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Frame-Metadata

README.md

Frame Meta Data

This app shows how to send and receive metadata associated with each video frame.

Using a custom video capturer

App uses a custom video capturer to send metadata and a custom video renderer to recieve metadata:

publisher = new Publisher.Builder(MainActivity.this)
    .capturer(sendFrameMetaDataCapturer)
    .renderer(receiveFrameMetaDataRenderer)
    .build();

Send frame metadata

The SendFrameMetaDataCapturer class extends the BaseVideoCapturer class, defined in the OpenTok Android SDK. The setCustomMetadataSource method provides metadata to be send with each video frame:

SendFrameMetaDataCapturer sendFrameMetaDataCapturer = new SendFrameMetaDataCapturer(MainActivity.this);

// metadata to be send
sendFrameMetaDataCapturer.setCustomMetadataSource(() -> {
    String timestamp = getCurrentTimeStamp();
    return timestamp.getBytes();
});

Under the hood above metadata is added to the frame inside SendFrameMetaDataCapturer.onPreviewFrame method:

if (metadataSource != null) {
    byte[] frameMetadata = customMetadataSource.retrieveMetadata();

    provideByteArrayFrame(data,
            NV21,
            captureWidth,
            captureHeight,
            currentRotation,
            isFrontCamera(),
            frameMetadata);
}

Receive frame metadata

The ReceiveFrameMetaDataRenderer class extends the BaseVideoRenderer class, defined in the OpenTok Android SDK. The setCustomMetadataListener method allows to retrieve metadata from incomming video frames:

ReceiveFrameMetaDataRenderer receiveFrameMetaDataRenderer = new ReceiveFrameMetaDataRenderer(MainActivity.this);

// Retrieved metadata
receiveFrameMetaDataRenderer.setCustomMetadataListener(metadata -> {
    String timestamp = null;

    try {
        timestamp = new String(metadata, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }

});

nther the hood above metadata is retrieved from the frame inside ReceiveFrameMetaDataRenderer.MyRenderer.onDrawFrame method:

if (customMetadataListener != null) {
    customMetadataListener.onMetadataReady(currentFrame.getMetadata());
}

Further Reading