Allow selection of different stream variants in the player (#815)

* WIP video quality selector

* The quality selector works even though it is not pretty

* Support getting and setting variant name. Closes #743

* Sort video qualities

* Fix odd looking selected states of menubutton items

* Fix comment

models/streamOutputVariant.go

@@ -1,9 +1,16 @@
 package models
 
-import "encoding/json"
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+)
 
 // StreamOutputVariant defines the output specifics of a single HLS stream variant.
 type StreamOutputVariant struct {
+	// Name is an optional human-readable label for this stream output.
+	Name string `json:"name"`
+
 	// Enable passthrough to copy the video and/or audio directly from the
 	// incoming stream and disable any transcoding.  It will ignore any of
 	// the below settings.
@@ -76,6 +83,43 @@ func (q *StreamOutputVariant) GetIsAudioPassthrough() bool {
 	return false
 }
 
+// GetName will return the human readable name for this stream output.
+func (q *StreamOutputVariant) GetName() string {
+	bitrate := getBitrateString(q.VideoBitrate)
+
+	if q.Name != "" {
+		return q.Name
+	} else if q.IsVideoPassthrough {
+		return "Source"
+	} else if q.ScaledHeight == 720 && q.ScaledWidth == 1080 {
+		return fmt.Sprintf("720p @%s", bitrate)
+	} else if q.ScaledHeight == 1080 && q.ScaledWidth == 1920 {
+		return fmt.Sprintf("1080p @%s", bitrate)
+	} else if q.ScaledHeight != 0 {
+		return fmt.Sprintf("%dh", q.ScaledHeight)
+	} else if q.ScaledWidth != 0 {
+		return fmt.Sprintf("%dw", q.ScaledWidth)
+	} else {
+		return fmt.Sprintf("%s@%dfps", bitrate, q.Framerate)
+	}
+}
+
+func getBitrateString(bitrate int) string {
+	if bitrate == 0 {
+		return ""
+	} else if bitrate < 1000 {
+		return fmt.Sprintf("%dKbps", bitrate)
+	} else if bitrate >= 1000 {
+		if math.Mod(float64(bitrate), 1000) == 0 {
+			return fmt.Sprintf("%dMbps", bitrate/1000.0)
+		} else {
+			return fmt.Sprintf("%.1fMbps", float32(bitrate)/1000.0)
+		}
+	}
+
+	return ""
+}
+
 // MarshalJSON is a custom JSON marshal function for video stream qualities.
 func (q *StreamOutputVariant) MarshalJSON() ([]byte, error) {
 	type Alias StreamOutputVariant