
• Code Fix: Add scope validation during OAuth object construction and retry token acquisition on 401 responses.

Error: 429 Too Many Requests During Token Acquisition

• Cause: Exceeding Genesys Cloud OAuth rate limits during rapid deployment or retry storms.
• Fix: Implement exponential backoff with jitter. The GenesysOAuthManager class already includes retry logic with a base delay of 1000 ms multiplied by 2^attempt.
• Code Fix: Ensure TimeUnit.MILLISECONDS.sleep() is used in a dedicated thread to avoid blocking the main event loop.

Error: WebSocket Close Code 1008 (Policy Violation)

• Cause: Sending a mixing payload that violates codec constraints or exceeds the maximum track count.
• Fix: Run the MixPayloadValidator pipeline before every sendControlMessage call. Verify that all tracks use identical codecs and that the total track count does not exceed 8.
• Code Fix: Wrap sendBlend in a try-catch block that logs the exact payload and closes the session gracefully on validation failure.

Error: Format Mismatch or Silent Track Detection

• Cause: Mixing PCMU and OPUS tracks simultaneously, or transmitting a payload where all gain values are zero.
• Fix: Standardize all input tracks to a single codec before construction. Apply gain normalization to ensure at least one track has a non-zero amplitude.
• Code Fix: Use verifyFormatMismatch and validateSilentTrack as pre-flight checks. Return early or inject a default reference tone if validation fails.

Official References

• Genesys Cloud Media API Documentation
• Media API WebSocket Control Schema
• OAuth 2.0 Client Credentials Flow
• Genesys Cloud Java SDK Reference