Index: webrtc/modules/audio_processing/utility/blocker.h |
diff --git a/webrtc/modules/audio_processing/utility/blocker.h b/webrtc/modules/audio_processing/utility/blocker.h |
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-/* |
- * Copyright (c) 2014 The WebRTC project authors. All Rights Reserved. |
- * |
- * Use of this source code is governed by a BSD-style license |
- * that can be found in the LICENSE file in the root of the source |
- * tree. An additional intellectual property rights grant can be found |
- * in the file PATENTS. All contributing project authors may |
- * be found in the AUTHORS file in the root of the source tree. |
- */ |
- |
-#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_BLOCKER_H_ |
-#define WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_BLOCKER_H_ |
- |
-#include <memory> |
- |
-#include "webrtc/common_audio/channel_buffer.h" |
-#include "webrtc/modules/audio_processing/utility/audio_ring_buffer.h" |
- |
-namespace webrtc { |
- |
-// The callback function to process audio in the time domain. Input has already |
-// been windowed, and output will be windowed. The number of input channels |
-// must be >= the number of output channels. |
-class BlockerCallback { |
- public: |
- virtual ~BlockerCallback() {} |
- |
- virtual void ProcessBlock(const float* const* input, |
- size_t num_frames, |
- size_t num_input_channels, |
- size_t num_output_channels, |
- float* const* output) = 0; |
-}; |
- |
-// The main purpose of Blocker is to abstract away the fact that often we |
-// receive a different number of audio frames than our transform takes. For |
-// example, most FFTs work best when the fft-size is a power of 2, but suppose |
-// we receive 20ms of audio at a sample rate of 48000. That comes to 960 frames |
-// of audio, which is not a power of 2. Blocker allows us to specify the |
-// transform and all other necessary processing via the Process() callback |
-// function without any constraints on the transform-size |
-// (read: |block_size_|) or received-audio-size (read: |chunk_size_|). |
-// We handle this for the multichannel audio case, allowing for different |
-// numbers of input and output channels (for example, beamforming takes 2 or |
-// more input channels and returns 1 output channel). Audio signals are |
-// represented as deinterleaved floats in the range [-1, 1]. |
-// |
-// Blocker is responsible for: |
-// - blocking audio while handling potential discontinuities on the edges |
-// of chunks |
-// - windowing blocks before sending them to Process() |
-// - windowing processed blocks, and overlap-adding them together before |
-// sending back a processed chunk |
-// |
-// To use blocker: |
-// 1. Impelment a BlockerCallback object |bc|. |
-// 2. Instantiate a Blocker object |b|, passing in |bc|. |
-// 3. As you receive audio, call b.ProcessChunk() to get processed audio. |
-// |
-// A small amount of delay is added to the first received chunk to deal with |
-// the difference in chunk/block sizes. This delay is <= chunk_size. |
-// |
-// Ownership of window is retained by the caller. That is, Blocker makes a |
-// copy of window and does not attempt to delete it. |
-class Blocker { |
- public: |
- Blocker(size_t chunk_size, |
- size_t block_size, |
- size_t num_input_channels, |
- size_t num_output_channels, |
- const float* window, |
- size_t shift_amount, |
- BlockerCallback* callback); |
- |
- void ProcessChunk(const float* const* input, |
- size_t chunk_size, |
- size_t num_input_channels, |
- size_t num_output_channels, |
- float* const* output); |
- |
- private: |
- const size_t chunk_size_; |
- const size_t block_size_; |
- const size_t num_input_channels_; |
- const size_t num_output_channels_; |
- |
- // The number of frames of delay to add at the beginning of the first chunk. |
- const size_t initial_delay_; |
- |
- // The frame index into the input buffer where the first block should be read |
- // from. This is necessary because shift_amount_ is not necessarily a |
- // multiple of chunk_size_, so blocks won't line up at the start of the |
- // buffer. |
- size_t frame_offset_; |
- |
- // Since blocks nearly always overlap, there are certain blocks that require |
- // frames from the end of one chunk and the beginning of the next chunk. The |
- // input and output buffers are responsible for saving those frames between |
- // calls to ProcessChunk(). |
- // |
- // Both contain |initial delay| + |chunk_size| frames. The input is a fairly |
- // standard FIFO, but due to the overlap-add it's harder to use an |
- // AudioRingBuffer for the output. |
- AudioRingBuffer input_buffer_; |
- ChannelBuffer<float> output_buffer_; |
- |
- // Space for the input block (can't wrap because of windowing). |
- ChannelBuffer<float> input_block_; |
- |
- // Space for the output block (can't wrap because of overlap/add). |
- ChannelBuffer<float> output_block_; |
- |
- std::unique_ptr<float[]> window_; |
- |
- // The amount of frames between the start of contiguous blocks. For example, |
- // |shift_amount_| = |block_size_| / 2 for a Hann window. |
- size_t shift_amount_; |
- |
- BlockerCallback* callback_; |
-}; |
- |
-} // namespace webrtc |
- |
-#endif // WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_BLOCKER_H_ |