Add resolution extraction from JPEG screenshots in tester

.claude/skills/add_protocol_strix/SKILL.md

@@ -70,7 +70,7 @@ func rtspHandler(rawURL string) (core.Producer, error) {
 }
 ```
 
-**Data flow**: URL -> GetHandler(url) -> handler(url) -> core.Producer -> GetMedias() -> codecs, latency -> getScreenshot() -> Result
+**Data flow**: URL -> GetHandler(url) -> handler(url) -> core.Producer -> GetMedias() -> codecs, latency -> getScreenshot() -> jpegSize() -> Result (with width, height)
 
 **Key**: The handler ONLY needs to return a `core.Producer`. Everything else (codecs extraction, screenshot capture, session management) is handled automatically by `worker.go`.
 
@@ -491,7 +491,7 @@ The tester uses:
 2. `GetTrack()` + `Start()` -- to capture screenshot (keyframe)
 3. `Stop()` -- to clean up
 
-### How screenshot works (pkg/tester/worker.go)
+### How screenshot and resolution work (pkg/tester/worker.go)
 
 1. `getScreenshot(prod)` is called after successful Dial
 2. Creates `magic.NewKeyframe()` consumer
@@ -501,8 +501,26 @@ The tester uses:
 6. Waits for first keyframe via `cons.WriteTo()` with 10s timeout
 7. If H264/H265 -- converts to JPEG via ffmpeg
 8. If already JPEG -- uses as-is
+9. `jpegSize(jpeg)` extracts width and height from JPEG SOF0/SOF2 marker
+10. Resolution stored in `Result.Width` and `Result.Height`
 
-This works automatically for ANY protocol that returns a valid `core.Producer`. You do NOT need to implement screenshot logic per protocol.
+This works automatically for ANY protocol that returns a valid `core.Producer`. You do NOT need to implement screenshot or resolution logic per protocol.
+
+### Result struct (pkg/tester/session.go)
+
+```go
+type Result struct {
+    Source     string   `json:"source"`
+    Screenshot string   `json:"screenshot,omitempty"`
+    Codecs     []string `json:"codecs,omitempty"`
+    Width      int      `json:"width,omitempty"`      // from JPEG screenshot
+    Height     int      `json:"height,omitempty"`      // from JPEG screenshot
+    LatencyMs  int64    `json:"latency_ms,omitempty"`
+    Skipped    bool     `json:"skipped,omitempty"`
+}
+```
+
+Resolution is extracted from the JPEG screenshot, not from SDP or protocol-specific data. This means width/height are only available when a screenshot was successfully captured. The frontend uses these values to classify streams as Main (HD) or Sub (SD).
 
 ### magic.NewKeyframe() (pkg/magic/keyframe.go)
 

pkg/tester/session.go

@@ -27,8 +27,8 @@ type Result struct {
 	Source     string   `json:"source"`
 	Screenshot string   `json:"screenshot,omitempty"`
 	Codecs     []string `json:"codecs,omitempty"`
-	Width      uint16   `json:"width,omitempty"`
+	Width      int      `json:"width,omitempty"`
-	Height     uint16   `json:"height,omitempty"`
+	Height     int      `json:"height,omitempty"`
 	LatencyMs  int64    `json:"latency_ms,omitempty"`
 	Skipped    bool     `json:"skipped,omitempty"`
 }

pkg/tester/worker.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/AlexxIT/go2rtc/pkg/core"
-	"github.com/AlexxIT/go2rtc/pkg/h264"
 	"github.com/AlexxIT/go2rtc/pkg/magic"
 )
 
@@ -67,31 +66,18 @@ func testURL(s *Session, rawURL string) {
 	latency := time.Since(start).Milliseconds()
 
 	var codecs []string
-	var width, height uint16
-
 	for _, media := range prod.GetMedias() {
 		if media.Direction != core.DirectionRecvonly {
 			continue
 		}
 		for _, codec := range media.Codecs {
 			codecs = append(codecs, codec.Name)
-
-			// extract resolution from first video codec SPS
-			if width == 0 && codec.Name == core.CodecH264 {
-				if spsBytes, _ := h264.GetParameterSet(codec.FmtpLine); spsBytes != nil {
-					if sps := h264.DecodeSPS(spsBytes); sps != nil {
-						width, height = sps.Width(), sps.Height()
-					}
-				}
-			}
 		}
 	}
 
 	r := &Result{
 		Source:    rawURL,
 		Codecs:   codecs,
-		Width:    width,
-		Height:   height,
 		LatencyMs: latency,
 	}
 
@@ -110,6 +96,7 @@ func testURL(s *Session, rawURL string) {
 		if jpeg != nil {
 			idx := s.AddScreenshot(jpeg)
 			r.Screenshot = fmt.Sprintf("/api/test/screenshot?id=%s&i=%d", s.ID, idx)
+			r.Width, r.Height = jpegSize(jpeg)
 		}
 	}
 
@@ -167,6 +154,27 @@ matched:
 	return once.Buffer(), cons.CodecName()
 }
 
+// jpegSize extracts width and height from JPEG SOF0/SOF2 marker
+func jpegSize(data []byte) (int, int) {
+	for i := 2; i < len(data)-9; {
+		if data[i] != 0xFF {
+			return 0, 0
+		}
+		marker := data[i+1]
+		size := int(data[i+2])<<8 | int(data[i+3])
+
+		// SOF0 (0xC0) or SOF2 (0xC2) -- baseline or progressive
+		if marker == 0xC0 || marker == 0xC2 {
+			h := int(data[i+5])<<8 | int(data[i+6])
+			w := int(data[i+7])<<8 | int(data[i+8])
+			return w, h
+		}
+
+		i += 2 + size
+	}
+	return 0, 0
+}
+
 func toJPEG(raw []byte) []byte {
 	cmd := exec.Command("ffmpeg",
 		"-hide_banner", "-loglevel", "error",