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avfilter.h
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1 /*
2  * filter layer
3  * Copyright (c) 2007 Bobby Bingham
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVFILTER_AVFILTER_H
23 #define AVFILTER_AVFILTER_H
24 
25 /**
26  * @file
27  * @ingroup lavfi
28  * Main libavfilter public API header
29  */
30 
31 /**
32  * @defgroup lavfi Libavfilter - graph-based frame editing library
33  * @{
34  */
35 
36 #include <stddef.h>
37 
38 #include "libavutil/avutil.h"
39 #include "libavutil/dict.h"
40 #include "libavutil/frame.h"
41 #include "libavutil/log.h"
42 #include "libavutil/samplefmt.h"
43 #include "libavutil/pixfmt.h"
44 #include "libavutil/rational.h"
45 
46 #include "libavfilter/version.h"
47 
48 /**
49  * Return the LIBAVFILTER_VERSION_INT constant.
50  */
51 unsigned avfilter_version(void);
52 
53 /**
54  * Return the libavfilter build-time configuration.
55  */
56 const char *avfilter_configuration(void);
57 
58 /**
59  * Return the libavfilter license.
60  */
61 const char *avfilter_license(void);
62 
63 typedef struct AVFilterContext AVFilterContext;
64 typedef struct AVFilterLink AVFilterLink;
65 typedef struct AVFilterPad AVFilterPad;
66 typedef struct AVFilterFormats AVFilterFormats;
67 
68 #if FF_API_AVFILTERBUFFER
69 /**
70  * A reference-counted buffer data type used by the filter system. Filters
71  * should not store pointers to this structure directly, but instead use the
72  * AVFilterBufferRef structure below.
73  */
74 typedef struct AVFilterBuffer {
75  uint8_t *data[8]; ///< buffer data for each plane/channel
76 
77  /**
78  * pointers to the data planes/channels.
79  *
80  * For video, this should simply point to data[].
81  *
82  * For planar audio, each channel has a separate data pointer, and
83  * linesize[0] contains the size of each channel buffer.
84  * For packed audio, there is just one data pointer, and linesize[0]
85  * contains the total size of the buffer for all channels.
86  *
87  * Note: Both data and extended_data will always be set, but for planar
88  * audio with more channels that can fit in data, extended_data must be used
89  * in order to access all channels.
90  */
91  uint8_t **extended_data;
92  int linesize[8]; ///< number of bytes per line
93 
94  /** private data to be used by a custom free function */
95  void *priv;
96  /**
97  * A pointer to the function to deallocate this buffer if the default
98  * function is not sufficient. This could, for example, add the memory
99  * back into a memory pool to be reused later without the overhead of
100  * reallocating it from scratch.
101  */
102  void (*free)(struct AVFilterBuffer *buf);
103 
104  int format; ///< media format
105  int w, h; ///< width and height of the allocated buffer
106  unsigned refcount; ///< number of references to this buffer
107 } AVFilterBuffer;
108 
109 #define AV_PERM_READ 0x01 ///< can read from the buffer
110 #define AV_PERM_WRITE 0x02 ///< can write to the buffer
111 #define AV_PERM_PRESERVE 0x04 ///< nobody else can overwrite the buffer
112 #define AV_PERM_REUSE 0x08 ///< can output the buffer multiple times, with the same contents each time
113 #define AV_PERM_REUSE2 0x10 ///< can output the buffer multiple times, modified each time
114 #define AV_PERM_NEG_LINESIZES 0x20 ///< the buffer requested can have negative linesizes
115 #define AV_PERM_ALIGN 0x40 ///< the buffer must be aligned
116 
117 #define AVFILTER_ALIGN 16 //not part of ABI
118 
119 /**
120  * Audio specific properties in a reference to an AVFilterBuffer. Since
121  * AVFilterBufferRef is common to different media formats, audio specific
122  * per reference properties must be separated out.
123  */
124 typedef struct AVFilterBufferRefAudioProps {
125  uint64_t channel_layout; ///< channel layout of audio buffer
126  int nb_samples; ///< number of audio samples per channel
127  int sample_rate; ///< audio buffer sample rate
128  int channels; ///< number of channels (do not access directly)
129 } AVFilterBufferRefAudioProps;
130 
131 /**
132  * Video specific properties in a reference to an AVFilterBuffer. Since
133  * AVFilterBufferRef is common to different media formats, video specific
134  * per reference properties must be separated out.
135  */
136 typedef struct AVFilterBufferRefVideoProps {
137  int w; ///< image width
138  int h; ///< image height
139  AVRational sample_aspect_ratio; ///< sample aspect ratio
140  int interlaced; ///< is frame interlaced
141  int top_field_first; ///< field order
142  enum AVPictureType pict_type; ///< picture type of the frame
143  int key_frame; ///< 1 -> keyframe, 0-> not
144  int qp_table_linesize; ///< qp_table stride
145  int qp_table_size; ///< qp_table size
146  int8_t *qp_table; ///< array of Quantization Parameters
147 } AVFilterBufferRefVideoProps;
148 
149 /**
150  * A reference to an AVFilterBuffer. Since filters can manipulate the origin of
151  * a buffer to, for example, crop image without any memcpy, the buffer origin
152  * and dimensions are per-reference properties. Linesize is also useful for
153  * image flipping, frame to field filters, etc, and so is also per-reference.
154  *
155  * TODO: add anything necessary for frame reordering
156  */
157 typedef struct AVFilterBufferRef {
158  AVFilterBuffer *buf; ///< the buffer that this is a reference to
159  uint8_t *data[8]; ///< picture/audio data for each plane
160  /**
161  * pointers to the data planes/channels.
162  *
163  * For video, this should simply point to data[].
164  *
165  * For planar audio, each channel has a separate data pointer, and
166  * linesize[0] contains the size of each channel buffer.
167  * For packed audio, there is just one data pointer, and linesize[0]
168  * contains the total size of the buffer for all channels.
169  *
170  * Note: Both data and extended_data will always be set, but for planar
171  * audio with more channels that can fit in data, extended_data must be used
172  * in order to access all channels.
