Per-tile stream quality (high/low), fps cap, latency flags

Cameras carry multiple stream URLs (streams: high/medium/low); each
tile picks one via Quality (auto/high/low). Small tiles can pull the
low substream to cut Pi decode load. discover --enable-rtsp takes a
comma list (high,low), enables each channel, records all enabled ones.
TUI: q cycles a tile quality (shown in the tile); discover enables
high+low. Player: --framedrop + low-delay demuxer flags; player.max_fps.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/config/config.go

@@ -80,6 +80,9 @@ type Player struct {
 	Profile string `yaml:"profile"`
 	// ExtraArgs are appended verbatim to every mpv invocation.
 	ExtraArgs []string `yaml:"extra_args,omitempty"`
+	// MaxFPS caps the rendered frame rate (mpv --vf=fps). 0 = uncapped. Trims
+	// render/scale load; the bigger decode lever is using substreams.
+	MaxFPS int `yaml:"max_fps,omitempty"`
 	// RestartBackoffSeconds is how long to wait before relaunching a stream
 	// that exited or stalled.
 	RestartBackoffSeconds int `yaml:"restart_backoff_seconds,omitempty"`
@@ -92,12 +95,62 @@ type Camera struct {
 	ID string `yaml:"id,omitempty"`
 	// Name is the human label and the key layouts reference. Must be unique.
 	Name string `yaml:"name"`
-	// RTSP is the fully-resolved stream URL.
-	RTSP string `yaml:"rtsp"`
+	// RTSP is a single fully-resolved stream URL. Kept for backward
+	// compatibility and manual entries; Streams takes precedence when present.
+	RTSP string `yaml:"rtsp,omitempty"`
+	// Streams maps a quality ("high"|"medium"|"low") to its stream URL, so a
+	// tile can choose per-tile which to pull. Populated by discovery.
+	Streams map[string]string `yaml:"streams,omitempty"`
 	// Disabled hides the camera from selection without deleting it.
 	Disabled bool `yaml:"disabled,omitempty"`
 }
 
+// Qualities in preference order, high to low.
+var Qualities = []string{"high", "medium", "low"}
+
+// StreamURL returns the URL for the requested quality, falling back sensibly:
+// the exact quality, then any lower quality, then any stream at all, then the
+// legacy single RTSP field.
+func (c Camera) StreamURL(quality string) string {
+	if len(c.Streams) > 0 {
+		if quality != "" {
+			if u := c.Streams[quality]; u != "" {
+				return u
+			}
+		}
+		// Fall back down the preference list from the requested quality.
+		start := 0
+		for i, q := range Qualities {
+			if q == quality {
+				start = i
+				break
+			}
+		}
+		for _, q := range Qualities[start:] {
+			if u := c.Streams[q]; u != "" {
+				return u
+			}
+		}
+		for _, q := range Qualities {
+			if u := c.Streams[q]; u != "" {
+				return u
+			}
+		}
+	}
+	return c.RTSP
+}
+
+// AvailableQualities lists the qualities this camera actually has, high to low.
+func (c Camera) AvailableQualities() []string {
+	var out []string
+	for _, q := range Qualities {
+		if c.Streams[q] != "" {
+			out = append(out, q)
+		}
+	}
+	return out
+}
+
 // MaxTiles caps how many simultaneous streams a layout may show. Decoding
 // more than this on a Pi 4 is impractical even with substreams.
 const MaxTiles = 16
@@ -125,6 +178,9 @@ type Tile struct {
 	Row     int    `yaml:"row"`
 	ColSpan int    `yaml:"colspan,omitempty"` // defaults to 1
 	RowSpan int    `yaml:"rowspan,omitempty"` // defaults to 1
+	// Quality selects which stream to pull for this tile: "high"|"medium"|
+	// "low". Empty means the camera's best available (see Camera.StreamURL).
+	Quality string `yaml:"quality,omitempty"`
 }
 
 // Span returns the tile's spans with zero values normalized to 1.