text: /*
   * Copyright (C) 2011-2013 Michael Niedermayer (michaelni@gmx.at)
   *
   * This file is part of libswresample
   *
   * libswresample is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * libswresample is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with libswresample; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef SWRESAMPLE_SWRESAMPLE_H
  #define SWRESAMPLE_SWRESAMPLE_H
  
  /**
   * @file
   * @ingroup lswr
   * libswresample public header
   */
  
  /**
   * @defgroup lswr Libswresample
   * @{
   *
   * Libswresample (lswr) is a library that handles audio resampling, sample
   * format conversion and mixing.
   *
   * Interaction with lswr is done through SwrContext, which is
   * allocated with swr_alloc() or swr_alloc_set_opts(). It is opaque, so all parameters
   * must be set with the @ref avoptions API.
   *
   * The first thing you will need to do in order to use lswr is to allocate
   * SwrContext. This can be done with swr_alloc() or swr_alloc_set_opts(). If you
   * are using the former, you must set options through the @ref avoptions API.
   * The latter function provides the same feature, but it allows you to set some
   * common options in the same statement.
   *
   * For example the following code will setup conversion from planar float sample
   * format to interleaved signed 16-bit integer, downsampling from 48kHz to
   * 44.1kHz and downmixing from 5.1 channels to stereo (using the default mixing
   * matrix). This is using the swr_alloc() function.
   * @code
   * SwrContext *swr = swr_alloc();
   * av_opt_set_channel_layout(swr, "in_channel_layout",  AV_CH_LAYOUT_5POINT1, 0);
   * av_opt_set_channel_layout(swr, "out_channel_layout", AV_CH_LAYOUT_STEREO,  0);
   * av_opt_set_int(swr, "in_sample_rate",     48000,                0);
   * av_opt_set_int(swr, "out_sample_rate",    44100,                0);
   * av_opt_set_sample_fmt(swr, "in_sample_fmt",  AV_SAMPLE_FMT_FLTP, 0);
   * av_opt_set_sample_fmt(swr, "out_sample_fmt", AV_SAMPLE_FMT_S16,  0);
   * @endcode
   *
   * The same job can be done using swr_alloc_set_opts() as well:
   * @code
   * SwrContext *swr = swr_alloc_set_opts(NULL,  // we're allocating a new context
   *                       AV_CH_LAYOUT_STEREO,  // out_ch_layout
   *                       AV_SAMPLE_FMT_S16,    // out_sample_fmt
   *                       44100,                // out_sample_rate
   *                       AV_CH_LAYOUT_5POINT1, // in_ch_layout
   *                       AV_SAMPLE_FMT_FLTP,   // in_sample_fmt
   *                       48000,                // in_sample_rate
   *                       0,                    // log_offset
   *                       NULL);                // log_ctx
   * @endcode
   *
   * Once all values have been set, it must be initialized with swr_init(). If
   * you need to change the conversion parameters, you can change the parameters
   * using @ref AVOptions, as described above in the first example; or by using
   * swr_alloc_set_opts(), but with the first argument the allocated context.
   * You must then call swr_init() again.
   *
   * The conversion itself is done by repeatedly calling swr_convert().
   * Note that the samples may get buffered in swr if you provide insufficient
   * output space or if sample rate conversion is done, which requires "future"
   * samples. Samples that do not require future input can be retrieved at any
   * time by using swr_convert() (in_count can be set to 0).
   * At the end of conversion the resampling buffer can be flushed by calling
   * swr_convert() with NULL in and 0 in_count.
   *
   * The samples used in the conversion process can be managed with the libavutil
   * @ref lavu_sampmanip "samples manipulation" API, including av_samples_alloc()
   * function used in the following example.
   *
   * The delay between input and output, can at any time be found by using
   * swr_get_delay().
   *
   * The following code demonstrates the conversion loop assuming the parameters
   * from above and caller-defined functions get_input() and handle_output():
   * @code
   * uint8_t **input;
   * int in_samples;
   *
   * while (get_input(&input, &in_samples)) {
   *     uint8_t *output;
   *     int out_samples = av_rescale_rnd(swr_get_delay(swr, 48000) +
   *                                      in_samples, 44100, 48000, AV_ROUND_UP);
   *     av_samples_alloc(&output, NULL, 2, out_samples,
   *                      AV_SAMPLE_FMT_S16, 0);
   *     out_samples = swr_convert(swr, &output, out_samples,
   *                                      input, in_samples);
   *     handle_output(output, out_samples);
   *     av_freep(&output);
   * }
   * @endcode
   *
   * When the conversion is finished, the conversion
   * context and everything associated with it must be freed with swr_free().
   * A swr_close() function is also available, but it exists mainly for
   * compatibility with libavresample, and is not required to be called.
   *
   * There will be no memory leak if the data is not completely flushed before
   * swr_free().
   */
  
