Fix incorrect CHANNELS reporting for AC3/EC3

Fixes #313

Change-Id: I0b8d8081cda8aaa4db2ca4916bfc6721bfa3bd22

packager/media/codecs/ac3_audio_util.cc

@@ -0,0 +1,52 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/codecs/ac3_audio_util.h"
+
+#include "packager/base/strings/string_number_conversions.h"
+#include "packager/media/base/bit_reader.h"
+#include "packager/media/base/rcheck.h"
+
+namespace shaka {
+namespace media {
+
+namespace {
+
+// ASTC Standard A/52:2012 Table 5.8 Audio Coding Mode.
+const uint8_t kAc3NumChannelsTable[] = {2, 1, 2, 3, 3, 4, 4, 5};
+
+bool ExtractAc3Data(const std::vector<uint8_t>& ac3_data,
+                    uint8_t* audio_coding_mode,
+                    bool* lfe_channel_on) {
+  BitReader bit_reader(ac3_data.data(), ac3_data.size());
+
+  // fscod: 2 bits
+  // bsid: 5 bits
+  // bsmod: 3 bits
+  // acmod: 3 bits
+  // lfeon: 1 bit
+  // bit_rate_code: 5 bits
+  RCHECK(bit_reader.SkipBits(10));
+  RCHECK(bit_reader.ReadBits(3, audio_coding_mode));
+  RCHECK(bit_reader.ReadBits(1, lfe_channel_on));
+  return true;
+}
+
+}  // namespace
+
+size_t GetAc3NumChannels(const std::vector<uint8_t>& ac3_data) {
+  uint8_t audio_coding_mode;
+  bool lfe_channel_on;
+  if (!ExtractAc3Data(ac3_data, &audio_coding_mode, &lfe_channel_on)) {
+    LOG(WARNING) << "Seeing invalid AC3 data: "
+                 << base::HexEncode(ac3_data.data(), ac3_data.size());
+    return 0;
+  }
+  return kAc3NumChannelsTable[audio_coding_mode] + (lfe_channel_on ? 1 : 0);
+}
+
+}  // namespace media
+}  // namespace shaka

packager/media/codecs/ac3_audio_util.h

@@ -0,0 +1,27 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+//
+// AC3 audio utility functions.
+
+#ifndef PACKAGER_MEDIA_CODECS_AC3_AUDIO_UTIL_H_
+#define PACKAGER_MEDIA_CODECS_AC3_AUDIO_UTIL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <vector>
+
+namespace shaka {
+namespace media {
+
+/// Parse data from AC3Specific box and calculate number of channels.
+/// @return The number of channels associated with the input ac3 data on
+///         success; otherwise 0 is returned.
+size_t GetAc3NumChannels(const std::vector<uint8_t>& ac3_data);
+
+}  // namespace media
+}  // namespace shaka
+
+#endif  // PACKAGER_MEDIA_CODECS_AC3_AUDIO_UTIL_H_

packager/media/codecs/ac3_audio_util_unittest.cc

@@ -0,0 +1,30 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include <gtest/gtest.h>
+
+#include "packager/media/codecs/ac3_audio_util.h"
+
+namespace shaka {
+namespace media {
+
+TEST(Ac3AudioUtilTest, ChannelTest1) {
+  // audio_coding_mode is 7, which is Left, Center, Right, Left surround, Right
+  // surround. LFE channel on.
+  const std::vector<uint8_t> ac3_data = {0x10, 0x3d, 0xc0};
+
+  EXPECT_EQ(6u, GetAc3NumChannels(ac3_data));
+}
+
+TEST(Ac3AudioUtilTest, ChannelTest2) {
+  // audio_coding_mode is 2, which is Left and Right. LFE channel off.
+  const std::vector<uint8_t> ac3_data = {0x10, 0x11, 0xc0};
+
+  EXPECT_EQ(2u, GetAc3NumChannels(ac3_data));
+}
+
+}  // namespace media
+}  // namespace shaka

packager/media/codecs/codecs.gyp

@@ -15,6 +15,8 @@
       'sources': [
         'aac_audio_specific_config.cc',
         'aac_audio_specific_config.h',
+        'ac3_audio_util.cc',
+        'ac3_audio_util.h',
         'avc_decoder_configuration_record.cc',
         'avc_decoder_configuration_record.h',
         'decoder_configuration_record.cc',
@@ -61,6 +63,7 @@
       'type': '<(gtest_target_type)',
       'sources': [
         'aac_audio_specific_config_unittest.cc',
+        'ac3_audio_util_unittest.cc',
         'avc_decoder_configuration_record_unittest.cc',
         'ec3_audio_util_unittest.cc',
         'es_descriptor_unittest.cc',