173  */
174  uint8_t **extended_data;
175  int linesize[8]; ///< number of bytes per line
176 
177  AVFilterBufferRefVideoProps *video; ///< video buffer specific properties
178  AVFilterBufferRefAudioProps *audio; ///< audio buffer specific properties
179 
180  /**
181  * presentation timestamp. The time unit may change during
182  * filtering, as it is specified in the link and the filter code
183  * may need to rescale the PTS accordingly.
184  */
185  int64_t pts;
186  int64_t pos; ///< byte position in stream, -1 if unknown
187 
188  int format; ///< media format
189 
190  int perms; ///< permissions, see the AV_PERM_* flags
191 
192  enum AVMediaType type; ///< media type of buffer data
193 
194  AVDictionary *metadata; ///< dictionary containing metadata key=value tags
195 } AVFilterBufferRef;
196 
197 /**
198  * Copy properties of src to dst, without copying the actual data
199  */
201 void avfilter_copy_buffer_ref_props(AVFilterBufferRef *dst, AVFilterBufferRef *src);
202 
203 /**
204  * Add a new reference to a buffer.
205  *
206  * @param ref an existing reference to the buffer
207  * @param pmask a bitmask containing the allowable permissions in the new
208  * reference
209  * @return a new reference to the buffer with the same properties as the
210  * old, excluding any permissions denied by pmask
211  */
213 AVFilterBufferRef *avfilter_ref_buffer(AVFilterBufferRef *ref, int pmask);
214 
215 /**
216  * Remove a reference to a buffer. If this is the last reference to the
217  * buffer, the buffer itself is also automatically freed.
218  *
219  * @param ref reference to the buffer, may be NULL
220  *
221  * @note it is recommended to use avfilter_unref_bufferp() instead of this
222  * function
223  */
225 void avfilter_unref_buffer(AVFilterBufferRef *ref);
226 
227 /**
228  * Remove a reference to a buffer and set the pointer to NULL.
229  * If this is the last reference to the buffer, the buffer itself
230  * is also automatically freed.
231  *
232  * @param ref pointer to the buffer reference
233  */
235 void avfilter_unref_bufferp(AVFilterBufferRef **ref);
236 #endif
237 
238 /**
239  * Get the number of channels of a buffer reference.
240  */
242 int avfilter_ref_get_channels(AVFilterBufferRef *ref);
243 
244 #if FF_API_AVFILTERPAD_PUBLIC
245 /**
246  * A filter pad used for either input or output.
247  *
248  * See doc/filter_design.txt for details on how to implement the methods.
249  *
250  * @warning this struct might be removed from public API.
251  * users should call avfilter_pad_get_name() and avfilter_pad_get_type()
252  * to access the name and type fields; there should be no need to access
253  * any other fields from outside of libavfilter.
254  */
255 struct AVFilterPad {
256  /**
257  * Pad name. The name is unique among inputs and among outputs, but an
258  * input may have the same name as an output. This may be NULL if this
259  * pad has no need to ever be referenced by name.
260  */
261  const char *name;
262 
263  /**
264  * AVFilterPad type.
265  */
266  enum AVMediaType type;
267 
268  /**
269  * Input pads:
270  * Minimum required permissions on incoming buffers. Any buffer with
271  * insufficient permissions will be automatically copied by the filter
272  * system to a new buffer which provides the needed access permissions.
273  *
274  * Output pads:
275  * Guaranteed permissions on outgoing buffers. Any buffer pushed on the
276  * link must have at least these permissions; this fact is checked by
277  * asserts. It can be used to optimize buffer allocation.
278  */
279  attribute_deprecated int min_perms;
280 
281  /**
282  * Input pads:
283  * Permissions which are not accepted on incoming buffers. Any buffer
284  * which has any of these permissions set will be automatically copied
285  * by the filter system to a new buffer which does not have those
286  * permissions. This can be used to easily disallow buffers with
287  * AV_PERM_REUSE.
288  *
289  * Output pads:
290  * Permissions which are automatically removed on outgoing buffers. It
291  * can be used to optimize buffer allocation.
292  */
293  attribute_deprecated int rej_perms;
294 
295  /**
296  * @deprecated unused
297  */
298  int (*start_frame)(AVFilterLink *link, AVFilterBufferRef *picref);
299 
300  /**
301  * Callback function to get a video buffer. If NULL, the filter system will
302  * use ff_default_get_video_buffer().
303  *
304  * Input video pads only.
305  */
306  AVFrame *(*get_video_buffer)(AVFilterLink *link, int w, int h);
307 
308  /**
309  * Callback function to get an audio buffer. If NULL, the filter system will
310  * use ff_default_get_audio_buffer().
311  *
312  * Input audio pads only.
313  */
314  AVFrame *(*get_audio_buffer)(AVFilterLink *link, int nb_samples);
315 
316  /**
317  * @deprecated unused
318  */
319  int (*end_frame)(AVFilterLink *link);
320 
321  /**
322  * @deprecated unused
323  */
324  int (*draw_slice)(AVFilterLink *link, int y, int height, int slice_dir);
325 
326  /**
327  * Filtering callback. This is where a filter receives a frame with
328  * audio/video data and should do its processing.
329  *
330  * Input pads only.
331  *
332  * @return >= 0 on success, a negative AVERROR on error. This function
333  * must ensure that frame is properly unreferenced on error if it
334  * hasn't been passed on to another filter.
335  */
336  int (*filter_frame)(AVFilterLink *link, AVFrame *frame);
337 
338  /**
339  * Frame poll callback. This returns the number of immediately available
340  * samples. It should return a positive value if the next request_frame()
341  * is guaranteed to return one frame (with no delay).
342  *
343  * Defaults to just calling the source poll_frame() method.
344  *
345  * Output pads only.
346  */
347  int (*poll_frame)(AVFilterLink *link);
348 
349  /**
350  * Frame request callback. A call to this should result in at least one
351  * frame being output over the given link. This should return zero on
352  * success, and another value on error.
353  * See ff_request_frame() for the error codes with a specific
354  * meaning.
355  *
356  * Output pads only.
357  */
358  int (*request_frame)(AVFilterLink *link);
359 
360  /**
361  * Link configuration callback.
362  *
363  * For output pads, this should set the following link properties:
364  * video: width, height, sample_aspect_ratio, time_base
365  * audio: sample_rate.
366  *
367  * This should NOT set properties such as format, channel_layout, etc which
368  * are negotiated between filters by the filter system using the
369  * query_formats() callback before this function is called.
