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ffmpeg/libavfilter/avfilter.h

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/*
* filter layer
* Copyright (c) 2007 Bobby Bingham
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVFILTER_AVFILTER_H
#define AVFILTER_AVFILTER_H
/**
* @file
* @ingroup lavfi
* external API header
*/
/**
* @defgroup lavfi Libavfilter
* @{
*/
#include <stddef.h>
#include "libavutil/avutil.h"
#include "libavutil/dict.h"
#include "libavutil/log.h"
#include "libavutil/samplefmt.h"
#include "libavutil/pixfmt.h"
#include "libavutil/rational.h"
#include "libavfilter/version.h"
/**
* Return the LIBAVFILTER_VERSION_INT constant.
*/
unsigned avfilter_version(void);
/**
* Return the libavfilter build-time configuration.
*/
const char *avfilter_configuration(void);
/**
* Return the libavfilter license.
*/
const char *avfilter_license(void);
/**
* Get the class for the AVFilterContext struct.
*/
const AVClass *avfilter_get_class(void);
typedef struct AVFilterContext AVFilterContext;
typedef struct AVFilterLink AVFilterLink;
typedef struct AVFilterPad AVFilterPad;
typedef struct AVFilterFormats AVFilterFormats;
/**
* A reference-counted buffer data type used by the filter system. Filters
* should not store pointers to this structure directly, but instead use the
* AVFilterBufferRef structure below.
*/
typedef struct AVFilterBuffer {
uint8_t *data[8]; ///< buffer data for each plane/channel
/**
* pointers to the data planes/channels.
*
* For video, this should simply point to data[].
*
* For planar audio, each channel has a separate data pointer, and
* linesize[0] contains the size of each channel buffer.
* For packed audio, there is just one data pointer, and linesize[0]
* contains the total size of the buffer for all channels.
*
* Note: Both data and extended_data will always be set, but for planar
* audio with more channels that can fit in data, extended_data must be used
* in order to access all channels.
*/
uint8_t **extended_data;
int linesize[8]; ///< number of bytes per line
/** private data to be used by a custom free function */
void *priv;
/**
* A pointer to the function to deallocate this buffer if the default
* function is not sufficient. This could, for example, add the memory
* back into a memory pool to be reused later without the overhead of
* reallocating it from scratch.
*/
void (*free)(struct AVFilterBuffer *buf);
int format; ///< media format
int w, h; ///< width and height of the allocated buffer
unsigned refcount; ///< number of references to this buffer
} AVFilterBuffer;
#define AV_PERM_READ 0x01 ///< can read from the buffer
#define AV_PERM_WRITE 0x02 ///< can write to the buffer
#define AV_PERM_PRESERVE 0x04 ///< nobody else can overwrite the buffer
#define AV_PERM_REUSE 0x08 ///< can output the buffer multiple times, with the same contents each time
#define AV_PERM_REUSE2 0x10 ///< can output the buffer multiple times, modified each time
#define AV_PERM_NEG_LINESIZES 0x20 ///< the buffer requested can have negative linesizes
#define AV_PERM_ALIGN 0x40 ///< the buffer must be aligned
#define AVFILTER_ALIGN 16 //not part of ABI
/**
* Audio specific properties in a reference to an AVFilterBuffer. Since
* AVFilterBufferRef is common to different media formats, audio specific
* per reference properties must be separated out.
*/
typedef struct AVFilterBufferRefAudioProps {
uint64_t channel_layout; ///< channel layout of audio buffer
int nb_samples; ///< number of audio samples per channel
int sample_rate; ///< audio buffer sample rate
int channels; ///< number of channels (do not access directly)
} AVFilterBufferRefAudioProps;
/**
* Video specific properties in a reference to an AVFilterBuffer. Since
* AVFilterBufferRef is common to different media formats, video specific
* per reference properties must be separated out.
*/
typedef struct AVFilterBufferRefVideoProps {
int w; ///< image width
int h; ///< image height
AVRational sample_aspect_ratio; ///< sample aspect ratio
int interlaced; ///< is frame interlaced
int top_field_first; ///< field order
enum AVPictureType pict_type; ///< picture type of the frame
int key_frame; ///< 1 -> keyframe, 0-> not
int qp_table_linesize; ///< qp_table stride
int qp_table_size; ///< qp_table size
int8_t *qp_table; ///< array of Quantization Parameters
} AVFilterBufferRefVideoProps;
/**
* A reference to an AVFilterBuffer. Since filters can manipulate the origin of
* a buffer to, for example, crop image without any memcpy, the buffer origin
* and dimensions are per-reference properties. Linesize is also useful for
* image flipping, frame to field filters, etc, and so is also per-reference.
