3 * Copyright (c) 2007 Bobby Bingham
5 * This file is part of FFmpeg.
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.
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.
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
22 #ifndef AVFILTER_AVFILTER_H
23 #define AVFILTER_AVFILTER_H
27 #include "libavutil/avutil.h"
28 #include "libavutil/log.h"
29 #include "libavutil/samplefmt.h"
30 #include "libavutil/pixfmt.h"
31 #include "libavutil/rational.h"
33 #include "libavfilter/version.h"
36 * Return the LIBAVFILTER_VERSION_INT constant.
38 unsigned avfilter_version(void);
41 * Return the libavfilter build-time configuration.
43 const char *avfilter_configuration(void);
46 * Return the libavfilter license.
48 const char *avfilter_license(void);
51 * Get the class for the AVFilterContext struct.
53 const AVClass *avfilter_get_class(void);
55 typedef struct AVFilterContext AVFilterContext;
56 typedef struct AVFilterLink AVFilterLink;
57 typedef struct AVFilterPad AVFilterPad;
58 typedef struct AVFilterFormats AVFilterFormats;
61 * A reference-counted buffer data type used by the filter system. Filters
62 * should not store pointers to this structure directly, but instead use the
63 * AVFilterBufferRef structure below.
65 typedef struct AVFilterBuffer {
66 uint8_t *data[8]; ///< buffer data for each plane/channel
69 * pointers to the data planes/channels.
71 * For video, this should simply point to data[].
73 * For planar audio, each channel has a separate data pointer, and
74 * linesize[0] contains the size of each channel buffer.
75 * For packed audio, there is just one data pointer, and linesize[0]
76 * contains the total size of the buffer for all channels.
78 * Note: Both data and extended_data will always be set, but for planar
79 * audio with more channels that can fit in data, extended_data must be used
80 * in order to access all channels.
82 uint8_t **extended_data;
83 int linesize[8]; ///< number of bytes per line
85 /** private data to be used by a custom free function */
88 * A pointer to the function to deallocate this buffer if the default
89 * function is not sufficient. This could, for example, add the memory
90 * back into a memory pool to be reused later without the overhead of
91 * reallocating it from scratch.
93 void (*free)(struct AVFilterBuffer *buf);
95 int format; ///< media format
96 int w, h; ///< width and height of the allocated buffer
97 unsigned refcount; ///< number of references to this buffer
100 #define AV_PERM_READ 0x01 ///< can read from the buffer
101 #define AV_PERM_WRITE 0x02 ///< can write to the buffer
102 #define AV_PERM_PRESERVE 0x04 ///< nobody else can overwrite the buffer
103 #define AV_PERM_REUSE 0x08 ///< can output the buffer multiple times, with the same contents each time
104 #define AV_PERM_REUSE2 0x10 ///< can output the buffer multiple times, modified each time
105 #define AV_PERM_NEG_LINESIZES 0x20 ///< the buffer requested can have negative linesizes
106 #define AV_PERM_ALIGN 0x40 ///< the buffer must be aligned
108 #define AVFILTER_ALIGN 16 //not part of ABI
111 * Audio specific properties in a reference to an AVFilterBuffer. Since
112 * AVFilterBufferRef is common to different media formats, audio specific
113 * per reference properties must be separated out.
115 typedef struct AVFilterBufferRefAudioProps {
116 uint64_t channel_layout; ///< channel layout of audio buffer
117 int nb_samples; ///< number of audio samples per channel
118 int sample_rate; ///< audio buffer sample rate
119 } AVFilterBufferRefAudioProps;
122 * Video specific properties in a reference to an AVFilterBuffer. Since
123 * AVFilterBufferRef is common to different media formats, video specific
124 * per reference properties must be separated out.
126 typedef struct AVFilterBufferRefVideoProps {
127 int w; ///< image width
128 int h; ///< image height
129 AVRational sample_aspect_ratio; ///< sample aspect ratio
130 int interlaced; ///< is frame interlaced
131 int top_field_first; ///< field order
132 enum AVPictureType pict_type; ///< picture type of the frame
133 int key_frame; ///< 1 -> keyframe, 0-> not
134 } AVFilterBufferRefVideoProps;
137 * A reference to an AVFilterBuffer. Since filters can manipulate the origin of
138 * a buffer to, for example, crop image without any memcpy, the buffer origin
139 * and dimensions are per-reference properties. Linesize is also useful for
140 * image flipping, frame to field filters, etc, and so is also per-reference.
