FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
swresample.h
Go to the documentation of this file.
1 /*
2  * Copyright (C) 2011-2013 Michael Niedermayer (michaelni@gmx.at)
3  *
4  * This file is part of libswresample
5  *
6  * libswresample is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * libswresample is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with libswresample; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #ifndef SWRESAMPLE_SWRESAMPLE_H
22 #define SWRESAMPLE_SWRESAMPLE_H
23 
24 /**
25  * @file
26  * @ingroup lswr
27  * libswresample public header
28  */
29 
30 /**
31  * @defgroup lswr Libswresample
32  * @{
33  *
34  * Libswresample (lswr) is a library that handles audio resampling, sample
35  * format conversion and mixing.
36  *
37  * Interaction with lswr is done through SwrContext, which is
38  * allocated with swr_alloc() or swr_alloc_set_opts(). It is opaque, so all parameters
39  * must be set with the @ref avoptions API.
40  *
41  * The first thing you will need to do in order to use lswr is to allocate
42  * SwrContext. This can be done with swr_alloc() or swr_alloc_set_opts(). If you
43  * are using the former, you must set options through the @ref avoptions API.
44  * The latter function provides the same feature, but it allows you to set some
45  * common options in the same statement.
46  *
47  * For example the following code will setup conversion from planar float sample
48  * format to interleaved signed 16-bit integer, downsampling from 48kHz to
49  * 44.1kHz and downmixing from 5.1 channels to stereo (using the default mixing
50  * matrix). This is using the swr_alloc() function.
51  * @code
52  * SwrContext *swr = swr_alloc();
53  * av_opt_set_channel_layout(swr, "in_channel_layout", AV_CH_LAYOUT_5POINT1, 0);
54  * av_opt_set_channel_layout(swr, "out_channel_layout", AV_CH_LAYOUT_STEREO, 0);
55  * av_opt_set_int(swr, "in_sample_rate", 48000, 0);
56  * av_opt_set_int(swr, "out_sample_rate", 44100, 0);
57  * av_opt_set_sample_fmt(swr, "in_sample_fmt", AV_SAMPLE_FMT_FLTP, 0);
58  * av_opt_set_sample_fmt(swr, "out_sample_fmt", AV_SAMPLE_FMT_S16, 0);
59  * @endcode
60  *
61  * The same job can be done using swr_alloc_set_opts() as well:
62  * @code
63  * SwrContext *swr = swr_alloc_set_opts(NULL, // we're allocating a new context
64  * AV_CH_LAYOUT_STEREO, // out_ch_layout
65  * AV_SAMPLE_FMT_S16, // out_sample_fmt
66  * 44100, // out_sample_rate
67  * AV_CH_LAYOUT_5POINT1, // in_ch_layout
68  * AV_SAMPLE_FMT_FLTP, // in_sample_fmt
69  * 48000, // in_sample_rate
70  * 0, // log_offset
71  * NULL); // log_ctx
72  * @endcode
73  *
74  * Once all values have been set, it must be initialized with swr_init(). If
75  * you need to change the conversion parameters, you can change the parameters
76  * using @ref AVOptions, as described above in the first example; or by using
77  * swr_alloc_set_opts(), but with the first argument the allocated context.
78  * You must then call swr_init() again.
79  *
80  * The conversion itself is done by repeatedly calling swr_convert().
81  * Note that the samples may get buffered in swr if you provide insufficient
82  * output space or if sample rate conversion is done, which requires "future"
83  * samples. Samples that do not require future input can be retrieved at any
84  * time by using swr_convert() (in_count can be set to 0).
85  * At the end of conversion the resampling buffer can be flushed by calling
86  * swr_convert() with NULL in and 0 in_count.
87  *
88  * The samples used in the conversion process can be managed with the libavutil
89  * @ref lavu_sampmanip "samples manipulation" API, including av_samples_alloc()
90  * function used in the following example.
91  *
92  * The delay between input and output, can at any time be found by using
93  * swr_get_delay().
94  *
95  * The following code demonstrates the conversion loop assuming the parameters
96  * from above and caller-defined functions get_input() and handle_output():
97  * @code
98  * uint8_t **input;
99  * int in_samples;
100  *
101  * while (get_input(&input, &in_samples)) {
102  * uint8_t *output;
103  * int out_samples = av_rescale_rnd(swr_get_delay(swr, 48000) +
104  * in_samples, 44100, 48000, AV_ROUND_UP);
105  * av_samples_alloc(&output, NULL, 2, out_samples,
106  * AV_SAMPLE_FMT_S16, 0);
107  * out_samples = swr_convert(swr, &output, out_samples,
108  * input, in_samples);
109  * handle_output(output, out_samples);
110  * av_freep(&output);
111  * }
112  * @endcode
113  *
114  * When the conversion is finished, the conversion
115  * context and everything associated with it must be freed with swr_free().
