/**
* Retransmits a packet to {@link #channel}. If the destination supports the RTX format, the
* packet will be encapsulated in RTX, otherwise, the packet will be retransmitted as-is.
*
* @param pkt the packet to retransmit.
* @param after the {@code TransformEngine} in the chain of {@code TransformEngine}s of the
* associated {@code MediaStream} after which the injection of {@code pkt} is to begin
* @return {@code true} if the packet was successfully retransmitted, {@code false} otherwise.
*/
public boolean retransmit(RawPacket pkt, TransformEngine after) {
boolean destinationSupportsRtx = channel.getRtxPayloadType() != -1;
boolean retransmitPlain;
if (destinationSupportsRtx) {
long rtxSsrc = getPairedSsrc(pkt.getSSRC());
if (rtxSsrc == -1) {
logger.warn("Cannot find SSRC for RTX, retransmitting plain.");
retransmitPlain = true;
} else {
retransmitPlain = !encapsulateInRtxAndTransmit(pkt, rtxSsrc);
}
} else {
retransmitPlain = true;
}
if (retransmitPlain) {
MediaStream mediaStream = channel.getStream();
if (mediaStream != null) {
try {
mediaStream.injectPacket(pkt, /* data */ true, after);
} catch (TransmissionFailedException tfe) {
logger.warn("Failed to retransmit a packet.");
return false;
}
}
}
return true;
}
/** Implements {@link PacketTransformer#transform(RawPacket[])}. {@inheritDoc} */
@Override
public RawPacket transform(RawPacket pkt) {
byte rtxPt;
if (pkt != null
&& (rtxPt = channel.getRtxPayloadType()) != -1
&& pkt.getPayloadType() == rtxPt) {
pkt = handleRtxPacket(pkt);
}
return pkt;
}
/**
* Handles an RTX packet and returns it.
*
* @param pkt the packet to handle.
* @return the packet
*/
private RawPacket handleRtxPacket(RawPacket pkt) {
boolean destinationSupportsRtx = channel.getRtxPayloadType() != -1;
RawPacket mediaPacket = createMediaPacket(pkt);
if (mediaPacket != null) {
RawPacketCache cache = channel.getStream().getPacketCache();
if (cache != null) {
cache.cachePacket(mediaPacket);
}
}
if (destinationSupportsRtx) {
pkt.setSequenceNumber(
getNextRtxSequenceNumber(pkt.getSSRC() & 0xffffffffL, pkt.getSequenceNumber()));
} else {
// If the media packet was not reconstructed, drop the RTX packet
// (by returning null).
return mediaPacket;
}
return pkt;
}