142 * TODO: add anything necessary for frame reordering
144 typedef struct AVFilterBufferRef {
145 AVFilterBuffer *buf; ///< the buffer that this is a reference to
146 uint8_t *data[8]; ///< picture/audio data for each plane
148 * pointers to the data planes/channels.
150 * For video, this should simply point to data[].
152 * For planar audio, each channel has a separate data pointer, and
153 * linesize[0] contains the size of each channel buffer.
154 * For packed audio, there is just one data pointer, and linesize[0]
155 * contains the total size of the buffer for all channels.
157 * Note: Both data and extended_data will always be set, but for planar
158 * audio with more channels that can fit in data, extended_data must be used
159 * in order to access all channels.
161 uint8_t **extended_data;
162 int linesize[8]; ///< number of bytes per line
164 AVFilterBufferRefVideoProps *video; ///< video buffer specific properties
165 AVFilterBufferRefAudioProps *audio; ///< audio buffer specific properties
168 * presentation timestamp. The time unit may change during
169 * filtering, as it is specified in the link and the filter code
170 * may need to rescale the PTS accordingly.
173 int64_t pos; ///< byte position in stream, -1 if unknown
175 int format; ///< media format
177 int perms; ///< permissions, see the AV_PERM_* flags
179 enum AVMediaType type; ///< media type of buffer data
183 * Copy properties of src to dst, without copying the actual data
185 void avfilter_copy_buffer_ref_props(AVFilterBufferRef *dst, AVFilterBufferRef *src);
188 * Add a new reference to a buffer.
190 * @param ref an existing reference to the buffer
191 * @param pmask a bitmask containing the allowable permissions in the new
193 * @return a new reference to the buffer with the same properties as the
194 * old, excluding any permissions denied by pmask
196 AVFilterBufferRef *avfilter_ref_buffer(AVFilterBufferRef *ref, int pmask);
199 * Remove a reference to a buffer. If this is the last reference to the
200 * buffer, the buffer itself is also automatically freed.
202 * @param ref reference to the buffer, may be NULL
204 * @note it is recommended to use avfilter_unref_bufferp() instead of this
207 void avfilter_unref_buffer(AVFilterBufferRef *ref);
210 * Remove a reference to a buffer and set the pointer to NULL.
211 * If this is the last reference to the buffer, the buffer itself
212 * is also automatically freed.
214 * @param ref pointer to the buffer reference
216 void avfilter_unref_bufferp(AVFilterBufferRef **ref);
218 #if FF_API_AVFILTERPAD_PUBLIC
220 * A filter pad used for either input or output.
222 * See doc/filter_design.txt for details on how to implement the methods.
224 * @warning this struct might be removed from public API.
225 * users should call avfilter_pad_get_name() and avfilter_pad_get_type()
226 * to access the name and type fields; there should be no need to access
227 * any other fields from outside of libavfilter.
231 * Pad name. The name is unique among inputs and among outputs, but an
232 * input may have the same name as an output. This may be NULL if this
233 * pad has no need to ever be referenced by name.
240 enum AVMediaType type;
244 * Minimum required permissions on incoming buffers. Any buffer with
245 * insufficient permissions will be automatically copied by the filter
246 * system to a new buffer which provides the needed access permissions.
249 * Guaranteed permissions on outgoing buffers. Any buffer pushed on the
250 * link must have at least these permissions; this fact is checked by
251 * asserts. It can be used to optimize buffer allocation.
257 * Permissions which are not accepted on incoming buffers. Any buffer
258 * which has any of these permissions set will be automatically copied
259 * by the filter system to a new buffer which does not have those
260 * permissions. This can be used to easily disallow buffers with
264 * Permissions which are automatically removed on outgoing buffers. It
265 * can be used to optimize buffer allocation.
270 * Callback called before passing the first slice of a new frame. If
271 * NULL, the filter layer will default to storing a reference to the
272 * picture inside the link structure.
274 * The reference given as argument is also available in link->cur_buf.
275 * It can be stored elsewhere or given away, but then clearing
276 * link->cur_buf is advised, as it is automatically unreferenced.
