gh-77171 Support WAVE_FORMAT_EXTENSIBLE in the wave module (GH-96777)

The test file, a modified version of Lib/test/audiodata/pluck-pcm24.wav, was provided by Andrea Celletti on the bug tracker.

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

1 files changed, 15 insertions, 7 deletions

diff --git a/Lib/wave.py b/Lib/wave.py
index 9a45574..e446174 100644
--- a/Lib/wave.py
+++ b/Lib/wave.py
@@ -83,6 +83,7 @@ class Error(Exception):
     pass
 
 WAVE_FORMAT_PCM = 0x0001
+WAVE_FORMAT_EXTENSIBLE = 0xFFFE
 
 _array_fmts = None, 'b', 'h', None, 'i'
 
@@ -377,16 +378,23 @@ class Wave_read:
             wFormatTag, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack_from('<HHLLH', chunk.read(14))
         except struct.error:
             raise EOFError from None
-        if wFormatTag == WAVE_FORMAT_PCM:
+        if wFormatTag != WAVE_FORMAT_PCM and wFormatTag != WAVE_FORMAT_EXTENSIBLE:
+            raise Error('unknown format: %r' % (wFormatTag,))
+        try:
+            sampwidth = struct.unpack_from('<H', chunk.read(2))[0]
+        except struct.error:
+            raise EOFError from None
+        if wFormatTag == WAVE_FORMAT_EXTENSIBLE:
             try:
-                sampwidth = struct.unpack_from('<H', chunk.read(2))[0]
+                # Only the first 2 bytes (of 16) of SubFormat are needed.
+                cbSize, wValidBitsPerSample, dwChannelMask, SubFormatFmt = struct.unpack_from('<HHLH', chunk.read(10))
             except struct.error:
                 raise EOFError from None
-            self._sampwidth = (sampwidth + 7) // 8
-            if not self._sampwidth:
-                raise Error('bad sample width')
-        else:
-            raise Error('unknown format: %r' % (wFormatTag,))
+            if SubFormatFmt != WAVE_FORMAT_PCM:
+                raise Error(f'unknown format: {SubFormatFmt}')
+        self._sampwidth = (sampwidth + 7) // 8
+        if not self._sampwidth:
+            raise Error('bad sample width')
         if not self._nchannels:
             raise Error('bad # of channels')
         self._framesize = self._nchannels * self._sampwidth