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 +79,88 @@
   EXPECT_EQ(0, expected_test);
 }
 
+TEST(AudioUtilTest, MixStreams_u8) {
+  // Test MixStreams() on 8 bit samples.
+  uint8 dst_u8[kNumberOfSamples] = { 14, 0x44, 0x80, 0xff };
+  uint8 src_u8[kNumberOfSamples] = { 4, 0x40, 0x80, 0xff };
+  uint8 expected_u8[kNumberOfSamples] = { 0,  /* saturation */
+                                          (0x44 - 128) + (0x40 - 128) / 4 + 128,
+                                          (0x80 - 128) + (0x80 - 128) / 4 + 128,
+                                          0xff /* saturation */ };
+  media::MixStreams(dst_u8, src_u8, sizeof(dst_u8), sizeof(src_u8[0]), 0.25f);
+  int expected_test = memcmp(dst_u8, expected_u8, sizeof(expected_u8));
+  EXPECT_EQ(0, expected_test);
+}
+
+TEST(AudioUtilTest, MixStreams_u8_one) {
+  // 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) + 128,
+                                          (0x80 - 128) + (0x80 - 128) + 128,
+                                          0xff /* saturation */ };
+  media::MixStreams(dst_u8, src_u8, sizeof(dst_u8), sizeof(src_u8[0]), 1.0f);
+  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 };