*
* TODO: add anything necessary for frame reordering
*/
typedef struct AVFilterBufferRef {
AVFilterBuffer *buf; ///< the buffer that this is a reference to
uint8_t *data[8]; ///< picture/audio data for each plane
/**
* pointers to the data planes/channels.
*
* For video, this should simply point to data[].
*
* For planar audio, each channel has a separate data pointer, and
* linesize[0] contains the size of each channel buffer.
* For packed audio, there is just one data pointer, and linesize[0]
* contains the total size of the buffer for all channels.
*
* Note: Both data and extended_data will always be set, but for planar
* audio with more channels that can fit in data, extended_data must be used
* in order to access all channels.
*/
uint8_t **extended_data;
int linesize[8]; ///< number of bytes per line
AVFilterBufferRefVideoProps *video; ///< video buffer specific properties
AVFilterBufferRefAudioProps *audio; ///< audio buffer specific properties
/**
* presentation timestamp. The time unit may change during
* filtering, as it is specified in the link and the filter code
* may need to rescale the PTS accordingly.
*/
int64_t pts;
int64_t pos; ///< byte position in stream, -1 if unknown
int format; ///< media format
int perms; ///< permissions, see the AV_PERM_* flags
enum AVMediaType type; ///< media type of buffer data
AVDictionary *metadata; ///< dictionary containing metadata key=value tags
} AVFilterBufferRef;
/**
* Copy properties of src to dst, without copying the actual data
*/
void avfilter_copy_buffer_ref_props(AVFilterBufferRef *dst, AVFilterBufferRef *src);
/**
* Add a new reference to a buffer.
*
* @param ref an existing reference to the buffer
* @param pmask a bitmask containing the allowable permissions in the new
* reference
* @return a new reference to the buffer with the same properties as the
* old, excluding any permissions denied by pmask
*/
AVFilterBufferRef *avfilter_ref_buffer(AVFilterBufferRef *ref, int pmask);
/**
* Remove a reference to a buffer. If this is the last reference to the
* buffer, the buffer itself is also automatically freed.
*
* @param ref reference to the buffer, may be NULL
*
* @note it is recommended to use avfilter_unref_bufferp() instead of this
* function
*/
void avfilter_unref_buffer(AVFilterBufferRef *ref);
/**
* Remove a reference to a buffer and set the pointer to NULL.
* If this is the last reference to the buffer, the buffer itself
* is also automatically freed.
*
* @param ref pointer to the buffer reference
*/
void avfilter_unref_bufferp(AVFilterBufferRef **ref);
/**
* Get the number of channels of a buffer reference.
*/
int avfilter_ref_get_channels(AVFilterBufferRef *ref);
#if FF_API_AVFILTERPAD_PUBLIC
/**
* A filter pad used for either input or output.
*
* See doc/filter_design.txt for details on how to implement the methods.
*
* @warning this struct might be removed from public API.
* users should call avfilter_pad_get_name() and avfilter_pad_get_type()
* to access the name and type fields; there should be no need to access
* any other fields from outside of libavfilter.
*/
struct AVFilterPad {
/**
* Pad name. The name is unique among inputs and among outputs, but an
* input may have the same name as an output. This may be NULL if this
* pad has no need to ever be referenced by name.
*/
const char *name;
/**
* AVFilterPad type.
*/
enum AVMediaType type;
/**
* Input pads:
* Minimum required permissions on incoming buffers. Any buffer with
* insufficient permissions will be automatically copied by the filter
* system to a new buffer which provides the needed access permissions.
*
* Output pads:
* Guaranteed permissions on outgoing buffers. Any buffer pushed on the
* link must have at least these permissions; this fact is checked by
* asserts. It can be used to optimize buffer allocation.
