Encoder testing

audio-encoder.rkt

@@ -119,17 +119,17 @@
       (ensure-open! fmt)
       (set! frames-written (+ frames-written ((audio-encoder-write encoder) backend-handle fmt buffer buf-len))))
 
-    (define (ensure-flac-converter! input-format)
-      ;; FLAC encoding may be used as a sample-rate conversion target, for example
-      ;; 96 kHz -> 48 kHz.  That conversion is not a property of libFLAC itself;
-      ;; it must happen on the decoded PCM stream before process_interleaved.
-      (when (and (eq? kind 'flac)
-                 (eq? converter #f)
-                 (pcm-conversion-needed? input-format settings))
-        (set! converter (make-pcm-converter input-format settings))))
+    (define (ensure-converter! input-format)
+      ;; FLAC may need conversion because the caller requested a target sample
+      ;; rate or bit depth.  Opus is deliberately not routed through this
+      ;; converter by default: libopusenc accepts the source input rate and has
+      ;; its own resampler, and opus-encoder.rkt feeds it float PCM directly.
+      (when (and (eq? kind 'flac) (eq? converter #f))
+        (when (pcm-conversion-needed? input-format settings)
+          (set! converter (make-pcm-converter input-format settings)))))
 
     (define (write-converted! input-format buffer buf-len)
-      (ensure-flac-converter! input-format)
+      (ensure-converter! input-format)
       (cond [converter
              (let-values (((out out-samples) (pcm-converter-convert converter buffer buf-len input-format)))
                (when (> out-samples 0)