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# Functions to read to and write from wave files.
# Does not support many kinds of wave files, such as compressed data.
⟨Read, Write, Read_set, Read_coerce⟩⇐
"wav.bqn takes a single option namespace, or no arguments" ! 1≥≠•args
o ← ≠◶⟨•Import∘"options.bqn", ⊑⟩ •args
# The output from Read, or input to Write, is either:
# - A list of:
# The sample rate (in Hz)
# The PCM format (see below)
# PCM data, which has shape n‿l for n channels with l samples.
# - The PCM data only
# (options.freq and options.fmt are used for rate and format)
#
# Read returns the plain PCM data if the settings matched the
# options while Read_set and Read_coerce always return the
# plain data.
# A PCM format consists of the type of audio and the bit depth.
# The type is one of:
# 1 unsigned integer
# 3 floating point
# Other audio formats may be supported in the future.
# Wave file header format
wh ← {
# Field properties are:
# len: Length of field in bytes
# typ: Whether to leave as chars (c) or convert to an integer (i)
# err: Behavior on invalid value: fail (e), warn (w), or ignore (.)
# (Fields with ? depend on context)
# name: Field name
# def: How to compute value
len‿typ‿err‿name‿def ⇐ <˘⍉>⟨
4‿'c'‿'e'‿"chunkID" ‿⟨"RIFF"⟩
4‿'i'‿'w'‿"chunkSize" ‿⟨20++´,"subchunk1Size","subchunk2Size"⟩
4‿'c'‿'e'‿"format" ‿⟨"WAVE"⟩
4‿'c'‿'e'‿"subchunk1ID" ‿⟨"fmt "⟩
4‿'i'‿'?'‿"subchunk1Size"‿⟨16⟩
2‿'i'‿'.'‿"audioFormat" ‿⟨⟩
2‿'i'‿'.'‿"numChannels" ‿⟨⟩
4‿'i'‿'.'‿"sampleRate" ‿⟨⟩
4‿'i'‿'w'‿"byteRate" ‿⟨×´÷8˙,"sampleRate","numChannels","bitsPerSample"⟩
2‿'i'‿'w'‿"blockAlign" ‿⟨×´÷8˙,"numChannels","bitsPerSample"⟩
2‿'i'‿'.'‿"bitsPerSample"‿⟨⟩
4‿'c'‿'?'‿"subchunk2ID" ‿⟨"data"⟩
4‿'i'‿'.'‿"subchunk2Size"‿⟨⟩
⟩
def ↩ name⊸⊐⌾(1⊸↓)⍟(1<≠)¨ def
# Topological order for field definitions
order ⇐ {{𝕊⍟(l>○≠⊢)⟜(𝕩∾·/𝕨⊸<)𝕨∨∧´∘⊏⟜𝕨¨l}⟜/0¨l←𝕩} 1↓¨def
# Then fill blank definitions with a self-reference
def ↩ ↕∘≠⊸({⊑‿𝕨⍟(0=≠)𝕩}¨) def
# Turn list of values into namespace
makeNS ⇐ •BQN "{"∾(1↓∾"‿"⊸∾¨name)∾"←𝕩}"
}
# Return an undoable (⁼) function to convert bytes to PCM data.
_audioConvert ← {
audioFormat‿bitsPerSample ← 𝕗
"Bits per sample must be a multiple of 8" ! 0=8|bitsPerSample
"Bits per sample cannot exceed 64" ! bitsPerSample ≤ 64
l ← bitsPerSample÷8
_withInv_ ← {F _𝕣_ G: {𝕊:F𝕩 ; 𝕊⁼:G𝕩}}
# Convert 𝕗-byte sequences to ints
_int ← {
b ← 256
(+⟜(b⊸×)˝˜⟜(-(b÷2)≤¯1⊸⊏)·⍉⌊‿𝕗⥊⊢) _withInv_ (⥊∘⍉∘>b|⌊∘÷⟜b⍟(↕𝕗))
}
# Convert int to float
_float ← {e‿m‿b←𝕗 # exponent and mantissa length in bits; bias
maxval←(1-2⋆-m+1)×2⋆(2⋆e)-b+1
{
𝕩 ×↩ 2⋆-m
p‿s ← (2⋆e) (| ≍○< ⌊∘÷˜) ⌊𝕩
p +↩ ¬n←0<p
(¯1⋆s)×(2⋆p-b) × n+1|𝕩
}_withInv_{
s←𝕩<0 ⋄ 𝕩↩maxval⌊|𝕩
p←0⌈b+⌊2⋆⁼𝕩 ⋄ h←p+s×2⋆e
p +↩ ¬n←0<p
⌊0.5 + (2⋆m) × h + n-˜𝕩×2⋆b-p
}
}
# Look up the appropriate function
{
1:
l _int -⟜@ ;
3:
"Float formats other than 32-bit are not supported" ! 4=l
8‿23‿127 _float ·4 _int -⟜@ ;
𝕩:
0 !˜ "Unsupported audio format: " ∾ •Repr audioFormat
}audioFormat
}
# 𝕨 is audioFormat‿bitsPerSample.
# Force 𝕩 to fit in format 𝕨, emitting approprate warnings.
ForceFormat ← { f‿b 𝕊 pcm:
Dither ← {
•Out⍟o.warn_dither "Signal is non-integral; dithering..."
