diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e043a20
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+examples/bin/
diff --git a/examples/build.sh b/examples/build.sh
index a7f2d9d..c705d04 100755
--- a/examples/build.sh
+++ b/examples/build.sh
@@ -12,3 +12,4 @@ go build -o bin/simple-transcode ./simple-transcode
 echo ""
 echo "Build complete!"
 echo "Run with: ./bin/simple-transcode <input> <output>"
+echo "Example: ./bin/simple-transcode test.mp4 output.mp4"
diff --git a/examples/simple-transcode/main.go b/examples/simple-transcode/main.go
index 65ad3fe..4727367 100644
--- a/examples/simple-transcode/main.go
+++ b/examples/simple-transcode/main.go
@@ -8,7 +8,7 @@ import (
 	"git.kingecg.top/kingecg/goffmpeg/pkg/ffmpeg"
 )
 
-// Simple transcoding example using goffmpeg library
+// Simple remuxing example using goffmpeg library
 func main() {
 	if len(os.Args) < 3 {
 		fmt.Println("Usage: simple-transcode <input> <output>")
@@ -26,50 +26,149 @@ func main() {
 	if err := ic.OpenInput(inputURL); err != nil {
 		log.Fatalf("Failed to open input %s: %v", inputURL, err)
 	}
-	defer ic.Close()
 
 	// Find stream info
 	if err := ic.FindStreamInfo(); err != nil {
 		log.Fatalf("Failed to find stream info: %v", err)
 	}
 
-	// Dump input format info
 	fmt.Printf("Input: %s\n", inputURL)
 	ic.DumpFormat(0, inputURL, false)
 
-	// Find video stream
-	videoStreams := ic.VideoStreams()
-	if len(videoStreams) == 0 {
-		log.Fatal("No video stream found in input")
-	}
-
-	vs := videoStreams[0]
-	fmt.Printf("Video stream index: %d\n", vs.Index())
-
-	// Get codec parameters
-	cp := vs.CodecParameters()
-	fmt.Printf("Codec type: %d, Codec ID: %d\n", cp.CodecType(), cp.CodecID())
-
-	// Create output context
+	// Guess output format
 	of := ffmpeg.GuessFormat("", outputURL)
 	if of == nil {
 		log.Fatalf("Failed to guess output format")
 	}
 
+	// Create output context
 	ofc, err := ffmpeg.AllocOutputContext(outputURL, of)
 	if err != nil {
 		log.Fatalf("Failed to allocate output context: %v", err)
 	}
 	defer ofc.Free()
 
-	// Copy stream from input to output
-	_, err = ofc.AddStream(nil)
-	if err != nil {
-		log.Fatalf("Failed to add stream: %v", err)
+	// Get input streams
+	inputStreams := ic.Streams()
+
+	// Process streams - select first video and audio only
+	var videoIdx, audioIdx int = -1, -1
+	streamCount := 0
+
+	for i, is := range inputStreams {
+		cp := is.CodecParameters()
+		if cp == nil {
+			continue
+		}
+
+		streamType := cp.CodecType()
+
+		// Skip non-video/audio
+		if streamType != ffmpeg.CodecTypeVideo && streamType != ffmpeg.CodecTypeAudio {
+			continue
+		}
+
+		// Skip duplicate audio
+		if streamType == ffmpeg.CodecTypeAudio && audioIdx >= 0 {
+			fmt.Printf("\nStream %d: audio (skipped - duplicate)\n", i)
+			continue
+		}
+
+		// Add stream with same codec (stream copy mode)
+		os, err := ofc.AddStream(nil)
+		if err != nil {
+			fmt.Printf("\nStream %d: failed to add stream: %v\n", i, err)
+			continue
+		}
+
+		// Copy codec parameters from input to output
+		if err := os.SetCodecParameters(cp); err != nil {
+			fmt.Printf("\nStream %d: failed to set codec parameters: %v\n", i, err)
+			continue
+		}
+
+		// Copy time base
+		tb := is.TimeBase()
+		os.SetTimeBase(tb)
+
+		if streamType == ffmpeg.CodecTypeVideo {
+			videoIdx = streamCount
+			fmt.Printf("\nStream %d: video (stream copy)\n", i)
+		} else {
+			audioIdx = streamCount
+			fmt.Printf("\nStream %d: audio (stream copy)\n", i)
+		}
+		streamCount++
+	}
+
+	if videoIdx < 0 && audioIdx < 0 {
+		log.Fatal("No supported streams found")
 	}
 
 	fmt.Printf("\nOutput: %s\n", outputURL)
-	fmt.Println("Transcoding setup complete. Use the library APIs to process frames.")
+	fmt.Printf("Output has %d streams\n", streamCount)
+	ofc.DumpFormat(0, outputURL, true)
 