*/
int min_perms;
/**
* Input pads:
* Permissions which are not accepted on incoming buffers. Any buffer
* which has any of these permissions set will be automatically copied
* by the filter system to a new buffer which does not have those
* permissions. This can be used to easily disallow buffers with
* AV_PERM_REUSE.
*
* Output pads:
* Permissions which are automatically removed on outgoing buffers. It
* can be used to optimize buffer allocation.
*/
int rej_perms;
/**
* @deprecated unused
*/
int (*start_frame)(AVFilterLink *link, AVFilterBufferRef *picref);
/**
* Callback function to get a video buffer. If NULL, the filter system will
* use ff_default_get_video_buffer().
*
* Input video pads only.
*/
AVFilterBufferRef *(*get_video_buffer)(AVFilterLink *link, int perms, int w, int h);
/**
* Callback function to get an audio buffer. If NULL, the filter system will
* use ff_default_get_audio_buffer().
*
* Input audio pads only.
*/
AVFilterBufferRef *(*get_audio_buffer)(AVFilterLink *link, int perms,
int nb_samples);
/**
* @deprecated unused
*/
int (*end_frame)(AVFilterLink *link);
/**
* @deprecated unused
*/
int (*draw_slice)(AVFilterLink *link, int y, int height, int slice_dir);
/**
* Filtering callback. This is where a filter receives a frame with
* audio/video data and should do its processing.
*
* Input pads only.
*
* @return >= 0 on success, a negative AVERROR on error. This function
* must ensure that frame is properly unreferenced on error if it
* hasn't been passed on to another filter.
*/
int (*filter_frame)(AVFilterLink *link, AVFilterBufferRef *frame);
/**
* Frame poll callback. This returns the number of immediately available
* samples. It should return a positive value if the next request_frame()
* is guaranteed to return one frame (with no delay).
*
* Defaults to just calling the source poll_frame() method.
*
* Output pads only.
*/
int (*poll_frame)(AVFilterLink *link);
/**
* Frame request callback. A call to this should result in at least one
* frame being output over the given link. This should return zero on
* success, and another value on error.
* See ff_request_frame() for the error codes with a specific
* meaning.
*
* Output pads only.
*/
int (*request_frame)(AVFilterLink *link);
/**
* Link configuration callback.
*
* For output pads, this should set the following link properties:
* video: width, height, sample_aspect_ratio, time_base
* audio: sample_rate.
*
* This should NOT set properties such as format, channel_layout, etc which
* are negotiated between filters by the filter system using the
* query_formats() callback before this function is called.
*
* For input pads, this should check the properties of the link, and update
* the filter's internal state as necessary.
*
* For both input and output pads, this should return zero on success,
* and another value on error.
*/
int (*config_props)(AVFilterLink *link);
/**
* The filter expects a fifo to be inserted on its input link,
* typically because it has a delay.
*
* input pads only.
*/
int needs_fifo;
};
#endif
/**
* Get the name of an AVFilterPad.
*
* @param pads an array of AVFilterPads
* @param pad_idx index of the pad in the array it; is the caller's
* responsibility to ensure the index is valid
*
* @return name of the pad_idx'th pad in pads
*/
const char *avfilter_pad_get_name(AVFilterPad *pads, int pad_idx);
/**
* Get the type of an AVFilterPad.
*
* @param pads an array of AVFilterPads
* @param pad_idx index of the pad in the array; it is the caller's
* responsibility to ensure the index is valid
*
* @return type of the pad_idx'th pad in pads
*/
enum AVMediaType avfilter_pad_get_type(AVFilterPad *pads, int pad_idx);
/**
* Filter definition. This defines the pads a filter contains, and all the
* callback functions used to interact with the filter.
*/
typedef struct AVFilter {
const char *name; ///< filter name
/**
* A description for the filter. You should use the
* NULL_IF_CONFIG_SMALL() macro to define it.
*/
const char *description;
const AVFilterPad *inputs; ///< NULL terminated list of inputs. NULL if none
const AVFilterPad *outputs; ///< NULL terminated list of outputs. NULL if none
/*****************************************************************
* All fields below this line are not part of the public API. They
* may not be used outside of libavfilter and can be changed and
* removed at will.
* New public fields should be added right above.
*****************************************************************
*/
/**
* Filter initialization function. Args contains the user-supplied
* parameters. FIXME: maybe an AVOption-based system would be better?
