From 9a7b7ac512a7d065fd4ed0744b323a195f94459f Mon Sep 17 00:00:00 2001
From: xh <xaver.himmelsbach@campoint.net>
Date: Wed, 14 Oct 2020 15:28:10 +0200
Subject: [PATCH 1/3] Adds method to append additional options

---
 ffmpeg/ffmpeg.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/ffmpeg/ffmpeg.go b/ffmpeg/ffmpeg.go
index 013bc6a..14fc2e8 100644
--- a/ffmpeg/ffmpeg.go
+++ b/ffmpeg/ffmpeg.go
@@ -134,6 +134,11 @@ func (t *Transcoder) WithOptions(opts transcoder.Options) transcoder.Transcoder
 	return t
 }
 
+func (t *Transcoder) WithAdditionalOptions(opts transcoder.Options) transcoder.Transcoder {
+	t.options = append(t.options, opts.GetStrArguments()...)
+	return t
+}
+
 // validate ...
 func (t *Transcoder) validate() error {
 	if t.config.FfmpegBinPath == "" {

From cb57beb39e9cc666f2008f10ca936cf7c63f6f05 Mon Sep 17 00:00:00 2001
From: xh <xaver.himmelsbach@campoint.net>
Date: Thu, 15 Oct 2020 11:56:09 +0200
Subject: [PATCH 2/3] make it possible to use multiple options and output files
 and make options set in the transcoder object available in general

---
 ffmpeg/ffmpeg.go | 55 +++++++++++++++++++++++++++++++++++++++---------
 transcoder.go    |  1 +
 2 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/ffmpeg/ffmpeg.go b/ffmpeg/ffmpeg.go
index 14fc2e8..3ff0487 100644
--- a/ffmpeg/ffmpeg.go
+++ b/ffmpeg/ffmpeg.go
@@ -21,8 +21,8 @@ import (
 type Transcoder struct {
 	config           *Config
 	input            string
-	output           string
-	options          []string
+	output           []string
+	options          [][]string
 	metadata         *Metadata
 	inputPipeReader  *io.ReadCloser
 	outputPipeReader *io.ReadCloser
@@ -55,11 +55,31 @@ func (t *Transcoder) Start(opts transcoder.Options) (<-chan transcoder.Progress,
 		return nil, err
 	}
 
-	// Get executable flags
+	// Append input file and standard options
 	args := append([]string{"-i", t.input}, opts.GetStrArguments()...)
+	outputLength := len(t.output)
+	optionsLength := len(t.options)
 
-	// Append output flag
-	args = append(args, []string{t.output}...)
+	if outputLength == 1 && optionsLength == 0 {
+		// Just append the 1 output file we've got
+		args = append(args, t.output[0])
+	} else {
+		for index, out := range t.output {
+			// Get executable flags
+			// If we are at the last output file but still have several options, append them all at once
+			if index == outputLength-1 && outputLength < optionsLength {
+				for i := index; i < len(t.options); i++ {
+					args = append(args, t.options[i]...)
+				}
+				// Otherwise just append the current options
+			} else {
+				args = append(args, t.options[index]...)
+			}
+
+			// Append output flag
+			args = append(args, out)
+		}
+	}
 
 	// Initialize command
 	cmd := exec.Command(t.config.FfmpegBinPath, args...)
@@ -106,7 +126,7 @@ func (t *Transcoder) Input(arg string) transcoder.Transcoder {
 
 // Output ...
 func (t *Transcoder) Output(arg string) transcoder.Transcoder {
-	t.output = arg
+	t.output = append(t.output, arg)
 	return t
 }
 
@@ -128,14 +148,15 @@ func (t *Transcoder) OutputPipe(w *io.WriteCloser, r *io.ReadCloser) transcoder.
 	return t
 }
 
-// WithOptions ...
+// WithOptions Sets the options object
 func (t *Transcoder) WithOptions(opts transcoder.Options) transcoder.Transcoder {
-	t.options = opts.GetStrArguments()
+	t.options = [][]string{opts.GetStrArguments()}
 	return t
 }
 
+// WithAdditionalOptions Appends an additional options object
 func (t *Transcoder) WithAdditionalOptions(opts transcoder.Options) transcoder.Transcoder {
-	t.options = append(t.options, opts.GetStrArguments()...)
+	t.options = append(t.options, opts.GetStrArguments())
 	return t
 }
 
@@ -149,10 +170,24 @@ func (t *Transcoder) validate() error {
 		return errors.New("missing input option")
 	}
 
-	if t.output == "" {
+	outputLength := len(t.output)
+
+	if outputLength == 0 {
 		return errors.New("missing output option")
 	}
 
+	// length of output files being greater than length of options would produce an invalid ffmpeg command
+	// unless there is only 1 output file, which obviously wouldn't be a problem
+	if outputLength > len(t.options) && outputLength != 1 {
+		return errors.New("number of options and output files does not match")
+	}
+
+	for index, output := range t.output {
+		if output == "" {
+			return errors.New(fmt.Sprintf("output at index %d is an empty string", index))
+		}
+	}
+
 	return nil
 }
 
diff --git a/transcoder.go b/transcoder.go
index a4da0b6..012055c 100644
--- a/transcoder.go
+++ b/transcoder.go
@@ -10,4 +10,5 @@ type Transcoder interface {
 	Output(o string) Transcoder
 	OutputPipe(w *io.WriteCloser, r *io.ReadCloser) Transcoder
 	WithOptions(opts Options) Transcoder
+	WithAdditionalOptions(opts Options) Transcoder
 }

From 10c7d3155d72f80992e34b4abd339798b0ec8465 Mon Sep 17 00:00:00 2001
From: xh <xaver.himmelsbach@campoint.net>
Date: Thu, 15 Oct 2020 14:31:00 +0200
Subject: [PATCH 3/3] replace error.New(fmt.Sprintf) with fmt.Errorf

---
 ffmpeg/ffmpeg.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ffmpeg/ffmpeg.go b/ffmpeg/ffmpeg.go
index 3ff0487..9ac83ab 100644
--- a/ffmpeg/ffmpeg.go
+++ b/ffmpeg/ffmpeg.go
@@ -184,7 +184,7 @@ func (t *Transcoder) validate() error {
 
 	for index, output := range t.output {
 		if output == "" {
-			return errors.New(fmt.Sprintf("output at index %d is an empty string", index))
+			return fmt.Errorf("output at index %d is an empty string", index)
 		}
 	}