fix(videochannel): increase timeouts to handle SFU renegotiation delays

internal/e2e/stress_test.go

@@ -212,10 +212,12 @@ func streamPatternForDuration(conn net.Conn, duration time.Duration, chunkSize i
 	if chunkSize <= 0 {
 		chunkSize = 4096
 	}
-	// Per-chunk roundtrip deadline. Slow transports (videochannel) can
-	// take seconds+ per chunk in practice; 15s gives ample margin
-	// without making genuine stalls hang forever.
-	const chunkTimeout = 15 * time.Second
+	// Per-chunk roundtrip deadline. Videochannel uses per-fragment acks
+	// with up to 20 retransmit attempts; during SFU renegotiation frames
+	// can be lost for several seconds, triggering the full retransmit
+	// cycle (~40s worst case). 45s covers that while still catching
+	// genuine stalls within a reasonable time.
+	const chunkTimeout = 45 * time.Second
 
 	start := time.Now()
 	deadline := start.Add(duration)

internal/e2e/tunnel_test.go

@@ -933,12 +933,12 @@ func e2eTransportOptions(transportName string) transport.Options {
 	switch transportName {
 	case "videochannel":
 		return videochannel.Options{
-			Width:      320,
-			Height:     320,
-			FPS:        25,
-			Bitrate:    "500k",
+			Width:      1080,
+			Height:     1080,
+			FPS:        10,
+			Bitrate:    "1000k",
 			HW:         videoHWNone,
-			QRSize:     256,
+			QRSize:     512,
 			QRRecovery: "low",
 			Codec:      "qrcode",
 			TileModule: 4,

internal/transport/videochannel/transport.go

@@ -23,7 +23,7 @@ import (
 const (
 	defaultMaxPayloadSize = 16 * 1024
 	defaultFragmentSize   = 256
-	defaultAckTimeout     = 300 * time.Millisecond
+	defaultAckTimeout     = 1 * time.Second
 	defaultFrameInterval  = 40 * time.Millisecond
 	defaultConnectTimeout = 30 * time.Second
 	maxSendAttempts       = 20
@@ -301,7 +301,7 @@ func perAttemptAckTimeout(fragments, fps int) time.Duration {
 		fps = 25
 	}
 	frameInterval := time.Second / time.Duration(fps)
-	estimated := time.Duration(fragments) * frameInterval * 2
+	estimated := time.Duration(fragments) * frameInterval * 3
 	if estimated < defaultAckTimeout {
 		return defaultAckTimeout
 	}

internal/transport/videochannel/transport_unit_test.go

@@ -262,8 +262,8 @@ func TestPerAttemptAckTimeoutScalesWithFragments(t *testing.T) {
 		t.Fatalf("perAttemptAckTimeout(2,25) = %v, want %v", got, defaultAckTimeout)
 	}
 
-	// 16 fragments @ 25 FPS: 16 * 40ms * 2 = 1280ms.
-	if got, want := perAttemptAckTimeout(16, 25), 1280*time.Millisecond; got != want {
+	// 16 fragments @ 25 FPS: 16 * 40ms * 3 = 1920ms.
+	if got, want := perAttemptAckTimeout(16, 25), 1920*time.Millisecond; got != want {
 		t.Fatalf("perAttemptAckTimeout(16,25) = %v, want %v", got, want)
 	}