Introduce AudioHash for fuzzy audio matching.

The old MD5 approach is too strict due to differences in floating
point implementations on each platform.  AudioHash provides a simple
algorithm for ensuring signals are within roughly -40 dBFS.

BUG=168204
TEST=media_unittests on Linux && Win.


Review URL: https://chromiumcodereview.appspot.com/12925002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@189197 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 12 insertions, 53 deletions

diff --git a/media/audio/null_audio_sink.cc b/media/audio/null_audio_sink.cc
index 8fee966..5c4f67a 100644
--- a/media/audio/null_audio_sink.cc
+++ b/media/audio/null_audio_sink.cc
@@ -6,9 +6,8 @@
 
 #include "base/bind.h"
 #include "base/message_loop_proxy.h"
-#include "base/stringprintf.h"
-#include "base/sys_byteorder.h"
 #include "media/audio/fake_audio_consumer.h"
+#include "media/base/audio_hash.h"
 
 namespace media {
 
@@ -17,8 +16,6 @@ NullAudioSink::NullAudioSink(
     : initialized_(false),
       playing_(false),
       callback_(NULL),
-      hash_audio_for_testing_(false),
-      channels_(0),
       message_loop_(message_loop) {
 }
 
@@ -27,16 +24,7 @@ NullAudioSink::~NullAudioSink() {}
 void NullAudioSink::Initialize(const AudioParameters& params,
                                RenderCallback* callback) {
   DCHECK(!initialized_);
-
   fake_consumer_.reset(new FakeAudioConsumer(message_loop_, params));
-
-  if (hash_audio_for_testing_) {
-    channels_ = params.channels();
-    md5_channel_contexts_.reset(new base::MD5Context[params.channels()]);
-    for (int i = 0; i < params.channels(); i++)
-      base::MD5Init(&md5_channel_contexts_[i]);
-  }
-
   callback_ = callback;
   initialized_ = true;
 }
@@ -85,47 +73,19 @@ void NullAudioSink::CallRender(AudioBus* audio_bus) {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   int frames_received = callback_->Render(audio_bus, 0);
-  if (!hash_audio_for_testing_ || frames_received <= 0)
+  if (!audio_hash_ || frames_received <= 0)
     return;
 
-  DCHECK_EQ(sizeof(float), sizeof(uint32));
-  int channels = audio_bus->channels();
-  for (int channel_idx = 0; channel_idx < channels; ++channel_idx) {
-    float* channel = audio_bus->channel(channel_idx);
-    for (int frame_idx = 0; frame_idx < frames_received; frame_idx++) {
-      // Convert float to uint32 w/o conversion loss.
-      uint32 frame = base::ByteSwapToLE32(bit_cast<uint32>(channel[frame_idx]));
-      base::MD5Update(&md5_channel_contexts_[channel_idx], base::StringPiece(
-          reinterpret_cast<char*>(&frame), sizeof(frame)));
-    }
-  }
+  audio_hash_->Update(audio_bus, frames_received);
 }
 
 void NullAudioSink::StartAudioHashForTesting() {
   DCHECK(!initialized_);
-  hash_audio_for_testing_ = true;
+  audio_hash_.reset(new AudioHash());
 }
 
 std::string NullAudioSink::GetAudioHashForTesting() {
-  DCHECK(hash_audio_for_testing_);
-
-  base::MD5Digest digest;
-  if (channels_ == 0) {
-    // If initialize failed or was never called, ensure we return an empty hash.
-    base::MD5Context context;
-    base::MD5Init(&context);
-    base::MD5Final(&digest, &context);
-  } else {
-    // Hash all channels into the first channel.
-    for (int i = 1; i < channels_; i++) {
-      base::MD5Final(&digest, &md5_channel_contexts_[i]);
-      base::MD5Update(&md5_channel_contexts_[0], base::StringPiece(
-          reinterpret_cast<char*>(&digest), sizeof(base::MD5Digest)));
-    }
-    base::MD5Final(&digest, &md5_channel_contexts_[0]);
-  }
-
-  return base::MD5DigestToBase16(digest);
+  return audio_hash_ ? audio_hash_->ToString() : "";
 }
 
 }  // namespace media
diff --git a/media/audio/null_audio_sink.h b/media/audio/null_audio_sink.h
index 9fb7237..37022b7 100644
--- a/media/audio/null_audio_sink.h
+++ b/media/audio/null_audio_sink.h
@@ -5,7 +5,8 @@
 #ifndef MEDIA_AUDIO_NULL_AUDIO_SINK_H_
 #define MEDIA_AUDIO_NULL_AUDIO_SINK_H_
 
-#include "base/md5.h"
+#include <string>
+
 #include "base/memory/scoped_ptr.h"
 #include "media/base/audio_renderer_sink.h"
 
@@ -15,6 +16,7 @@ class MessageLoopProxy;
 
 namespace media {
 class AudioBus;
+class AudioHash;
 class FakeAudioConsumer;
 
 class MEDIA_EXPORT NullAudioSink
@@ -31,11 +33,10 @@ class MEDIA_EXPORT NullAudioSink
   virtual void Play() OVERRIDE;
   virtual bool SetVolume(double volume) OVERRIDE;
 
-  // Enables audio frame hashing and reinitializes the MD5 context.  Must be
-  // called prior to Initialize().
+  // Enables audio frame hashing.  Must be called prior to Initialize().
   void StartAudioHashForTesting();
 
-  // Returns the MD5 hash of all audio frames seen since the last reset.
+  // Returns the hash of all audio frames seen since construction.
   std::string GetAudioHashForTesting();
 
  protected:
@@ -49,10 +50,8 @@ class MEDIA_EXPORT NullAudioSink
   bool playing_;
   RenderCallback* callback_;
 
-  // Controls whether or not a running MD5 hash is computed for audio frames.
-  bool hash_audio_for_testing_;
-  int channels_;
-  scoped_array<base::MD5Context> md5_channel_contexts_;
+  // Controls whether or not a running hash is computed for audio frames.
+  scoped_ptr<AudioHash> audio_hash_;
 
   scoped_refptr<base::MessageLoopProxy> message_loop_;
   scoped_ptr<FakeAudioConsumer> fake_consumer_;