370  *
371  * For input pads, this should check the properties of the link, and update
372  * the filter's internal state as necessary.
373  *
374  * For both input and output pads, this should return zero on success,
375  * and another value on error.
376  */
377  int (*config_props)(AVFilterLink *link);
378 
379  /**
380  * The filter expects a fifo to be inserted on its input link,
381  * typically because it has a delay.
382  *
383  * input pads only.
384  */
385  int needs_fifo;
386 
387  int needs_writable;
388 };
389 #endif
390 
391 /**
392  * Get the number of elements in a NULL-terminated array of AVFilterPads (e.g.
393  * AVFilter.inputs/outputs).
394  */
395 int avfilter_pad_count(const AVFilterPad *pads);
396 
397 /**
398  * Get the name of an AVFilterPad.
399  *
400  * @param pads an array of AVFilterPads
401  * @param pad_idx index of the pad in the array it; is the caller's
402  * responsibility to ensure the index is valid
403  *
404  * @return name of the pad_idx'th pad in pads
405  */
406 const char *avfilter_pad_get_name(const AVFilterPad *pads, int pad_idx);
407 
408 /**
409  * Get the type of an AVFilterPad.
410  *
411  * @param pads an array of AVFilterPads
412  * @param pad_idx index of the pad in the array; it is the caller's
413  * responsibility to ensure the index is valid
414  *
415  * @return type of the pad_idx'th pad in pads
416  */
417 enum AVMediaType avfilter_pad_get_type(const AVFilterPad *pads, int pad_idx);
418 
419 /**
420  * The number of the filter inputs is not determined just by AVFilter.inputs.
421  * The filter might add additional inputs during initialization depending on the
422  * options supplied to it.
423  */
424 #define AVFILTER_FLAG_DYNAMIC_INPUTS (1 << 0)
425 /**
426  * The number of the filter outputs is not determined just by AVFilter.outputs.
427  * The filter might add additional outputs during initialization depending on
428  * the options supplied to it.
429  */
430 #define AVFILTER_FLAG_DYNAMIC_OUTPUTS (1 << 1)
431 /**
432  * The filter supports multithreading by splitting frames into multiple parts
433  * and processing them concurrently.
434  */
435 #define AVFILTER_FLAG_SLICE_THREADS (1 << 2)
436 /**
437  * Some filters support a generic "enable" expression option that can be used
438  * to enable or disable a filter in the timeline. Filters supporting this
439  * option have this flag set. When the enable expression is false, the default
440  * no-op filter_frame() function is called in place of the filter_frame()
441  * callback defined on each input pad, thus the frame is passed unchanged to
442  * the next filters.
443  */
444 #define AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC (1 << 16)
445 /**
446  * Same as AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC, except that the filter will
447  * have its filter_frame() callback(s) called as usual even when the enable
448  * expression is false. The filter will disable filtering within the
449  * filter_frame() callback(s) itself, for example executing code depending on
450  * the AVFilterContext->is_disabled value.
451  */
452 #define AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL (1 << 17)
453 /**
454  * Handy mask to test whether the filter supports or no the timeline feature
455  * (internally or generically).
456  */
457 #define AVFILTER_FLAG_SUPPORT_TIMELINE (AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL)
458 
459 /**
460  * Filter definition. This defines the pads a filter contains, and all the
461  * callback functions used to interact with the filter.
462  */
463 typedef struct AVFilter {
464  /**
465  * Filter name. Must be non-NULL and unique among filters.
466  */
467  const char *name;
468 
469  /**
470  * A description of the filter. May be NULL.
471  *
472  * You should use the NULL_IF_CONFIG_SMALL() macro to define it.
473  */
474  const char *description;
475 
476  /**
477  * List of inputs, terminated by a zeroed element.
478  *
479  * NULL if there are no (static) inputs. Instances of filters with
480  * AVFILTER_FLAG_DYNAMIC_INPUTS set may have more inputs than present in
481  * this list.
482  */
484  /**
485  * List of outputs, terminated by a zeroed element.
486  *
487  * NULL if there are no (static) outputs. Instances of filters with
488  * AVFILTER_FLAG_DYNAMIC_OUTPUTS set may have more outputs than present in
489  * this list.
490  */
492 
493  /**
494  * A class for the private data, used to declare filter private AVOptions.
495  * This field is NULL for filters that do not declare any options.
496  *
497  * If this field is non-NULL, the first member of the filter private data
498  * must be a pointer to AVClass, which will be set by libavfilter generic
499  * code to this class.
500  */
502 
503  /**
504  * A combination of AVFILTER_FLAG_*
505  */
506  int flags;
507 
508  /*****************************************************************
509  * All fields below this line are not part of the public API. They
510  * may not be used outside of libavfilter and can be changed and
511  * removed at will.
512  * New public fields should be added right above.
513  *****************************************************************
514  */
515 
516  /**
517  * Filter initialization function.
518  *
519  * This callback will be called only once during the filter lifetime, after
520  * all the options have been set, but before links between filters are
521  * established and format negotiation is done.
522  *
523  * Basic filter initialization should be done here. Filters with dynamic
524  * inputs and/or outputs should create those inputs/outputs here based on
525  * provided options. No more changes to this filter's inputs/outputs can be
526  * done after this callback.
527  *
528  * This callback must not assume that the filter links exist or frame
529  * parameters are known.
530  *
531  * @ref AVFilter.uninit "uninit" is guaranteed to be called even if
532  * initialization fails, so this callback does not have to clean up on
533  * failure.
534  *
535  * @return 0 on success, a negative AVERROR on failure
536  */
537  int (*init)(AVFilterContext *ctx);
538 
539  /**
540  * Should be set instead of @ref AVFilter.init "init" by the filters that
541  * want to pass a dictionary of AVOptions to nested contexts that are
542  * allocated during init.
543  *
544  * On return, the options dict should be freed and replaced with one that
545  * contains all the options which could not be processed by this filter (or
546  * with NULL if all the options were processed).
547  *
548  * Otherwise the semantics is the same as for @ref AVFilter.init "init".
549  */
551 
552  /**
553  * Filter uninitialization function.
554  *
555  * Called only once right before the filter is freed. Should deallocate any
556  * memory held by the filter, release any buffer references, etc. It does
557  * not need to deallocate the AVFilterContext.priv memory itself.