*/
int (*init)(AVFilterContext *ctx, const char *args);
/**
* Filter uninitialization function. Should deallocate any memory held
* by the filter, release any buffer references, etc. This does not need
* to deallocate the AVFilterContext->priv memory itself.
*/
void (*uninit)(AVFilterContext *ctx);
/**
* Queries formats/layouts supported by the filter and its pads, and sets
* the in_formats/in_chlayouts for links connected to its output pads,
* and out_formats/out_chlayouts for links connected to its input pads.
*
* @return zero on success, a negative value corresponding to an
* AVERROR code otherwise
*/
int (*query_formats)(AVFilterContext *);
int priv_size; ///< size of private data to allocate for the filter
/**
* Make the filter instance process a command.
*
* @param cmd the command to process, for handling simplicity all commands must be alphanumeric only
* @param arg the argument for the command
* @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.
* @param flags if AVFILTER_CMD_FLAG_FAST is set and the command would be
* time consuming then a filter should treat it like an unsupported command
*
* @returns >=0 on success otherwise an error code.
* AVERROR(ENOSYS) on unsupported commands
*/
int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);
/**
* Filter initialization function, alternative to the init()
* callback. Args contains the user-supplied parameters, opaque is
* used for providing binary data.
*/
int (*init_opaque)(AVFilterContext *ctx, const char *args, void *opaque);
const AVClass *priv_class; ///< private class, containing filter specific options
} AVFilter;
/** An instance of a filter */
struct AVFilterContext {
const AVClass *av_class; ///< needed for av_log()
AVFilter *filter; ///< the AVFilter of which this is an instance
char *name; ///< name of this filter instance
AVFilterPad *input_pads; ///< array of input pads
AVFilterLink **inputs; ///< array of pointers to input links
#if FF_API_FOO_COUNT
unsigned input_count; ///< @deprecated use nb_inputs
#endif
unsigned nb_inputs; ///< number of input pads
AVFilterPad *output_pads; ///< array of output pads
AVFilterLink **outputs; ///< array of pointers to output links
#if FF_API_FOO_COUNT
unsigned output_count; ///< @deprecated use nb_outputs
#endif
unsigned nb_outputs; ///< number of output pads
void *priv; ///< private data for use by the filter
struct AVFilterCommand *command_queue;
};
/**
* A link between two filters. This contains pointers to the source and
* destination filters between which this link exists, and the indexes of
* the pads involved. In addition, this link also contains the parameters
* which have been negotiated and agreed upon between the filter, such as
* image dimensions, format, etc.
*/
struct AVFilterLink {
AVFilterContext *src; ///< source filter
AVFilterPad *srcpad; ///< output pad on the source filter
AVFilterContext *dst; ///< dest filter
AVFilterPad *dstpad; ///< input pad on the dest filter
enum AVMediaType type; ///< filter media type
/* These parameters apply only to video */
int w; ///< agreed upon image width
int h; ///< agreed upon image height
AVRational sample_aspect_ratio; ///< agreed upon sample aspect ratio
/* These parameters apply only to audio */
uint64_t channel_layout; ///< channel layout of current buffer (see libavutil/channel_layout.h)
int sample_rate; ///< samples per second
int format; ///< agreed upon media format
/**
* Define the time base used by the PTS of the frames/samples
* which will pass through this link.
* During the configuration stage, each filter is supposed to
* change only the output timebase, while the timebase of the
* input link is assumed to be an unchangeable property.
*/
AVRational time_base;
/*****************************************************************
* All fields below this line are not part of the public API. They
* may not be used outside of libavfilter and can be changed and
* removed at will.
* New public fields should be added right above.
*****************************************************************
*/
/**
* Lists of formats and channel layouts supported by the input and output
* filters respectively. These lists are used for negotiating the format
* to actually be used, which will be loaded into the format and
* channel_layout members, above, when chosen.
*
*/
AVFilterFormats *in_formats;
AVFilterFormats *out_formats;
/**
* Lists of channel layouts and sample rates used for automatic
* negotiation.
*/
AVFilterFormats *in_samplerates;
AVFilterFormats *out_samplerates;
struct AVFilterChannelLayouts *in_channel_layouts;
struct AVFilterChannelLayouts *out_channel_layouts;
/**
* Audio only, the destination filter sets this to a non-zero value to
* request that buffers with the given number of samples should be sent to
* it. AVFilterPad.needs_fifo must also be set on the corresponding input
* pad.
