text: /*******************************************************************************
   * Copyright 2009-2016 Jörg Müller
   *
   * 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.
   ******************************************************************************/
  
  #pragma once
  
  #include "AUD_Types.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * Retrieves the sample specification of the sound.
   * \param sound The sound to retrieve from.
   * \return The sample specification of the sound.
   * \note This function creates a reader from the sound and deletes it again.
   */
  extern AUD_API AUD_Specs AUD_Sound_getSpecs(AUD_Sound* sound);
  
  /**
   * Retrieves the approximate length of the sound.
   * \param sound The sound to retrieve from.
   * \return The length of the sound in samples.
   * \note This function creates a reader from the sound and deletes it again.
   */
  extern AUD_API int AUD_getLength(AUD_Sound* sound);
  
  /**
   * Reads a sound's samples into memory.
   * \param sound The sound to read.
   * \param length Pointer to store the length of memory read.
   * \param specs Pointer to store the data's sample specification.
   * \return A pointer to the sample data.
   * \warning The data has to be freed with AUD_Sound_freeData.
   */
  extern AUD_API sample_t* AUD_Sound_data(AUD_Sound* sound, int* length, AUD_Specs* specs);
  
  /**
   * Frees a buffer previously allocated with AUD_Sound_data.
   * \param data The buffer to be freed.
   */
  extern AUD_API void AUD_Sound_freeData(sample_t* data);
  
  /**
   * Writes the sound to a file.
   * \param sound The sound to write.
   * \param filename The path to write to..
   * \param rate The sample rate to write with.
   * \param channels The number of channels to write with.
   * \param format The sample format to write with.
   * \param container The container format for the file.
   * \param codec The codec to use in the file.
   * \param bitrate The bitrate to write with.
   * \param buffersize The size of the writing buffer.
   * \return A nullptr or an error message in case of error.
   * \note Most parameters can be set to zero for default values.
   */
  extern AUD_API const char* AUD_Sound_write(AUD_Sound* sound, const char* filename, AUD_SampleRate rate, AUD_Channels channels, AUD_SampleFormat format, AUD_Container container, AUD_Codec codec, int bitrate, int buffersize);
  
  /**
   * Creates a sound from a data buffer.
   * \param data The data as interleaved samples.
   * \param length The data's length in samples.
   * \param specs The data's sample specification.
   * \return A handle of the sound.
   * \note The data gets copied to an internal memory buffer.
   *       The pointer does not need to stay valid for the lifetime of the object.
   */
  extern AUD_API AUD_Sound* AUD_Sound_buffer(sample_t* data, int length, AUD_Specs specs);
  
  /**
   * Loads a sound file from a memory buffer.
   * \param buffer The buffer which contains the sound file.
   * \param size The size of the buffer.
   * \return A handle of the sound file.
   */
  extern AUD_API AUD_Sound* AUD_Sound_bufferFile(unsigned char* buffer, int size);
  
  /**
   * Caches a sound into a memory buffer.
   * \param sound The sound to cache.
   * \return A handle of the cached sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_cache(AUD_Sound* sound);
  
  /**
   * Loads a sound file.
   * \param filename The filename of the sound file.
   * \return A handle of the sound file.
   */
  extern AUD_API AUD_Sound* AUD_Sound_file(const char* filename);
  
  /**
   * Creates a sawtooth sound.
   * \param frequency The frequency of the generated sawtooth sound.
   * \param rate The sample rate of the sawtooth sound.
   * \return A handle of the sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_sawtooth(float frequency, AUD_SampleRate rate);
  
  /**
   * Creates a quiet sound.
   * \return A handle of the sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_silence();
  
  /**
   * Creates a sine sound.
   * \param frequency The frequency of the generated sine sound.
   * \param rate The sample rate of the sine sound.
   * \return A handle of the sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_sine(float frequency, AUD_SampleRate rate);
  
  /**
   * Creates a square sound.
   * \param frequency The frequency of the generated square sound.
   * \param rate The sample rate of the square sound.
   * \return A handle of the sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_square(float frequency, AUD_SampleRate rate);
  