558  *
559  * This callback may be called even if @ref AVFilter.init "init" was not
560  * called or failed, so it must be prepared to handle such a situation.
561  */
563 
564  /**
565  * Query formats supported by the filter on its inputs and outputs.
566  *
567  * This callback is called after the filter is initialized (so the inputs
568  * and outputs are fixed), shortly before the format negotiation. This
569  * callback may be called more than once.
570  *
571  * This callback must set AVFilterLink.out_formats on every input link and
572  * AVFilterLink.in_formats on every output link to a list of pixel/sample
573  * formats that the filter supports on that link. For audio links, this
574  * filter must also set @ref AVFilterLink.in_samplerates "in_samplerates" /
575  * @ref AVFilterLink.out_samplerates "out_samplerates" and
576  * @ref AVFilterLink.in_channel_layouts "in_channel_layouts" /
577  * @ref AVFilterLink.out_channel_layouts "out_channel_layouts" analogously.
578  *
579  * This callback may be NULL for filters with one input, in which case
580  * libavfilter assumes that it supports all input formats and preserves
581  * them on output.
582  *
583  * @return zero on success, a negative value corresponding to an
584  * AVERROR code otherwise
585  */
587 
588  int priv_size; ///< size of private data to allocate for the filter
589 
590  /**
591  * Used by the filter registration system. Must not be touched by any other
592  * code.
593  */
594  struct AVFilter *next;
595 
596  /**
597  * Make the filter instance process a command.
598  *
599  * @param cmd the command to process, for handling simplicity all commands must be alphanumeric only
600  * @param arg the argument for the command
601  * @param res a buffer with size res_size where the filter(s) can return a response. This must not change when the command is not supported.
602  * @param flags if AVFILTER_CMD_FLAG_FAST is set and the command would be
603  * time consuming then a filter should treat it like an unsupported command
604  *
605  * @returns >=0 on success otherwise an error code.
606  * AVERROR(ENOSYS) on unsupported commands
607  */
608  int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);
609 
610  /**
611  * Filter initialization function, alternative to the init()
612  * callback. Args contains the user-supplied parameters, opaque is
613  * used for providing binary data.
614  */
615  int (*init_opaque)(AVFilterContext *ctx, void *opaque);
616 } AVFilter;
617 
618 /**
619  * Process multiple parts of the frame concurrently.
620  */
621 #define AVFILTER_THREAD_SLICE (1 << 0)
622 
623 typedef struct AVFilterInternal AVFilterInternal;
624 
625 /** An instance of a filter */
627  const AVClass *av_class; ///< needed for av_log() and filters common options
628 
629  const AVFilter *filter; ///< the AVFilter of which this is an instance
630 
631  char *name; ///< name of this filter instance
632 
633  AVFilterPad *input_pads; ///< array of input pads
634  AVFilterLink **inputs; ///< array of pointers to input links
635 #if FF_API_FOO_COUNT
636  unsigned input_count; ///< @deprecated use nb_inputs
637 #endif
638  unsigned nb_inputs; ///< number of input pads
639 
640  AVFilterPad *output_pads; ///< array of output pads
641  AVFilterLink **outputs; ///< array of pointers to output links
642 #if FF_API_FOO_COUNT
643  unsigned output_count; ///< @deprecated use nb_outputs
644 #endif
645  unsigned nb_outputs; ///< number of output pads
646 
647  void *priv; ///< private data for use by the filter
648 
649  struct AVFilterGraph *graph; ///< filtergraph this filter belongs to
650 
651  /**
652  * Type of multithreading being allowed/used. A combination of
653  * AVFILTER_THREAD_* flags.
654  *
655  * May be set by the caller before initializing the filter to forbid some
656  * or all kinds of multithreading for this filter. The default is allowing
657  * everything.
658  *
659  * When the filter is initialized, this field is combined using bit AND with
660  * AVFilterGraph.thread_type to get the final mask used for determining
661  * allowed threading types. I.e. a threading type needs to be set in both
662  * to be allowed.
663  *
664  * After the filter is initialzed, libavfilter sets this field to the
665  * threading type that is actually used (0 for no multithreading).
666  */
668 
669  /**
670  * An opaque struct for libavfilter internal use.
671  */
672  AVFilterInternal *internal;
673 
675 
676  char *enable_str; ///< enable expression string
677  void *enable; ///< parsed expression (AVExpr*)
678  double *var_values; ///< variable values for the enable expression
679  int is_disabled; ///< the enabled state from the last expression evaluation
680 };
681 
682 /**
683  * A link between two filters. This contains pointers to the source and
684  * destination filters between which this link exists, and the indexes of
685  * the pads involved. In addition, this link also contains the parameters
686  * which have been negotiated and agreed upon between the filter, such as
687  * image dimensions, format, etc.
688  */
689 struct AVFilterLink {
690  AVFilterContext *src; ///< source filter
691  AVFilterPad *srcpad; ///< output pad on the source filter
692 
693  AVFilterContext *dst; ///< dest filter
694  AVFilterPad *dstpad; ///< input pad on the dest filter
695 
696  enum AVMediaType type; ///< filter media type
697 
698  /* These parameters apply only to video */
699  int w; ///< agreed upon image width
700  int h; ///< agreed upon image height
701  AVRational sample_aspect_ratio; ///< agreed upon sample aspect ratio
702  /* These parameters apply only to audio */
703  uint64_t channel_layout; ///< channel layout of current buffer (see libavutil/channel_layout.h)
704  int sample_rate; ///< samples per second
705 
706  int format; ///< agreed upon media format
707 
708  /**
709  * Define the time base used by the PTS of the frames/samples
710  * which will pass through this link.
711  * During the configuration stage, each filter is supposed to
712  * change only the output timebase, while the timebase of the
713  * input link is assumed to be an unchangeable property.
714  */
716 
717  /*****************************************************************
718  * All fields below this line are not part of the public API. They
719  * may not be used outside of libavfilter and can be changed and
720  * removed at will.
721  * New public fields should be added right above.
722  *****************************************************************
723  */
724  /**
725  * Lists of formats and channel layouts supported by the input and output
726  * filters respectively. These lists are used for negotiating the format
727  * to actually be used, which will be loaded into the format and
728  * channel_layout members, above, when chosen.
