Implementation of WaveSmplReader

docs/source/references.rst

@@ -36,6 +36,11 @@ iXML
 * `Gallery Software iXML Specification <http://www.gallery.co.uk/ixml/>`_
 
 
+Sampler Metadata
+----------------
+
+* `RecordingBlogs.com — Sample chunk (of a Wave file)<https://www.recordingblogs.com/wiki/sample-chunk-of-a-wave-file>`_
+
 RIFF Metadata
 -------------
 * `1991. Multimedia Programming Interface and Data Specifications 1.0 <https://www.aelius.com/njh/wavemetatools/doc/riffmci.pdf>`_

wavinfo/wave_smpl_reader.py

@@ -0,0 +1,78 @@
+import struct
+
+from enum import IntEnum
+from typing import Tuple, NamedTuple, List
+
+
+class WaveSmplLoop(NamedTuple):
+    ident: int 
+    loop_type: int 
+    start: int 
+    end: int
+    fraction: int
+    repetition_count: int
+
+
+class WaveSmplReader:
+    
+    def __init__(self, smpl_data: bytes):
+        """
+        Read sampler metadata from smpl chunk.
+        """
+        
+        header_field_fmt = "<IIIIIIbbbbII"
+        loop_field_fmt = "<IIIIII"
+        header_size = struct.calcsize(header_field_fmt)
+        loop_size = struct.calcsize(loop_field_fmt)
+
+        unpacked_data = struct.unpack(header_field_fmt, 
+                                      smpl_data[0:header_size])
+
+        #: The MIDI Manufacturer's Association code for the sampler manufactuer,
+        #: or 0 if not specific.
+        self.manufacturer: int = unpacked_data[0]
+
+        #: The manufacturer-assigned code for their specific sampler model, or
+        #: 0 if not specific.
+        self.product: int = unpacked_data[1]
+
+        #: The number of nanoseconds in one audio frame.
+        self.sample_period: int = unpacked_data[2]
+
+        #: The MIDI note number for the loops in this sample 
+        self.midi_note: int = unpacked_data[3]
+
+        #: The number of semitones above the MIDI note the loops tune for.
+        self.midi_pitch_fraction: int = unpacked_data[4]
+
+        #: SMPTE timecode format, one of (0, 24, 25, 29, 30)
+        self.smpte_format: int = unpacked_data[5]
+
+        #: The SMPTE offset to apply, as a tuple of four ints representing 
+        #: hh, mm, ss, ff
+        self.smpte_offset: Tuple[int, int, int, int]  = unpacked_data[6:10]
+        
+        loop_count = unpacked_data[10]
+        sampler_udata_length = unpacked_data[11]
+
+        #: List of loops in the file.
+        self.sample_loops: List[WaveSmplLoop] = [] 
+        
+        loop_buffer = smpl_data[header_field_fmt:
+                                header_field_fmt + loop_size * loop_count]
+
+        for unpacked_loop in struct.iter_unpack(loop_field_fmt, loop_buffer):
+            self.sample_loops.append(WaveSmplLoop(
+                ident=unpacked_loop[0], 
+                loop_type=unpacked_loop[1],
+                start=unpacked_loop[2],
+                end=unpacked_loop[3],
+                fraction=unpacked_loop[4],
+                repetition_count=unpacked_loop[5]))
+
+        #: Sampler-specific user data.
+        self.sampler_udata: bytes = smpl_data[
+                header_field_fmt + loop_size * loop_count : 
+                header_field_fmt + loop_size * loop_count + sampler_udata_length]
+
+