add foramt chose for subtitlse

goutubedl.go

@@ -232,6 +232,7 @@ type Options struct {
 	DownloadThumbnail       bool
 	DownloadSubtitles       bool
 	DownloadSubtitlesLang   []string
+	DownloadSubtitlesFormat string
 	DownloadSections        string // --download-sections
 	Impersonate             string // --impersonate
 
@@ -491,6 +492,9 @@ func infoFromURL(
 		}
 
 		for _, caption := range info.AutomaticCaptions[lang] {
+			if caption.Ext != options.DownloadSubtitlesFormat {
+				continue
+			}
 			resp, respErr := get(caption.URL)
 			if respErr == nil {
 				buf, err := io.ReadAll(resp.Body)