91 lines
3.8 KiB
Racket
91 lines
3.8 KiB
Racket
(module flac-encoder racket/base
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(require "libflac-ffi.rkt"
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"flac-definitions.rkt")
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(provide flac-encoder-available?
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flac-encoder-default-settings
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flac-encoder-prepare-settings
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flac-encoder-open
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flac-encoder-write
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flac-encoder-finish)
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(define (flac-encoder-available?) #t)
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(define (copy-hash h)
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(let ((out (make-hash)))
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(for-each (lambda (k) (hash-set! out k (hash-ref h k))) (hash-keys h))
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out))
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(define (hash-ref/default h k default)
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(if (hash-has-key? h k) (hash-ref h k) default))
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(define (hash-merge base override)
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(let ((out (copy-hash base)))
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(when (hash? override)
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(for-each (lambda (k) (hash-set! out k (hash-ref override k))) (hash-keys override)))
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out))
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(define (flac-encoder-default-settings)
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(make-hash '((compression-level . 5)
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(verify? . #f)
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(blocksize . 0))))
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(define (source-value v source)
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(if (eq? v 'source) source v))
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(define (safe-flac-bits bits)
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(cond [(and (integer? bits) (or (= bits 8) (= bits 12) (= bits 16) (= bits 20) (= bits 24))) bits]
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[(and (integer? bits) (< bits 16)) 16]
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[else 24]))
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(define (flac-encoder-prepare-settings settings format)
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(let* ((base (flac-encoder-default-settings))
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(h (hash-merge base settings))
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;; In encoder settings, 'sample-rate means the requested output rate.
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;; 'target-sample-rate is accepted as an explicit alias for readability.
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(source-rate (hash-ref format 'sample-rate))
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(source-channels (hash-ref format 'channels))
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(source-bits (hash-ref/default format 'bits-per-sample 24))
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(rate (source-value (hash-ref/default h 'target-sample-rate
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(hash-ref/default h 'sample-rate source-rate))
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source-rate))
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(channels (source-value (hash-ref/default h 'target-channels
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(hash-ref/default h 'channels source-channels))
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source-channels))
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(bits0 (source-value (hash-ref/default h 'target-bits-per-sample
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(hash-ref/default h 'bits-per-sample source-bits))
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source-bits))
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(bits (safe-flac-bits bits0))
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(total (hash-ref/default h 'total-samples (hash-ref/default format 'total-samples #f))))
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(hash-set! h 'sample-rate rate)
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(hash-set! h 'channels channels)
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(hash-set! h 'bits-per-sample bits)
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(when (hash-has-key? h 'target-sample-rate) (hash-remove! h 'target-sample-rate))
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(when (hash-has-key? h 'target-channels) (hash-remove! h 'target-channels))
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(when (hash-has-key? h 'target-bits-per-sample) (hash-remove! h 'target-bits-per-sample))
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(when (and total (integer? total) (>= total 0)) (hash-set! h 'total-samples total))
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(unless (hash-has-key? h 'streamable-subset?) (hash-set! h 'streamable-subset? (<= bits 24)))
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h))
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(define (flac-encoder-open output-file settings format)
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(let* ((file (if (path? output-file) (path->string output-file) output-file))
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(resolved (flac-encoder-prepare-settings settings format))
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(handler (flac-ffi-encoder-handler)))
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(handler 'new)
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(handler 'configure resolved)
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(handler 'init file)
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(make-flac-encoder-handle handler resolved format file)))
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(define (flac-encoder-write handle buf-info buffer buf-len)
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((flac-encoder-handle-ffi-encoder-handler handle) 'write buffer buf-len buf-info))
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(define (flac-encoder-finish handle)
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(let ((handler (flac-encoder-handle-ffi-encoder-handler handle)))
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(dynamic-wind
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void
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(lambda () (handler 'finish))
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(lambda () (handler 'delete)))))
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) ; end of module
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