Add software audio mixing to the audio utils.

media/audio/audio_util_unittest.cc

Index: media/audio/audio_util_unittest.cc
===================================================================
--- media/audio/audio_util_unittest.cc	(revision 125439)
+++ media/audio/audio_util_unittest.cc	(working copy)
@@ -79,6 +79,75 @@
   EXPECT_EQ(0, expected_test);
 }
 
+TEST(AudioUtilTest, MixStreams_u8) {
+  // Test MixStreams() on 8 bit samples.
+  uint8 dst_u8[kNumberOfSamples] = { 44, 0x44, 0x80, 0xff };
+  uint8 src_u8[kNumberOfSamples] = { 4, 0x40, 0x80, 0xff };
+  uint8 expected_u8[kNumberOfSamples] = { 0,  /* saturation */
+                                          (0x44 - 128) + (0x40 - 128) / 2 + 128,
+                                          (0x80 - 128) + (0x80 - 128) / 2 + 128,
+                                          0xff /* saturation */ };
+  media::MixStreams(dst_u8, src_u8, sizeof(dst_u8), sizeof(src_u8[0]), 0.5f);

[vrk (LEFT CHROMIUM), 2012/03/12 18:40:24]

It looks like you are adjusting the volume in most of these, except the tests
with "_one" appended to the name. Seems like it'd make more sense to test volume
and stream format separately.

Maybe change the u8, s16, and s32 tests to be at full volume (1.0), then have a
u8_HalfVolume, s16_QuarterVolume, s32_ThreeQuarters volume or something like
that?

[enal1, 2012/03/12 21:20:53]

Added missing test and changed u8 test. Now we test size (1, 2, 4) on volume
(0.25, 1.0).

[vrk (LEFT CHROMIUM), 2012/03/20 00:27:53]

Thanks enal! Can you do the name change as well? (e.g.
MixStreams_u8_QuarterVolume instead of MixStreams_u8, MixStreams_u8_FullVolume
instead of MixStreams_u8_one).

+  int expected_test = memcmp(dst_u8, expected_u8, sizeof(expected_u8));
+  EXPECT_EQ(0, expected_test);
+}
+
+TEST(AudioUtilTest, MixStreams_s16) {
+  // Test MixStreams() on 16 bit samples.
+  int16 dst_s16[kNumberOfSamples] = { -4, 0x40, -32760, 32760 };
+  int16 src_s16[kNumberOfSamples] = { -4, 0x40, -123, 123 };
+  int16 expected_s16[kNumberOfSamples] = { -5, 0x50, -32768, 32767 };
+  media::MixStreams(dst_s16,
+                    src_s16,
+                    sizeof(dst_s16),
+                    sizeof(src_s16[0]),
+                    0.25f);
+  int expected_test = memcmp(dst_s16, expected_s16, sizeof(expected_s16));
+  EXPECT_EQ(0, expected_test);
+}
+
+TEST(AudioUtilTest, MixStreams_s16_one) {
+  // Test MixStreams() on 16 bit samples.
+  int16 dst_s16[kNumberOfSamples] = { -4, 0x40, -32760, 32760 };
+  int16 src_s16[kNumberOfSamples] = { -4, 0x40, -123, 123 };
+  int16 expected_s16[kNumberOfSamples] = { -8, 0x80, -32768, 32767 };
+  media::MixStreams(dst_s16,
+                    src_s16,
+                    sizeof(dst_s16),
+                    sizeof(src_s16[0]),
+                    1.0f);
+  int expected_test = memcmp(dst_s16, expected_s16, sizeof(expected_s16));
+  EXPECT_EQ(0, expected_test);
+}
+
+TEST(AudioUtilTest, MixStreams_s32) {
+  // Test MixStreams() on 32 bit samples.
+  int32 dst_s32[kNumberOfSamples] = { -4, 0x40, -32768, 2147483640 };
+  int32 src_s32[kNumberOfSamples] = { -4, 0x40, -32768, 123 };
+  int32 expected_s32[kNumberOfSamples] = { -5, 0x50, -40960, 2147483647 };
+  media::MixStreams(dst_s32,
+                    src_s32,
+                    sizeof(dst_s32),
+                    sizeof(src_s32[0]),
+                    0.25f);
+  int expected_test = memcmp(dst_s32, expected_s32, sizeof(expected_s32));
+  EXPECT_EQ(0, expected_test);
+}
+
+TEST(AudioUtilTest, MixStreams_s32_one) {
+  // Test MixStreams() on 32 bit samples.
+  int32 dst_s32[kNumberOfSamples] = { -4, 0x40, -32768, 2147483640 };
+  int32 src_s32[kNumberOfSamples] = { -4, 0x40, -32768, 123 };
+  int32 expected_s32[kNumberOfSamples] = { -8, 0x80, -65536, 2147483647 };
+  media::MixStreams(dst_s32,
+                    src_s32,
+                    sizeof(dst_s32),
+                    sizeof(src_s32[0]),
+                    1.0);
+  int expected_test = memcmp(dst_s32, expected_s32, sizeof(expected_s32));
+  EXPECT_EQ(0, expected_test);
+}
+
 TEST(AudioUtilTest, FoldChannels_u8) {
   // Test FoldChannels() on 8 bit samples.
   uint8 samples_u8[6] = { 100, 150, 130, 70, 130, 170 };