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fix medias wrongly marked as back channels (bluenviron/mediamtx#5074) #970

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Merged
aler9 merged 1 commit into from
Dec 24, 2025
Merged

fix medias wrongly marked as back channels (bluenviron/mediamtx#5074) #970

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22 changes: 20 additions & 2 deletions pkg/description/session.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ func atLeastOneHasMID(medias []*Media) bool {
return false
}

func atLeastOneDoesntHaveMID(medias []*Media) bool {
func atLeastOneDoesNotHaveMID(medias []*Media) bool {
for _, media := range medias {
if media.ID == "" {
return true
Expand All @@ -30,6 +30,15 @@ func atLeastOneDoesntHaveMID(medias []*Media) bool {
return false
}

func atLeastOneIsNotBackChannel(medias []*Media) bool {
for _, media := range medias {
if !media.IsBackChannel {
return true
}
}
return false
}

func hasMediaWithID(medias []*Media, id string) bool {
for _, media := range medias {
if media.ID == id {
Expand Down Expand Up @@ -119,10 +128,19 @@ func (d *Session) Unmarshal(ssd *sdp.SessionDescription) error {
d.Medias[i] = &m
}

if atLeastOneHasMID(d.Medias) && atLeastOneDoesntHaveMID(d.Medias) {
if atLeastOneHasMID(d.Medias) && atLeastOneDoesNotHaveMID(d.Medias) {
return fmt.Errorf("media IDs sent partially")
}

// Some cameras mark medias as back channels even though they are not.
// Try to detect this by checking whether in the full SDP there are both
// back channels and standard channels, unmarking back channels otherwise.
if !atLeastOneIsNotBackChannel(d.Medias) {
for _, m := range d.Medias {
m.IsBackChannel = false
}
}

