channel_mixer.h revision 5821806d5e7f356e8fa4b058a389a808ea183019
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Copyright (c) 2012 The Chromium Authors. All rights reserved. 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// found in the LICENSE file. 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#ifndef MEDIA_BASE_CHANNEL_MIXER_H_ 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#define MEDIA_BASE_CHANNEL_MIXER_H_ 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include <vector> 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "base/basictypes.h" 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "media/base/channel_layout.h" 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "media/base/media_export.h" 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace media { 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)class AudioBus; 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// ChannelMixer is for converting audio between channel layouts. The conversion 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// matrix is built upon construction and used during each Transform() call. The 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// algorithm works by generating a conversion matrix mapping each output channel 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// to list of input channels. The transform renders all of the output channels, 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// with each output channel rendered according to a weighted sum of the relevant 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// input channels as defined in the matrix. 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)class MEDIA_EXPORT ChannelMixer { 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) public: 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ChannelMixer(ChannelLayout input, ChannelLayout output); 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ~ChannelMixer(); 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Transforms all channels from |input| into |output| channels. 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void Transform(const AudioBus* input, AudioBus* output); 315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) private: 335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Constructor helper methods for managing unaccounted input channels. 345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void AccountFor(Channels ch); 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool IsUnaccounted(Channels ch); 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Helper methods for checking if |ch| exists in either |input_layout_| or 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // |output_layout_| respectively. 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool HasInputChannel(Channels ch); 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool HasOutputChannel(Channels ch); 415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Constructor helper methods for updating |matrix_| with the proper value for 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // mixing |input_ch| into |output_ch|. MixWithoutAccounting() does not remove 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // the channel from |unaccounted_inputs_|. 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void Mix(Channels input_ch, Channels output_ch, float scale); 465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void MixWithoutAccounting(Channels input_ch, Channels output_ch, float scale); 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Input and output channel layout provided during construction. 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ChannelLayout input_layout_; 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ChannelLayout output_layout_; 515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Helper variable for tracking which inputs are currently unaccounted, should 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // be empty after construction completes. 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Channels> unaccounted_inputs_; 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // 2D matrix of output channels to input channels. 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector< std::vector<float> > matrix_; 585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Optimization case for when we can simply remap the input channels to output 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // channels and don't need to do a multiply-accumulate loop over |matrix_|. 615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool remapping_; 625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DISALLOW_COPY_AND_ASSIGN(ChannelMixer); 645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} // namespace media 675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#endif // MEDIA_BASE_CHANNEL_MIXER_H_ 69