Axml implementation

wavinfo/wave_axml_reader.py

@@ -1,14 +1,54 @@
+"""
+ADM Reader
+"""
+
+from struct import unpack, unpack_from, calcsize
+from dataclasses import dataclass
+
 from lxml import etree as ET
-from collections import namedtuple
+
+@dataclass
+class ChannelEntry:
+    """
+    A `chna` chunk table entry.
+    """
+
+    track_index: int
+    "Track index (indexed from 1)"
+
+    uid: str
+    "audioTrackUID"
+
+    track_ref: str
+    "audioTrackFormatID"
+
+    pack_ref: str
+    "audioPackFormatID"
 
 
-class WaveAxmlReader:
+class WavAxmlReader:
     """
     Reads XML data from an EBU ADM (Audio Definiton Model) WAV File.
     """
 
-    def __init__(self, axml_data, ) -> None:
+    def __init__(self, axml_data: bytes, chna_data: bytes) -> None:
-        pass
+        header_fmt = "<HH"
+        uid_fmt = "<H12s14s11sx"
 
+        self.axml = ET.fromstring(axml_data)
 
+        self.track_count, uid_count = unpack(header_fmt, chna_data)
 
+        self.channel_uids = []
+
+        offset = calcsize(header_fmt)
+        for _ in range(uid_count):
+
+            track_index, uid, track_ref, pack_ref = unpack_from(uid_fmt, chna_data, offset)
+
+            # these values are either ascii or all null
+
+            self.channel_uids.append(ChannelEntry(track_index,
+                uid.decode('ascii') , track_ref.decode('ascii'), pack_ref.decode('ascii')))
+
+            offset += calcsize(uid_fmt)

wavinfo/wave_reader.py

@@ -9,6 +9,7 @@ from .riff_parser import parse_chunk, ChunkDescriptor, ListChunkDescriptor
 from .wave_ixml_reader import WavIXMLFormat
 from .wave_bext_reader import WavBextReader
 from .wave_info_reader import WavInfoChunkReader
+from .wave_axml_reader import WavAxmlReader
 
 #: Calculated statistics about the audio data.
 WavDataDescriptor = namedtuple('WavDataDescriptor', 'byte_count frame_count')
@@ -75,6 +76,9 @@ class WavInfoReader:
         #: :class:`wavinfo.wave_ixml_reader.WavIXMLFormat` with iXML metadata
         self.ixml = self._get_ixml(wavfile)
 
+        #: :class:`wavinfo.wave_axml_reader.WavAxmlReader` with ADM metadata
+        self.adm  = self._get_axml(wavfile)
+
         #: :class:`wavinfo.wave_info_reader.WavInfoChunkReader` with RIFF INFO metadata
         self.info = self._get_info(wavfile, encoding=self.info_encoding)
         self.data = self._describe_data()
@@ -130,6 +134,11 @@ class WavInfoReader:
         bext_data = self._find_chunk_data(b'bext', f, default_none=True)
         return WavBextReader(bext_data, encoding) if bext_data else None
 
+    def _get_axml(self, f):
+        axml = self._find_chunk_data(b'axml', f, default_none=True)
+        chna = self._find_chunk_data(b'chna', f, default_none=True)
+        return WavAxmlReader(axml_data=axml, chna_data=chna)
+
     def _get_ixml(self, f):
         ixml_data = self._find_chunk_data(b'iXML', f, default_none=True)
         return None if ixml_data is None else WavIXMLFormat(ixml_data.rstrip(b'\0'))