fix merge output; support error to stdout

examples/example_test.go

@@ -49,3 +49,12 @@ func TestSimpleS3StreamExample(t *testing.T) {
 		Run()
 	assert.Nil(t, err)
 }
+
+func TestExampleMultipleOutput(t *testing.T) {
+	input := ffmpeg.Input("./sample_data/in1.mp4").Split()
+	out1 := input.Get("0").Filter("scale", ffmpeg.Args{"1920:-1"}).Output("./sample_data/1920.mp4", ffmpeg.KwArgs{"b:v": "5000k"})
+	out2 := input.Get("1").Filter("scale", ffmpeg.Args{"1280:-1"}).Output("./sample_data/1280.mp4", ffmpeg.KwArgs{"b:v": "2800k"})
+
+	err := ffmpeg.MergeOutputs(out1, out2).OverWriteOutput().ErrorToStdOut().Run()
+	assert.Nil(t, err)
+}

ffmpeg.go

@@ -52,10 +52,7 @@ func (s *Stream) OverwriteOutput(stream *Stream) *Stream {
 }
 
 // Include all given outputs in one ffmpeg command line
-func (s *Stream) MergeOutputs(streams ...*Stream) *Stream {
-	if s.Type != "OutputStream" {
-		panic("cannot merge outputs on non-OutputStream")
-	}
+func MergeOutputs(streams ...*Stream) *Stream {
 	return NewMergeOutputsNode("merge_output", streams).Stream("", "")
 }
 

node.go

@@ -260,7 +260,7 @@ func (n *Node) GetFilter(outgoingEdges []DagEdge) string {
 	if n.name == "split" || n.name == "asplit" {
 		args = []string{fmt.Sprintf("%d", len(outgoingEdges))}
 	}
-	args = Args(args).EscapeWith("\\'=:")
+	// args = Args(args).EscapeWith("\\'=:")
 	for _, k := range kwargs.EscapeWith("\\'=:").SortedKeys() {
 		v := getString(kwargs[k])
 		if v != "" {

run.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"sort"
 	"strings"
@@ -225,6 +226,15 @@ func (s *Stream) WithOutput(out ...io.Writer) *Stream {
 	return s
 }
 
+func (s *Stream) WithErrorOutput(out io.Writer) *Stream {
+	s.Context = context.WithValue(s.Context, "Stderr", out)
+	return s
+}
+
+func (s *Stream) ErrorToStdOut() *Stream {
+	return s.WithErrorOutput(os.Stdout)
+}
+
 // for test
 func (s *Stream) Compile() *exec.Cmd {
 	args := s.GetArgs()