  #include <stdint.h>
  #include "libavutil/frame.h"
  #include "libavutil/samplefmt.h"
  
  #include "libswresample/version.h"
  
  #if LIBSWRESAMPLE_VERSION_MAJOR < 1
  #define SWR_CH_MAX 32   ///< Maximum number of channels
  #endif
  
  /**
   * @name Option constants
   * These constants are used for the @ref avoptions interface for lswr.
   * @{
   *
   */
  
  #define SWR_FLAG_RESAMPLE 1 ///< Force resampling even if equal sample rate
  //TODO use int resample ?
  //long term TODO can we enable this dynamically?
  
  /** Dithering algorithms */
  enum SwrDitherType {
      SWR_DITHER_NONE = 0,
      SWR_DITHER_RECTANGULAR,
      SWR_DITHER_TRIANGULAR,
      SWR_DITHER_TRIANGULAR_HIGHPASS,
  
      SWR_DITHER_NS = 64,         ///< not part of API/ABI
      SWR_DITHER_NS_LIPSHITZ,
      SWR_DITHER_NS_F_WEIGHTED,
      SWR_DITHER_NS_MODIFIED_E_WEIGHTED,
      SWR_DITHER_NS_IMPROVED_E_WEIGHTED,
      SWR_DITHER_NS_SHIBATA,
      SWR_DITHER_NS_LOW_SHIBATA,
      SWR_DITHER_NS_HIGH_SHIBATA,
      SWR_DITHER_NB,              ///< not part of API/ABI
  };
  
  /** Resampling Engines */
  enum SwrEngine {
      SWR_ENGINE_SWR,             /**< SW Resampler */
      SWR_ENGINE_SOXR,            /**< SoX Resampler */
      SWR_ENGINE_NB,              ///< not part of API/ABI
  };
  
  /** Resampling Filter Types */
  enum SwrFilterType {
      SWR_FILTER_TYPE_CUBIC,              /**< Cubic */
      SWR_FILTER_TYPE_BLACKMAN_NUTTALL,   /**< Blackman Nuttall windowed sinc */
      SWR_FILTER_TYPE_KAISER,             /**< Kaiser windowed sinc */
  };
  
  /**
   * @}
   */
  
  /**
   * The libswresample context. Unlike libavcodec and libavformat, this structure
   * is opaque. This means that if you would like to set options, you must use
   * the @ref avoptions API and cannot directly set values to members of the
   * structure.
   */
  typedef struct SwrContext SwrContext;
  
  /**
   * Get the AVClass for SwrContext. It can be used in combination with
   * AV_OPT_SEARCH_FAKE_OBJ for examining options.
   *
   * @see av_opt_find().
   * @return the AVClass of SwrContext
   */
  const AVClass *swr_get_class(void);
  
  /**
   * @name SwrContext constructor functions
   * @{
   */
  
  /**
   * Allocate SwrContext.
   *
   * If you use this function you will need to set the parameters (manually or
   * with swr_alloc_set_opts()) before calling swr_init().
   *
   * @see swr_alloc_set_opts(), swr_init(), swr_free()
   * @return NULL on error, allocated context otherwise
   */
  struct SwrContext *swr_alloc(void);
  
