142 lines
4.7 KiB
Racket
142 lines
4.7 KiB
Racket
(module mp3-decoder racket/base
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(require ffi/unsafe
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"libmpg123-ffi.rkt"
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"private/utils.rkt"
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(prefix-in fin: finalizer)
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)
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(provide mp3-open
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mp3-valid?
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mp3-read
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mp3-stop
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mp3-seek
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)
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(define-struct mp3-handle
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(if cb-info cb-audio
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(stop #:mutable)
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(seek #:mutable)
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(reading #:mutable)
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(format #:mutable)
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)
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#:transparent
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)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Functions to do the good stuff
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define mp3-handles '())
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(register-finalizer mp3-handles
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(λ (handles)
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(for-each (λ (handle)
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(handle 'delete)) handles)))
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(define (mp3-valid? mp3-file)
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#t)
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(define audio-type 'mp3)
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(define (report-format handle current-pcm-pos)
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((mp3-handle-cb-info handle) (mp3-handle-format handle)))
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(define (give-audio handle info pos buffer size)
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(let ((h (mp3-handle-format handle)))
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(hash-set! h 'sample pos)
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(hash-set! h 'current-time (exact->inexact (/ pos (hash-ref h 'sample-rate))))
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((mp3-handle-cb-audio handle) h buffer size)))
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(define (mp3-open mp3-file* cb-stream-info cb-audio)
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(let ((mp3-file (if (path? mp3-file*) (path->string mp3-file*) mp3-file*)))
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(if (file-exists? mp3-file)
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(let ((handler (if (null? mp3-handles)
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(let ((h (mpg123-ffi-decoder-handler)))
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(h 'new)
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h)
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(let ((h (car mp3-handles)))
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(set! mp3-handles (cdr mp3-handles))
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h))))
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(handler 'init mp3-file)
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(let ((h (make-mp3-handle handler
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cb-stream-info
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cb-audio
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#f
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#f
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#f
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#f
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)))
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(handler 'format
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(λ (rate channels sample-bits sample-bytes pcm-length)
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(let ((f (make-hash)))
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(hash-set! f 'duration (exact->inexact (/ pcm-length rate)))
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(hash-set! f 'sample-rate rate)
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(hash-set! f 'channels channels)
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(hash-set! f 'bits-per-sample sample-bits)
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(hash-set! f 'bytes-per-sample sample-bytes)
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(hash-set! f 'total-samples pcm-length)
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(set-mp3-handle-format! h f)
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)
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)
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)
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(report-format h 0)
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h))
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#f)))
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(define (mp3-read handle)
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(let* ((ffi-handler (mp3-handle-if handle))
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(cb-info (mp3-handle-cb-info handle))
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(cb-audio (mp3-handle-cb-audio handle))
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)
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(set-mp3-handle-reading! handle #t)
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(let loop ()
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(if (eq? (mp3-handle-stop handle) #t)
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(begin
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(dbg-sound "Stopping mp3 decoding")
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(set-mp3-handle-reading! handle #f)
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'stopped-reading
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)
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(begin
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(unless (eq? (mp3-handle-seek handle) #f)
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(dbg-sound "Seeking to ~a" (mp3-handle-seek handle))
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(ffi-handler 'seek (mp3-handle-seek handle))
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(set-mp3-handle-seek! handle #f))
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(ffi-handler 'read
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(λ (info pos buffer size)
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(if (eq? info 'done)
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(set-mp3-handle-stop! handle #t)
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(give-audio handle info pos buffer size)
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))
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)
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(loop)
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)
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))
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(ffi-handler 'close)
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(set! mp3-handles (cons ffi-handler mp3-handles))
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)
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)
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(define (mp3-seek handle percentage)
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(let ((fmt (mp3-handle-format handle)))
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(let ((total-samples (hash-ref fmt 'total-samples)))
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(unless (or
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(eq? total-samples #f)
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(= total-samples -1))
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(let ((sample (inexact->exact (round (* (exact->inexact (/ percentage 100.0)) total-samples)))))
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(set-mp3-handle-seek! handle sample))
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)
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)
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)
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)
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(define (mp3-stop handle)
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(set-mp3-handle-stop! handle #t)
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(while (mp3-handle-reading handle)
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(sleep 0.01))
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)
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); end of module
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