Extend downsampling ratios greater than 2:1

Also improve robustness to choice of sampling rate or buffer size
such that increasing either by 10x does not cause overflow.

Bug: 12979141
Bug: 15933066
Change-Id: If7989bd745d1bee3bdf811b8b7c978543ccafb65

1 files changed, 29 insertions, 0 deletions

diff --git a/include/media/AudioResamplerPublic.h b/include/media/AudioResamplerPublic.h
new file mode 100644
index 0000000..97847a0
--- /dev/null
+++ b/include/media/AudioResamplerPublic.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_AUDIO_RESAMPLER_PUBLIC_H
+#define ANDROID_AUDIO_RESAMPLER_PUBLIC_H
+
+// AUDIO_RESAMPLER_DOWN_RATIO_MAX is the maximum ratio between the original
+// audio sample rate and the target rate when downsampling,
+// as permitted in the audio framework, e.g. AudioTrack and AudioFlinger.
+// In practice, it is not recommended to downsample more than 6:1
+// for best audio quality, even though the audio framework permits a larger
+// downsampling ratio.
+// TODO: replace with an API
+#define AUDIO_RESAMPLER_DOWN_RATIO_MAX 256
+
+#endif // ANDROID_AUDIO_RESAMPLER_PUBLIC_H