o.Dither 𝕩
}
Clip ← {
•Out⍟o.warn_clip "Signal out of bounds; clipping..."
max ⌊ min ⌈ 𝕩
}
min‿max ← (-≍-⟜1) 2⋆b-1
(Clip⍟(min⊸> ∨○(∨´⥊) >⟜max) Dither∘⊣⍟≢⟜⌊)⍟(f=1) pcm
}
Decode ← {
If ← {𝕏⍟𝕎@}´
While ← {𝕨{𝕊∘𝔾⍟𝔽𝕩}𝕩@}´
# Integer from little-endian unsigned bytes
ToInt ← 256⊸×⊸+˜´ -⟜@
hdr‿dat ← wh.len +´⊸(↑ ≍○< ↓) 𝕩
# Assign field values to field names.
hdr ↩ ('i'=wh.typ) ToInt∘⊢⍟⊣¨ wh.len /⊸⊔ hdr
subchunk1Size‿subchunk2Size‿subchunk2ID‿audioFormat‿bitsPerSample‿sampleRate‿numChannels ← wh.MakeNS hdr
# Handle extensible format
"subchunk1Size is invalid" ! 0‿2‿24 ∊˜ se←subchunk1Size-16
If (se>0)‿{𝕤
! se = 2 + ToInt 2↑subchunk2ID
ext←@ ⋄ ext‿dat ↩ se (↑ ≍○< ↓) dat
If (se>2)‿{𝕤
If (audioFormat = 65534)‿{𝕤⋄ audioFormat ↩ ToInt 4↑ext }
}
}
# Ignore remaining subchunks
s ← subchunk2Size
While {𝕤⋄"data"≢subchunk2ID}‿{𝕤
subchunk2ID‿s‿dat ↩ (4⊸↑ ≍○< ToInt∘((4+↕4)⊸⊏) ≍○< 8⊸↓) s ↓ dat
subchunk2Size +↩ s+8
}
# Check that fields match their definitions
e ← hdr ≢⟜(⊑{𝕎𝕩⊏hdr}1⊸↓)¨ wh.def
Msg ← "Values for fields " ∾ (∾∾⟜" "¨) ∾ "are incorrect"˙
_alert ← {(𝔽∘Msg /⟜(wh.name))⍟(∨´) e ∧ wh.err⊸∊}
!⟜0 _alert "e"∾(se<0)/"?"
(•Out "Warning: "∾⊢) _alert "w"
fmt ← audioFormat‿bitsPerSample
Cvt ← fmt _audioConvert
⟨sampleRate, fmt, ⍉ ⌊‿numChannels ⥊ Cvt⎊(⊣⊘Cvt subchunk2Size⊸↑) dat⟩
}
Encode ← { rate‿fmt‿pcm:
! 2 ≥ =pcm
pcm ⥊⟜0⊸↓˜↩ 2
dat ← fmt _audioConvert⁼ fmt ForceFormat ⥊⍉pcm
iname‿ival ← <˘⍉∘‿2⥊⟨
"sampleRate" , rate
"numChannels" , ≠pcm
"subchunk2Size", ≠dat
"audioFormat" , 0⊑fmt
"bitsPerSample", 1⊑fmt
⟩
val ← def ← (⥊∘<¨ival)⌾((wh.name⊐iname)⊸⊏) wh.def
{ val ↩ (⊑{𝕎𝕩⊏val}1⊸↓)⌾(𝕩⊸⊑) val }¨ wh.order
hdr ← ∾ (wh.len×wh.typ='i') 256{@+𝕗|⌊∘÷⟜𝕗⍟(↕𝕨)𝕩}⍟(>⟜0)¨ val
hdr ∾ dat
}
ReadFull ← Decode∘{ o.FBytes 𝕩 }
Read ← { ¯1⊸⊑⍟(⟨o.freq,o.fmt⟩ ≡ 2⊸↑) ReadFull 𝕩 }
Write ← { 𝕩 o.FBytes Encode(⟨o.freq,o.fmt⟩∾<)⍟(1≥≡) 𝕨 }
# Read, setting o.freq and o.fmt as a side effect.
Read_set ← { t←ReadFull 𝕩 ⋄ o.Set ¯1↓t ⋄ ¯1⊑t }
# Read, resampling to fit current frequency, using options.Resample
Read_coerce ← { ((o.freq∾˜0⊸⊑) o.Resample ¯1⊸⊑) ReadFull 𝕩 }
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