Method matchRemoteCodec

mediaengine.go:463–534

Look up a codec and enable if it exists. nolint:cyclop

(
	remoteCodec RTPCodecParameters,
	typ RTPCodecType,
	exactMatches, partialMatches []RTPCodecParameters,
)

//
//nolint:cyclop
func (m *MediaEngine) matchRemoteCodec(
	remoteCodec RTPCodecParameters,
	typ RTPCodecType,
	exactMatches, partialMatches []RTPCodecParameters,
) (RTPCodecParameters, codecMatchType, error) {
	codecs := m.videoCodecs
	if typ == RTPCodecTypeAudio {
		codecs = m.audioCodecs
	}

	remoteFmtp := fmtp.Parse(
		remoteCodec.RTPCodecCapability.MimeType,
		remoteCodec.RTPCodecCapability.ClockRate,
		remoteCodec.RTPCodecCapability.Channels,
		remoteCodec.RTPCodecCapability.SDPFmtpLine)

	if apt, hasApt := remoteFmtp.Parameter("apt"); hasApt { //nolint:nestif
		payloadType, err := strconv.ParseUint(apt, 10, 8)
		if err != nil {
			return RTPCodecParameters{}, codecMatchNone, err
		}

		aptMatch := codecMatchNone
		var aptCodec RTPCodecParameters
		for _, codec := range exactMatches {
			if codec.PayloadType == PayloadType(payloadType) {
				aptMatch = codecMatchExact
				aptCodec = codec

				break
			}
		}

		if aptMatch == codecMatchNone {
			for _, codec := range partialMatches {
				if codec.PayloadType == PayloadType(payloadType) {
					aptMatch = codecMatchPartial
					aptCodec = codec

					break
				}
			}
		}

		if aptMatch == codecMatchNone {
			return RTPCodecParameters{}, codecMatchNone, nil // not an error, we just ignore this codec we don't support
		}

		// replace the apt value with the original codec's payload type
		toMatchCodec := remoteCodec
		if aptMatched, mt := codecParametersFuzzySearch(aptCodec, codecs); mt == aptMatch {
			toMatchCodec.SDPFmtpLine = strings.Replace(
				toMatchCodec.SDPFmtpLine,
				fmt.Sprintf("apt=%d", payloadType),
				fmt.Sprintf("apt=%d", aptMatched.PayloadType),
				1,
			)
		}