  /**
   * Creates a triangle sound.
   * \param frequency The frequency of the generated triangle sound.
   * \param rate The sample rate of the triangle sound.
   * \return A handle of the sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_triangle(float frequency, AUD_SampleRate rate);
  
  /**
   * Accumulates a sound by summing over positive input differences thus generating a monotonic sigal.
   * If additivity is set to true negative input differences get added too, but positive ones with a factor of two.
   * Note that with additivity the signal is not monotonic anymore.
   * \param sound The sound to accumulate.
   * \param additive Whether the accumulation should be additive or not.
   * \return A handle of the accumulated sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_accumulate(AUD_Sound* sound, int additive);
  
  /**
   * Attack-Decay-Sustain-Release envelopes the volume of a sound.
   * Note: there is currently no way to trigger the release with this API.
   * \param sound The sound to filter.
   * \param attack The attack time in seconds.
   * \param decay The decay time in seconds.
   * \param sustain The sustain level.
   * \param release The release time in seconds.
   * \return A handle of the filtered sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_ADSR(AUD_Sound* sound, float attack, float decay, float sustain, float release);
  
  /**
   * Delays a sound.
   * \param sound The sound to dealy.
   * \param delay The delay in seconds.
   * \return A handle of the delayed sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_delay(AUD_Sound* sound, float delay);
  
  /**
   * Envelopes a sound.
   * \param sound The sound to envelope.
   * \param attack The attack factor.
   * \param release The release factor.
   * \param threshold The general threshold value.
   * \param arthreshold The attack/release threshold value.
   * \return A handle of the enveloped sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_envelope(AUD_Sound* sound, float attack, float release, float threshold, float arthreshold);
  
  /**
   * Fade in a sound.
   * \param sound The sound to be fade in.
   * \param start The time when the fading should start in seconds.
   * \param length The duration of the fade in seconds.
   * \return A handle of the faded sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_fadein(AUD_Sound* sound, float start, float length);
  
  /**
   * Fade out a sound.
   * \param sound The sound to be fade out.
   * \param start The time when the fading should start in seconds.
   * \param length The duration of the fade in seconds.
   * \return A handle of the faded sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_fadeout(AUD_Sound* sound, float start, float length);
  
  /**
   * Filter a sound.
   * \param sound The sound to be filtered.
   * \param b The nominator filter coefficients, may be NULL.
   * \param b_length The length of the b array.
   * \param a The denominator filter coefficients, may be NULL.
   * \param a_length The length of the a array.
   * \return A handle of the filtered sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_filter(AUD_Sound* sound, float* b, int b_length, float* a, int a_length);
  
  /**
   * Highpass filters a sound.
   * \param sound The sound to filter.
   * \param frequency The filter cut-off frequency.
   * \param Q The filter quality. If usunsure which value to use, pass 1.0f.
   * \return A handle of the filtered sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_highpass(AUD_Sound* sound, float frequency, float Q);
  
  /**
   * Limits a sound.
   * \param sound The sound to limit.
   * \param start The start time in seconds.
   * \param end The stop time in seconds.
   * \return A handle of the limited sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_limit(AUD_Sound* sound, float start, float end);
  
  /**
   * Loops a sound.
   * \param sound The sound to loop.
   * \param count How often the sound should be looped. Negative values mean endlessly.
   * \return A handle of the looped sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_loop(AUD_Sound* sound, int count);
  
  /**
   * Lowpass filters a sound.
   * \param sound The sound to filter.
   * \param frequency The filter cut-off frequency.
   * \param Q The filter quality. If usunsure which value to use, pass 1.0f.
   * \return A handle of the filtered sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_lowpass(AUD_Sound* sound, float frequency, float Q);
  
  /**
   * Modulates two sound, which means multiplying the sound samples.
   * \param first The first sound.
   * \param second The second sound.
   * \return A handle of the modulated sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_modulate(AUD_Sound* first, AUD_Sound* second);
  
