diff --git a/bbb-download.go b/bbb-download.go
index 604a4cc..2420c35 100644
--- a/bbb-download.go
+++ b/bbb-download.go
@@ -143,7 +143,7 @@ func main() {
 			"-i", path.Join(presentationId, imgnames[j]),
 			"-t", fmt.Sprint(durations[j]),
 			"-pix_fmt", "yuv420p",
-			"-vf", "scale=-1:720",
+			"-vf", "scale=-1:1080",
 			path.Join(presentationId, vidnames[j]))
 		err = cmd.Run()
 		if err != nil {
@@ -188,101 +188,59 @@ func main() {
 	fmt.Println("slide videos merged")
 
 	// download webcams
+	webcamsFile := ""
 	fmt.Println("downloading webcams")
 	err = DownloadFile(path.Join(presentationId, "webcams.webm"), webcamsWebmUrl)
 	if err != nil {
-		err = DownloadFile(path.Join(presentationId, "orig-webcams.mp4"), webcamsMp4Url)
+		err = DownloadFile(path.Join(presentationId, "webcams.mp4"), webcamsMp4Url)
 		if err != nil {
-			fmt.Println("Failed to download webcams:", err.Error())
-			return
-		}
-		cmd = exec.Command("ffmpeg",
-			"-i", path.Join(presentationId, "orig-webcams.mp4"),
-			"-framerate", "1",
-			"-q:a", "0",
-			"-q:v", "0",
-			"-vf", "scale=-1:720",
-			path.Join(presentationId, "webcams.mp4"))
-		err = cmd.Run()
-		if err != nil {
-			fmt.Println("Failed to convert orig-webcams.mp4 to MP4:", err.Error())
-			return
+			fmt.Println("No webcams")
+		} else {
+			fmt.Println("webcams.mp4 file is downloaded")
+			webcamsFile = path.Join(presentationId, "webcams.mp4")
 		}
 	} else {
-		// Successful download, convert to MP4
 		fmt.Println("webcams.webm file is downloaded")
-		fmt.Println("converting webcams.webm to webcams.mp4")
-		cmd = exec.Command("ffmpeg",
-			"-i", path.Join(presentationId, "webcams.webm"),
-			"-framerate", "1",
-			"-q:a", "0",
-			"-q:v", "0",
-			"-vf", "scale=-1:720",
-			path.Join(presentationId, "webcams.mp4"))
-		err = cmd.Run()
-		if err != nil {
-			fmt.Println("Failed to convert webcams.webm to MP4:", err.Error())
-			return
-		}
+		webcamsFile = path.Join(presentationId, "webcams.webm")
 	}
 
 	// download deskshare
-	deskshare := true
+	deskshareFile := ""
 	fmt.Println("downloading deskshare")
 	err = DownloadFile(path.Join(presentationId, "deskshare.webm"), deskshareWebmUrl)
 	if err != nil {
-		err = DownloadFile(path.Join(presentationId, "orig-deskshare.mp4"), deskshareMp4Url)
+		err = DownloadFile(path.Join(presentationId, "deskshare.mp4"), deskshareMp4Url)
 		if err != nil {
 			fmt.Println("No deskshare")
-			deskshare = false
 		} else {
-			cmd = exec.Command("ffmpeg",
-				"-i", path.Join(presentationId, "orig-deskshare.mp4"),
-				"-framerate", "1",
-				"-q:a", "0",
-				"-q:v", "0",
-				"-vf", "scale=-1:720",
-				path.Join(presentationId, "deskshare.mp4"))
-			err = cmd.Run()
-			if err != nil {
-				fmt.Println("Failed to convert orig-deskshare.mp4 to MP4:", err.Error())
-				return
-			}
+			fmt.Println("deskshare.mp4 file is downloaded")
+			deskshareFile = path.Join(presentationId, "deskshare.mp4")
 		}
 	} else {
-		// Successful download, convert to MP4
 		fmt.Println("deskshare.webm file is downloaded")
-		fmt.Println("converting deskshare.webm to deskshare.mp4")
-		cmd = exec.Command("ffmpeg",
-			"-i", path.Join(presentationId, "deskshare.webm"),
-			"-framerate", "1",
-			"-q:a", "0",
-			"-q:v", "0",
-			"-vf", "scale=-1:720",
-			path.Join(presentationId, "deskshare.mp4"))
-		err = cmd.Run()
-		if err != nil {
-			fmt.Println("Failed to convert deskshare.webm to MP4:", err.Error())
-			return
-		}
+		deskshareFile = path.Join(presentationId, "deskshare.webm")
 	}
 
 	fmt.Println("merging slides, webcams and deskshare side by side")
-	cmd = exec.Command("ffmpeg",
-		"-i", path.Join(presentationId, "slides.mp4"),
-		"-i", path.Join(presentationId, "webcams.mp4"),
-		"-i", path.Join(presentationId, "deskshare.mp4"),
-		"-framerate", "1",
-		"-filter_complex", "hstack=inputs=3",
-		meetingName+".mp4")
-	if !deskshare {
-		cmd = exec.Command("ffmpeg",
-			"-i", path.Join(presentationId, "slides.mp4"),
-			"-i", path.Join(presentationId, "webcams.mp4"),
-			"-framerate", "1",
-			"-filter_complex", "hstack=inputs=2",
-			meetingName+".mp4")
+	streams := 1
+	cmd = exec.Command("ffmpeg", "-i", path.Join(presentationId, "slides.mp4"))
+	if webcamsFile != "" {
+		cmd.Args = append(cmd.Args, "-i")
+		cmd.Args = append(cmd.Args, webcamsFile)
+		streams++
 	}
+	if deskshareFile != "" {
+		cmd.Args = append(cmd.Args, "-i")
+		cmd.Args = append(cmd.Args, deskshareFile)
+		streams++
+	}
+	cmd.Args = append(cmd.Args, "-c")
+	cmd.Args = append(cmd.Args, "copy")
+	for i := 0; i < streams; i++ {
+		cmd.Args = append(cmd.Args, "-map")
+		cmd.Args = append(cmd.Args, strconv.Itoa(i))
+	}
+	cmd.Args = append(cmd.Args, meetingName+".mkv")
 	err = cmd.Run()
 	if err != nil {
 		fmt.Println("Failed to merge slides and webcams:", err.Error())