/// <summary>
/// Get a mapping in codec payloads and encodings in the given Producer RTP
/// parameters as values expected by the Router.
///
/// It may throw if invalid or non supported RTP parameters are given.
/// </summary>
public static RtpMapping GetProducerRtpParametersMapping(RtpParameters parameters, RtpCapabilities caps)
{
var rtpMapping = new RtpMapping
{
Codecs = new List <RtpMappingCodec>(),
Encodings = new List <RtpMappingEncoding>()
};
// Match parameters media codecs to capabilities media codecs.
var codecToCapCodec = new Dictionary <RtpCodecParameters, RtpCodecCapability>();
foreach (var codec in parameters.Codecs)
{
if (IsRtxMimeType(codec.MimeType))
{
continue;
}
// Search for the same media codec in capabilities.
var matchedCapCodec = caps.Codecs
.Where(capCodec => MatchCodecs(codec, capCodec, true, true))
.FirstOrDefault();
codecToCapCodec[codec] = matchedCapCodec ?? throw new Exception($"unsupported codec[mimeType:{ codec.MimeType }, payloadType:{ codec.PayloadType }, Channels:{ codec.Channels }]");
}
// Match parameters RTX codecs to capabilities RTX codecs.
foreach (var codec in parameters.Codecs)
{
if (!IsRtxMimeType(codec.MimeType))
{
continue;
}
// Search for the associated media codec.
var associatedMediaCodec = parameters.Codecs
.Where(mediaCodec => MatchCodecsWithPayloadTypeAndApt(mediaCodec.PayloadType, codec.Parameters))
.FirstOrDefault();
if (associatedMediaCodec == null)
{
throw new Exception($"missing media codec found for RTX PT { codec.PayloadType}");
}
var capMediaCodec = codecToCapCodec[associatedMediaCodec];
// Ensure that the capabilities media codec has a RTX codec.
var associatedCapRtxCodec = caps.Codecs
.Where(capCodec => IsRtxMimeType(capCodec.MimeType) && MatchCodecsWithPayloadTypeAndApt(capMediaCodec.PreferredPayloadType, capCodec.Parameters))
.FirstOrDefault();
codecToCapCodec[codec] = associatedCapRtxCodec ?? throw new Exception($"no RTX codec for capability codec PT { capMediaCodec.PreferredPayloadType}");
}
// Generate codecs mapping.
foreach (var item in codecToCapCodec)
{
rtpMapping.Codecs.Add(new RtpMappingCodec
{
PayloadType = item.Key.PayloadType,
MappedPayloadType = item.Value.PreferredPayloadType !.Value,
});
/// <summary>
/// Generate RTP parameters to be internally used by Consumers given the RTP
/// parameters in a Producer and the RTP capabilities in the Router.
/// </summary>
public static RtpParameters GetConsumableRtpParameters(MediaKind kind, RtpParameters parameters, RtpCapabilities caps, RtpMapping rtpMapping)
{
var consumableParams = new RtpParameters
{
Codecs = new List <RtpCodecParameters>(),
HeaderExtensions = new List <RtpHeaderExtensionParameters>(),
Encodings = new List <RtpEncodingParameters>(),
Rtcp = new RtcpParameters(),
};
foreach (var codec in parameters.Codecs)
{
if (IsRtxMimeType(codec.MimeType))
{
continue;
}
var consumableCodecPt = rtpMapping.Codecs
.Where(entry => entry.PayloadType == codec.PayloadType)
.Select(m => m.MappedPayloadType)
.FirstOrDefault();
var matchedCapCodec = caps.Codecs
.Where(capCodec => capCodec.PreferredPayloadType == consumableCodecPt)
.FirstOrDefault();
var consumableCodec = new RtpCodecParameters
{
MimeType = matchedCapCodec.MimeType,
PayloadType = matchedCapCodec.PreferredPayloadType.Value, // TODO: (alby)注意 null 引用
ClockRate = matchedCapCodec.ClockRate,
Channels = matchedCapCodec.Channels,
Parameters = codec.Parameters, // Keep the Producer codec parameters.
RtcpFeedback = matchedCapCodec.RtcpFeedback
};
consumableParams.Codecs.Add(consumableCodec);
var consumableCapRtxCodec = caps.Codecs
.Where(capRtxCodec => IsRtxMimeType(capRtxCodec.MimeType) && MatchCodecsWithPayloadTypeAndApt(consumableCodec.PayloadType, capRtxCodec.Parameters))
.FirstOrDefault();
if (consumableCapRtxCodec != null)
{
var consumableRtxCodec = new RtpCodecParameters
{
MimeType = consumableCapRtxCodec.MimeType,
PayloadType = consumableCapRtxCodec.PreferredPayloadType.Value, // TODO: (alby)注意 null 引用
ClockRate = consumableCapRtxCodec.ClockRate,
Channels = consumableCapRtxCodec.Channels,
Parameters = consumableCapRtxCodec.Parameters, // Keep the Producer codec parameters.
RtcpFeedback = consumableCapRtxCodec.RtcpFeedback
};
consumableParams.Codecs.Add(consumableRtxCodec);
}
}
foreach (var capExt in caps.HeaderExtensions) // TODO: (alby)注意 null 引用
{
// Just take RTP header extension that can be used in Consumers.
if (capExt.Kind != kind || (capExt.Direction != RtpHeaderExtensionDirection.SendReceive && capExt.Direction != RtpHeaderExtensionDirection.SendOnly))
{
continue;
}
var consumableExt = new RtpHeaderExtensionParameters
{
Uri = capExt.Uri,
Id = capExt.PreferredId,
Encrypt = capExt.PreferredEncrypt,
Parameters = new Dictionary <string, object>(),
};
consumableParams.HeaderExtensions.Add(consumableExt);
}
// Clone Producer encodings since we'll mangle them.
var consumableEncodings = parameters.Encodings.DeepClone <List <RtpEncodingParameters> >();
for (var i = 0; i < consumableEncodings.Count; ++i)
{
var consumableEncoding = consumableEncodings[i];
var mappedSsrc = rtpMapping.Encodings[i].MappedSsrc;
// Remove useless fields.
// 在 Node.js 实现中，rid, rtx, codecPayloadType 被 delete 了。
consumableEncoding.Rid = null;
consumableEncoding.Rtx = null;
consumableEncoding.CodecPayloadType = null;
// Set the mapped ssrc.
consumableEncoding.Ssrc = mappedSsrc;
consumableParams.Encodings.Add(consumableEncoding);
}
consumableParams.Rtcp = new RtcpParameters
{
CNAME = parameters.Rtcp.CNAME, // TODO: (alby)注意 null 引用
ReducedSize = true,
Mux = true,
};
return(consumableParams);
}