generic audio decoder framework implemented

flac-decoder.rkt

@@ -48,6 +48,8 @@
            (channels (hash-ref h 'channels))
            (block-size (hash-ref h 'blocksize)))
       (hash-set! h 'duration (flac-duration handle))
+      (let ((sample (hash-ref h 'number)))
+        (hash-set! h 'sample sample))
       (set! last-buffer buffer)
       (set! last-buf-len block-size)
       (hash-set! kinds type #t)
@@ -70,12 +72,17 @@
                       (hash-ref mh 'channels)
                       (hash-ref mh 'bits-per-sample)
                       (hash-ref mh 'total-samples))))
+             (let ((duration (exact->inexact
+                              (/ (hash-ref mh 'total-samples)
+                                 (hash-ref mh 'sample-rate)))))
+               (hash-set! mh 'duration duration))
              (set-flac-handle-stream-info! handle si)
              (let ((cb (flac-handle-cb-stream-info handle)))
                (when (procedure? cb)
-                 (cb si))))))
+                 (cb mh))))))
         )
-      ))
+      )
+    )
 
   (define (flac-read handle)
     (let* ((ffi-handler (flac-handle-ffi-decoder-handler handle))