277 * The reference must not be unreferenced before end_frame(), as it may
278 * still be in use by the automatic copy mechanism.
280 * Input video pads only.
282 * @return >= 0 on success, a negative AVERROR on error. picref will be
283 * unreferenced by the caller in case of error.
285 int (*start_frame)(AVFilterLink *link, AVFilterBufferRef *picref);
288 * Callback function to get a video buffer. If NULL, the filter system will
289 * use avfilter_default_get_video_buffer().
291 * Input video pads only.
293 AVFilterBufferRef *(*get_video_buffer)(AVFilterLink *link, int perms, int w, int h);
296 * Callback function to get an audio buffer. If NULL, the filter system will
297 * use avfilter_default_get_audio_buffer().
299 * Input audio pads only.
301 AVFilterBufferRef *(*get_audio_buffer)(AVFilterLink *link, int perms,
305 * Callback called after the slices of a frame are completely sent. If
306 * NULL, the filter layer will default to releasing the reference stored
307 * in the link structure during start_frame().
309 * Input video pads only.
311 * @return >= 0 on success, a negative AVERROR on error.
313 int (*end_frame)(AVFilterLink *link);
316 * Slice drawing callback. This is where a filter receives video data
317 * and should do its processing.
319 * Input video pads only.
321 * @return >= 0 on success, a negative AVERROR on error.
323 int (*draw_slice)(AVFilterLink *link, int y, int height, int slice_dir);
326 * Samples filtering callback. This is where a filter receives audio data
327 * and should do its processing.
329 * Input audio pads only.
331 * @return >= 0 on success, a negative AVERROR on error. This function
332 * must ensure that samplesref is properly unreferenced on error if it
333 * hasn't been passed on to another filter.
335 int (*filter_samples)(AVFilterLink *link, AVFilterBufferRef *samplesref);
338 * Frame poll callback. This returns the number of immediately available
339 * samples. It should return a positive value if the next request_frame()
340 * is guaranteed to return one frame (with no delay).
342 * Defaults to just calling the source poll_frame() method.
346 int (*poll_frame)(AVFilterLink *link);
349 * Frame request callback. A call to this should result in at least one
350 * frame being output over the given link. This should return zero on
351 * success, and another value on error.
352 * See ff_request_frame() for the error codes with a specific
357 int (*request_frame)(AVFilterLink *link);
360 * Link configuration callback.
362 * For output pads, this should set the following link properties:
363 * video: width, height, sample_aspect_ratio, time_base
364 * audio: sample_rate.
366 * This should NOT set properties such as format, channel_layout, etc which
367 * are negotiated between filters by the filter system using the
368 * query_formats() callback before this function is called.
370 * For input pads, this should check the properties of the link, and update
371 * the filter's internal state as necessary.
373 * For both input and output pads, this should return zero on success,
374 * and another value on error.
376 int (*config_props)(AVFilterLink *link);
379 * The filter expects a fifo to be inserted on its input link,
380 * typically because it has a delay.
389 * Get the name of an AVFilterPad.
391 * @param pads an array of AVFilterPads
392 * @param pad_idx index of the pad in the array it; is the caller's
393 * responsibility to ensure the index is valid
395 * @return name of the pad_idx'th pad in pads
397 const char *avfilter_pad_get_name(AVFilterPad *pads, int pad_idx);
400 * Get the type of an AVFilterPad.
402 * @param pads an array of AVFilterPads
403 * @param pad_idx index of the pad in the array; it is the caller's
404 * responsibility to ensure the index is valid
406 * @return type of the pad_idx'th pad in pads
408 enum AVMediaType avfilter_pad_get_type(AVFilterPad *pads, int pad_idx);
410 /** default handler for end_frame() for video inputs */
412 int avfilter_default_end_frame(AVFilterLink *link);
415 * Filter definition. This defines the pads a filter contains, and all the
416 * callback functions used to interact with the filter.
418 typedef struct AVFilter {
419 const char *name; ///< filter name
422 * A description for the filter. You should use the
423 * NULL_IF_CONFIG_SMALL() macro to define it.
425 const char *description;
427 const AVFilterPad *inputs; ///< NULL terminated list of inputs. NULL if none
428 const AVFilterPad *outputs; ///< NULL terminated list of outputs. NULL if none
430 /*****************************************************************
431 * All fields below this line are not part of the public API. They
432 * may not be used outside of libavfilter and can be changed and
434 * New public fields should be added right above.
