io.pkts.framer.RTCPFramer Maven / Gradle / Ivy
/**
*
*/
package io.pkts.framer;
import io.pkts.buffer.Buffer;
import io.pkts.packet.TransportPacket;
import io.pkts.packet.rtcp.RtcpPacket;
import io.pkts.protocol.Protocol;
import java.io.IOException;
/**
* @author [email protected]
*/
public final class RTCPFramer implements Framer {
/**
*
*/
public RTCPFramer() {
// left empty intentionally
}
@Override
public Protocol getProtocol() {
return Protocol.RTCP;
}
/**
* There is no real good test to make sure that the data indeed is an RTP packet. Appendix 2 in
* RFC3550 describes one way of doing it but you really need a sequence of packets in order to
* be able to determine if this indeed is a RTP packet or not. The best is to analyze the
* session negotiation but here we are just looking at a single packet so can't do that.
*
* Also, RTP and RTCP packets are hard to distinguish from each other and you really need help
* from outside such as from the Session Description Protocol but until we connect things
* together we will do a simple check so that we do not pick up RTCP packets. Note, this check
* is not super safe, see RFC 5761.
*
* {@inheritDoc}
*/
@Override
public boolean accept(final Buffer data) throws IOException {
// a RTP packet has at least 12 bytes. Check that
if (data.getReadableBytes() < 12) {
// not enough bytes but see if we actually could
// get another 12 bytes by forcing the underlying
// implementation to read further ahead
data.markReaderIndex();
try {
final Buffer b = data.readBytes(12);
if (b.capacity() < 12) {
return false;
}
} catch (final IndexOutOfBoundsException e) {
// guess not...
// System.err.println("But still!!!");
// e.printStackTrace();
}
data.resetReaderIndex();
}
// both RTP and RTCP has a 2 in this field
// so if that isn't the case then it cannot
// be RTP nor RTCP
final byte b = data.getByte(0);
if (!((b & 0xC0) >> 6 == 0x02)) {
return false;
}
// The second byte is for RTCP equal to the Packet Type (pt)
// and if following the guidelines of RFC 5761 (section 4) then
// RTP Payload Type + 128 != RTCP Packet Type
final byte b2 = data.getByte(1);
if (b2 == (byte) 0xc8 || b2 == (byte) 0xc9 || b2 == (byte) 0xca || b2 == (byte) 0xcb || b2 == (byte) 0xcc) {
return false;
}
return true;
}
@Override
public RtcpPacket frame(final TransportPacket parent, final Buffer buffer) throws IOException {
if (parent == null) {
throw new IllegalArgumentException("The parent frame cannot be null");
}
return null;
}
}