Audio Encoder laag.

2026-06-08 10:27:05 +02:00
parent 696ef1b978
commit 444d62edac
7 changed files with 836 additions and 1 deletions
@@ -0,0 +1,82 @@
+(module flac-encoder racket/base
+
+  (require "libflac-ffi.rkt"
+           "flac-definitions.rkt")
+
+  (provide flac-encoder-available?
+           flac-encoder-default-settings
+           flac-encoder-prepare-settings
+           flac-encoder-open
+           flac-encoder-write
+           flac-encoder-finish)
+
+  (define (flac-encoder-available?) #t)
+
+  (define (copy-hash h)
+    (let ((out (make-hash)))
+      (for-each (lambda (k) (hash-set! out k (hash-ref h k))) (hash-keys h))
+      out))
+
+  (define (hash-ref/default h k default)
+    (if (hash-has-key? h k) (hash-ref h k) default))
+
+  (define (hash-merge base override)
+    (let ((out (copy-hash base)))
+      (when (hash? override)
+        (for-each (lambda (k) (hash-set! out k (hash-ref override k))) (hash-keys override)))
+      out))
+
+  (define (flac-encoder-default-settings)
+    (make-hash '((compression-level . 5)
+                 (verify? . #f)
+                 (blocksize . 0))))
+
+  (define (safe-flac-bits bits)
+    (cond [(and (integer? bits) (or (= bits 8) (= bits 12) (= bits 16) (= bits 20) (= bits 24))) bits]
+          [(and (integer? bits) (< bits 16)) 16]
+          [else 24]))
+
+  (define (flac-encoder-prepare-settings settings format)
+    (let* ((base (flac-encoder-default-settings))
+           (h (hash-merge base settings))
+           ;; In encoder settings, 'sample-rate means the requested output rate.
+           ;; 'target-sample-rate is accepted as an explicit alias for readability.
+           (rate (hash-ref/default h 'target-sample-rate
+                                   (hash-ref/default h 'sample-rate (hash-ref format 'sample-rate))))
+           (channels (hash-ref/default h 'target-channels
+                                       (hash-ref/default h 'channels (hash-ref format 'channels))))
+           (bits0 (hash-ref/default h 'target-bits-per-sample
+                                    (hash-ref/default h 'bits-per-sample
+                                                      (hash-ref/default format 'bits-per-sample 24))))
+           (bits (safe-flac-bits bits0))
+           (total (hash-ref/default h 'total-samples (hash-ref/default format 'total-samples #f))))
+      (hash-set! h 'sample-rate rate)
+      (hash-set! h 'channels channels)
+      (hash-set! h 'bits-per-sample bits)
+      (when (hash-has-key? h 'target-sample-rate) (hash-remove! h 'target-sample-rate))
+      (when (hash-has-key? h 'target-channels) (hash-remove! h 'target-channels))
+      (when (hash-has-key? h 'target-bits-per-sample) (hash-remove! h 'target-bits-per-sample))
+      (when (and total (integer? total) (>= total 0)) (hash-set! h 'total-samples total))
+      (unless (hash-has-key? h 'streamable-subset?) (hash-set! h 'streamable-subset? (<= bits 24)))
+      h))
+
+  (define (flac-encoder-open output-file settings format)
+    (let* ((file (if (path? output-file) (path->string output-file) output-file))
+           (resolved (flac-encoder-prepare-settings settings format))
+           (handler (flac-ffi-encoder-handler)))
+      (handler 'new)
+      (handler 'configure resolved)
+      (handler 'init file)
+      (make-flac-encoder-handle handler resolved format file)))
+
+  (define (flac-encoder-write handle buf-info buffer buf-len)
+    ((flac-encoder-handle-ffi-encoder-handler handle) 'write buffer buf-len buf-info))
+
+  (define (flac-encoder-finish handle)
+    (let ((handler (flac-encoder-handle-ffi-encoder-handler handle)))
+      (dynamic-wind
+       void
+       (lambda () (handler 'finish))
+       (lambda () (handler 'delete)))))
+
+  ) ; end of module