packager/media/codecs/ec3_audio_util.cc

@@ -4,9 +4,12 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 
+#include "packager/media/codecs/ec3_audio_util.h"
+
+#include "packager/base/macros.h"
+#include "packager/base/strings/string_number_conversions.h"
 #include "packager/media/base/bit_reader.h"
 #include "packager/media/base/rcheck.h"
-#include "packager/media/codecs/ec3_audio_util.h"
 
 namespace shaka {
 namespace media {
@@ -49,6 +52,13 @@ enum kEC3AudioChannelMap {
   kLFE2 = 0x2,
   kLFEScreen = 0x1
 };
+// Number of channels for the channel bit above. The first entry corresponds to
+// kLeft, which has one channel. All the XxxPairs bits have two channels.
+const size_t kChannelCountArray[] = {
+    1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 1, 2, 1, 1,
+};
+static_assert(arraysize(kChannelCountArray) == 16u,
+              "Channel count array should have 16 entries.");
 
 // EC3 Audio coding mode map (acmod) to determine EC3 audio channel layout. The
 // value stands for the existence of Left, Center, Right, Left surround, and
@@ -118,13 +128,17 @@ bool ExtractEc3Data(const std::vector<uint8_t>& ec3_data,
 
 }  // namespace
 
-bool CalculateEC3ChannelMap(const std::vector<uint8_t>& ec3_data, uint32_t* channel_map) {
+bool CalculateEC3ChannelMap(const std::vector<uint8_t>& ec3_data,
+                            uint32_t* channel_map) {
   uint8_t audio_coding_mode;
   bool lfe_channel_on;
   uint16_t dependent_substreams_layout;
   if (!ExtractEc3Data(ec3_data, &audio_coding_mode, &lfe_channel_on,
-                      &dependent_substreams_layout))
+                      &dependent_substreams_layout)) {
+    LOG(WARNING) << "Seeing invalid EC3 data: "
+                 << base::HexEncode(ec3_data.data(), ec3_data.size());
     return false;
+  }
 
   // Dependent substreams layout bit map:
   // Bit,    Location
@@ -151,5 +165,21 @@ bool CalculateEC3ChannelMap(const std::vector<uint8_t>& ec3_data, uint32_t* chan
   return true;
 }
 
+size_t GetEc3NumChannels(const std::vector<uint8_t>& ec3_data) {
+  uint32_t channel_map;
+  if (!CalculateEC3ChannelMap(ec3_data, &channel_map))
+    return 0;
+
+  size_t num_channels = 0;
+  int bit = kLeft;
+  for (size_t channel_count : kChannelCountArray) {
+    if (channel_map & bit)
+      num_channels += channel_count;
+    bit >>= 1;
+  }
+  DCHECK_EQ(bit, 0);
+  return num_channels;
+}
+
 }  // namespace media
 }  // namespace shaka

packager/media/codecs/ec3_audio_util.h

@@ -9,6 +9,7 @@
 #ifndef PACKAGER_MEDIA_CODECS_EC3_AUDIO_UTIL_H_
 #define PACKAGER_MEDIA_CODECS_EC3_AUDIO_UTIL_H_
 
+#include <stddef.h>
 #include <stdint.h>
 #include <vector>
 
@@ -21,6 +22,11 @@ namespace media {
 bool CalculateEC3ChannelMap(const std::vector<uint8_t>& ec3_data,
                             uint32_t* channel_map);
 
+/// Parse data from EC3Specific box and calculate number of channels.
+/// @return The number of channels associated with the input ec3 data on
+///         success; otherwise 0 is returned.
+size_t GetEc3NumChannels(const std::vector<uint8_t>& ec3_data);
+
 }  // namespace media
 }  // namespace shaka
 

packager/media/codecs/ec3_audio_util_unittest.cc

@@ -6,44 +6,43 @@
 
 #include <gtest/gtest.h>
 
-#include "packager/base/macros.h"
 #include "packager/media/codecs/ec3_audio_util.h"
 
 namespace shaka {
 namespace media {
 
-TEST(EC3AudioUtilTest, CalculateEC3ChannelMapTest1) {
+TEST(EC3AudioUtilTest, ChannelTest1) {
   // audio_coding_mode is 7, which is Left, Center, Right, Left surround, Right
   // surround. No dependent substreams. LFE channel on.
-  const uint8_t kEc3Data[] = {0, 0, 0, 0x0f, 0};
+  const std::vector<uint8_t> ec3_data = {0, 0, 0, 0x0f, 0};
+
   uint32_t channel_map;
-  EXPECT_TRUE(CalculateEC3ChannelMap(
-      std::vector<uint8_t>(kEc3Data, kEc3Data + arraysize(kEc3Data)),
-      &channel_map));
+  EXPECT_TRUE(CalculateEC3ChannelMap(ec3_data, &channel_map));
   EXPECT_EQ(0xF801u, channel_map);
+  EXPECT_EQ(6u, GetEc3NumChannels(ec3_data));
 }
 