116  * A swr_close() function is also available, but it exists mainly for
117  * compatibility with libavresample, and is not required to be called.
118  *
119  * There will be no memory leak if the data is not completely flushed before
120  * swr_free().
121  */
122 
123 #include <stdint.h>
124 #include "libavutil/frame.h"
125 #include "libavutil/samplefmt.h"
126 
127 #include "libswresample/version.h"
128 
129 #if LIBSWRESAMPLE_VERSION_MAJOR < 1
130 #define SWR_CH_MAX 32 ///< Maximum number of channels
131 #endif
132 
133 /**
134  * @name Option constants
135  * These constants are used for the @ref avoptions interface for lswr.
136  * @{
137  *
138  */
139 
140 #define SWR_FLAG_RESAMPLE 1 ///< Force resampling even if equal sample rate
141 //TODO use int resample ?
142 //long term TODO can we enable this dynamically?
143 
144 /** Dithering algorithms */
150 
151  SWR_DITHER_NS = 64, ///< not part of API/ABI
159  SWR_DITHER_NB, ///< not part of API/ABI
160 };
161 
162 /** Resampling Engines */
163 enum SwrEngine {
164  SWR_ENGINE_SWR, /**< SW Resampler */
165  SWR_ENGINE_SOXR, /**< SoX Resampler */
166  SWR_ENGINE_NB, ///< not part of API/ABI
167 };
168 
169 /** Resampling Filter Types */
171  SWR_FILTER_TYPE_CUBIC, /**< Cubic */
172  SWR_FILTER_TYPE_BLACKMAN_NUTTALL, /**< Blackman Nuttall Windowed Sinc */
173  SWR_FILTER_TYPE_KAISER, /**< Kaiser Windowed Sinc */
174 };
175 
176 /**
177  * @}
178  */
179 
180 /**
181  * The libswresample context. Unlike libavcodec and libavformat, this structure
182  * is opaque. This means that if you would like to set options, you must use
183  * the @ref avoptions API and cannot directly set values to members of the
184  * structure.
185  */
186 typedef struct SwrContext SwrContext;
187 
188 /**
189  * Get the AVClass for SwrContext. It can be used in combination with
190  * AV_OPT_SEARCH_FAKE_OBJ for examining options.
191  *
192  * @see av_opt_find().
193  * @return the AVClass of SwrContext
194  */
195 const AVClass *swr_get_class(void);
196 
197 /**
198  * @name SwrContext constructor functions
199  * @{
200  */
201 
202 /**
203  * Allocate SwrContext.
204  *
205  * If you use this function you will need to set the parameters (manually or
206  * with swr_alloc_set_opts()) before calling swr_init().
207  *
208  * @see swr_alloc_set_opts(), swr_init(), swr_free()
209  * @return NULL on error, allocated context otherwise
210  */
211 struct SwrContext *swr_alloc(void);
212 
213 /**
214  * Initialize context after user parameters have been set.
215  * @note The context must be configured using the AVOption API.
216  *
217  * @see av_opt_set_int()
218  * @see av_opt_set_dict()
219  *
220  * @param[in,out] s Swr context to initialize
221  * @return AVERROR error code in case of failure.
222  */
223 int swr_init(struct SwrContext *s);
224 
225 /**
226  * Check whether an swr context has been initialized or not.
227  *
228  * @param[in] s Swr context to check
229  * @see swr_init()
230  * @return positive if it has been initialized, 0 if not initialized
231  */
232 int swr_is_initialized(struct SwrContext *s);
233 
234 /**
235  * Allocate SwrContext if needed and set/reset common parameters.
236  *
237  * This function does not require s to be allocated with swr_alloc(). On the
238  * other hand, swr_alloc() can use swr_alloc_set_opts() to set the parameters
239  * on the allocated context.
240  *
241  * @param s existing Swr context if available, or NULL if not
242  * @param out_ch_layout output channel layout (AV_CH_LAYOUT_*)
243  * @param out_sample_fmt output sample format (AV_SAMPLE_FMT_*).
244  * @param out_sample_rate output sample rate (frequency in Hz)
245  * @param in_ch_layout input channel layout (AV_CH_LAYOUT_*)
246  * @param in_sample_fmt input sample format (AV_SAMPLE_FMT_*).
247  * @param in_sample_rate input sample rate (frequency in Hz)
248  * @param log_offset logging level offset
249  * @param log_ctx parent logging context, can be NULL
250  *
251  * @see swr_init(), swr_free()
252  * @return NULL on error, allocated context otherwise
253  */
254 struct SwrContext *swr_alloc_set_opts(struct SwrContext *s,
257  int log_offset, void *log_ctx);
258 
259 /**
260  * @}
261  *
262  * @name SwrContext destructor functions
263  * @{
264  */
265 
266 /**
267  * Free the given SwrContext and set the pointer to NULL.
