fix 0x141a record parsing and add dante channel type detection

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dante_control.go

@@ -175,6 +175,7 @@ func (d *DanteFlows) LogAll() {
 		txCh        string
 		rxName      string
 		rxCh        string
+		channelType string
 	}
 	var allChannelFlows []channelFlow
 	var allNoChannelFlows []string
@@ -196,11 +197,18 @@ func (d *DanteFlows) LogAll() {
 				for _, ch := range sub.Channels {
 					parts := strings.Split(ch, "->")
 					if len(parts) == 2 {
+						rxPart := parts[1]
+						chType := ""
+						if idx := strings.LastIndex(rxPart, ":"); idx != -1 {
+							chType = rxPart[idx+1:]
+							rxPart = rxPart[:idx]
+						}
 						allChannelFlows = append(allChannelFlows, channelFlow{
 							sourceName:  sourceName,
 							txCh:        parts[0],
 							rxName:      subName,
-							rxCh:       parts[1],
+							rxCh:        rxPart,
+							channelType: chType,
 						})
 					} else {
 						allNoChannelFlows = append(allNoChannelFlows, fmt.Sprintf("%s -> %s[%s]", sourceName, subName, ch))
@@ -225,8 +233,12 @@ func (d *DanteFlows) LogAll() {
 	sort.Strings(allNoChannelFlows)
 
 	for _, cf := range allChannelFlows {
+		if cf.channelType != "" {
+			log.Printf("[sigusr1]   %s[%s] -> %s[%s] (%s)", cf.sourceName, cf.txCh, cf.rxName, cf.rxCh, cf.channelType)
+		} else {
 			log.Printf("[sigusr1]   %s[%s] -> %s[%s]", cf.sourceName, cf.txCh, cf.rxName, cf.rxCh)
 		}
+	}
 	for _, flow := range allNoChannelFlows {
 		log.Printf("[sigusr1]   %s", flow)
 	}
@@ -266,8 +278,11 @@ func (t *Tendrils) queryDanteDeviceWithPort(ip net.IP, port int) *DanteDeviceInf
 		if t.DebugDante {
 			log.Printf("[dante] %s: 0x3000 returned %d subscriptions, hasMulticast=%v", ip, len(info.Subscriptions), info.HasMulticast)
 		}
-		if len(info.Subscriptions) == 0 && info.RxChannelCount > 0 {
+		if info.RxChannelCount > 0 && (len(info.Subscriptions) == 0 || info.HasMulticast) {
-			info.Subscriptions = t.queryDanteSubscriptions3400(conn, ip, info.RxChannelCount)
+			subs3400 := t.queryDanteSubscriptions3400(conn, ip, info.RxChannelCount)
+			if len(subs3400) > 0 {
+				info.Subscriptions = subs3400
+			}
 		}
 	}
 
@@ -288,10 +303,30 @@ type DanteDeviceInfo struct {
 	HasMulticast   bool
 }
 
+type DanteChannelType uint16
+
+const (
+	DanteChannelUnknown DanteChannelType = 0
+	DanteChannelAudio   DanteChannelType = 0x000f
+	DanteChannelVideo   DanteChannelType = 0x000e
+)
+
+func (t DanteChannelType) String() string {
+	switch t {
+	case DanteChannelAudio:
+		return "audio"
+	case DanteChannelVideo:
+		return "video"
+	default:
+		return ""
+	}
+}
+
 type DanteSubscription struct {
 	RxChannel     int
 	TxDeviceName  string
 	TxChannelName string
+	ChannelType   DanteChannelType
 }
 
 func buildDantePacket(cmd uint16, args []byte) []byte {
@@ -610,12 +645,34 @@ func (t *Tendrils) queryDanteSubscriptions3400(conn *net.UDPConn, ip net.IP, rxC
 				break
 			}
 			rawOffset := int(binary.BigEndian.Uint16(resp[offsetPos : offsetPos+2]))
-			if rawOffset+48 > len(resp) {
+			if rawOffset+28 > len(resp) {
 				continue
 			}
 