729  *
730  */
733 
734  /**
735  * Lists of channel layouts and sample rates used for automatic
736  * negotiation.
737  */
742 
743  /**
744  * Audio only, the destination filter sets this to a non-zero value to
745  * request that buffers with the given number of samples should be sent to
746  * it. AVFilterPad.needs_fifo must also be set on the corresponding input
747  * pad.
748  * Last buffer before EOF will be padded with silence.
749  */
751 
752  /** stage of the initialization of the link properties (dimensions, etc) */
753  enum {
754  AVLINK_UNINIT = 0, ///< not started
755  AVLINK_STARTINIT, ///< started, but incomplete
756  AVLINK_INIT ///< complete
757  } init_state;
758 
760 
761  /**
762  * Graph the filter belongs to.
763  */
765 
766  /**
767  * Current timestamp of the link, as defined by the most recent
768  * frame(s), in AV_TIME_BASE units.
769  */
770  int64_t current_pts;
771 
772  /**
773  * Index in the age array.
774  */
776 
777  /**
778  * Frame rate of the stream on the link, or 1/0 if unknown;
779  * if left to 0/0, will be automatically be copied from the first input
780  * of the source filter if it exists.
781  *
782  * Sources should set it to the best estimation of the real frame rate.
783  * Filters should update it if necessary depending on their function.
784  * Sinks can use it to set a default output frame rate.
785  * It is similar to the r_frame_rate field in AVStream.
786  */
788 
789  /**
790  * Buffer partially filled with samples to achieve a fixed/minimum size.
791  */
793 
794  /**
795  * Size of the partial buffer to allocate.
796  * Must be between min_samples and max_samples.
797  */
799 
800  /**
801  * Minimum number of samples to filter at once. If filter_frame() is
802  * called with fewer samples, it will accumulate them in partial_buf.
803  * This field and the related ones must not be changed after filtering
804  * has started.
805  * If 0, all related fields are ignored.
806  */
808 
809  /**
810  * Maximum number of samples to filter at once. If filter_frame() is
811  * called with more samples, it will split them.
812  */
814 
815  /**
816  * The buffer reference currently being received across the link by the
817  * destination filter. This is used internally by the filter system to
818  * allow automatic copying of buffers which do not have sufficient
819  * permissions for the destination. This should not be accessed directly
820  * by the filters.
821  */
822  AVFilterBufferRef *cur_buf_copy;
823 
824  /**
825  * True if the link is closed.
826  * If set, all attemps of start_frame, filter_frame or request_frame
827  * will fail with AVERROR_EOF, and if necessary the reference will be
828  * destroyed.
829  * If request_frame returns AVERROR_EOF, this flag is set on the
830  * corresponding link.
831  * It can be set also be set by either the source or the destination
832  * filter.
833  */
834  int closed;
835 
836  /**
837  * Number of channels.
838  */
839  int channels;
840 
841  /**
842  * True if a frame is being requested on the link.
843  * Used internally by the framework.
844  */
845  unsigned frame_requested;
846 
847  /**
848  * Link processing flags.
849  */
850  unsigned flags;
851 
852  /**
853  * Number of past frames sent through the link.
854  */
855  int64_t frame_count;
856 };
857 
858 /**
859  * Link two filters together.
860  *
861  * @param src the source filter
862  * @param srcpad index of the output pad on the source filter
863  * @param dst the destination filter
864  * @param dstpad index of the input pad on the destination filter
865  * @return zero on success
866  */
867 int avfilter_link(AVFilterContext *src, unsigned srcpad,
868  AVFilterContext *dst, unsigned dstpad);
869 
870 /**
871  * Free the link in *link, and set its pointer to NULL.
872  */
873 void avfilter_link_free(AVFilterLink **link);
874 
875 /**
876  * Get the number of channels of a link.
877  */
879 
880 /**
881  * Set the closed field of a link.
882  */
883 void avfilter_link_set_closed(AVFilterLink *link, int closed);
884 
885 /**
886  * Negotiate the media format, dimensions, etc of all inputs to a filter.
887  *
888  * @param filter the filter to negotiate the properties for its inputs
889  * @return zero on successful negotiation
890  */
892 
893 #if FF_API_AVFILTERBUFFER
894 /**
895  * Create a buffer reference wrapped around an already allocated image
896  * buffer.
897  *
898  * @param data pointers to the planes of the image to reference
899  * @param linesize linesizes for the planes of the image to reference
900  * @param perms the required access permissions
901  * @param w the width of the image specified by the data and linesize arrays
902  * @param h the height of the image specified by the data and linesize arrays
903  * @param format the pixel format of the image specified by the data and linesize arrays
904  */
906 AVFilterBufferRef *
907 avfilter_get_video_buffer_ref_from_arrays(uint8_t * const data[4], const int linesize[4], int perms,
908  int w, int h, enum AVPixelFormat format);
909 
910 /**
911  * Create an audio buffer reference wrapped around an already
912  * allocated samples buffer.
913  *
914  * See avfilter_get_audio_buffer_ref_from_arrays_channels() for a version
915  * that can handle unknown channel layouts.
916  *
917  * @param data pointers to the samples plane buffers
918  * @param linesize linesize for the samples plane buffers
919  * @param perms the required access permissions
920  * @param nb_samples number of samples per channel
921  * @param sample_fmt the format of each sample in the buffer to allocate
922  * @param channel_layout the channel layout of the buffer
923  */
925 AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays(uint8_t **data,
926  int linesize,
927  int perms,
928  int nb_samples,
929  enum AVSampleFormat sample_fmt,
930  uint64_t channel_layout);
931 /**
932  * Create an audio buffer reference wrapped around an already
933  * allocated samples buffer.
934  *
935  * @param data pointers to the samples plane buffers
936  * @param linesize linesize for the samples plane buffers
937  * @param perms the required access permissions
938  * @param nb_samples number of samples per channel
939  * @param sample_fmt the format of each sample in the buffer to allocate
940  * @param channels the number of channels of the buffer
941  * @param channel_layout the channel layout of the buffer,
942  * must be either 0 or consistent with channels
943  */
945 AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays_channels(uint8_t **data,
946  int linesize,
947  int perms,
948  int nb_samples,
949  enum AVSampleFormat sample_fmt,
950  int channels,
951  uint64_t channel_layout);
952 
953 #endif
954 
955 
956 #define AVFILTER_CMD_FLAG_ONE 1 ///< Stop once a filter understood the command (for target=all for example), fast filters are favored automatically
957 #define AVFILTER_CMD_FLAG_FAST 2 ///< Only execute command when its fast (like a video out that supports contrast adjustment in hw)
958 
959 /**
960  * Make the filter instance process a command.