268  *
269  * @param[in] s a pointer to a pointer to Swr context
270  */
271 void swr_free(struct SwrContext **s);
272 
273 /**
274  * Closes the context so that swr_is_initialized() returns 0.
275  *
276  * The context can be brought back to life by running swr_init(),
277  * swr_init() can also be used without swr_close().
278  * This function is mainly provided for simplifying the usecase
279  * where one tries to support libavresample and libswresample.
280  *
281  * @param[in,out] s Swr context to be closed
282  */
283 void swr_close(struct SwrContext *s);
284 
285 /**
286  * @}
287  *
288  * @name Core conversion functions
289  * @{
290  */
291 
292 /** Convert audio.
293  *
294  * in and in_count can be set to 0 to flush the last few samples out at the
295  * end.
296  *
297  * If more input is provided than output space then the input will be buffered.
298  * You can avoid this buffering by providing more output space than input.
299  * Conversion will run directly without copying whenever possible.
300  *
301  * @param s allocated Swr context, with parameters set
302  * @param out output buffers, only the first one need be set in case of packed audio
303  * @param out_count amount of space available for output in samples per channel
304  * @param in input buffers, only the first one need to be set in case of packed audio
305  * @param in_count number of input samples available in one channel
306  *
307  * @return number of samples output per channel, negative value on error
308  */
309 int swr_convert(struct SwrContext *s, uint8_t **out, int out_count,
310  const uint8_t **in , int in_count);
311 
312 /**
313  * Convert the next timestamp from input to output
314  * timestamps are in 1/(in_sample_rate * out_sample_rate) units.
315  *
316  * @note There are 2 slightly differently behaving modes.
317  * @li When automatic timestamp compensation is not used, (min_compensation >= FLT_MAX)
318  * in this case timestamps will be passed through with delays compensated
319  * @li When automatic timestamp compensation is used, (min_compensation < FLT_MAX)
320  * in this case the output timestamps will match output sample numbers.
321  * See ffmpeg-resampler(1) for the two modes of compensation.
322  *
323  * @param s[in] initialized Swr context
324  * @param pts[in] timestamp for the next input sample, INT64_MIN if unknown
325  * @see swr_set_compensation(), swr_drop_output(), and swr_inject_silence() are
326  * function used internally for timestamp compensation.
327  * @return the output timestamp for the next output sample
328  */
329 int64_t swr_next_pts(struct SwrContext *s, int64_t pts);
330 
331 /**
332  * @}
333  *
334  * @name Low-level option setting functions
335  * These functons provide a means to set low-level options that is not possible
336  * with the AVOption API.
337  * @{
338  */
339 
340 /**
341  * Activate resampling compensation ("soft" compensation). This function is
342  * internally called when needed in swr_next_pts().
343  *
344  * @param[in,out] s allocated Swr context. If it is not initialized,
345  * or SWR_FLAG_RESAMPLE is not set, swr_init() is
346  * called with the flag set.
347  * @param[in] sample_delta delta in PTS per sample
348  * @param[in] compensation_distance number of samples to compensate for
349  * @return >= 0 on success, AVERROR error codes if:
350  * @li @c s is NULL,
351  * @li @c compensation_distance is less than 0,
352  * @li @c compensation_distance is 0 but sample_delta is not,
353  * @li compensation unsupported by resampler, or
354  * @li swr_init() fails when called.
355  */
356 int swr_set_compensation(struct SwrContext *s, int sample_delta, int compensation_distance);
357 
358 /**
359  * Set a customized input channel mapping.
360  *
361  * @param[in,out] s allocated Swr context, not yet initialized
362  * @param[in] channel_map customized input channel mapping (array of channel
363  * indexes, -1 for a muted channel)
364  * @return >= 0 on success, or AVERROR error code in case of failure.
365  */
366 int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map);
367 
368 /**
369  * Set a customized remix matrix.
370  *
371  * @param s allocated Swr context, not yet initialized
372  * @param matrix remix coefficients; matrix[i + stride * o] is
373  * the weight of input channel i in output channel o
374  * @param stride offset between lines of the matrix
375  * @return >= 0 on success, or AVERROR error code in case of failure.
376  */
377 int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride);
378 
379 /**
380  * @}
381  *
382  * @name Sample handling functions
383  * @{
384  */
385 
386 /**
387  * Drops the specified number of output samples.
388  *
389  * This function, along with swr_inject_silence(), is called by swr_next_pts()
390  * if needed for "hard" compensation.
