move RTP decoders/encoders into pkt/rtpcodecs

pkg/rtpcodecs/rtplpcm/decoder.go

@@ -0,0 +1,37 @@
+package rtplpcm
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/pion/rtp"
+
+	"github.com/aler9/gortsplib/pkg/rtptimedec"
+)
+
+// Decoder is a RTP/LPCM decoder.
+type Decoder struct {
+	BitDepth     int
+	SampleRate   int
+	ChannelCount int
+
+	timeDecoder *rtptimedec.Decoder
+	sampleSize  int
+}
+
+// Init initializes the decoder.
+func (d *Decoder) Init() {
+	d.timeDecoder = rtptimedec.New(d.SampleRate)
+	d.sampleSize = d.BitDepth * d.ChannelCount / 8
+}
+
+// Decode decodes audio samples from a RTP packet.
+// It returns audio samples and PTS of the first sample.
+func (d *Decoder) Decode(pkt *rtp.Packet) ([]byte, time.Duration, error) {
+	plen := len(pkt.Payload)
+	if (plen % d.sampleSize) != 0 {
+		return nil, 0, fmt.Errorf("received payload of wrong size")
+	}
+
+	return pkt.Payload, d.timeDecoder.Decode(pkt.Timestamp), nil
+}