* Last buffer before EOF will be padded with silence.
*/
int request_samples;
/** stage of the initialization of the link properties (dimensions, etc) */
enum {
AVLINK_UNINIT = 0, ///< not started
AVLINK_STARTINIT, ///< started, but incomplete
AVLINK_INIT ///< complete
} init_state;
/**
* The buffer reference currently being sent across the link by the source
* filter. This is used internally by the filter system to allow
* automatic copying of buffers which do not have sufficient permissions
* for the destination. This should not be accessed directly by the
* filters.
*/
AVFilterBufferRef *src_buf;
/**
* The buffer reference to the frame sent across the link by the
* source filter, which is read by the destination filter. It is
* automatically set up by ff_start_frame().
*
* Depending on the permissions, it may either be the same as
* src_buf or an automatic copy of it.
*
* It is automatically freed by the filter system when calling
* ff_end_frame(). In case you save the buffer reference
* internally (e.g. if you cache it for later reuse), or give it
* away (e.g. if you pass the reference to the next filter) it
* must be set to NULL before calling ff_end_frame().
*/
AVFilterBufferRef *cur_buf;
/**
* The buffer reference to the frame which is sent to output by
* the source filter.
*
* If no start_frame callback is defined on the link destination pad,
* ff_start_frame() will automatically request a new buffer on the
* first output link of the destination filter. The reference to
* the buffer so obtained is stored in the out_buf field on the
* output link.
*
* It can also be set by the filter code in case the filter needs
* to access the output buffer later. For example the filter code
* may set it in a custom start_frame, and access it in
* draw_slice.
*
* It is automatically freed by the filter system in
* ff_end_frame().
*/
AVFilterBufferRef *out_buf;
struct AVFilterPool *pool;
/**
* Graph the filter belongs to.
*/
struct AVFilterGraph *graph;
/**
* Current timestamp of the link, as defined by the most recent
* frame(s), in AV_TIME_BASE units.
*/
int64_t current_pts;
/**
* Index in the age array.
*/
int age_index;
/**
* Frame rate of the stream on the link, or 1/0 if unknown;
* if left to 0/0, will be automatically be copied from the first input
* of the source filter if it exists.
*
* Sources should set it to the best estimation of the real frame rate.
* Filters should update it if necessary depending on their function.
* Sinks can use it to set a default output frame rate.
* It is similar to the r_frame_rate field in AVStream.
*/
AVRational frame_rate;
/**
* Buffer partially filled with samples to achieve a fixed/minimum size.
*/
AVFilterBufferRef *partial_buf;
/**
* Size of the partial buffer to allocate.
* Must be between min_samples and max_samples.
*/
int partial_buf_size;
/**
* Minimum number of samples to filter at once. If filter_frame() is
* called with fewer samples, it will accumulate them in partial_buf.
* This field and the related ones must not be changed after filtering
* has started.
* If 0, all related fields are ignored.
*/
int min_samples;
/**
* Maximum number of samples to filter at once. If filter_frame() is
* called with more samples, it will split them.
*/
int max_samples;
/**
* The buffer reference currently being received across the link by the
* destination filter. This is used internally by the filter system to
* allow automatic copying of buffers which do not have sufficient
* permissions for the destination. This should not be accessed directly
* by the filters.
*/
AVFilterBufferRef *cur_buf_copy;
/**
* True if the link is closed.
* If set, all attemps of start_frame, filter_frame or request_frame
* will fail with AVERROR_EOF, and if necessary the reference will be
* destroyed.
* If request_frame returns AVERROR_EOF, this flag is set on the
* corresponding link.
* It can be set also be set by either the source or the destination
* filter.
*/
int closed;
/**
* Number of channels.
*/
int channels;
};
/**
* Link two filters together.
*
* @param src the source filter
* @param srcpad index of the output pad on the source filter
* @param dst the destination filter
* @param dstpad index of the input pad on the destination filter
* @return zero on success
*/
int avfilter_link(AVFilterContext *src, unsigned srcpad,
AVFilterContext *dst, unsigned dstpad);
/**
* Free the link in *link, and set its pointer to NULL.