391  *
392  * @param s allocated Swr context
393  * @param count number of samples to be dropped
394  *
395  * @return >= 0 on success, or a negative AVERROR code on failure
396  */
397 int swr_drop_output(struct SwrContext *s, int count);
398 
399 /**
400  * Injects the specified number of silence samples.
401  *
402  * This function, along with swr_drop_output(), is called by swr_next_pts()
403  * if needed for "hard" compensation.
404  *
405  * @param s allocated Swr context
406  * @param count number of samples to be dropped
407  *
408  * @return >= 0 on success, or a negative AVERROR code on failure
409  */
410 int swr_inject_silence(struct SwrContext *s, int count);
411 
412 /**
413  * Gets the delay the next input sample will experience relative to the next output sample.
414  *
415  * Swresample can buffer data if more input has been provided than available
416  * output space, also converting between sample rates needs a delay.
417  * This function returns the sum of all such delays.
418  * The exact delay is not necessarily an integer value in either input or
419  * output sample rate. Especially when downsampling by a large value, the
420  * output sample rate may be a poor choice to represent the delay, similarly
421  * for upsampling and the input sample rate.
422  *
423  * @param s swr context
424  * @param base timebase in which the returned delay will be:
425  * @li if it's set to 1 the returned delay is in seconds
426  * @li if it's set to 1000 the returned delay is in milliseconds
427  * @li if it's set to the input sample rate then the returned
428  * delay is in input samples
429  * @li if it's set to the output sample rate then the returned
430  * delay is in output samples
431  * @li if it's the least common multiple of in_sample_rate and
432  * out_sample_rate then an exact rounding-free delay will be
433  * returned
434  * @returns the delay in 1 / @c base units.
435  */
436 int64_t swr_get_delay(struct SwrContext *s, int64_t base);
437 
438 /**
439  * @}
440  *
441  * @name Configuration accessors
442  * @{
443  */
444 
445 /**
446  * Return the @ref LIBSWRESAMPLE_VERSION_INT constant.
447  *
448  * This is useful to check if the build-time libswresample has the same version
449  * as the run-time one.
450  *
451  * @returns the unsigned int-typed version
452  */
453 unsigned swresample_version(void);
454 
455 /**
456  * Return the swr build-time configuration.
457  *
458  * @returns the build-time @c ./configure flags
459  */
460 const char *swresample_configuration(void);
461 
462 /**
463  * Return the swr license.
464  *
465  * @returns the license of libswresample, determined at build-time
466  */
467 const char *swresample_license(void);
468 
469 /**
470  * @}
471  *
472  * @name AVFrame based API
473  * @{
474  */
475 
476 /**
477  * Convert the samples in the input AVFrame and write them to the output AVFrame.
478  *
479  * Input and output AVFrames must have channel_layout, sample_rate and format set.
480  *
481  * If the output AVFrame does not have the data pointers allocated the nb_samples
482  * field will be set using av_frame_get_buffer()
483  * is called to allocate the frame.
484  *
485  * The output AVFrame can be NULL or have fewer allocated samples than required.
486  * In this case, any remaining samples not written to the output will be added
487  * to an internal FIFO buffer, to be returned at the next call to this function
488  * or to swr_convert().
489  *
490  * If converting sample rate, there may be data remaining in the internal
491  * resampling delay buffer. swr_get_delay() tells the number of
492  * remaining samples. To get this data as output, call this function or
493  * swr_convert() with NULL input.
494  *
495  * If the SwrContext configuration does not match the output and
496  * input AVFrame settings the conversion does not take place and depending on
497  * which AVFrame is not matching AVERROR_OUTPUT_CHANGED, AVERROR_INPUT_CHANGED
498  * or the result of a bitwise-OR of them is returned.
499  *
500  * @see swr_delay()
501  * @see swr_convert()
502  * @see swr_get_delay()
503  *
504  * @param swr audio resample context
505  * @param output output AVFrame
506  * @param input input AVFrame
507  * @return 0 on success, AVERROR on failure or nonmatching
508  * configuration.
509  */
511  AVFrame *output, const AVFrame *input);
512 
513 /**
514  * Configure or reconfigure the SwrContext using the information
515  * provided by the AVFrames.
516  *
517  * The original resampling context is reset even on failure.
518  * The function calls swr_close() internally if the context is open.
519  *
520  * @see swr_close();
521  *
522  * @param swr audio resample context
523  * @param output output AVFrame
524  * @param input input AVFrame
525  * @return 0 on success, AVERROR on failure.
526  */
527 int swr_config_frame(SwrContext *swr, const AVFrame *out, const AVFrame *in);
528 
529 /**
530  * @}
531  * @}
532  */
533 
534 #endif /* SWRESAMPLE_SWRESAMPLE_H */