org.jitsi.impl.neomedia.rtcp

Class NACKPacket

java.lang.Object

net.sf.fmj.media.rtp.util.Packet

net.sf.fmj.media.rtp.RTCPPacket

org.jitsi.impl.neomedia.rtcp.RTCPFBPacket

org.jitsi.impl.neomedia.rtcp.NACKPacket

public class NACKPacket
extends RTCPFBPacket

A class which represents an RTCP Generic NACK feedback message, as defined in RFC4585 Section 6.2.1. The RTCP packet structure is:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |V=2|P| FMT=1   |   PT=205      |             length            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  SSRC of packet sender                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  SSRC of media source                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                           FCI                                 |
 |                          [...]                                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 The Feedback Control Information (FCI) field consists of one or more
 32-bit words, each with the following structure:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             PID               |             BLP               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 

Author:

Boris Grozev, George Politis

Field Summary

Fields

Modifier and Type	Field and Description
static int	FMT The value of the "fmt" field for a NACK packet.

Fields inherited from class org.jitsi.impl.neomedia.rtcp.RTCPFBPacket

fci, fmt, PSFB, RTPFB, senderSSRC, sourceSSRC

Fields inherited from class net.sf.fmj.media.rtp.RTCPPacket

APP, base, BYE, COMPOUND, RR, SDES, SR, type

Fields inherited from class net.sf.fmj.media.rtp.util.Packet

data, flags, length, offset, receiptTime, received

Constructor Summary

Constructors

Constructor and Description
NACKPacket(long senderSSRC, long sourceSSRC, Collection<Integer> lostPackets) Initializes a new NACKPacket instance with specific "packet sender SSRC" and "media source SSRC" values and which describes a specific set of sequence numbers.
NACKPacket(net.sf.fmj.media.rtp.RTCPCompoundPacket base) Initializes a new NACKPacket instance.

Method Summary

Modifier and Type	Method and Description
Collection<Integer>	getLostPackets()
static Collection<Integer>	getLostPackets(org.jitsi.utils.ByteArrayBuffer baf)
static Collection<Integer>	getLostPacketsFci(org.jitsi.utils.ByteArrayBuffer fciBuffer)
static boolean	isNACKPacket(org.jitsi.utils.ByteArrayBuffer baf) Gets a boolean indicating whether or not the RTCP packet specified in the ByteArrayBuffer that is passed as an argument is a NACK packet or not.
String	toString()

Methods inherited from class org.jitsi.impl.neomedia.rtcp.RTCPFBPacket

assemble, calcLength, getFCI, getSenderSSRC, getSourceSSRC, getSourceSSRC, isPSFBPacket, isRTCPFBPacket, isRTPFBPacket, toRawPacket

Methods inherited from class net.sf.fmj.media.rtp.util.Packet

clone

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

FMT

public static final int FMT

The value of the "fmt" field for a NACK packet.

See Also:

Constant Field Values

Constructor Detail

NACKPacket

public NACKPacket(net.sf.fmj.media.rtp.RTCPCompoundPacket base)

Initializes a new NACKPacket instance.

Parameters:

base -

NACKPacket

public NACKPacket(long senderSSRC,
                  long sourceSSRC,
                  Collection<Integer> lostPackets)

Initializes a new NACKPacket instance with specific "packet sender SSRC" and "media source SSRC" values and which describes a specific set of sequence numbers.

Parameters:

senderSSRC - the value to use for the "packet sender SSRC" field.

sourceSSRC - the value to use for the "media source SSRC" field.

lostPackets - the set of RTP sequence numbers which this NACK packet is to describe. Note that this implementation is not optimized and might not always use the minimal possible number of bytes to describe a given set of packets. Specifically, it does not take into account that sequence numbers wrap at 2^16 and fails to pack numbers close to 2^16 with those close to 0.

Method Detail

isNACKPacket

public static boolean isNACKPacket(org.jitsi.utils.ByteArrayBuffer baf)

Gets a boolean indicating whether or not the RTCP packet specified in the ByteArrayBuffer that is passed as an argument is a NACK packet or not.

Parameters:

baf - the ByteArrayBuffer

Returns:

true if the byte array buffer holds a NACK packet, otherwise false.

getLostPackets

public static Collection<Integer> getLostPackets(org.jitsi.utils.ByteArrayBuffer baf)

Parameters:

baf - the NACK packet.

Returns:

the set of sequence numbers reported lost in a NACK packet represented by a ByteArrayBuffer.

getLostPacketsFci

public static Collection<Integer> getLostPacketsFci(org.jitsi.utils.ByteArrayBuffer fciBuffer)

Parameters:

fciBuffer - the ByteArrayBuffer which represents the FCI field of a NACK packet.

Returns:

the set of sequence numbers reported lost in the FCI field of a NACK packet represented by a ByteArrayBuffer.

getLostPackets

public Collection<Integer> getLostPackets()

Returns:

the set of sequence numbers reported lost in this NACK packet.

toString

public String toString()

Overrides:

toString in class RTCPFBPacket