Hold AudioConverterRef via ScopedTypeRef

There were two issues with the way AudioConverterRef was used by
AudioToolboxAudioDecoder:

  - `decoder_` was a plain pointer that was used uninitialized if
    AudioConverterNew() was never called

  - CreateAACDecoder() leaked an AudioConverter object upon
    re-initialization.

Both issues are fixed automatically by using base::ScopedTypeRef, and
potential future similar issues are easier to avoid this way too.

Fixed: 1394683
Change-Id: I9f4c4695c931ee840dd2c40ce0db31d144ec0b1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4061479
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Auto-Submit: Wojciech Dzierżanowski <wdzierzanowski@opera.com>
Cr-Commit-Position: refs/heads/main@{#1077615}

media/filters/mac/audio_toolbox_audio_decoder.cc

@@ -128,17 +128,26 @@ OSStatus ProvideInputCallback(AudioConverterRef decoder,
 
 }  // namespace
 
-AudioToolboxAudioDecoder::AudioToolboxAudioDecoder() = default;
-
-AudioToolboxAudioDecoder::~AudioToolboxAudioDecoder() {
-  if (!decoder_)
-    return;
+// static
+AudioConverterRef
+AudioToolboxAudioDecoder::ScopedAudioConverterRefTraits::Retain(
+    AudioConverterRef converter) {
+  NOTREACHED() << "Only compatible with ASSUME policy";
+  return converter;
+}
 
-  const auto result = AudioConverterDispose(decoder_);
+// static
+void AudioToolboxAudioDecoder::ScopedAudioConverterRefTraits::Release(
+    AudioConverterRef converter) {
+  const auto result = AudioConverterDispose(converter);
   OSSTATUS_DLOG_IF(WARNING, result != noErr, result)
       << "AudioConverterDispose() failed";
 }
 
+AudioToolboxAudioDecoder::AudioToolboxAudioDecoder() = default;
+
+AudioToolboxAudioDecoder::~AudioToolboxAudioDecoder() = default;
+
 AudioDecoderType AudioToolboxAudioDecoder::GetDecoderType() const {
   return AudioDecoderType::kAudioToolbox;
 }
@@ -160,6 +169,9 @@ void AudioToolboxAudioDecoder::Initialize(const AudioDecoderConfig& config,
     return;
   }
 
+  // This decoder supports re-initialization.
+  decoder_.reset();
+
   output_cb_ = output_cb;
   BindToCurrentLoop(std::move(init_cb))
       .Run(CreateAACDecoder(config)
@@ -280,7 +292,8 @@ bool AudioToolboxAudioDecoder::CreateAACDecoder(
       output_format.mBitsPerChannel / 8;
 
   // Create the decoder.
-  auto result = AudioConverterNew(&input_format, &output_format, &decoder_);
+  auto result = AudioConverterNew(&input_format, &output_format,
+                                  decoder_.InitializeInto());
   if (result != noErr) {
     OSSTATUS_DLOG(ERROR, result) << "AudioConverterNew() failed";
     return false;

media/filters/mac/audio_toolbox_audio_decoder.h

@@ -42,10 +42,18 @@ class MEDIA_EXPORT AudioToolboxAudioDecoder : public AudioDecoder {
   bool NeedsBitstreamConversion() const override;
 
  private:
+  struct ScopedAudioConverterRefTraits {
+    static AudioConverterRef InvalidValue() { return nullptr; }
+    static AudioConverterRef Retain(AudioConverterRef converter);
+    static void Release(AudioConverterRef converter);
+  };
+  using ScopedAudioConverterRef =
+      base::ScopedTypeRef<AudioConverterRef, ScopedAudioConverterRefTraits>;
+
   bool CreateAACDecoder(const AudioDecoderConfig& config);
 
   // "Converter" for turning encoded samples into raw audio.
-  AudioConverterRef decoder_;
+  ScopedAudioConverterRef decoder_;
 
   // Actual channel count and layout from decoder, may be different than config.
   uint32_t channel_count_ = 0u;