/// <summary>
/// Encode the packets that are in the data BufferChunk array and place the
/// encoded result over GF16 in the checksum packets that are in
/// the result BufferChunk array. This method encode the size on the first 2
/// bytes of the checksum packet and the data after that. Every checksum BufferChunk
/// has the same size, which is the size of the largest BufferChunk in the data BufferChunk
/// array, plus one if this BufferChunk doesn't end on a 16 bits boundary, plus
/// two to store the encoded length
/// </summary>
/// <param name="data">The data BufferChunk array (left part of the multiplication)</param>
/// <param name="result"></param>
/// <param name="encode">The encoding Vandermonde GF16 matrix (right part of the multiplication)</param>
public static void EncodeRS(BufferChunk[] data, BufferChunk[] checksum, UInt16[,] encode)
{
// Get the length in byte of largest BufferChunk in the data BufferChunk array
// (which is an array of BufferChunk that could have different sizes)
int maxDataLength = GetMaxLength(data);
// The checksum packet as a even number of bytes so we can stay with GF16
// and not have to use GF8 for the last byte when length odd
int checksumNbRowsByte = maxDataLength;
if ((maxDataLength & 1) == 1)
{
checksumNbRowsByte += 1;
}
// Add 2 more bytes to store the length
checksumNbRowsByte += CFec.SIZE_OVERHEAD;
// Encode the length of the data and place that on the first 2 bytes
// of the checksum BufferChunk
EncodeRSLength(data, checksum, encode);
// Start to put encoded data at index + 2, because the 2 first bytes
// of the checksum already contain the encoded size
for (int i = 0; i < checksum.Length; i++)
{
BufferChunk bc = checksum[i];
bc.Reset(bc.Index + CFec.SIZE_OVERHEAD, checksumNbRowsByte - CFec.SIZE_OVERHEAD);
// Reset all of the checksum packets so they have no data
// TODO - Temporary workaround for column based approach - JVE 7/6/2004
bc.Clear();
}
// Place all the packets in a 16bits boundary to avoid byte operation
// Important: This suppose that the memory reserved for all the bc passed in param
// to this method ends on a 16bits boundary (so at least one addition availabe byte
// when the last item is on a even address)
Queue paddedData = new Queue();
AddPadding(data, 0, paddedData);
// Encode the data and place the encoded information in the checksum BufferChunk
EncodeRSData(data, checksum, encode, maxDataLength);
// Earlier, we changed the boundary of all data BufferChunk
// that was not ending on a 16 bits boundary in order to have
// better performance during the encoding. Now we need to
// restore the data to their original state to be clean.
RemovePadding(paddedData);
// Restore the BufferChunk index in the checksum checksum BufferChunk
// to 0 to be clean. Earlier, We changed the index in order to encode
// the data after the encoding length.
for (int i = 0; i < checksum.Length; i++)
{
BufferChunk bc = checksum[i];
bc.Reset(bc.Index - CFec.SIZE_OVERHEAD, checksumNbRowsByte);
}
}
/// <summary>
/// Decode to retrieve the length of the missing data packet(s) (null entries) in the
/// data BufferChunk array and set the length of the packets in the recovery BufferChunk array.
/// We have to do that because every data packet could have a different length.