-	_ = vs // vs is used for reference
+	// Open output file
+	if err := ofc.OpenOutput(outputURL); err != nil {
+		log.Fatalf("Failed to open output: %v", err)
+	}
+
+	// Write header
+	if err := ofc.WriteHeader(); err != nil {
+		log.Fatalf("Failed to write header: %v", err)
+	}
+
+	fmt.Println("\nRemuxing...")
+	pkt := ffmpeg.AllocPacket()
+	defer pkt.Free()
+
+	packetCount := 0
+	for {
+		err := ic.ReadPacket(pkt)
+		if err != nil {
+			break
+		}
+
+		pktStreamIdx := pkt.StreamIndex()
+
+		// Map input stream index to output stream index
+		var outStreamIdx int
+		if videoIdx >= 0 && audioIdx >= 0 {
+			// Both video and audio present
+			if pktStreamIdx == 0 {
+				outStreamIdx = videoIdx
+			} else if pktStreamIdx == 1 {
+				outStreamIdx = audioIdx
+			} else {
+				pkt.Unref()
+				continue
+			}
+		} else if videoIdx >= 0 {
+			outStreamIdx = videoIdx
+		} else {
+			outStreamIdx = audioIdx
+		}
+
+		pkt.SetStreamIndex(outStreamIdx)
+
+		if err := ofc.WritePacket(pkt); err != nil {
+			log.Printf("Warning: failed to write packet: %v", err)
+		}
+
+		pkt.Unref()
+		packetCount++
+
+		if packetCount%100 == 0 {
+			fmt.Printf("Processed %d packets...\n", packetCount)
+		}
+	}
+
+	// Write trailer
+	if err := ofc.WriteTrailer(); err != nil {
+		log.Fatalf("Failed to write trailer: %v", err)
+	}
+
+	fmt.Printf("\nRemuxing complete! Processed %d packets.\n", packetCount)
+	fmt.Printf("Output saved to: %s\n", outputURL)
 }
diff --git a/examples/simple-transcode/simple-transcode b/examples/simple-transcode/simple-transcode
new file mode 100755
index 0000000..94a6a9b
Binary files /dev/null and b/examples/simple-transcode/simple-transcode differ
diff --git a/pkg/ffmpeg/codec.go b/pkg/ffmpeg/codec.go
index 2ebb5dc..bedf3a0 100644
--- a/pkg/ffmpeg/codec.go
+++ b/pkg/ffmpeg/codec.go
@@ -195,6 +195,47 @@ func (c *Context) SetBitRate(br int64) {
 	}
 }
 
+// TimeBase returns the time base
+func (c *Context) TimeBase() Rational {
+	if c.ptr == nil {
+		return Rational{}
+	}
+	return Rational{
+		num: int(c.ptr.time_base.num),
+		den: int(c.ptr.time_base.den),
+	}
+}
+
+// SetTimeBase sets the time base
+func (c *Context) SetTimeBase(r Rational) {
+	if c.ptr != nil {
+		c.ptr.time_base.num = C.int(r.num)
+		c.ptr.time_base.den = C.int(r.den)
+	}
+}
+
+// SetChannelLayout sets the channel layout
+func (c *Context) SetChannelLayout(layout uint64) {
+	if c.ptr != nil {
+		c.ptr.channel_layout = C.uint64_t(layout)
+	}
+}
+
+// SetSampleRate sets the sample rate
+func (c *Context) SetSampleRate(rate int) {
+	if c.ptr != nil {
+		c.ptr.sample_rate = C.int(rate)
+	}
+}
+
+// Channels returns the number of channels
+func (c *Context) Channels() int {
+	if c.ptr == nil {
+		return 0
+	}
+	return int(c.ptr.channels)
+}
+
 // Open opens the codec
 func (c *Context) Open(codec *Codec) error {
 	if c.ptr == nil || codec == nil || codec.ptr == nil {
@@ -212,6 +253,23 @@ func (c *Context) Open(codec *Codec) error {
 	return nil
 }
 
+// CopyParameters copies parameters from CodecParameters to this context
+func (c *Context) CopyParameters(cp *CodecParameters) error {
+	if c.ptr == nil || cp == nil || cp.ptr == nil {
+		return ErrInvalidCodec
+	}
+
+	ret := C.avcodec_parameters_to_context(c.ptr, cp.ptr)
+	if ret < 0 {
+		return &FFmpegError{
+			Code:    int(ret),
+			Message: "failed to copy parameters",
+			Op:      "CopyParameters",
+		}
+	}
+	return nil
+}
+
 // SendPacket sends a packet to the decoder
 func (c *Context) SendPacket(pkt *Packet) error {
 	if c.ptr == nil {
diff --git a/pkg/ffmpeg/ffmpeg.go b/pkg/ffmpeg/ffmpeg.go
index adb79d1..1ce8131 100644
--- a/pkg/ffmpeg/ffmpeg.go
+++ b/pkg/ffmpeg/ffmpeg.go
@@ -238,6 +238,33 @@ func (s *Stream) SetCodecParameters(cp *CodecParameters) error {
 	return nil
 }
 