  /**
   * Changes the pitch of a sound.
   * \param sound The sound to change.
   * \param factor The factor to change the pitch with.
   * \return A handle of the pitched sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_pitch(AUD_Sound* sound, float factor);
  
  /**
   * Rechannels the sound.
   * \param sound The sound to rechannel.
   * \param channels The new channel configuration.
   * \return The rechanneled sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_rechannel(AUD_Sound* sound, AUD_Channels channels);
  
  /**
   * Resamples the sound.
   * \param sound The sound to resample.
   * \param rate The new sample rate.
   * \param high_quality When true use a higher quality but slower resampler.
   * \return The resampled sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_resample(AUD_Sound* sound, AUD_SampleRate rate, bool high_quality);
  
  /**
   * Reverses a sound. Make sure the sound source can be reversed.
   * \param sound The sound to reverse.
   * \return A handle of the reversed sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_reverse(AUD_Sound* sound);
  
  /**
   * Sums the samples of a sound.
   * \param sound The sound to sum.
   * \return A handle of the summed sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_sum(AUD_Sound* sound);
  
  /**
   * Turns a sound into a square wave by thresholding.
   * \param sound The sound to threshold.
   * \param threshold Threshold value over which an amplitude counts non-zero.
   * \return A handle of the thresholded sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_threshold(AUD_Sound* sound, float threshold);
  
  /**
   * Changes the volume of a sound.
   * \param sound The sound to change.
   * \param volume The new volume of the sound. Should be in the range 0 to 1. Use higher values with caution.
   * \return A handle of the amplified sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_volume(AUD_Sound* sound, float volume);
  
  /**
   * Joins two sound, which means playing them one after the other.
   * \param first The first sound.
   * \param second The second sound.
   * \return A handle of the joined sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_join(AUD_Sound* first, AUD_Sound* second);
  
  /**
   * Mixes two sound, which means superposing the sound samples.
   * \param first The first sound.
   * \param second The second sound.
   * \return A handle of the mixed sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_mix(AUD_Sound* first, AUD_Sound* second);
  
  /**
   * Ping pongs a sound.
   * \param sound The sound to ping pong.
   * \return A handle of the ping pong sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_pingpong(AUD_Sound* sound);
  
  /**
   * Unloads a sound of any type.
   * \param sound The handle of the sound.
   */
  extern AUD_API void AUD_Sound_free(AUD_Sound* sound);
  
  /**
   * Copies a sound.
   * \param sound Sound to copy.
   * \return Copied sound.
   */
  extern AUD_API AUD_Sound* AUD_Sound_copy(AUD_Sound* sound);
  
  /**
   * Creates an empty sound list that can contain several sounds.
   * \param random A flag that indicates how the list will be played: Randomly or sequentially.
   *				if 0 the playback will be sequential, if not 0 the playback will be random.
   * \return A handle of the sound list.
   */
  extern AUD_API AUD_Sound* AUD_Sound_list(int random);
  
  /**
  * Adds a new sound to a sound list.
   * \param list The sound list in which the sound will be added.
   * \param sound The sound that will be added to the list.
   * \return 0 if the sound couldn't be added (the list parameter isn't a sound list).
  */
  extern AUD_API int AUD_SoundList_addSound(AUD_Sound* list, AUD_Sound* sound);
  
  /**
   * Creates a sound that will be restarted when sought backwards. If the original sound is a sound list, the playing sound can change.
   * \param sound The handle of the sound.
   * \return A handle of the mutable sound.
  */
  extern AUD_API AUD_Sound* AUD_Sound_mutable(AUD_Sound* sound);
  
  #ifdef WITH_CONVOLUTION
  	extern AUD_API AUD_Sound* AUD_Sound_Convolver(AUD_Sound* sound, AUD_ImpulseResponse* filter, AUD_ThreadPool* threadPool);
  	extern AUD_API AUD_Sound* AUD_Sound_Binaural(AUD_Sound* sound, AUD_HRTF* hrtfs, AUD_Source* source, AUD_ThreadPool* threadPool);
  #endif
  
  #ifdef __cplusplus
  }
  #endif
  