diff --git a/data.go b/data.go
index 1555411..f5cf68d 100644
--- a/data.go
+++ b/data.go
@@ -6,16 +6,17 @@ import (
 )
 
 type Anime struct {
-	Name        string
-	Length      int64
-	Size        int64
-	Width       int
-	Height      int
-	FrameRate   float64
-	TotalFrames int
-	Streams     []*ffprobe.Stream
-	Path        string
-	Status      AnimeStatus
+	Name               string
+	Length             int64
+	Size               int64
+	Width              int
+	Height             int
+	FrameRate          float64
+	TotalFrames        int
+	HasSubtitlesStream bool
+	Streams            []*ffprobe.Stream
+	Path               string
+	Status             AnimeStatus
 }
 
 type Shader struct {
diff --git a/gui.go b/gui.go
index a4783b2..57a62bc 100644
--- a/gui.go
+++ b/gui.go
@@ -21,7 +21,7 @@ const encoderTooltip = "Codec for encoding output file. In most cases GPU based
 	"AV1 is compatible only with RTX 4000+ and RX 6500XT+"
 const crfTooltip = "Constant Rate Factor parameter encoder. \nDon't set it too high - file will be very big. " +
 	"\n\nCorrect values: 0 - 51 \nIf you don't know what to enter, leave it as 20"
-const outputFormatTooltip = "If your input file have subtitles stream (mainly in MKV files) you MUST select MKV as output, otherwise ffmpeg will throw error"
+const outputFormatTooltip = "If your input file contains subtitles streams you must use MKV as output format due to other formats limitations"
 const compatibilityModeTooltip = "Should be used only for compatibility troubleshooting, disables most of features"
 const debugModeTooltip = "Show more detailed logs, useful for troubleshooting and debugging"
 
@@ -160,18 +160,18 @@ LOOP:
 		divider, _ := strconv.ParseFloat(frameRateSplit[1], 64)
 
 		anime := Anime{
-			Name:        pathSplit[len(pathSplit)-1],
-			Length:      int64(data.Format.DurationSeconds * 1000),
-			Size:        file.Size(),
-			Width:       videoStream.Width,
-			Height:      videoStream.Height,
-			FrameRate:   base / divider,
-			TotalFrames: int((base / divider) * data.Format.DurationSeconds),
-			Path:        path,
-			Streams:     data.Streams,
-			Status:      NotStarted,
+			Name:               pathSplit[len(pathSplit)-1],
+			Length:             int64(data.Format.DurationSeconds * 1000),
+			Size:               file.Size(),
+			Width:              videoStream.Width,
+			Height:             videoStream.Height,
+			FrameRate:          base / divider,
+			TotalFrames:        int((base / divider) * data.Format.DurationSeconds),
+			HasSubtitlesStream: data.FirstSubtitleStream() != nil,
+			Path:               path,
+			Streams:            data.Streams,
+			Status:             NotStarted,
 		}
-
 		animeList = append(animeList, anime)
 		totalProgress = fmt.Sprintf("%d / %d", calcFinished(), len(animeList))
 		logMessage("Added file "+path, false)
diff --git a/main.go b/main.go
index f2df818..aff2998 100644
--- a/main.go
+++ b/main.go
@@ -150,6 +150,15 @@ func startProcessing() {
 		animeList[index].Status = Processing
 		g.Update()
 
+		if anime.HasSubtitlesStream && outputFormat != "mkv" {
+			animeList[index].Status = Error
+			buttonLabel = "Start"
+			processing = false
+			logMessage("File "+anime.Name+" contains subtitles stream, output format must be MKV", false)
+			g.Update()
+			return
+		}
+
 		outputPath := fmt.Sprintf("%s_upscaled.%s", strings.TrimSuffix(anime.Path, filepath.Ext(anime.Path)), strings.ToLower(outputFormat))
 		ffmpegParams := buildUpscalingParams(anime, resolution, shader, outputPath)