  /**
   * Initialize context after user parameters have been set.
   * @note The context must be configured using the AVOption API.
   *
   * @see av_opt_set_int()
   * @see av_opt_set_dict()
   *
   * @param[in,out]   s Swr context to initialize
   * @return AVERROR error code in case of failure.
   */
  int swr_init(struct SwrContext *s);
  
  /**
   * Check whether an swr context has been initialized or not.
   *
   * @param[in]       s Swr context to check
   * @see swr_init()
   * @return positive if it has been initialized, 0 if not initialized
   */
  int swr_is_initialized(struct SwrContext *s);
  
  /**
   * Allocate SwrContext if needed and set/reset common parameters.
   *
   * This function does not require s to be allocated with swr_alloc(). On the
   * other hand, swr_alloc() can use swr_alloc_set_opts() to set the parameters
   * on the allocated context.
   *
   * @param s               existing Swr context if available, or NULL if not
   * @param out_ch_layout   output channel layout (AV_CH_LAYOUT_*)
   * @param out_sample_fmt  output sample format (AV_SAMPLE_FMT_*).
   * @param out_sample_rate output sample rate (frequency in Hz)
   * @param in_ch_layout    input channel layout (AV_CH_LAYOUT_*)
   * @param in_sample_fmt   input sample format (AV_SAMPLE_FMT_*).
   * @param in_sample_rate  input sample rate (frequency in Hz)
   * @param log_offset      logging level offset
   * @param log_ctx         parent logging context, can be NULL
   *
   * @see swr_init(), swr_free()
   * @return NULL on error, allocated context otherwise
   */
  struct SwrContext *swr_alloc_set_opts(struct SwrContext *s,
                                        int64_t out_ch_layout, enum AVSampleFormat out_sample_fmt, int out_sample_rate,
                                        int64_t  in_ch_layout, enum AVSampleFormat  in_sample_fmt, int  in_sample_rate,
                                        int log_offset, void *log_ctx);
  
  /**
   * @}
   *
   * @name SwrContext destructor functions
   * @{
   */
  
  /**
   * Free the given SwrContext and set the pointer to NULL.
   *
   * @param[in] s a pointer to a pointer to Swr context
   */
  void swr_free(struct SwrContext **s);
  
  /**
   * Closes the context so that swr_is_initialized() returns 0.
   *
   * The context can be brought back to life by running swr_init(),
   * swr_init() can also be used without swr_close().
   * This function is mainly provided for simplifying the usecase
   * where one tries to support libavresample and libswresample.
   *
   * @param[in,out] s Swr context to be closed
   */
  void swr_close(struct SwrContext *s);
  
  /**
   * @}
   *
   * @name Core conversion functions
   * @{
   */
  
  /** Convert audio.
   *
   * in and in_count can be set to 0 to flush the last few samples out at the
   * end.
   *
   * If more input is provided than output space, then the input will be buffered.
   * You can avoid this buffering by using swr_get_out_samples() to retrieve an
   * upper bound on the required number of output samples for the given number of
   * input samples. Conversion will run directly without copying whenever possible.
   *
   * @param s         allocated Swr context, with parameters set
   * @param out       output buffers, only the first one need be set in case of packed audio
   * @param out_count amount of space available for output in samples per channel
   * @param in        input buffers, only the first one need to be set in case of packed audio
   * @param in_count  number of input samples available in one channel
   *
   * @return number of samples output per channel, negative value on error
   */
  int swr_convert(struct SwrContext *s, uint8_t **out, int out_count,
                                  const uint8_t **in , int in_count);
  