for _, attr := range ssd.Attributes {
if attr.Key == "group" && strings.HasPrefix(attr.Value, "FEC ") {
group := SessionFECGroup(strings.Split(attr.Value[len("FEC "):], " "))
Expand Down
159 changes: 151 additions & 8 deletions pkg/description/session_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -269,7 +269,6 @@ var casesSession = []struct {
"t=0 0\r\n" +
"m=audio 0 RTP/AVP 111 103 104 9 102 0 8 106 105 13 110 112 113 126\r\n" +
"a=mid:audio\r\n" +
"a=sendonly\r\n" +
"a=control\r\n" +
"a=rtpmap:111 opus/48000/2\r\n" +
"a=fmtp:111 sprop-stereo=0\r\n" +
Expand All @@ -288,7 +287,6 @@ var casesSession = []struct {
"a=rtpmap:126 telephone-event/8000\r\n" +
"m=video 0 RTP/AVP 96 97 98 99 100 101 127 124 125\r\n" +
"a=mid:video\r\n" +
"a=sendonly\r\n" +
"a=control\r\n" +
"a=rtpmap:96 VP8/90000\r\n" +
"a=rtpmap:97 rtx/90000\r\n" +
Expand All @@ -307,9 +305,8 @@ var casesSession = []struct {
Title: ``,
Medias: []*Media{
{
ID: "audio",
Type: MediaTypeAudio,
IsBackChannel: true,
ID: "audio",
Type: MediaTypeAudio,
Formats: []format.Format{
&format.Opus{
PayloadTyp: 111,
Expand Down Expand Up @@ -381,9 +378,8 @@ var casesSession = []struct {
},
},
{
ID: "video",
Type: MediaTypeVideo,
IsBackChannel: true,
ID: "video",
Type: MediaTypeVideo,
Formats: []format.Format{
&format.VP8{
PayloadTyp: 96,
Expand Down Expand Up @@ -827,6 +823,153 @@ var casesSession = []struct {
},
},
},
{
"issue mediamtx/5074 (fake back channel)",
"v=0\n" +
"o=- 1645677566 1 IN IP4 *****\n" +
"s=Streamed by \"IDS uEye Live RTSP Server\"\n" +
"i=session information\n" +
"t=0 0\n" +
"a=tool:IDS uEye Live RTSP Server:Jul 17 2025 - 13:23:42\n" +
"a=type:broadcast\n" +
"a=control:*\n" +
"a=range:npt=0-\n" +
"m=video 0 RTP/AVP 96\n" +
"c=IN IP4 *****\n" +
"a=sendonly\n" +
"a=rtpmap:96 H264/90000\n" +
"a=fmtp:96 packetization-mode=1; profile-level-id=4D4028; " +
"sprop-parameter-sets=Z01AKI2NQDwBE/LgLcBAQFAAAD6AAARlDoYAUVAABfXgu8uNDACioAAL68F3lwo=,aO44gA==;\n" +
"a=cliprect:0,0,1080,1920\n" +
"a=control:rtsp://*****/video=video1\n",
"v=0\r\n" +
"o=- 0 0 IN IP4 127.0.0.1\r\n" +
"s=Streamed by \"IDS uEye Live RTSP Server\"\r\n" +
"c=IN IP4 0.0.0.0\r\n" +
"t=0 0\r\n" +
"m=video 0 RTP/AVP 96\r\n" +
"a=control:rtsp://*****/video=video1\r\n" +
"a=rtpmap:96 H264/90000\r\n" +
"a=fmtp:96 packetization-mode=1; profile-level-id=4D4028; " +
"sprop-parameter-sets=Z01AKI2NQDwBE/LgLcBAQFAAAD6AAARlDoYAUVAABfXgu8uNDACioAAL68F3lwo=,aO44gA==\r\n",
Session{
Title: `Streamed by "IDS uEye Live RTSP Server"`,
Medias: []*Media{
{
Type: "video",
Control: "rtsp://*****/video=video1",
Formats: []format.Format{&format.H264{
PayloadTyp: 96,
PacketizationMode: 1,
// ProfileLevelID: "4D4028",
SPS: []byte{
0x67, 0x4d, 0x40, 0x28, 0x8d, 0x8d, 0x40, 0x3c,
0x01, 0x13, 0xf2, 0xe0, 0x2d, 0xc0, 0x40, 0x40,
0x50, 0x00, 0x00, 0x3e, 0x80, 0x00, 0x04, 0x65,
0x0e, 0x86, 0x00, 0x51, 0x50, 0x00, 0x05, 0xf5,
0xe0, 0xbb, 0xcb, 0x8d, 0x0c, 0x00, 0xa2, 0xa0,
0x00, 0x0b, 0xeb, 0xc1, 0x77, 0x97, 0x0a,
},
PPS: []byte{0x68, 0xee, 0x38, 0x80},
}},
},
},
},
},
{
"issue mediamtx/5074 (real back channel)",
"v=0\n" +
"o=- 1 1 IN IP4 192.168.81.194:554\n" +
"s=L10013/video1 - ACES Server(SSDRTSPServer)\n" +
"t=0 0\n" +
"c=IN IP4 0.0.0.0\n" +
"a=control:*\n" +
"a=range:npt=now-\n" +
"m=video 0 RTP/AVP 96\n" +
"a=control:video\n" +
"a=rtpmap:96 H264/90000\n" +
"a=fmtp:96 sprop-parameter-sets=Z0IAHp2oKAv+WbgICAgQ,aM48gA==\n" +
"a=framerate:30\n" +
"a=recvonly\n" +
"m=audio 0 RTP/AVP 0\n" +
"a=control:audio\n" +
"a=rtpmap:0 PCMU/8000\n" +
"a=recvonly\n" +
"m=audio 0 RTP/AVP 0\n" +
"a=control:backchannel\n" +
"a=rtpmap:0 PCMU/8000\n" +
"a=sendonly\n" +
"m=application 0 RTP/AVP 98\n" +
"a=control:meta\n" +
"a=rtpmap:98 vnd.onvif.metadata/90000\n" +
"a=recvonly\n",
"v=0\r\n" +
"o=- 0 0 IN IP4 127.0.0.1\r\n" +
"s=L10013/video1 - ACES Server(SSDRTSPServer)\r\n" +
"c=IN IP4 0.0.0.0\r\n" +
"t=0 0\r\n" +
"m=video 0 RTP/AVP 96\r\n" +
"a=control:video\r\n" +
"a=rtpmap:96 H264/90000\r\n" +
"a=fmtp:96 profile-level-id=42001E; sprop-parameter-sets=Z0IAHp2oKAv+WbgICAgQ,aM48gA==\r\n" +
"m=audio 0 RTP/AVP 0\r\n" +
"a=control:audio\r\n" +
"a=rtpmap:0 PCMU/8000\r\n" +
"m=audio 0 RTP/AVP 0\r\n" +
"a=sendonly\r\n" +
"a=control:backchannel\r\n" +
"a=rtpmap:0 PCMU/8000\r\n" +
"m=application 0 RTP/AVP 98\r\n" +
"a=control:meta\r\n" +
"a=rtpmap:98 vnd.onvif.metadata/90000\r\n",
Session{
Title: `L10013/video1 - ACES Server(SSDRTSPServer)`,
Medias: []*Media{
{
Type: "video",
Control: "video",
Formats: []format.Format{&format.H264{
PayloadTyp: 96,
SPS: []byte{
0x67, 0x42, 0x00, 0x1e, 0x9d, 0xa8, 0x28, 0x0b,
0xfe, 0x59, 0xb8, 0x08, 0x08, 0x08, 0x10,
},
PPS: []byte{0x68, 0xce, 0x3c, 0x80},
}},
},
{
Type: "audio",
Control: "audio",
Formats: []format.Format{&format.G711{
PayloadTyp: 0,
MULaw: true,
SampleRate: 8000,
ChannelCount: 1,
}},
},
{
Type: "audio",
IsBackChannel: true,
Control: "backchannel",
Formats: []format.Format{&format.G711{
PayloadTyp: 0,
MULaw: true,
SampleRate: 8000,
ChannelCount: 1,
}},
},
{
Type: "application",
Control: "meta",
Formats: []format.Format{&format.Generic{
PayloadTyp: 98,
RTPMa: "vnd.onvif.metadata/90000",
ClockRat: 90000,
}},
},
},
},
},
}

func TestSessionUnmarshal(t *testing.T) {
Expand Down