961  * It is recommended to use avfilter_graph_send_command().
962  */
963 int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags);
964 
965 /** Initialize the filter system. Register all builtin filters. */
966 void avfilter_register_all(void);
967 
968 #if FF_API_OLD_FILTER_REGISTER
969 /** Uninitialize the filter system. Unregister all filters. */
971 void avfilter_uninit(void);
972 #endif
973 
974 /**
975  * Register a filter. This is only needed if you plan to use
976  * avfilter_get_by_name later to lookup the AVFilter structure by name. A
977  * filter can still by instantiated with avfilter_graph_alloc_filter even if it
978  * is not registered.
979  *
980  * @param filter the filter to register
981  * @return 0 if the registration was successful, a negative value
982  * otherwise
983  */
985 
986 /**
987  * Get a filter definition matching the given name.
988  *
989  * @param name the filter name to find
990  * @return the filter definition, if any matching one is registered.
991  * NULL if none found.
992  */
993 AVFilter *avfilter_get_by_name(const char *name);
994 
995 /**
996  * Iterate over all registered filters.
997  * @return If prev is non-NULL, next registered filter after prev or NULL if
998  * prev is the last filter. If prev is NULL, return the first registered filter.
999  */
1000 const AVFilter *avfilter_next(const AVFilter *prev);
1001 
1002 #if FF_API_OLD_FILTER_REGISTER
1003 /**
1004  * If filter is NULL, returns a pointer to the first registered filter pointer,
1005  * if filter is non-NULL, returns the next pointer after filter.
1006  * If the returned pointer points to NULL, the last registered filter
1007  * was already reached.
1008  * @deprecated use avfilter_next()
1009  */
1011 AVFilter **av_filter_next(AVFilter **filter);
1012 #endif
1013 
1014 #if FF_API_AVFILTER_OPEN
1015 /**
1016  * Create a filter instance.
1017  *
1018  * @param filter_ctx put here a pointer to the created filter context
1019  * on success, NULL on failure
1020  * @param filter the filter to create an instance of
1021  * @param inst_name Name to give to the new instance. Can be NULL for none.
1022  * @return >= 0 in case of success, a negative error code otherwise
1023  * @deprecated use avfilter_graph_alloc_filter() instead
1024  */
1026 int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name);
1027 #endif
1028 
1029 
1030 #if FF_API_AVFILTER_INIT_FILTER
1031 /**
1032  * Initialize a filter.
1033  *
1034  * @param filter the filter to initialize
1035  * @param args A string of parameters to use when initializing the filter.
1036  * The format and meaning of this string varies by filter.
1037  * @param opaque Any extra non-string data needed by the filter. The meaning
1038  * of this parameter varies by filter.
1039  * @return zero on success
1040  */
1042 int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque);
1043 #endif
1044 
1045 /**
1046  * Initialize a filter with the supplied parameters.
1047  *
1048  * @param ctx uninitialized filter context to initialize
1049  * @param args Options to initialize the filter with. This must be a
1050  * ':'-separated list of options in the 'key=value' form.
1051  * May be NULL if the options have been set directly using the
1052  * AVOptions API or there are no options that need to be set.
1053  * @return 0 on success, a negative AVERROR on failure
1054  */
1055 int avfilter_init_str(AVFilterContext *ctx, const char *args);
1056 
1057 /**
1058  * Initialize a filter with the supplied dictionary of options.
1059  *
1060  * @param ctx uninitialized filter context to initialize
1061  * @param options An AVDictionary filled with options for this filter. On
1062  * return this parameter will be destroyed and replaced with
1063  * a dict containing options that were not found. This dictionary
1064  * must be freed by the caller.
1065  * May be NULL, then this function is equivalent to
1066  * avfilter_init_str() with the second parameter set to NULL.
1067  * @return 0 on success, a negative AVERROR on failure
1068  *
1069  * @note This function and avfilter_init_str() do essentially the same thing,
1070  * the difference is in manner in which the options are passed. It is up to the
1071  * calling code to choose whichever is more preferable. The two functions also
1072  * behave differently when some of the provided options are not declared as
1073  * supported by the filter. In such a case, avfilter_init_str() will fail, but
1074  * this function will leave those extra options in the options AVDictionary and
1075  * continue as usual.
1076  */
1078 
1079 /**
1080  * Free a filter context. This will also remove the filter from its
1081  * filtergraph's list of filters.
1082  *
1083  * @param filter the filter to free
1084  */
1086 
1087 /**
1088  * Insert a filter in the middle of an existing link.
1089  *
1090  * @param link the link into which the filter should be inserted
1091  * @param filt the filter to be inserted
1092  * @param filt_srcpad_idx the input pad on the filter to connect
1093  * @param filt_dstpad_idx the output pad on the filter to connect
1094  * @return zero on success
1095  */
1097  unsigned filt_srcpad_idx, unsigned filt_dstpad_idx);
1098 
1099 #if FF_API_AVFILTERBUFFER
1100 /**
1101  * Copy the frame properties of src to dst, without copying the actual
1102  * image data.
1103  *
1104  * @return 0 on success, a negative number on error.
1105  */
1107 int avfilter_copy_frame_props(AVFilterBufferRef *dst, const AVFrame *src);
1108 
1109 /**
1110  * Copy the frame properties and data pointers of src to dst, without copying
1111  * the actual data.
1112  *
1113  * @return 0 on success, a negative number on error.
1114  */
1116 int avfilter_copy_buf_props(AVFrame *dst, const AVFilterBufferRef *src);
1117 #endif
1118 
1119 /**
1120  * @return AVClass for AVFilterContext.
1121  *
1122  * @see av_opt_find().