-TEST(EC3AudioUtilTest, CalculateEC3ChannelMapTest2) {
+TEST(EC3AudioUtilTest, ChannelTest2) {
   // audio_coding_mode is 2, which is Left and Right. No dependent substreams.
   // LFE channel off.
-  const uint8_t kEc3Data[] = {0, 0, 0, 0x04, 0};
+  const std::vector<uint8_t> ec3_data = {0, 0, 0, 0x04, 0};
+
   uint32_t channel_map;
-  EXPECT_TRUE(CalculateEC3ChannelMap(
-      std::vector<uint8_t>(kEc3Data, kEc3Data + arraysize(kEc3Data)),
-      &channel_map));
+  EXPECT_TRUE(CalculateEC3ChannelMap(ec3_data, &channel_map));
   EXPECT_EQ(0xA000u, channel_map);
+  EXPECT_EQ(2u, GetEc3NumChannels(ec3_data));
 }
 
-TEST(EC3AudioUtilTest, CalculateEC3ChannelMapTest3) {
+TEST(EC3AudioUtilTest, ChannelTest3) {
   // audio_coding_mode is 3, which is Left, Center, and Right. Dependent
   // substreams layout is 0b100000011, which is Left center/ Right center pair,
   // Left rear surround/ Right rear surround pair, LFE2 on. LFE channel on.
-  const uint8_t kEc3Data[] = {0, 0, 0, 0x07, 0x07, 0x03};
+  const std::vector<uint8_t> ec3_data = {0, 0, 0, 0x07, 0x07, 0x03};
+
   uint32_t channel_map;
-  EXPECT_TRUE(CalculateEC3ChannelMap(
-      std::vector<uint8_t>(kEc3Data, kEc3Data + arraysize(kEc3Data)),
-      &channel_map));
+  EXPECT_TRUE(CalculateEC3ChannelMap(ec3_data, &channel_map));
   EXPECT_EQ(0xE603u, channel_map);
+  EXPECT_EQ(9u, GetEc3NumChannels(ec3_data));
 }
 
 }  // namespace media

packager/media/formats/mp4/mp4_media_parser.cc

@@ -21,7 +21,9 @@
 #include "packager/media/base/media_sample.h"
 #include "packager/media/base/rcheck.h"
 #include "packager/media/base/video_stream_info.h"
+#include "packager/media/codecs/ac3_audio_util.h"
 #include "packager/media/codecs/avc_decoder_configuration_record.h"
+#include "packager/media/codecs/ec3_audio_util.h"
 #include "packager/media/codecs/es_descriptor.h"
 #include "packager/media/codecs/hevc_decoder_configuration_record.h"
 #include "packager/media/codecs/vp_codec_configuration_record.h"
@@ -438,12 +440,12 @@ bool MP4MediaParser::ParseMoov(BoxReader* reader) {
           break;
         case FOURCC_ac_3:
           codec_config = entry.dac3.data;
-          num_channels = entry.channelcount;
+          num_channels = static_cast<uint8_t>(GetAc3NumChannels(codec_config));
           sampling_frequency = entry.samplerate;
           break;
         case FOURCC_ec_3:
           codec_config = entry.dec3.data;
-          num_channels = entry.channelcount;
+          num_channels = static_cast<uint8_t>(GetEc3NumChannels(codec_config));
           sampling_frequency = entry.samplerate;
           break;
         case FOURCC_Opus:

packager/media/formats/mp4/mp4_muxer.cc

@@ -348,8 +348,15 @@ void MP4Muxer::GenerateAudioTrak(const AudioStreamInfo* audio_info,
       break;
   }
 
-  audio.channelcount = audio_info->num_channels();
-  audio.samplesize = audio_info->sample_bits();
+  if (audio_info->codec() == kCodecAC3 || audio_info->codec() == kCodecEAC3) {
+    // AC3 and EC3 does not fill in actual channel count and sample size in
+    // sample description entry. Instead, two constants are used.
+    audio.channelcount = 2;
+    audio.samplesize = 16;
+  } else {
+    audio.channelcount = audio_info->num_channels();
+    audio.samplesize = audio_info->sample_bits();
+  }
   audio.samplerate = audio_info->sampling_frequency();
   SampleTable& sample_table = trak->media.information.sample_table;
   SampleDescription& sample_description = sample_table.description;