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trying to overcome gapless problems with mpg123 (very small tick left) and facilitate output to wav

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Hans Dijkema
2026-04-23 11:03:47 +02:00
parent 4bbfa43501
commit 3fd5fdbdd5
5 changed files with 120 additions and 77 deletions
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mp3-decoder.rkt
+48 -32
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@@ -28,37 +28,52 @@
;; Functions to do the good stuff
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define mp3-handles '())
(register-finalizer mp3-handles
(λ (handles)
(for-each (λ (handle)
(handle 'delete)) handles)))
(define (mp3-valid? mp3-file)
#t)
(define audio-type 'mp3)
(define last-rate 44200) ; An assumption for if we've got nothing
(define last-channels 2) ; An assumption for if we've got nothing
(define last-bits 16) ; An assumption for if we've got nothing
(define (correct-format-hash h)
(let ((rate (hash-ref h 'sample-rate #f)))
(when (eq? rate #f)
(hash-set! h 'sample-rate last-rate)))
(let ((channels (hash-ref h 'channels #f)))
(when (eq? channels #f)
(hash-set! h 'channels last-channels)))
(let ((bits (hash-ref h 'bits-per-sample #f)))
(when (eq? bits #f)
(hash-set! h 'bits-per-sample last-bits)))
(let ((total-samples (hash-ref h 'total-samples #f)))
(when (eq? total-samples #f)
(hash-set! h 'total-samples 0)
(hash-set! h 'duration 0)))
)
(define (report-format handle current-pcm-pos)
(dbg-sound "Reporting format at pcm-pos: ~a" current-pcm-pos)
(let ((h (mp3-handle-format handle)))
(set! last-rate (hash-ref h 'sample-rate))
(set! last-channels (hash-ref h 'channels))
(set! last-bits (hash-ref h 'bits-per-sample)))
((mp3-handle-cb-info handle) (mp3-handle-format handle)))
(define (give-audio handle info pos buffer size)
(let ((h (mp3-handle-format handle)))
(correct-format-hash h)
(hash-set! h 'sample pos)
(hash-set! h 'current-time (exact->inexact (/ pos (hash-ref h 'sample-rate))))
(let ((sample-rate (hash-ref h 'sample-rate last-rate)))
(hash-set! h 'current-time (exact->inexact (/ pos sample-rate))))
((mp3-handle-cb-audio handle) h buffer size)))
(define (mp3-open mp3-file* cb-stream-info cb-audio)
(let ((mp3-file (if (path? mp3-file*) (path->string mp3-file*) mp3-file*)))
(if (file-exists? mp3-file)
(let ((handler (if (null? mp3-handles)
(let ((h (mpg123-ffi-decoder-handler)))
(h 'new)
h)
(let ((h (car mp3-handles)))
(set! mp3-handles (cdr mp3-handles))
h))))
(let ((handler (mpg123-ffi-decoder-handler)))
(handler 'new)
(handler 'init mp3-file)
(let ((h (make-mp3-handle handler
cb-stream-info
@@ -66,26 +81,25 @@
#f
#f
#f
#f
(make-hash)
)))
(handler 'format
(λ (rate channels sample-bits sample-bytes pcm-length)
(let ((f (make-hash)))
(hash-set! f 'duration (exact->inexact (/ pcm-length rate)))
(hash-set! f 'sample-rate rate)
(hash-set! f 'channels channels)
(hash-set! f 'bits-per-sample sample-bits)
(hash-set! f 'bytes-per-sample sample-bytes)
(hash-set! f 'total-samples pcm-length)
(set-mp3-handle-format! h f)
)
)
)
(report-format h 0)
h))
#f)))
(define (handle-format handle pcm-pos rate channels sample-bits sample-bytes pcm-length)
(let ((f (make-hash)))
(hash-set! f 'duration (exact->inexact (/ pcm-length rate)))
(hash-set! f 'sample-rate rate)
(hash-set! f 'channels channels)
(hash-set! f 'bits-per-sample sample-bits)
(hash-set! f 'bytes-per-sample sample-bytes)
(hash-set! f 'total-samples pcm-length)
(set-mp3-handle-format! handle f)
)
(report-format handle pcm-pos)
)
(define (mp3-read handle)
(let* ((ffi-handler (mp3-handle-if handle))
(cb-info (mp3-handle-cb-info handle))
@@ -110,18 +124,20 @@
(set-mp3-handle-stop! handle #t)
(give-audio handle info pos buffer size)
))
(λ (pcm-pos rate channels sample-bits sample-bytes pcm-length)
(handle-format handle pcm-pos rate channels sample-bits sample-bytes pcm-length))
)
(loop)
)
))
(ffi-handler 'close)
(set! mp3-handles (cons ffi-handler mp3-handles))
(ffi-handler 'delete)
)
)
(define (mp3-seek handle percentage)
(let ((fmt (mp3-handle-format handle)))
(let ((total-samples (hash-ref fmt 'total-samples)))
(let ((total-samples (hash-ref fmt 'total-samples 0)))
(unless (or
(eq? total-samples #f)
(= total-samples -1))