1123  */
1124 const AVClass *avfilter_get_class(void);
1125 
1127 
1128 typedef struct AVFilterGraph {
1130 #if FF_API_FOO_COUNT
1132  unsigned filter_count_unused;
1133 #endif
1135 #if !FF_API_FOO_COUNT
1136  unsigned nb_filters;
1137 #endif
1138 
1139  char *scale_sws_opts; ///< sws options to use for the auto-inserted scale filters
1140  char *resample_lavr_opts; ///< libavresample options to use for the auto-inserted resample filters
1141 #if FF_API_FOO_COUNT
1142  unsigned nb_filters;
1143 #endif
1144 
1145  /**
1146  * Type of multithreading allowed for filters in this graph. A combination
1147  * of AVFILTER_THREAD_* flags.
1148  *
1149  * May be set by the caller at any point, the setting will apply to all
1150  * filters initialized after that. The default is allowing everything.
1151  *
1152  * When a filter in this graph is initialized, this field is combined using
1153  * bit AND with AVFilterContext.thread_type to get the final mask used for
1154  * determining allowed threading types. I.e. a threading type needs to be
1155  * set in both to be allowed.
1156  */
1158 
1159  /**
1160  * Maximum number of threads used by filters in this graph. May be set by
1161  * the caller before adding any filters to the filtergraph. Zero (the
1162  * default) means that the number of threads is determined automatically.
1163  */
1165 
1166  /**
1167  * Opaque object for libavfilter internal use.
1168  */
1170 
1171  char *aresample_swr_opts; ///< swr options to use for the auto-inserted aresample filters, Access ONLY through AVOptions
1172 
1173  /**
1174  * Private fields
1175  *
1176  * The following fields are for internal use only.
1177  * Their type, offset, number and semantic can change without notice.
1178  */
1179 
1182 
1184 } AVFilterGraph;
1185 
1186 /**
1187  * Allocate a filter graph.
1188  */
1190 
1191 /**
1192  * Create a new filter instance in a filter graph.
1193  *
1194  * @param graph graph in which the new filter will be used
1195  * @param filter the filter to create an instance of
1196  * @param name Name to give to the new instance (will be copied to
1197  * AVFilterContext.name). This may be used by the caller to identify
1198  * different filters, libavfilter itself assigns no semantics to
1199  * this parameter. May be NULL.
1200  *
1201  * @return the context of the newly created filter instance (note that it is
1202  * also retrievable directly through AVFilterGraph.filters or with
1203  * avfilter_graph_get_filter()) on success or NULL or failure.
1204  */
1206  const AVFilter *filter,
1207  const char *name);
1208 
1209 /**
1210  * Get a filter instance with name name from graph.
1211  *
1212  * @return the pointer to the found filter instance or NULL if it
1213  * cannot be found.
1214  */
1216 
1217 #if FF_API_AVFILTER_OPEN
1218 /**
1219  * Add an existing filter instance to a filter graph.
1220  *
1221  * @param graphctx the filter graph
1222  * @param filter the filter to be added
1223  *
1224  * @deprecated use avfilter_graph_alloc_filter() to allocate a filter in a
1225  * filter graph
1226  */
1228 int avfilter_graph_add_filter(AVFilterGraph *graphctx, AVFilterContext *filter);
1229 #endif
1230 
1231 /**
1232  * Create and add a filter instance into an existing graph.
1233  * The filter instance is created from the filter filt and inited
1234  * with the parameters args and opaque.
1235  *
1236  * In case of success put in *filt_ctx the pointer to the created
1237  * filter instance, otherwise set *filt_ctx to NULL.
1238  *
1239  * @param name the instance name to give to the created filter instance
1240  * @param graph_ctx the filter graph
1241  * @return a negative AVERROR error code in case of failure, a non
1242  * negative value otherwise
1243  */
1245  const char *name, const char *args, void *opaque,
1246  AVFilterGraph *graph_ctx);
1247 
1248 /**
1249  * Enable or disable automatic format conversion inside the graph.
1250  *
1251  * Note that format conversion can still happen inside explicitly inserted
1252  * scale and aresample filters.
1253  *
1254  * @param flags any of the AVFILTER_AUTO_CONVERT_* constants
1255  */
1256 void avfilter_graph_set_auto_convert(AVFilterGraph *graph, unsigned flags);
1257 
1258 enum {
1259  AVFILTER_AUTO_CONVERT_ALL = 0, /**< all automatic conversions enabled */
1260  AVFILTER_AUTO_CONVERT_NONE = -1, /**< all automatic conversions disabled */
1261 };
1262 
1263 /**
1264  * Check validity and configure all the links and formats in the graph.
1265  *
1266  * @param graphctx the filter graph
1267  * @param log_ctx context used for logging
1268  * @return 0 in case of success, a negative AVERROR code otherwise
1269  */
1270 int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx);
1271 
1272 /**
1273  * Free a graph, destroy its links, and set *graph to NULL.
1274  * If *graph is NULL, do nothing.
1275  */
1276 void avfilter_graph_free(AVFilterGraph **graph);
1277 
1278 /**
1279  * A linked-list of the inputs/outputs of the filter chain.
1280  *
1281  * This is mainly useful for avfilter_graph_parse() / avfilter_graph_parse2(),
1282  * where it is used to communicate open (unlinked) inputs and outputs from and
1283  * to the caller.
1284  * This struct specifies, per each not connected pad contained in the graph, the
1285  * filter context and the pad index required for establishing a link.
1286  */
1287 typedef struct AVFilterInOut {
1288  /** unique name for this input/output in the list */
1289  char *name;
1290 
1291  /** filter context associated to this input/output */
1293 
1294  /** index of the filt_ctx pad to use for linking */
1295  int pad_idx;
1296 
1297  /** next input/input in the list, NULL if this is the last */
1299 } AVFilterInOut;
1300 
1301 /**
1302  * Allocate a single AVFilterInOut entry.
1303  * Must be freed with avfilter_inout_free().
1304  * @return allocated AVFilterInOut on success, NULL on failure.
1305  */
1307 
1308 /**
1309  * Free the supplied list of AVFilterInOut and set *inout to NULL.
1310  * If *inout is NULL, do nothing.
1311  */
1312 void avfilter_inout_free(AVFilterInOut **inout);
1313 
1314 #if HAVE_INCOMPATIBLE_LIBAV_ABI || !FF_API_OLD_GRAPH_PARSE
1315 /**
1316  * Add a graph described by a string to a graph.
