/// <summary>
/// Hides a message in WaveAudio object's Left and Right Audio channels.
/// </summary>
/// <param name="message">String Message to be hidden.</param>
public void HideMessage(string message)
{
/*Cache audio channel streams locally from WaveAudio object*/
List <short> leftStream = file.GetLeftStream();
List <short> rightStream = file.GetRightStream();
/*Hide Message in Streams*/
byte[] bufferMessage = System.Text.Encoding.UTF8.GetBytes(message); //Convert string Message into byte[]
short tempBit;
int bufferIndex = 0; //Set message stream index counter.
int bufferLength = bufferMessage.Length; //Get length of message stream.
int channelLength = leftStream.Count; //Get length of audio stream (both left and right streams have same length).
int storageBlock = (int)Math.Ceiling((double)bufferLength / (channelLength * 2)); //Get storage block range based of length of audio channel stream and message stream.
if (bufferLength > channelLength) //Check if message stream length is greater than a channel's audio stream length.
{
throw new MessageSizeExceededException("Message size is too large for target Audio stream."); //Throw an Exception.
}
/*Store message length info in first elements of left and right streams*/
leftStream[0] = (short)(bufferLength / 32767); //Store Quotient of actual size in first element of audio stream.
rightStream[0] = (short)(bufferLength % 32767); //Store Remainder of actual size in first element of audio stream.
for (int i = 1; i < leftStream.Count; i++) //Iterate over length of audio channel stream, skip first element since it contains message length, store message bits into left and right audio streams.
{
if (i < leftStream.Count) //Check if storing has not exceeded audio stream length.
{
if (bufferIndex < bufferLength && i % 8 > 7 - storageBlock && i % 8 <= 7) //Condition to target elements from the last position of every 8 bit block of audio stream (calculated based on storageBlock).
{
tempBit = (short)bufferMessage[bufferIndex++]; //Get message bit
leftStream.Insert(i, tempBit); //Replace audio data bit with message bit.
}
}
if (i < rightStream.Count)
{
if (bufferIndex < bufferLength && i % 8 > 7 - storageBlock && i % 8 <= 7)
{
tempBit = (short)bufferMessage[bufferIndex++];
rightStream.Insert(i, tempBit);
}
}
}
file.UpdateStreams(leftStream, rightStream); //Streams now have message hidden in it, update streams to actual WaveAudio object.
}