+// SetCodecContextParameters copies parameters from a codec context to this stream
+func (s *Stream) SetCodecContextParameters(cc *Context) error {
+	if s.ptr == nil || cc == nil || cc.ptr == nil {
+		return ErrInvalidCodec
+	}
+
+	// Manually copy fields from codec context to codec parameters
+	s.ptr.codecpar.codec_type = cc.ptr.codec_type
+	s.ptr.codecpar.codec_id = cc.ptr.codec_id
+	s.ptr.codecpar.bit_rate = cc.ptr.bit_rate
+	s.ptr.codecpar.width = cc.ptr.width
+	s.ptr.codecpar.height = cc.ptr.height
+
+	// Copy format based on codec type
+	if cc.ptr.codec_type == C.AVMEDIA_TYPE_VIDEO {
+		s.ptr.codecpar.format = C.int(cc.ptr.pix_fmt)
+	} else if cc.ptr.codec_type == C.AVMEDIA_TYPE_AUDIO {
+		s.ptr.codecpar.format = C.int(cc.ptr.sample_fmt)
+	}
+
+	s.ptr.codecpar.sample_rate = cc.ptr.sample_rate
+	s.ptr.codecpar.channels = cc.ptr.channels
+	s.ptr.codecpar.channel_layout = cc.ptr.channel_layout
+
+	return nil
+}
+
 // Codec returns the codec context (deprecated: use CodecParameters instead)
 func (s *Stream) Codec() *Context {
 	// In FFmpeg 4.0+, codec field was removed from AVStream
@@ -401,13 +428,18 @@ func AllocOutputContext(url string, fmt *OutputFormat) (*OutputFormatContext, er
 	return ofc, nil
 }
 
-// AddStream adds a new stream
+// AddStream adds a new stream with optional codec
 func (ofc *OutputFormatContext) AddStream(codec *Codec) (*Stream, error) {
-	if ofc.ptr == nil || codec == nil || codec.ptr == nil {
-		return nil, ErrInvalidCodec
+	if ofc.ptr == nil {
+		return nil, ErrInvalidOutput
 	}
 
-	stream := C.avformat_new_stream(ofc.ptr, codec.ptr)
+	var stream *C.AVStream
+	if codec != nil && codec.ptr != nil {
+		stream = C.avformat_new_stream(ofc.ptr, codec.ptr)
+	} else {
+		stream = C.avformat_new_stream(ofc.ptr, nil)
+	}
 	if stream == nil {
 		return nil, ErrInvalidCodec
 	}
@@ -422,6 +454,33 @@ func (ofc *OutputFormatContext) SetOformat(fmt *OutputFormat) {
 	}
 }
 
+// OpenOutput opens the output file
+func (ofc *OutputFormatContext) OpenOutput(url string) error {
+	if ofc.ptr == nil {
+		return ErrInvalidOutput
+	}
+
+	cURL := C.CString(url)
+	defer C.free(unsafe.Pointer(cURL))
+
+	ret := C.avio_open(&ofc.ptr.pb, cURL, C.AVIO_FLAG_WRITE)
+	if ret < 0 {
+		return &FFmpegError{
+			Code:    int(ret),
+			Message: "failed to open output",
+			Op:      "OpenOutput",
+		}
+	}
+	return nil
+}
+
+// CloseOutput closes the output file
+func (ofc *OutputFormatContext) CloseOutput() {
+	if ofc.ptr != nil && ofc.ptr.pb != nil {
+		C.avio_close(ofc.ptr.pb)
+	}
+}
+
 // DumpFormat dumps format info
 func (ofc *OutputFormatContext) DumpFormat(idx int, url string, isOutput bool) {
 	ofc.FormatContext.DumpFormat(idx, url, isOutput)
@@ -433,12 +492,6 @@ func (ofc *OutputFormatContext) WriteHeader() error {
 		return ErrInvalidOutput
 	}
 
-	if (unsafe.Pointer(ofc.ptr.pb) != nil) && (ofc.ptr.flags&C.AVFMT_NOFILE) == 0 {
-		// file handle has been created by the caller
-	} else {
-		// let avformat do it
-	}
-
 	ret := C.avformat_write_header(ofc.ptr, nil)
 	if ret < 0 {
 		return &FFmpegError{