Added capability information

audio-sniffer.rkt

@@ -10,6 +10,7 @@
          audio-sniff-format
          audio-sniff-format/extension
          audio-sniff-extension
+         audio-format-for-extension
          audio-format-matches?
          audio-format-known?)
 
@@ -46,6 +47,30 @@
              (substring s 1)
              s))])))
 
+(define (audio-format-for-extension* extension)
+  (let* ((text (string-downcase
+                (format "~a" extension)))
+         (normalized
+          (if (string-prefix? text ".")
+              (substring text 1)
+              text)))
+    (case (string->symbol normalized)
+      [(mp3 mp2 mp1) 'mp3]
+      [(flac) 'flac]
+      [(ogg oga) 'ogg]
+      [(opus) 'opus]
+      [(wav wave) 'wav]
+      [(aif aiff aifc) 'aiff]
+      [(m4a mp4 m4b m4p) 'mp4]
+      [(aac) 'aac]
+      [(alac) 'alac]
+      [(ac3) 'ac3]
+      [(ape) 'ape]
+      [(wv wvp wvpk wavpack) 'wavpack]
+      [(wma asf) 'wma]
+      [(webm mka mkv) 'matroska]
+      [else 'unknown])))
+
 (define (file-readable-status file)
   (cond
     [(not (file-exists? file)) 'file-not-found]
@@ -294,22 +319,9 @@
        fmt]
       [(not (eq? fmt 'unknown)) fmt]
       [else
-       (case (string->symbol (or (audio-sniff-extension* file) ""))
-         [(mp3 mp2 mp1) 'mp3]
-         [(flac) 'flac]
-         [(ogg oga) 'ogg]
-         [(opus) 'opus]
-         [(wav wave) 'wav]
-         [(aif aiff aifc) 'aiff]
-         [(m4a mp4 m4b m4p) 'mp4]
-         [(aac) 'aac]
-         [(alac) 'alac]
-         [(ac3) 'ac3]
-         [(ape) 'ape]
-         [(wv wvp wvpk wavpack) 'wavpack]
-         [(wma asf) 'wma]
-         [(webm mka mkv) 'matroska]
-         [else 'unknown])])))
+       (audio-format-for-extension*
+        (or (audio-sniff-extension* file)
+            ""))])))
 
 (define (audio-format-known?* fmt)
   (not (eq? (memq fmt audio-formats) #f)))
@@ -321,6 +333,10 @@
   (-> path-string? (or/c string? #f))
   (audio-sniff-extension* file))
 
+(define/contract (audio-format-for-extension extension)
+  (-> (or/c string? symbol?) audio-format?)
+  (audio-format-for-extension* extension))
+
 (define/contract (audio-sniff-format file)
   (-> path-string? audio-format?)
   (audio-sniff-format* file))