FFmpeg4/libavfilter/buffersrc.h

/*
 * 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_BUFFERSRC_H
#define AVFILTER_BUFFERSRC_H

/**
 * @file
 * @ingroup lavfi_buffersrc
 * Memory buffer source API.
 */

#include "avfilter.h"

/**
 * @defgroup lavfi_buffersrc Buffer source API
 * @ingroup lavfi
 * @{
 */

enum {

    /**
     * Do not check for format changes.
     */
    AV_BUFFERSRC_FLAG_NO_CHECK_FORMAT = 1,

    /**
     * Immediately push the frame to the output.
     */
    AV_BUFFERSRC_FLAG_PUSH = 4,

    /**
     * Keep a reference to the frame.
     * If the frame if reference-counted, create a new reference; otherwise
     * copy the frame data.
     */
    AV_BUFFERSRC_FLAG_KEEP_REF = 8,

};

/**
 * Get the number of failed requests.
 *
 * A failed request is when the request_frame method is called while no
 * frame is present in the buffer.
 * The number is reset when a frame is added.
 */
unsigned av_buffersrc_get_nb_failed_requests(AVFilterContext *buffer_src);

/**
 * This structure contains the parameters describing the frames that will be
 * passed to this filter.
 *
 * It should be allocated with av_buffersrc_parameters_alloc() and freed with
 * av_free(). All the allocated fields in it remain owned by the caller.
 */
typedef struct AVBufferSrcParameters {
    /**
     * video: the pixel format, value corresponds to enum AVPixelFormat
     * audio: the sample format, value corresponds to enum AVSampleFormat
     */
    int format;
    /**
     * The timebase to be used for the timestamps on the input frames.
     */
    AVRational time_base;

    /**
     * Video only, the display dimensions of the input frames.
     */
    int width, height;

    /**
     * Video only, the sample (pixel) aspect ratio.
     */
    AVRational sample_aspect_ratio;

    /**
     * Video only, the frame rate of the input video. This field must only be
     * set to a non-zero value if input stream has a known constant framerate
     * and should be left at its initial value if the framerate is variable or
     * unknown.
     */
    AVRational frame_rate;

    /**
     * Video with a hwaccel pixel format only. This should be a reference to an
     * AVHWFramesContext instance describing the input frames.
     */
    AVBufferRef *hw_frames_ctx;

    /**
     * Audio only, the audio sampling rate in samples per second.
     */
    int sample_rate;

    /**
     * Audio only, the audio channel layout
     */
    uint64_t channel_layout;
} AVBufferSrcParameters;

/**
 * Allocate a new AVBufferSrcParameters instance. It should be freed by the
 * caller with av_free().
 */
AVBufferSrcParameters *av_buffersrc_parameters_alloc(void);

/**
 * Initialize the buffersrc or abuffersrc filter with the provided parameters.
 * This function may be called multiple times, the later calls override the
 * previous ones. Some of the parameters may also be set through AVOptions, then
 * whatever method is used last takes precedence.
 *
 * @param ctx an instance of the buffersrc or abuffersrc filter
 * @param param the stream parameters. The frames later passed to this filter
 *              must conform to those parameters. All the allocated fields in
 *              param remain owned by the caller, libavfilter will make internal
 *              copies or references when necessary.
 * @return 0 on success, a negative AVERROR code on failure.
 */
int av_buffersrc_parameters_set(AVFilterContext *ctx, AVBufferSrcParameters *param);

/**
 * Add a frame to the buffer source.
 *
 * @param ctx   an instance of the buffersrc filter
 * @param frame frame to be added. If the frame is reference counted, this
 * function will make a new reference to it. Otherwise the frame data will be
 * copied.
 *
 * @return 0 on success, a negative AVERROR on error
 *
 * This function is equivalent to av_buffersrc_add_frame_flags() with the
 * AV_BUFFERSRC_FLAG_KEEP_REF flag.
 */
av_warn_unused_result
int av_buffersrc_write_frame(AVFilterContext *ctx, const AVFrame *frame);

/**
 * Add a frame to the buffer source.
 *
 * @param ctx   an instance of the buffersrc filter
 * @param frame frame to be added. If the frame is reference counted, this
 * function will take ownership of the reference(s) and reset the frame.
 * Otherwise the frame data will be copied. If this function returns an error,
 * the input frame is not touched.
 *
 * @return 0 on success, a negative AVERROR on error.
 *
 * @note the difference between this function and av_buffersrc_write_frame() is
 * that av_buffersrc_write_frame() creates a new reference to the input frame,
 * while this function takes ownership of the reference passed to it.
 *
 * This function is equivalent to av_buffersrc_add_frame_flags() without the
 * AV_BUFFERSRC_FLAG_KEEP_REF flag.
 */
av_warn_unused_result
int av_buffersrc_add_frame(AVFilterContext *ctx, AVFrame *frame);

/**
 * Add a frame to the buffer source.
 *
 * By default, if the frame is reference-counted, this function will take
 * ownership of the reference(s) and reset the frame. This can be controlled
 * using the flags.
 *
 * If this function returns an error, the input frame is not touched.
 *
 * @param buffer_src  pointer to a buffer source context
 * @param frame       a frame, or NULL to mark EOF
 * @param flags       a combination of AV_BUFFERSRC_FLAG_*
 * @return            >= 0 in case of success, a negative AVERROR code
 *                    in case of failure
 */
av_warn_unused_result
int av_buffersrc_add_frame_flags(AVFilterContext *buffer_src,
                                 AVFrame *frame, int flags);

/**
 * Close the buffer source after EOF.
 *
 * This is similar to passing NULL to av_buffersrc_add_frame_flags()
 * except it takes the timestamp of the EOF, i.e. the timestamp of the end
 * of the last frame.
 */
int av_buffersrc_close(AVFilterContext *ctx, int64_t pts, unsigned flags);

/**
 * @}
 */

#endif /* AVFILTER_BUFFERSRC_H */