435 *****************************************************************
439 * Filter initialization function. Args contains the user-supplied
440 * parameters. FIXME: maybe an AVOption-based system would be better?
442 int (*init)(AVFilterContext *ctx, const char *args);
445 * Filter uninitialization function. Should deallocate any memory held
446 * by the filter, release any buffer references, etc. This does not need
447 * to deallocate the AVFilterContext->priv memory itself.
449 void (*uninit)(AVFilterContext *ctx);
452 * Queries formats/layouts supported by the filter and its pads, and sets
453 * the in_formats/in_chlayouts for links connected to its output pads,
454 * and out_formats/out_chlayouts for links connected to its input pads.
456 * @return zero on success, a negative value corresponding to an
457 * AVERROR code otherwise
459 int (*query_formats)(AVFilterContext *);
461 int priv_size; ///< size of private data to allocate for the filter
464 * Make the filter instance process a command.
466 * @param cmd the command to process, for handling simplicity all commands must be alphanumeric only
467 * @param arg the argument for the command
468 * @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.
469 * @param flags if AVFILTER_CMD_FLAG_FAST is set and the command would be
470 * time consuming then a filter should treat it like an unsupported command
472 * @returns >=0 on success otherwise an error code.
473 * AVERROR(ENOSYS) on unsupported commands
475 int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);
478 * Filter initialization function, alternative to the init()
479 * callback. Args contains the user-supplied parameters, opaque is
480 * used for providing binary data.
482 int (*init_opaque)(AVFilterContext *ctx, const char *args, void *opaque);
484 const AVClass *priv_class; ///< private class, containing filter specific options
487 /** An instance of a filter */
488 struct AVFilterContext {
489 const AVClass *av_class; ///< needed for av_log()
491 AVFilter *filter; ///< the AVFilter of which this is an instance
493 char *name; ///< name of this filter instance
495 AVFilterPad *input_pads; ///< array of input pads
496 AVFilterLink **inputs; ///< array of pointers to input links
498 unsigned input_count; ///< @deprecated use nb_inputs
500 unsigned nb_inputs; ///< number of input pads
502 AVFilterPad *output_pads; ///< array of output pads
503 AVFilterLink **outputs; ///< array of pointers to output links
505 unsigned output_count; ///< @deprecated use nb_outputs
507 unsigned nb_outputs; ///< number of output pads
509 void *priv; ///< private data for use by the filter
511 struct AVFilterCommand *command_queue;
515 * A link between two filters. This contains pointers to the source and
516 * destination filters between which this link exists, and the indexes of
517 * the pads involved. In addition, this link also contains the parameters
518 * which have been negotiated and agreed upon between the filter, such as
519 * image dimensions, format, etc.
521 struct AVFilterLink {
522 AVFilterContext *src; ///< source filter
523 AVFilterPad *srcpad; ///< output pad on the source filter
525 AVFilterContext *dst; ///< dest filter
526 AVFilterPad *dstpad; ///< input pad on the dest filter
528 enum AVMediaType type; ///< filter media type
530 /* These parameters apply only to video */
531 int w; ///< agreed upon image width
532 int h; ///< agreed upon image height
533 AVRational sample_aspect_ratio; ///< agreed upon sample aspect ratio
534 /* These parameters apply only to audio */
535 uint64_t channel_layout; ///< channel layout of current buffer (see libavutil/audioconvert.h)
536 int sample_rate; ///< samples per second
538 int format; ///< agreed upon media format
541 * Define the time base used by the PTS of the frames/samples
542 * which will pass through this link.
543 * During the configuration stage, each filter is supposed to
544 * change only the output timebase, while the timebase of the
545 * input link is assumed to be an unchangeable property.
547 AVRational time_base;
549 /*****************************************************************
550 * All fields below this line are not part of the public API. They
551 * may not be used outside of libavfilter and can be changed and
553 * New public fields should be added right above.
554 *****************************************************************
557 * Lists of formats and channel layouts supported by the input and output
558 * filters respectively. These lists are used for negotiating the format
559 * to actually be used, which will be loaded into the format and
560 * channel_layout members, above, when chosen.