-			txChOffset := int(binary.BigEndian.Uint16(resp[rawOffset+44 : rawOffset+46]))
+			var channelType DanteChannelType
-			txDevOffset := int(binary.BigEndian.Uint16(resp[rawOffset+46 : rawOffset+48]))
+			var txChOffset, txDevOffset int
+
+			marker := binary.BigEndian.Uint16(resp[rawOffset : rawOffset+2])
+			if marker == 0x141c {
+				if rawOffset+48 > len(resp) {
+					log.Printf("[ERROR] [dante] %s: 0x3400 record %d at 0x%04x: 0x141c record truncated (need %d, have %d)", ip, i, rawOffset, rawOffset+48, len(resp))
+					continue
+				}
+				channelType = DanteChannelType(binary.BigEndian.Uint16(resp[rawOffset+14 : rawOffset+16]))
+				txChOffset = int(binary.BigEndian.Uint16(resp[rawOffset+44 : rawOffset+46]))
+				txDevOffset = int(binary.BigEndian.Uint16(resp[rawOffset+46 : rawOffset+48]))
+			} else if marker == 0x141a {
+				if rawOffset+48 > len(resp) {
+					log.Printf("[ERROR] [dante] %s: 0x3400 record %d at 0x%04x: 0x141a record truncated", ip, i, rawOffset)
+					continue
+				}
+				channelType = DanteChannelVideo
+				txChOffset = int(binary.BigEndian.Uint16(resp[rawOffset+44 : rawOffset+46]))
+				txDevOffset = int(binary.BigEndian.Uint16(resp[rawOffset+46 : rawOffset+48]))
+			} else {
+				log.Printf("[ERROR] [dante] %s: 0x3400 record %d at 0x%04x: unknown marker 0x%04x (bytes: %x)", ip, i, rawOffset, marker, resp[rawOffset:rawOffset+8])
+				continue
+			}
 
 			if txChOffset == 0 && txDevOffset == 0 {
 				continue
@@ -635,13 +692,14 @@ func (t *Tendrils) queryDanteSubscriptions3400(conn *net.UDPConn, ip net.IP, rxC
 
 			rxChannel := startChannel + i
 			if t.DebugDante {
-				log.Printf("[dante] %s: 0x3400 sub: rx=%d txDev=%q txCh=%q", ip, rxChannel, txDeviceName, txChannelName)
+				log.Printf("[dante] %s: 0x3400 sub: rx=%d txDev=%q txCh=%q type=%s", ip, rxChannel, txDeviceName, txChannelName, channelType)
 			}
 
 			subscriptions = append(subscriptions, DanteSubscription{
 				RxChannel:     rxChannel,
 				TxDeviceName:  txDeviceName,
 				TxChannelName: txChannelName,
+				ChannelType:   channelType,
 			})
 		}
 
@@ -674,8 +732,8 @@ func (t *Tendrils) probeDanteDeviceWithPort(ip net.IP, port int) {
 		needIGMPFallback := info.HasMulticast && info.Name != ""
 		for _, sub := range info.Subscriptions {
 			if t.DebugDante {
-				log.Printf("[dante] %s: subscription rx=%d -> %s@%s",
+				log.Printf("[dante] %s: subscription rx=%d -> %s@%s type=%s",
-					ip, sub.RxChannel, sub.TxChannelName, sub.TxDeviceName)
+					ip, sub.RxChannel, sub.TxChannelName, sub.TxDeviceName, sub.ChannelType)
 			}
 			if sub.TxDeviceName != "" && info.Name != "" {
 				txDeviceName := sub.TxDeviceName
@@ -684,8 +742,13 @@ func (t *Tendrils) probeDanteDeviceWithPort(ip net.IP, port int) {
 				}
 				channelInfo := ""
 				if sub.TxChannelName != "" {
+					typeStr := sub.ChannelType.String()
+					if typeStr != "" {
+						channelInfo = fmt.Sprintf("%s->%02d:%s", sub.TxChannelName, sub.RxChannel, typeStr)
+					} else {
 						channelInfo = fmt.Sprintf("%s->%02d", sub.TxChannelName, sub.RxChannel)
 					}
+				}
 				sourceNode := t.nodes.GetOrCreateByName(txDeviceName)
 				subscriberNode := t.nodes.GetOrCreateByName(info.Name)
 				t.danteFlows.Update(sourceNode, subscriberNode, channelInfo)

notes/dantepacket.md

@@ -72,19 +72,44 @@ Zero offset = no more records.
 
