示例#1
0
        /// <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.
        }