support/testing: test_audio_codec_base.py: new helper class

This is a helper class providing a template for testing audio codec
programs such as lame mp3 encoder, flac tools, ogg vorbis-tools, ...

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -1842,6 +1842,7 @@ F:	support/testing/tests/package/test_acpica.py
 F:	support/testing/tests/package/test_acpica/
 F:	support/testing/tests/package/test_apache.py
 F:	support/testing/tests/package/test_attr.py
+F:	support/testing/tests/package/test_audio_codec_base.py
 F:	support/testing/tests/package/test_bc.py
 F:	support/testing/tests/package/test_bcc.py
 F:	support/testing/tests/package/test_bcc/

support/testing/tests/package/test_audio_codec_base.py

@@ -0,0 +1,86 @@
+import math
+import os
+
+import infra.basetest
+
+
+class TestAudioCodecBase(infra.basetest.BRTest):
+    """Common class to test an audio codec package.
+
+    This base class builds a Buildroot system image containing the
+    package enabled in its config, start the emulator, login to it. It
+    prepares an input test WAV file containing a tone. This WAV file
+    is encoded into a new output file in the native encoder format. It
+    is then decoded to a new output WAV file. This final output WAV
+    file is checked to contain the expected tone generated in the
+    initial input WAV file. There is no specific check about file
+    size, nor audio quality. The acceptance criteria is the
+    recognition of the tone. Note: the tone generation is made with
+    the Sox package, and the tone recognition is made with the Aubio
+    package.
+
+    Each test case that inherits from this class must have:
+    __test__ = True  - to let nose2 know that it is a test case
+    config           - defconfig fragment with the packages to run the test
+    encode_test()    - the function that runs the encoder and produces an
+                       encoded file.
+    decode_test()    - the function that runs the decoder and produces a
+                       decode file.
+    """
+    __test__ = False
+    config = infra.basetest.BASIC_TOOLCHAIN_CONFIG + \
+        """
+        BR2_PACKAGE_AUBIO=y
+        BR2_PACKAGE_SOX=y
+        BR2_TARGET_ROOTFS_CPIO=y
+        # BR2_TARGET_ROOTFS_TAR is not set
+        """
+    input_file = "reference.wav"
+    decoded_file = "decoded.wav"
+    tone_freq = 440  # General Midi note A3
+
+    def login(self):
+        cpio_file = os.path.join(self.builddir, "images", "rootfs.cpio")
+        self.emulator.boot(arch="armv5",
+                           kernel="builtin",
+                           options=["-initrd", cpio_file])
+        self.emulator.login()
+
+    def test_run(self):
+        self.login()
+        self.prepare_data()
+        self.encode_test(self.input_file)
+        self.decode_test(self.decoded_file)
+        self.check_test()
+
+    def prepare_data(self):
+        # Generate a sinusoidal tone.
+        cmd = "sox -V -r 48000 -n -b 16 -c 1 "
+        cmd += self.input_file
+        cmd += f" synth 3 sin {self.tone_freq} vol -10dB"
+        self.assertRunOk(cmd)
+
+    def encode_test(self, input_filename):
+        msg = "method must be implemented in derived class"
+        raise NotImplementedError(msg)
+
+    def decode_test(self, output_filename):
+        msg = "method must be implemented in derived class"
+        raise NotImplementedError(msg)
+
+    def note_from_freq(self, freq):
+        """Return a note number from the input frequency in Hertz."""
+        return round((12 * math.log(freq / 440) / math.log(2)) + 69)
+
+    def check_test(self):
+        expected_note = self.note_from_freq(self.tone_freq)
+        out, ret = self.emulator.run(f"aubionotes {self.decoded_file}", timeout=20)
+        self.assertEqual(ret, 0)
+        note_found = False
+        for line in out:
+            values = line.split()
+            if len(values) == 3:
+                note = round(float(values[0]))
+                if note == expected_note:
+                    note_found = True
+        self.assertTrue(note_found, "The expected note was not found")