 ### Subscription Record
 
-Each record is 56+ bytes. The offset table points to record start.
+Two record formats exist, distinguished by marker position.
+
+#### Format 1: 0x141c records (numbered audio/video channels)
 
 ```
-record+0x00: [40] record_header
+record+0x00: u16  0x141c          # record marker
-record+0x28: u16  0x0608          # marker
+record+0x02: u16  channel_num     # RX channel number
-record+0x2a: u16  0x0000
+record+0x04: u16  0x0000
+record+0x06: u16  0x0003
+record+0x08: u16  channel_num     # repeated
+record+0x0a: u16  0x0000
+record+0x0c: u16  0x0000
+record+0x0e: u16  channel_type    # 0x000f=audio, 0x000e=video
+...
 record+0x2c: u16  tx_ch_offset    # absolute offset to TX channel name string
 record+0x2e: u16  tx_dev_offset   # absolute offset to TX device name string
-record+0x30: [4]  flags
-record+0x34: u32  0x02020000      # string marker
-record+0x38: ...  inline_strings  # (unreliable, use offsets above)
 ```
 
+**Channel type (at record+0x0e):**
+- `0x000f` = audio channel
+- `0x000e` = video channel
+
+#### Format 2: 0x141a records (special channels: Video, Serial, USB)
+
+```
+record+0x00: u16  0x141a          # record marker
+record+0x02: u16  channel_num     # e.g., 0x0009 = channel 9
+record+0x04: u16  ??
+record+0x06: u16  ??
+...
+record+0x2c: u16  tx_ch_offset    # same position as 0x141c
+record+0x2e: u16  tx_dev_offset   # same position as 0x141c
+```
+
+These are video channels (Dante AV "Video" aggregate channel).
+
+Both 0x141c and 0x141a records use the same offsets for tx_ch and tx_dev (+44 and +46).
+
 **Subscription status:**
 - Both offsets non-zero = subscribed
 - Both offsets zero = unsubscribed
@@ -126,9 +151,85 @@ Record at 0x0258 (RX ch 25):
 
 1. Check magic=0x28, command=0x3400, status=0x8112
 2. Read 16 offsets from 0x12-0x31
-3. For each non-zero offset:
+3. For each non-zero offset, detect record format:
-   - Read u16 at offset+0x2c (tx_ch_offset)
+   - If offset+0x00 == 0x141c: Format 1 (numbered channel)
-   - Read u16 at offset+0x2e (tx_dev_offset)
+     - channel_type at offset+0x0e (0x000f=audio, 0x000e=video)
-   - If both zero: skip (unsubscribed)
+     - tx_ch_offset at offset+0x2c
-   - Else: read null-terminated strings at those offsets
+     - tx_dev_offset at offset+0x2e
-   - RX channel = page_start + record_index
+   - If offset+0x00 == 0x141a: Format 2 (special channel)
+     - Assume video type
+     - tx_ch_offset at offset+0x2c (same as 0x141c)
+     - tx_dev_offset at offset+0x2e (same as 0x141c)
+4. If tx_ch_offset and tx_dev_offset are both zero: skip (unsubscribed)
+5. Read null-terminated strings at those offsets
+6. RX channel = page_start + record_index
+
+---
+
+## Additional Commands
+
+### 0x2000 - TX Channel Info
+
+Request args (6 bytes):
+```
+0x00: u16  0x0001
+0x02: u16  page_num
+0x04: u16  0x0000
+```
+
+Response contains TX channel entries:
+```
+0x00: u16  channel_num
+0x02: u16  channel_type    # see below
+0x04: u16  name_offset
+0x06: u16  unknown
+```
+
+Observed channel_type values:
+- `0x0107` = audio channel (seen on MICS, SQ-7, speaker devices)
+- `0x0007` = possibly video or different encoding?
+
+Sample rate `0xbb80` (48000) appears in responses.
+
+### 0x3600 - TX Flow Info
+
+Uses magic=0x28. Returns info about outgoing flows.
+
+Response includes IP addresses of flow destinations.
+
+---
+
+## Multicast Group Ranges
+
+Audio and video use different multicast IP ranges:
+- `239.69.x.x` - `239.71.x.x` = Dante audio multicast
+- `239.253.x.x` = Dante AV (video) multicast
+
+---
+
+## Channel Type Detection
+
+**SOLVED**: Audio vs video channels are distinguished by the channel_type field at record+0x0e in 0x3400 responses:
+- `0x000f` = audio channel
+- `0x000e` = video channel
+
+Dante AV devices (TX-*, RX-* naming convention) have both audio and video channels. The type must be checked per-channel, not per-device.
+
+---
+
+## Open Questions
+
+### Other Channel Types
+
+Video devices have additional channel types with marker 0x141a instead of 0x141c:
+- "Video" channels (the actual video stream)
+- "Serial" channels
+- "USB" channels
+
+These use a different record structure. Need to decode the 0x141a record format.
+
+### 0x2000 Channel Type Field
+
+The 0x2000 response has a channel_type field at entry+0x02. Observed values:
+- `0x0007` seen on Ultimo X (audio devices)
+- Need to compare with video device 0x2000 responses