563 AVFilterFormats *in_formats;
564 AVFilterFormats *out_formats;
567 * Lists of channel layouts and sample rates used for automatic
570 AVFilterFormats *in_samplerates;
571 AVFilterFormats *out_samplerates;
572 struct AVFilterChannelLayouts *in_channel_layouts;
573 struct AVFilterChannelLayouts *out_channel_layouts;
576 * Audio only, the destination filter sets this to a non-zero value to
577 * request that buffers with the given number of samples should be sent to
578 * it. AVFilterPad.needs_fifo must also be set on the corresponding input
580 * Last buffer before EOF will be padded with silence.
584 /** stage of the initialization of the link properties (dimensions, etc) */
586 AVLINK_UNINIT = 0, ///< not started
587 AVLINK_STARTINIT, ///< started, but incomplete
588 AVLINK_INIT ///< complete
592 * The buffer reference currently being sent across the link by the source
593 * filter. This is used internally by the filter system to allow
594 * automatic copying of buffers which do not have sufficient permissions
595 * for the destination. This should not be accessed directly by the
598 AVFilterBufferRef *src_buf;
601 * The buffer reference to the frame sent across the link by the
602 * source filter, which is read by the destination filter. It is
603 * automatically set up by ff_start_frame().
605 * Depending on the permissions, it may either be the same as
606 * src_buf or an automatic copy of it.
608 * It is automatically freed by the filter system when calling
609 * ff_end_frame(). In case you save the buffer reference
610 * internally (e.g. if you cache it for later reuse), or give it
611 * away (e.g. if you pass the reference to the next filter) it
612 * must be set to NULL before calling ff_end_frame().
614 AVFilterBufferRef *cur_buf;
617 * The buffer reference to the frame which is sent to output by
620 * If no start_frame callback is defined on a link,
621 * ff_start_frame() will automatically request a new buffer on the
622 * first output link of the destination filter. The reference to
623 * the buffer so obtained is stored in the out_buf field on the
626 * It can also be set by the filter code in case the filter needs
627 * to access the output buffer later. For example the filter code
628 * may set it in a custom start_frame, and access it in
631 * It is automatically freed by the filter system in
634 AVFilterBufferRef *out_buf;
636 struct AVFilterPool *pool;
639 * Graph the filter belongs to.
641 struct AVFilterGraph *graph;
644 * Current timestamp of the link, as defined by the most recent
645 * frame(s), in AV_TIME_BASE units.
650 * Index in the age array.
655 * Frame rate of the stream on the link, or 1/0 if unknown;
656 * if left to 0/0, will be automatically be copied from the first input
657 * of the source filter if it exists.
659 * Sources should set it to the best estimation of the real frame rate.
660 * Filters should update it if necessary depending on their function.
661 * Sinks can use it to set a default output frame rate.
662 * It is similar to the r_frame_rate field in AVStream.
664 AVRational frame_rate;
667 * Buffer partially filled with samples to achieve a fixed/minimum size.
669 AVFilterBufferRef *partial_buf;
672 * Size of the partial buffer to allocate.
673 * Must be between min_samples and max_samples.
675 int partial_buf_size;
678 * Minimum number of samples to filter at once. If filter_samples() is
679 * called with fewer samples, it will accumulate them in partial_buf.
680 * This field and the related ones must not be changed after filtering
682 * If 0, all related fields are ignored.
687 * Maximum number of samples to filter at once. If filter_samples() is
688 * called with more samples, it will split them.
693 * The buffer reference currently being received across the link by the
694 * destination filter. This is used internally by the filter system to
695 * allow automatic copying of buffers which do not have sufficient
696 * permissions for the destination. This should not be accessed directly
699 AVFilterBufferRef *cur_buf_copy;
702 * True if the link is closed.
703 * If set, all attemps of start_frame, filter_samples or request_frame
704 * will fail with AVERROR_EOF, and if necessary the reference will be
706 * If request_frame returns AVERROR_EOF, this flag is set on the
707 * corresponding link.
708 * It can be set also be set by either the source or the destination
715 * Link two filters together.
717 * @param src the source filter
718 * @param srcpad index of the output pad on the source filter
719 * @param dst the destination filter
720 * @param dstpad index of the input pad on the destination filter
721 * @return zero on success
723 int avfilter_link(AVFilterContext *src, unsigned srcpad,
724 AVFilterContext *dst, unsigned dstpad);
727 * Free the link in *link, and set its pointer to NULL.