/// </summary>
/// <param name="data">The data BufferChunk array</param>
/// <param name="checksum">The number of checksum packet(s) that were used to encode</param>
/// <param name="decode">The decoding GF16 matrix</param>
/// <param name="recovery">The recovery BufferChunk array to set the length of the recovered packets</param>
private static void DecodeRSLength(BufferChunk[] data, int checksum, GF16[,] decode, BufferChunk[] recovery)
{
// Important! For now I assume the following in the firstMatrix:
// - The array is always of size data + checksum
// - #checksum not null entries = #packet lost
// - recovery.length is exactly the number of data packet lost
// - checksum param is # checksum packets that were used to encode
// Get the length once to avoid having the overhead of getting it again inside a inner (performance)
// Note that this value is also used outside of this method, so we could have had a parameter too,
// but I prefer to get it here to avoid inconsitencies
int dataLength = data.Length;
int recoveryColumn = 0;
for (int dataColumn = 0; dataColumn < dataLength - checksum; dataColumn++)
{
// recover only the missing column
if (data[dataColumn] == null)
{
// Inverted matrix row index
int imRowIndex = 0;
// length of the recovered buffer
UInt16 currentLength = 0;
for (int dataIndex = 0; dataIndex < dataLength; dataIndex++)
{
// Perform the core operation mult with add in GF16
// TODO: We could crunch the column so we avoid this test
if (data[dataIndex] != null)
{
UInt16 length = 0;
if (dataIndex < dataLength - checksum) // For the data part, we get the length of the BufferChunk
{
length = (UInt16)data[dataIndex].Length;
}
else // For the checksum part, the encoded length is inside the first 2 bytes
{
length = data[dataIndex].GetUInt16(0);
}
UInt16 currentValue = GF16.Multiply(length, decode[dataColumn, imRowIndex].Value);
currentLength = GF16.Add(currentLength, currentValue);
imRowIndex++;
} // if
} // for column (do elementary operations)
BufferChunk bc = recovery[recoveryColumn];
bc.Reset(bc.Index, currentLength);
// Reset all of the recovery packets so they have no data
// TODO - Temporary workaround for column based approach - JVE 7/6/2004
bc.Clear();
recoveryColumn++;
} // if
} // for dataColumn
}
/// <summary>
/// Called by RtcpSender when it is time to collect Rtcp data
/// </summary>
/// <returns>A CompoundPacketBuilder</returns>
CompoundPacketBuilder RtcpSender.IRtpSession.RtcpReportIntervalReached()
{
// Limit the frequency of the cleanup in order to avoid participants and streams being
// inappropriately designated as stale. This can happen if we start up a lot of senders at once.
// Each sender triggers an RTCP packet which without the frequency limitation could
// increment the stale counter to its limit and cause the participant or stream to be removed.
bool cleanUpNow = false;
if (DateTime.Now > this.lastCleanUp.AddSeconds(5)) {
cleanUpNow = true;
this.lastCleanUp = DateTime.Now;
}
// A stale participant is one who is not sending Rtcp data
if (cleanUpNow)
CheckForStaleParticipants();
// Add participant data
Debug.Assert(participant.SSRC != 0);
cpb.ParticipantData(participant);
// Add Rtp data
if(rtpTraffic)
{
// A stale stream is one not sending Rtp traffic
if (cleanUpNow)
CheckForStaleStreams();
// Collect SenderReportPackets and SDESReports from each Sender
lock(rtpSenders)
{
foreach(RtpSender sender in rtpSenders.Values)
{
// this adds the SR and SDES packets
sender.UpdateRtcpData();
}
}
// add a sdes (source description)
//cpb.Add_SDESReport(participant.SSRC, participant);
// Collect ReceiverReports from each of the streams
lock(streamsAndIPs)
{
foreach(IPStreamPairHashtable.IPStreamPair ipsp in streamsAndIPs.Values)
{
if( ipsp.stream != null )
{
ipsp.stream.AddReceiverReport(cpb);
}
}
}
}
#if USE_APP_PACKET
// andrew: Add an app packet that reflects the time and the current venue...
if ((VenueName != null) && (this.groupEP != null))
{
string appPayload = VenueName + "#" + this.groupEP.Address.ToString();
long time = DateTime.Now.Ticks;
// 8 bytes for time + venue name
int count = 8 + utf8.GetByteCount(appPayload);
// count must be 4-byte alligned
int mod = count % 4;
if (mod != 0)
{
count += (4 - mod);
}
BufferChunk buffer = new BufferChunk(count);
buffer.Reset(0, count);
buffer.Clear();
buffer.SetInt64(0, time);
buffer.SetUTF8String(8, appPayload);
byte[] rawBytes = buffer.Buffer;
cpb.Add_APPReport(participant.SSRC, Rtcp.APP_PACKET_NAME, Rtcp.VENUE_APP_PACKET_SUBTYPE, rawBytes);
}
#endif
return cpb;
}