*/
void avfilter_link_free(AVFilterLink **link);
/**
* Get the number of channels of a link.
*/
int avfilter_link_get_channels(AVFilterLink *link);
/**
* Set the closed field of a link.
*/
void avfilter_link_set_closed(AVFilterLink *link, int closed);
/**
* Negotiate the media format, dimensions, etc of all inputs to a filter.
*
* @param filter the filter to negotiate the properties for its inputs
* @return zero on successful negotiation
*/
int avfilter_config_links(AVFilterContext *filter);
/**
* Create a buffer reference wrapped around an already allocated image
* buffer.
*
* @param data pointers to the planes of the image to reference
* @param linesize linesizes for the planes of the image to reference
* @param perms the required access permissions
* @param w the width of the image specified by the data and linesize arrays
* @param h the height of the image specified by the data and linesize arrays
* @param format the pixel format of the image specified by the data and linesize arrays
*/
AVFilterBufferRef *
avfilter_get_video_buffer_ref_from_arrays(uint8_t * const data[4], const int linesize[4], int perms,
int w, int h, enum AVPixelFormat format);
/**
* Create an audio buffer reference wrapped around an already
* allocated samples buffer.
*
* @param data pointers to the samples plane buffers
* @param linesize linesize for the samples plane buffers
* @param perms the required access permissions
* @param nb_samples number of samples per channel
* @param sample_fmt the format of each sample in the buffer to allocate
* @param channel_layout the channel layout of the buffer
*/
AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays(uint8_t **data,
int linesize,
int perms,
int nb_samples,
enum AVSampleFormat sample_fmt,
uint64_t channel_layout);
#define AVFILTER_CMD_FLAG_ONE 1 ///< Stop once a filter understood the command (for target=all for example), fast filters are favored automatically
#define AVFILTER_CMD_FLAG_FAST 2 ///< Only execute command when its fast (like a video out that supports contrast adjustment in hw)
/**
* Make the filter instance process a command.
* It is recommended to use avfilter_graph_send_command().
*/
int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags);
/** Initialize the filter system. Register all builtin filters. */
void avfilter_register_all(void);
/** Uninitialize the filter system. Unregister all filters. */
void avfilter_uninit(void);
/**
* Register a filter. This is only needed if you plan to use
* avfilter_get_by_name later to lookup the AVFilter structure by name. A
* filter can still by instantiated with avfilter_open even if it is not
* registered.
*
* @param filter the filter to register
* @return 0 if the registration was successful, a negative value
* otherwise
*/
int avfilter_register(AVFilter *filter);
/**
* Get a filter definition matching the given name.
*
* @param name the filter name to find
* @return the filter definition, if any matching one is registered.
* NULL if none found.
*/
AVFilter *avfilter_get_by_name(const char *name);
/**
* If filter is NULL, returns a pointer to the first registered filter pointer,
* if filter is non-NULL, returns the next pointer after filter.
* If the returned pointer points to NULL, the last registered filter
* was already reached.
*/
AVFilter **av_filter_next(AVFilter **filter);
/**
* Create a filter instance.
*
* @param filter_ctx put here a pointer to the created filter context
* on success, NULL on failure
* @param filter the filter to create an instance of
* @param inst_name Name to give to the new instance. Can be NULL for none.
* @return >= 0 in case of success, a negative error code otherwise
*/
int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name);
/**
* Initialize a filter.
*
* @param filter the filter to initialize
* @param args A string of parameters to use when initializing the filter.
* The format and meaning of this string varies by filter.
* @param opaque Any extra non-string data needed by the filter. The meaning
* of this parameter varies by filter.
* @return zero on success
*/
int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque);
/**
* Free a filter context.
*
* @param filter the filter to free
*/
void avfilter_free(AVFilterContext *filter);
/**
* Insert a filter in the middle of an existing link.
*
* @param link the link into which the filter should be inserted
* @param filt the filter to be inserted
* @param filt_srcpad_idx the input pad on the filter to connect
* @param filt_dstpad_idx the output pad on the filter to connect
* @return zero on success
*/
int avfilter_insert_filter(AVFilterLink *link, AVFilterContext *filt,
unsigned filt_srcpad_idx, unsigned filt_dstpad_idx);
/**
* @}
*/
#endif /* AVFILTER_AVFILTER_H */
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