  /**
   * Convert the next timestamp from input to output
   * timestamps are in 1/(in_sample_rate * out_sample_rate) units.
   *
   * @note There are 2 slightly differently behaving modes.
   *       @li When automatic timestamp compensation is not used, (min_compensation >= FLT_MAX)
   *              in this case timestamps will be passed through with delays compensated
   *       @li When automatic timestamp compensation is used, (min_compensation < FLT_MAX)
   *              in this case the output timestamps will match output sample numbers.
   *              See ffmpeg-resampler(1) for the two modes of compensation.
   *
   * @param s[in]     initialized Swr context
   * @param pts[in]   timestamp for the next input sample, INT64_MIN if unknown
   * @see swr_set_compensation(), swr_drop_output(), and swr_inject_silence() are
   *      function used internally for timestamp compensation.
   * @return the output timestamp for the next output sample
   */
  int64_t swr_next_pts(struct SwrContext *s, int64_t pts);
  
  /**
   * @}
   *
   * @name Low-level option setting functions
   * These functons provide a means to set low-level options that is not possible
   * with the AVOption API.
   * @{
   */
  
  /**
   * Activate resampling compensation ("soft" compensation). This function is
   * internally called when needed in swr_next_pts().
   *
   * @param[in,out] s             allocated Swr context. If it is not initialized,
   *                              or SWR_FLAG_RESAMPLE is not set, swr_init() is
   *                              called with the flag set.
   * @param[in]     sample_delta  delta in PTS per sample
   * @param[in]     compensation_distance number of samples to compensate for
   * @return    >= 0 on success, AVERROR error codes if:
   *            @li @c s is NULL,
   *            @li @c compensation_distance is less than 0,
   *            @li @c compensation_distance is 0 but sample_delta is not,
   *            @li compensation unsupported by resampler, or
   *            @li swr_init() fails when called.
   */
  int swr_set_compensation(struct SwrContext *s, int sample_delta, int compensation_distance);
  
  /**
   * Set a customized input channel mapping.
   *
   * @param[in,out] s           allocated Swr context, not yet initialized
   * @param[in]     channel_map customized input channel mapping (array of channel
   *                            indexes, -1 for a muted channel)
   * @return >= 0 on success, or AVERROR error code in case of failure.
   */
  int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map);
  
  /**
   * Set a customized remix matrix.
   *
   * @param s       allocated Swr context, not yet initialized
   * @param matrix  remix coefficients; matrix[i + stride * o] is
   *                the weight of input channel i in output channel o
   * @param stride  offset between lines of the matrix
   * @return  >= 0 on success, or AVERROR error code in case of failure.
   */
  int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride);
  
  /**
   * @}
   *
   * @name Sample handling functions
   * @{
   */
  
  /**
   * Drops the specified number of output samples.
   *
   * This function, along with swr_inject_silence(), is called by swr_next_pts()
   * if needed for "hard" compensation.
   *
   * @param s     allocated Swr context
   * @param count number of samples to be dropped
   *
   * @return >= 0 on success, or a negative AVERROR code on failure
   */
  int swr_drop_output(struct SwrContext *s, int count);
  
  /**
   * Injects the specified number of silence samples.
   *
   * This function, along with swr_drop_output(), is called by swr_next_pts()
   * if needed for "hard" compensation.
   *
   * @param s     allocated Swr context
   * @param count number of samples to be dropped
   *
   * @return >= 0 on success, or a negative AVERROR code on failure
   */
  int swr_inject_silence(struct SwrContext *s, int count);
  
  /**
   * Gets the delay the next input sample will experience relative to the next output sample.
   *
   * Swresample can buffer data if more input has been provided than available
   * output space, also converting between sample rates needs a delay.
   * This function returns the sum of all such delays.
   * The exact delay is not necessarily an integer value in either input or
   * output sample rate. Especially when downsampling by a large value, the
   * output sample rate may be a poor choice to represent the delay, similarly
   * for upsampling and the input sample rate.
   *
   * @param s     swr context
   * @param base  timebase in which the returned delay will be:
   *              @li if it's set to 1 the returned delay is in seconds
   *              @li if it's set to 1000 the returned delay is in milliseconds
   *              @li if it's set to the input sample rate then the returned
   *                  delay is in input samples
   *              @li if it's set to the output sample rate then the returned
   *                  delay is in output samples
   *              @li if it's the least common multiple of in_sample_rate and
   *                  out_sample_rate then an exact rounding-free delay will be
   *                  returned
   * @returns     the delay in 1 / @c base units.
   */
  int64_t swr_get_delay(struct SwrContext *s, int64_t base);
  