1317  *
1318  * @note The caller must provide the lists of inputs and outputs,
1319  * which therefore must be known before calling the function.
1320  *
1321  * @note The inputs parameter describes inputs of the already existing
1322  * part of the graph; i.e. from the point of view of the newly created
1323  * part, they are outputs. Similarly the outputs parameter describes
1324  * outputs of the already existing filters, which are provided as
1325  * inputs to the parsed filters.
1326  *
1327  * @param graph the filter graph where to link the parsed grap context
1328  * @param filters string to be parsed
1329  * @param inputs linked list to the inputs of the graph
1330  * @param outputs linked list to the outputs of the graph
1331  * @return zero on success, a negative AVERROR code on error
1332  */
1333 int avfilter_graph_parse(AVFilterGraph *graph, const char *filters,
1335  void *log_ctx);
1336 #else
1337 /**
1338  * Add a graph described by a string to a graph.
1339  *
1340  * @param graph the filter graph where to link the parsed graph context
1341  * @param filters string to be parsed
1342  * @param inputs pointer to a linked list to the inputs of the graph, may be NULL.
1343  * If non-NULL, *inputs is updated to contain the list of open inputs
1344  * after the parsing, should be freed with avfilter_inout_free().
1345  * @param outputs pointer to a linked list to the outputs of the graph, may be NULL.
1346  * If non-NULL, *outputs is updated to contain the list of open outputs
1347  * after the parsing, should be freed with avfilter_inout_free().
1348  * @return non negative on success, a negative AVERROR code on error
1349  * @deprecated Use avfilter_graph_parse_ptr() instead.
1350  */
1352 int avfilter_graph_parse(AVFilterGraph *graph, const char *filters,
1354  void *log_ctx);
1355 #endif
1356 
1357 /**
1358  * Add a graph described by a string to a graph.
1359  *
1360  * @param graph the filter graph where to link the parsed graph context
1361  * @param filters string to be parsed
1362  * @param inputs pointer to a linked list to the inputs of the graph, may be NULL.
1363  * If non-NULL, *inputs is updated to contain the list of open inputs
1364  * after the parsing, should be freed with avfilter_inout_free().
1365  * @param outputs pointer to a linked list to the outputs of the graph, may be NULL.
1366  * If non-NULL, *outputs is updated to contain the list of open outputs
1367  * after the parsing, should be freed with avfilter_inout_free().
1368  * @return non negative on success, a negative AVERROR code on error
1369  */
1370 int avfilter_graph_parse_ptr(AVFilterGraph *graph, const char *filters,
1372  void *log_ctx);
1373 
1374 /**
1375  * Add a graph described by a string to a graph.
1376  *
1377  * @param[in] graph the filter graph where to link the parsed graph context
1378  * @param[in] filters string to be parsed
1379  * @param[out] inputs a linked list of all free (unlinked) inputs of the
1380  * parsed graph will be returned here. It is to be freed
1381  * by the caller using avfilter_inout_free().
1382  * @param[out] outputs a linked list of all free (unlinked) outputs of the
1383  * parsed graph will be returned here. It is to be freed by the
1384  * caller using avfilter_inout_free().
1385  * @return zero on success, a negative AVERROR code on error
1386  *
1387  * @note This function returns the inputs and outputs that are left
1388  * unlinked after parsing the graph and the caller then deals with
1389  * them.
1390  * @note This function makes no reference whatsoever to already
1391  * existing parts of the graph and the inputs parameter will on return
1392  * contain inputs of the newly parsed part of the graph. Analogously
1393  * the outputs parameter will contain outputs of the newly created
1394  * filters.
1395  */
1396 int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,
1399 
1400 /**
1401  * Send a command to one or more filter instances.
1402  *
1403  * @param graph the filter graph
1404  * @param target the filter(s) to which the command should be sent
1405  * "all" sends to all filters
1406  * otherwise it can be a filter or filter instance name
1407  * which will send the command to all matching filters.
1408  * @param cmd the command to send, for handling simplicity all commands must be alphanumeric only
1409  * @param arg the argument for the command
1410  * @param res a buffer with size res_size where the filter(s) can return a response.
1411  *
1412  * @returns >=0 on success otherwise an error code.
1413  * AVERROR(ENOSYS) on unsupported commands
1414  */
1415 int avfilter_graph_send_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, char *res, int res_len, int flags);
1416 
1417 /**
1418  * Queue a command for one or more filter instances.
1419  *
1420  * @param graph the filter graph
1421  * @param target the filter(s) to which the command should be sent
1422  * "all" sends to all filters
1423  * otherwise it can be a filter or filter instance name
1424  * which will send the command to all matching filters.
1425  * @param cmd the command to sent, for handling simplicity all commands must be alphanummeric only
1426  * @param arg the argument for the command
1427  * @param ts time at which the command should be sent to the filter
1428  *
1429  * @note As this executes commands after this function returns, no return code
1430  * from the filter is provided, also AVFILTER_CMD_FLAG_ONE is not supported.
1431  */
1432 int avfilter_graph_queue_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, int flags, double ts);
1433 
1434 
1435 /**
1436  * Dump a graph into a human-readable string representation.
1437  *
1438  * @param graph the graph to dump
1439  * @param options formatting options; currently ignored
1440  * @return a string, or NULL in case of memory allocation failure;
1441  * the string must be freed using av_free
1442  */
1443 char *avfilter_graph_dump(AVFilterGraph *graph, const char *options);
1444 
1445 /**
1446  * Request a frame on the oldest sink link.
1447  *
1448  * If the request returns AVERROR_EOF, try the next.
1449  *
1450  * Note that this function is not meant to be the sole scheduling mechanism
1451  * of a filtergraph, only a convenience function to help drain a filtergraph
1452  * in a balanced way under normal circumstances.
1453  *
1454  * Also note that AVERROR_EOF does not mean that frames did not arrive on
1455  * some of the sinks during the process.
1456  * When there are multiple sink links, in case the requested link
1457  * returns an EOF, this may cause a filter to flush pending frames
1458  * which are sent to another sink link, although unrequested.
1459  *
1460  * @return the return value of ff_request_frame(),
1461  * or AVERROR_EOF if all links returned AVERROR_EOF
1462  */
1464 
1465 /**
1466  * @}
1467  */
1468 
1469 #endif /* AVFILTER_AVFILTER_H */