add video config evaluation.

internal/types/capture.go

@@ -1,7 +1,12 @@
 package types
 
 import (
+	"math"
+	"strings"
+	"fmt"
+
 	"github.com/pion/webrtc/v3/pkg/media"
+	"github.com/PaesslerAG/gval"
 
 	"demodesk/neko/internal/types/codec"
 )
@@ -43,3 +48,98 @@ type CaptureManager interface {
 	Video(videoID string) (StreamManager, bool)
 	VideoIDs() []string
 }
+
+type VideoConfig struct {
+	Codec       string            `mapstructure:"codec"`
+	Width       string            `mapstructure:"width"`        // expression
+	Height      string            `mapstructure:"height"`       // expression
+	Fps         string            `mapstructure:"fps"`          // expression
+	GstEncoder  string            `mapstructure:"gst_encoder"`
+	GstParams   map[string]string `mapstructure:"gst_params"`   // map of expressions
+	GstPipeline string            `mapstructure:"gst_pipeline"`
+}
+
+func (config *VideoConfig) GetCodec() (codec.RTPCodec, error) {
+	switch strings.ToLower(config.Codec) {
+	case "vp8":
+		return codec.VP8(), nil
+	case "vp9":
+		return codec.VP9(), nil
+	case "h264":
+		return codec.H264(), nil
+	default:
+		return codec.RTPCodec{}, fmt.Errorf("unknown codec")
+	}
+}
+
+func (config *VideoConfig) GetPipeline(screen ScreenSize) (string, error) {
+	if config.GstPipeline != "" {
+		return config.GstPipeline, nil
+	}
+
+	values := map[string]interface{}{
+		"width":  screen.Width,
+		"height": screen.Height,
+		"fps":    screen.Rate,
+	}
+
+	language := []gval.Language{
+		gval.Function("round", func(args ...interface{}) (interface{}, error) {
+			return (int)(math.Round(args[0].(float64))), nil
+		}),
+	}
+
+	// get fps pipeline
+	fpsPipeline := "video/x-raw ! videoconvert ! queue"
+	if config.Fps != "" {
+		var err error
+		val, err := gval.Evaluate(config.Fps, values, language...)
+		if err != nil {
+			return "", err
+		}
+	
+		if val != nil {
+			// TODO: To fraction.
+			fpsPipeline = fmt.Sprintf("video/x-raw,framerate=%v ! videoconvert ! queue", val)
+		}
+	}
+
+	// get scale pipeline
+	scalePipeline := ""
+	if config.Width != "" && config.Height != "" {
+		w, err := gval.Evaluate(config.Width, values, language...)
+		if err != nil {
+			return "", err
+		}
+
+		h, err := gval.Evaluate(config.Height, values, language...)
+		if err != nil {
+			return "", err
+		}
+
+		if w != nil && h != nil {
+			scalePipeline = fmt.Sprintf("! videoscale ! video/x-raw,width=%v,height=%v ! queue", w, h)
+		}
+	}
+
+	// get encoder pipeline
+	encPipeline := fmt.Sprintf("! %s", config.GstEncoder)
+	for key, expr := range config.GstParams {
+		if expr == "" {
+			continue
+		}
+
+		val, err := gval.Evaluate(expr, values, language...)
+		if err != nil {
+			return "", err
+		}
+
+		if val != nil {
+			encPipeline += fmt.Sprintf(" %s=%v", key, val)
+		} else {
+			encPipeline += fmt.Sprintf(" %s=%s", key, expr)
+		}
+	}
+
+	return fmt.Sprintf("%s %s %s", fpsPipeline, scalePipeline, encPipeline), nil
+}