  /**
   * Find an upper bound on the number of samples that the next swr_convert
   * call will output, if called with in_samples of input samples. This
   * depends on the internal state, and anything changing the internal state
   * (like further swr_convert() calls) will may change the number of samples
   * swr_get_out_samples() returns for the same number of input samples.
   *
   * @param in_samples    number of input samples.
   * @note any call to swr_inject_silence(), swr_convert(), swr_next_pts()
   *       or swr_set_compensation() invalidates this limit
   * @note it is recommended to pass the correct available buffer size
   *       to all functions like swr_convert() even if swr_get_out_samples()
   *       indicates that less would be used.
   * @returns an upper bound on the number of samples that the next swr_convert
   *          will output or a negative value to indicate an error
   */
  int swr_get_out_samples(struct SwrContext *s, int in_samples);
  
  /**
   * @}
   *
   * @name Configuration accessors
   * @{
   */
  
  /**
   * Return the @ref LIBSWRESAMPLE_VERSION_INT constant.
   *
   * This is useful to check if the build-time libswresample has the same version
   * as the run-time one.
   *
   * @returns     the unsigned int-typed version
   */
  unsigned swresample_version(void);
  
  /**
   * Return the swr build-time configuration.
   *
   * @returns     the build-time @c ./configure flags
   */
  const char *swresample_configuration(void);
  
  /**
   * Return the swr license.
   *
   * @returns     the license of libswresample, determined at build-time
   */
  const char *swresample_license(void);
  
  /**
   * @}
   *
   * @name AVFrame based API
   * @{
   */
  
  /**
   * Convert the samples in the input AVFrame and write them to the output AVFrame.
   *
   * Input and output AVFrames must have channel_layout, sample_rate and format set.
   *
   * If the output AVFrame does not have the data pointers allocated the nb_samples
   * field will be set using av_frame_get_buffer()
   * is called to allocate the frame.
   *
   * The output AVFrame can be NULL or have fewer allocated samples than required.
   * In this case, any remaining samples not written to the output will be added
   * to an internal FIFO buffer, to be returned at the next call to this function
   * or to swr_convert().
   *
   * If converting sample rate, there may be data remaining in the internal
   * resampling delay buffer. swr_get_delay() tells the number of
   * remaining samples. To get this data as output, call this function or
   * swr_convert() with NULL input.
   *
   * If the SwrContext configuration does not match the output and
   * input AVFrame settings the conversion does not take place and depending on
   * which AVFrame is not matching AVERROR_OUTPUT_CHANGED, AVERROR_INPUT_CHANGED
   * or the result of a bitwise-OR of them is returned.
   *
   * @see swr_delay()
   * @see swr_convert()
   * @see swr_get_delay()
   *
   * @param swr             audio resample context
   * @param output          output AVFrame
   * @param input           input AVFrame
   * @return                0 on success, AVERROR on failure or nonmatching
   *                        configuration.
   */
  int swr_convert_frame(SwrContext *swr,
                        AVFrame *output, const AVFrame *input);
  
  /**
   * Configure or reconfigure the SwrContext using the information
   * provided by the AVFrames.
   *
   * The original resampling context is reset even on failure.
   * The function calls swr_close() internally if the context is open.
   *
   * @see swr_close();
   *
   * @param swr             audio resample context
   * @param output          output AVFrame
   * @param input           input AVFrame
   * @return                0 on success, AVERROR on failure.
   */
  int swr_config_frame(SwrContext *swr, const AVFrame *out, const AVFrame *in);
  
  /**
   * @}
   * @}
   */
  
  #endif /* SWRESAMPLE_SWRESAMPLE_H */
  