Fix channel layout reporting for implicit signalling of AAC parametric stereo

BUG=226642
TEST=AACTest_TestImplicitSBR_ChannelConfig0,AACTest_TestImplicitSBR_ChannelConfig1


Review URL: https://chromiumcodereview.appspot.com/13648007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@192498 0039d316-1c4b-4281-b951-d872f2087c98

media/mp4/aac.cc

@@ -19,7 +19,7 @@ static const int kFrequencyMap[] = {
 
 namespace media {
 
-static ChannelLayout GetChannelLayout(uint8 channel_config) {
+static ChannelLayout ConvertChannelConfigToLayout(uint8 channel_config) {
   switch (channel_config) {
     case 1:
       return CHANNEL_LAYOUT_MONO;
@@ -130,9 +130,9 @@ bool AAC::Parse(const std::vector<uint8>& data) {
 
   // When Parametric Stereo is on, mono will be played as stereo.
   if (ps_present && channel_config_ == 1)
-    channel_layout_ = GetChannelLayout(2);
+    channel_layout_ = CHANNEL_LAYOUT_STEREO;
   else
-    channel_layout_ = GetChannelLayout(channel_config_);
+    channel_layout_ = ConvertChannelConfigToLayout(channel_config_);
 
   return frequency_ != 0 && channel_layout_ != CHANNEL_LAYOUT_UNSUPPORTED &&
       profile_ >= 1 && profile_ <= 4 && frequency_index_ != 0xf &&
@@ -154,7 +154,13 @@ int AAC::GetOutputSamplesPerSecond(bool sbr_in_mimetype) const {
   return std::min(2 * frequency_, 48000);
 }
 
-ChannelLayout AAC::channel_layout() const {
+ChannelLayout AAC::GetChannelLayout(bool sbr_in_mimetype) const {
+  // Check for implicit signalling of HE-AAC and indicate stereo output
+  // if the mono channel configuration is signalled.
+  // See ISO-14496-3 Section 1.6.6.1.2 for details about this special casing.
+  if (sbr_in_mimetype && channel_config_ == 1)
+    return CHANNEL_LAYOUT_STEREO;
+
   return channel_layout_;
 }
 

media/mp4/aac.h

@@ -38,7 +38,13 @@ class MEDIA_EXPORT AAC {
   // Returns the samples_per_second value that should used in an
   // AudioDecoderConfig.
   int GetOutputSamplesPerSecond(bool sbr_in_mimetype) const;
-  ChannelLayout channel_layout() const;
+
+  // Gets the channel layout for the AAC stream.
+  // |sbr_in_mimetype| should be set to true if the SBR mode is
+  // signalled in the mimetype. (ie mp4a.40.5 in the codecs parameter).
+  // Returns the channel_layout value that should used in an
+  // AudioDecoderConfig.
+  ChannelLayout GetChannelLayout(bool sbr_in_mimetype) const;
 
   // This function converts a raw AAC frame into an AAC frame with an ADTS
   // header. On success, the function returns true and stores the converted data

media/mp4/aac_unittest.cc

@@ -19,7 +19,7 @@ TEST(AACTest, BasicProfileTest) {
 
   EXPECT_TRUE(aac.Parse(data));
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(false), 44100);
-  EXPECT_EQ(aac.channel_layout(), CHANNEL_LAYOUT_STEREO);
+  EXPECT_EQ(aac.GetChannelLayout(false), CHANNEL_LAYOUT_STEREO);
 }
 
 TEST(AACTest, ExtensionTest) {
@@ -32,10 +32,33 @@ TEST(AACTest, ExtensionTest) {
   EXPECT_TRUE(aac.Parse(data));
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(false), 48000);
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(true), 48000);
-  EXPECT_EQ(aac.channel_layout(), CHANNEL_LAYOUT_STEREO);
+  EXPECT_EQ(aac.GetChannelLayout(false), CHANNEL_LAYOUT_STEREO);
 }
 
-TEST(AACTest, TestImplicitSBR) {
+// Test implicit SBR with mono channel config.
+// Mono channel layout should only be reported if SBR is not
+// specified. Otherwise stereo should be reported.
+// See ISO-14496-3 Section 1.6.6.1.2 for details about this special casing.
+TEST(AACTest, TestImplicitSBR_ChannelConfig0) {
+  AAC aac;
+  uint8 buffer[] = {0x13, 0x08};
+  std::vector<uint8> data;
+
+  data.assign(buffer, buffer + sizeof(buffer));
+
+  EXPECT_TRUE(aac.Parse(data));
+
+  // Test w/o implict SBR.
+  EXPECT_EQ(aac.GetOutputSamplesPerSecond(false), 24000);
+  EXPECT_EQ(aac.GetChannelLayout(false), CHANNEL_LAYOUT_MONO);
+
+  // Test implicit SBR.
+  EXPECT_EQ(aac.GetOutputSamplesPerSecond(true), 48000);
+  EXPECT_EQ(aac.GetChannelLayout(true), CHANNEL_LAYOUT_STEREO);
+}
+
+// Tests implicit SBR with a stereo channel config.
+TEST(AACTest, TestImplicitSBR_ChannelConfig1) {
   AAC aac;
   uint8 buffer[] = {0x13, 0x10};
   std::vector<uint8> data;
@@ -43,9 +66,14 @@ TEST(AACTest, TestImplicitSBR) {
   data.assign(buffer, buffer + sizeof(buffer));
 
   EXPECT_TRUE(aac.Parse(data));
+
+  // Test w/o implict SBR.
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(false), 24000);
+  EXPECT_EQ(aac.GetChannelLayout(false), CHANNEL_LAYOUT_STEREO);
+
+  // Test implicit SBR.
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(true), 48000);
-  EXPECT_EQ(aac.channel_layout(), CHANNEL_LAYOUT_STEREO);
+  EXPECT_EQ(aac.GetChannelLayout(true), CHANNEL_LAYOUT_STEREO);
 }
 
 TEST(AACTest, SixChannelTest) {
@@ -57,7 +85,7 @@ TEST(AACTest, SixChannelTest) {
 
   EXPECT_TRUE(aac.Parse(data));
   EXPECT_EQ(aac.GetOutputSamplesPerSecond(false), 48000);
-  EXPECT_EQ(aac.channel_layout(), CHANNEL_LAYOUT_5_1);
+  EXPECT_EQ(aac.GetChannelLayout(false), CHANNEL_LAYOUT_5_1);
 }
 
 TEST(AACTest, DataTooShortTest) {

media/mp4/mp4_stream_parser.cc

@@ -237,7 +237,7 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       is_audio_track_encrypted_ = entry.sinf.info.track_encryption.is_encrypted;
       DVLOG(1) << "is_audio_track_encrypted_: " << is_audio_track_encrypted_;
       audio_config.Initialize(kCodecAAC, sample_format,
-                              aac.channel_layout(),
+                              aac.GetChannelLayout(has_sbr_),
                               aac.GetOutputSamplesPerSecond(has_sbr_),
                               NULL, 0, is_audio_track_encrypted_, false);
       has_audio_ = true;