729 void avfilter_link_free(AVFilterLink **link);
732 * Set the closed field of a link.
734 void avfilter_link_set_closed(AVFilterLink *link, int closed);
737 * Negotiate the media format, dimensions, etc of all inputs to a filter.
739 * @param filter the filter to negotiate the properties for its inputs
740 * @return zero on successful negotiation
742 int avfilter_config_links(AVFilterContext *filter);
745 * Create a buffer reference wrapped around an already allocated image
748 * @param data pointers to the planes of the image to reference
749 * @param linesize linesizes for the planes of the image to reference
750 * @param perms the required access permissions
751 * @param w the width of the image specified by the data and linesize arrays
752 * @param h the height of the image specified by the data and linesize arrays
753 * @param format the pixel format of the image specified by the data and linesize arrays
756 avfilter_get_video_buffer_ref_from_arrays(uint8_t * const data[4], const int linesize[4], int perms,
757 int w, int h, enum PixelFormat format);
760 * Create an audio buffer reference wrapped around an already
761 * allocated samples buffer.
763 * @param data pointers to the samples plane buffers
764 * @param linesize linesize for the samples plane buffers
765 * @param perms the required access permissions
766 * @param nb_samples number of samples per channel
767 * @param sample_fmt the format of each sample in the buffer to allocate
768 * @param channel_layout the channel layout of the buffer
770 AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays(uint8_t **data,
774 enum AVSampleFormat sample_fmt,
775 uint64_t channel_layout);
778 #define AVFILTER_CMD_FLAG_ONE 1 ///< Stop once a filter understood the command (for target=all for example), fast filters are favored automatically
779 #define AVFILTER_CMD_FLAG_FAST 2 ///< Only execute command when its fast (like a video out that supports contrast adjustment in hw)
782 * Make the filter instance process a command.
783 * It is recommended to use avfilter_graph_send_command().
785 int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags);
787 /** Initialize the filter system. Register all builtin filters. */
788 void avfilter_register_all(void);
790 /** Uninitialize the filter system. Unregister all filters. */
791 void avfilter_uninit(void);
794 * Register a filter. This is only needed if you plan to use
795 * avfilter_get_by_name later to lookup the AVFilter structure by name. A
796 * filter can still by instantiated with avfilter_open even if it is not
799 * @param filter the filter to register
800 * @return 0 if the registration was successful, a negative value
803 int avfilter_register(AVFilter *filter);
806 * Get a filter definition matching the given name.
808 * @param name the filter name to find
809 * @return the filter definition, if any matching one is registered.
810 * NULL if none found.
812 AVFilter *avfilter_get_by_name(const char *name);
815 * If filter is NULL, returns a pointer to the first registered filter pointer,
816 * if filter is non-NULL, returns the next pointer after filter.
817 * If the returned pointer points to NULL, the last registered filter
818 * was already reached.
820 AVFilter **av_filter_next(AVFilter **filter);
823 * Create a filter instance.
825 * @param filter_ctx put here a pointer to the created filter context
826 * on success, NULL on failure
827 * @param filter the filter to create an instance of
828 * @param inst_name Name to give to the new instance. Can be NULL for none.
829 * @return >= 0 in case of success, a negative error code otherwise
831 int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name);
834 * Initialize a filter.
836 * @param filter the filter to initialize
837 * @param args A string of parameters to use when initializing the filter.
838 * The format and meaning of this string varies by filter.
839 * @param opaque Any extra non-string data needed by the filter. The meaning
840 * of this parameter varies by filter.
841 * @return zero on success
843 int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque);
846 * Free a filter context.
848 * @param filter the filter to free
850 void avfilter_free(AVFilterContext *filter);
853 * Insert a filter in the middle of an existing link.
855 * @param link the link into which the filter should be inserted
856 * @param filt the filter to be inserted
857 * @param filt_srcpad_idx the input pad on the filter to connect
858 * @param filt_dstpad_idx the output pad on the filter to connect
859 * @return zero on success
861 int avfilter_insert_filter(AVFilterLink *link, AVFilterContext *filt,
862 unsigned filt_srcpad_idx, unsigned filt_dstpad_idx);
864 #endif /* AVFILTER_AVFILTER_H */