gortsplib/pkg/formats/h264.go

package formats

import (
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"strconv"
	"strings"
	"sync"

	"github.com/pion/rtp"

	"github.com/bluenviron/gortsplib/v3/pkg/formats/rtph264"
	"github.com/bluenviron/mediacommon/pkg/codecs/h264"
)

// check whether a RTP/H264 packet contains a IDR, without decoding the packet.
func rtpH264ContainsIDR(pkt *rtp.Packet) bool {
	if len(pkt.Payload) == 0 {
		return false
	}

	typ := h264.NALUType(pkt.Payload[0] & 0x1F)

	switch typ {
	case h264.NALUTypeIDR:
		return true

	case 24: // STAP-A
		payload := pkt.Payload[1:]

		for len(payload) > 0 {
			if len(payload) < 2 {
				return false
			}

			size := uint16(payload[0])<<8 | uint16(payload[1])
			payload = payload[2:]

			if size == 0 || int(size) > len(payload) {
				return false
			}

			nalu := payload[:size]
			payload = payload[size:]

			typ = h264.NALUType(nalu[0] & 0x1F)
			if typ == h264.NALUTypeIDR {
				return true
			}
		}

		return false

	case 28: // FU-A
		if len(pkt.Payload) < 2 {
			return false
		}

		start := pkt.Payload[1] >> 7
		if start != 1 {
			return false
		}

		typ := h264.NALUType(pkt.Payload[1] & 0x1F)
		return (typ == h264.NALUTypeIDR)

	default:
		return false
	}
}

// H264 is a RTP format that uses the H264 codec, defined in MPEG-4 part 10.
// Specification: https://datatracker.ietf.org/doc/html/rfc6184
type H264 struct {
	PayloadTyp        uint8
	SPS               []byte
	PPS               []byte
	PacketizationMode int

	mutex sync.RWMutex
}

func (f *H264) unmarshal(payloadType uint8, clock string, codec string, rtpmap string, fmtp map[string]string) error {
	f.PayloadTyp = payloadType

	for key, val := range fmtp {
		switch key {
		case "sprop-parameter-sets":
			tmp := strings.Split(val, ",")
			if len(tmp) >= 2 {
				sps, err := base64.StdEncoding.DecodeString(tmp[0])
				if err != nil {
					return fmt.Errorf("invalid sprop-parameter-sets (%v)", val)
				}

				pps, err := base64.StdEncoding.DecodeString(tmp[1])
				if err != nil {
					return fmt.Errorf("invalid sprop-parameter-sets (%v)", val)
				}

				f.SPS = sps
				f.PPS = pps
			}

		case "packetization-mode":
			tmp, err := strconv.ParseUint(val, 10, 31)
			if err != nil {
				return fmt.Errorf("invalid packetization-mode (%v)", val)
			}

			f.PacketizationMode = int(tmp)
		}
	}

	return nil
}

// String implements Format.
func (f *H264) String() string {
	return "H264"
}

// ClockRate implements Format.
func (f *H264) ClockRate() int {
	return 90000
}

// PayloadType implements Format.
func (f *H264) PayloadType() uint8 {
	return f.PayloadTyp
}

// RTPMap implements Format.
func (f *H264) RTPMap() string {
	return "H264/90000"
}

// FMTP implements Format.
func (f *H264) FMTP() map[string]string {
	f.mutex.RLock()
	defer f.mutex.RUnlock()

	fmtp := make(map[string]string)

	if f.PacketizationMode != 0 {
		fmtp["packetization-mode"] = strconv.FormatInt(int64(f.PacketizationMode), 10)
	}

	var tmp []string
	if f.SPS != nil {
		tmp = append(tmp, base64.StdEncoding.EncodeToString(f.SPS))
	}
	if f.PPS != nil {
		tmp = append(tmp, base64.StdEncoding.EncodeToString(f.PPS))
	}
	if tmp != nil {
		fmtp["sprop-parameter-sets"] = strings.Join(tmp, ",")
	}
	if len(f.SPS) >= 4 {
		fmtp["profile-level-id"] = strings.ToUpper(hex.EncodeToString(f.SPS[1:4]))
	}

	return fmtp
}

// PTSEqualsDTS implements Format.
func (f *H264) PTSEqualsDTS(pkt *rtp.Packet) bool {
	return rtpH264ContainsIDR(pkt)
}

// CreateDecoder creates a decoder able to decode the content of the format.
func (f *H264) CreateDecoder() *rtph264.Decoder {
	d := &rtph264.Decoder{
		PacketizationMode: f.PacketizationMode,
	}
	d.Init()
	return d
}

// CreateEncoder creates an encoder able to encode the content of the format.
func (f *H264) CreateEncoder() *rtph264.Encoder {
	e := &rtph264.Encoder{
		PayloadType:       f.PayloadTyp,
		PacketizationMode: f.PacketizationMode,
	}
	e.Init()
	return e
}

// SafeSetParams sets the codec parameters.
func (f *H264) SafeSetParams(sps []byte, pps []byte) {
	f.mutex.Lock()
	defer f.mutex.Unlock()
	f.SPS = sps
	f.PPS = pps
}

// SafeParams returns the codec parameters.
func (f *H264) SafeParams() ([]byte, []byte) {
	f.mutex.RLock()
	defer f.mutex.RUnlock()
	return f.SPS, f.PPS
}