2021-05-11 19:59:24 +02:00
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package rtpconn
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import (
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"strings"
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"github.com/pion/rtp"
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"github.com/pion/rtp/codecs"
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)
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// isKeyframe determines if packet is the start of a keyframe.
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// It returns (true, true) if that is the case, (false, true) if that is
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// definitely not the case, and (false, false) if the information cannot
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// be determined.
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func isKeyframe(codec string, packet *rtp.Packet) (bool, bool) {
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2021-05-12 16:18:23 +02:00
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if strings.EqualFold(codec, "video/vp8") {
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2021-05-11 19:59:24 +02:00
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var vp8 codecs.VP8Packet
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_, err := vp8.Unmarshal(packet.Payload)
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if err != nil || len(vp8.Payload) < 1 {
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return false, false
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}
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if vp8.S != 0 && vp8.PID == 0 && (vp8.Payload[0]&0x1) == 0 {
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return true, true
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}
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return false, true
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2021-05-12 16:18:23 +02:00
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} else if strings.EqualFold(codec, "video/vp9") {
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2021-05-11 19:59:24 +02:00
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var vp9 codecs.VP9Packet
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_, err := vp9.Unmarshal(packet.Payload)
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if err != nil || len(vp9.Payload) < 1 {
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return false, false
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}
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if !vp9.B {
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return false, true
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}
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if (vp9.Payload[0] & 0xc0) != 0x80 {
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return false, false
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}
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profile := (vp9.Payload[0] >> 4) & 0x3
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if profile != 3 {
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return (vp9.Payload[0] & 0xC) == 0, true
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}
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return (vp9.Payload[0] & 0x6) == 0, true
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2021-05-12 16:18:23 +02:00
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} else if strings.EqualFold(codec, "video/h264") {
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2021-05-11 19:59:24 +02:00
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if len(packet.Payload) < 1 {
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return false, false
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}
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nalu := packet.Payload[0] & 0x1F
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if nalu == 0 {
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// reserved
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return false, false
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} else if nalu <= 23 {
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// simple NALU
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return nalu == 5, true
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} else if nalu == 24 || nalu == 25 || nalu == 26 || nalu == 27 {
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// STAP-A, STAP-B, MTAP16 or MTAP24
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i := 1
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if nalu == 25 || nalu == 26 || nalu == 27 {
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// skip DON
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i += 2
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}
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for i < len(packet.Payload) {
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if i+2 > len(packet.Payload) {
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return false, false
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}
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length := uint16(packet.Payload[i])<<8 |
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uint16(packet.Payload[i+1])
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i += 2
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if i+int(length) > len(packet.Payload) {
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return false, false
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}
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offset := 0
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if nalu == 26 {
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offset = 3
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} else if nalu == 27 {
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offset = 4
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}
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if offset >= int(length) {
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return false, false
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}
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n := packet.Payload[i+offset] & 0x1F
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if n == 5 {
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return true, true
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} else if n >= 24 {
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// is this legal?
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return false, false
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}
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i += int(length)
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}
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if i == len(packet.Payload) {
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return false, true
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}
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return false, false
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} else if nalu == 28 || nalu == 29 {
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// FU-A or FU-B
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if len(packet.Payload) < 2 {
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return false, false
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}
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if (packet.Payload[1] & 0x80) == 0 {
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// not a starting fragment
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return false, true
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}
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return (packet.Payload[1]&0x1F == 5), true
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}
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return false, false
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2021-05-12 16:18:23 +02:00
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} else {
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2021-05-11 19:59:24 +02:00
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return false, false
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}
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}
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