/*
 * 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
 */

/**
 * @file
 * @ingroup lavu_frame
 * reference-counted frame API
 */

#ifndef AVUTIL_FRAME_H
#define AVUTIL_FRAME_H

#include <stddef.h>
#include <stdint.h>

#include "avutil.h"
#include "buffer.h"
#include "channel_layout.h"
#include "dict.h"
#include "rational.h"
#include "samplefmt.h"
#include "pixfmt.h"
#include "version.h"


/**
 * @defgroup lavu_frame AVFrame
 * @ingroup lavu_data
 *
 * @{
 * AVFrame is an abstraction for reference-counted raw multimedia data.
 */

enum AVFrameSideDataType {
    /**
     * The data is the AVPanScan struct defined in libavcodec.
     */
    AV_FRAME_DATA_PANSCAN,
    /**
     * ATSC A53 Part 4 Closed Captions.
     * A53 CC bitstream is stored as uint8_t in AVFrameSideData.data.
     * The number of bytes of CC data is AVFrameSideData.size.
     */
    AV_FRAME_DATA_A53_CC,
    /**
     * Stereoscopic 3d metadata.
     * The data is the AVStereo3D struct defined in libavutil/stereo3d.h.
     */
    AV_FRAME_DATA_STEREO3D,
    /**
     * The data is the AVMatrixEncoding enum defined in libavutil/channel_layout.h.
     */
    AV_FRAME_DATA_MATRIXENCODING,
    /**
     * Metadata relevant to a downmix procedure.
     * The data is the AVDownmixInfo struct defined in libavutil/downmix_info.h.
     */
    AV_FRAME_DATA_DOWNMIX_INFO,
    /**
     * ReplayGain information in the form of the AVReplayGain struct.
     */
    AV_FRAME_DATA_REPLAYGAIN,
    /**
     * This side data contains a 3x3 transformation matrix describing an affine
     * transformation that needs to be applied to the frame for correct
     * presentation.
     *
     * See libavutil/display.h for a detailed description of the data.
     */
    AV_FRAME_DATA_DISPLAYMATRIX,
    /**
     * Active Format Description data consisting of a single byte as specified
     * in ETSI TS 101 154 using AVActiveFormatDescription enum.
     */
    AV_FRAME_DATA_AFD,
    /**
     * Motion vectors exported by some codecs (on demand through the export_mvs
     * flag set in the libavcodec AVCodecContext flags2 option).
     * The data is the AVMotionVector struct defined in
     * libavutil/motion_vector.h.
     */
    AV_FRAME_DATA_MOTION_VECTORS,
    /**
     * Recommmends skipping the specified number of samples. This is exported
     * only if the "skip_manual" AVOption is set in libavcodec.
     * This has the same format as AV_PKT_DATA_SKIP_SAMPLES.
     * @code
     * u32le number of samples to skip from start of this packet
     * u32le number of samples to skip from end of this packet
     * u8    reason for start skip
     * u8    reason for end   skip (0=padding silence, 1=convergence)
     * @endcode
     */
    AV_FRAME_DATA_SKIP_SAMPLES,
    /**
     * This side data must be associated with an audio frame and corresponds to
     * enum AVAudioServiceType defined in avcodec.h.
     */
    AV_FRAME_DATA_AUDIO_SERVICE_TYPE,
    /**
     * Mastering display metadata associated with a video frame. The payload is
     * an AVMasteringDisplayMetadata type and contains information about the
     * mastering display color volume.
     */
    AV_FRAME_DATA_MASTERING_DISPLAY_METADATA,
    /**
     * The GOP timecode in 25 bit timecode format. Data format is 64-bit integer.
     * This is set on the first frame of a GOP that has a temporal reference of 0.
     */
    AV_FRAME_DATA_GOP_TIMECODE,

    /**
     * The data represents the AVSphericalMapping structure defined in
     * libavutil/spherical.h.
     */
    AV_FRAME_DATA_SPHERICAL,

    /**
     * Content light level (based on CTA-861.3). This payload contains data in
     * the form of the AVContentLightMetadata struct.
     */
    AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,

    /**
     * The data contains an ICC profile as an opaque octet buffer following the
     * format described by ISO 15076-1 with an optional name defined in the
     * metadata key entry "name".
     */
    AV_FRAME_DATA_ICC_PROFILE,

    /**
     * Timecode which conforms to SMPTE ST 12-1. The data is an array of 4 uint32_t
     * where the first uint32_t describes how many (1-3) of the other timecodes are used.
     * The timecode format is described in the documentation of av_timecode_get_smpte_from_framenum()
     * function in libavutil/timecode.h.
     */
    AV_FRAME_DATA_S12M_TIMECODE,

    /**
     * HDR dynamic metadata associated with a video frame. The payload is
     * an AVDynamicHDRPlus type and contains information for color
     * volume transform - application 4 of SMPTE 2094-40:2016 standard.
     */
    AV_FRAME_DATA_DYNAMIC_HDR_PLUS,

    /**
     * Regions Of Interest, the data is an array of AVRegionOfInterest type, the number of
     * array element is implied by AVFrameSideData.size / AVRegionOfInterest.self_size.
     */
    AV_FRAME_DATA_REGIONS_OF_INTEREST,

    /**
     * Encoding parameters for a video frame, as described by AVVideoEncParams.
     */
    AV_FRAME_DATA_VIDEO_ENC_PARAMS,

    /**
     * User data unregistered metadata associated with a video frame.
     * This is the H.26[45] UDU SEI message, and shouldn't be used for any other purpose
     * The data is stored as uint8_t in AVFrameSideData.data which is 16 bytes of
     * uuid_iso_iec_11578 followed by AVFrameSideData.size - 16 bytes of user_data_payload_byte.
     */
    AV_FRAME_DATA_SEI_UNREGISTERED,

    /**
     * Film grain parameters for a frame, described by AVFilmGrainParams.
     * Must be present for every frame which should have film grain applied.
     */
    AV_FRAME_DATA_FILM_GRAIN_PARAMS,

    /**
     * Bounding boxes for object detection and classification,
     * as described by AVDetectionBBoxHeader.
     */
    AV_FRAME_DATA_DETECTION_BBOXES,

    /**
     * Dolby Vision RPU raw data, suitable for passing to x265
     * or other libraries. Array of uint8_t, with NAL emulation
     * bytes intact.
     */
    AV_FRAME_DATA_DOVI_RPU_BUFFER,

    /**
     * Parsed Dolby Vision metadata, suitable for passing to a software
     * implementation. The payload is the AVDOVIMetadata struct defined in
     * libavutil/dovi_meta.h.
     */
    AV_FRAME_DATA_DOVI_METADATA,

    /**
     * HDR Vivid dynamic metadata associated with a video frame. The payload is
     * an AVDynamicHDRVivid type and contains information for color
     * volume transform - CUVA 005.1-2021.
     */
    AV_FRAME_DATA_DYNAMIC_HDR_VIVID,
};

enum AVActiveFormatDescription {
    AV_AFD_SAME         = 8,
    AV_AFD_4_3          = 9,
    AV_AFD_16_9         = 10,
    AV_AFD_14_9         = 11,
    AV_AFD_4_3_SP_14_9  = 13,
    AV_AFD_16_9_SP_14_9 = 14,
    AV_AFD_SP_4_3       = 15,
};


/**
 * Structure to hold side data for an AVFrame.
 *
 * sizeof(AVFrameSideData) is not a part of the public ABI, so new fields may be added
 * to the end with a minor bump.
 */
typedef struct AVFrameSideData {
    enum AVFrameSideDataType type;
    uint8_t *data;
    size_t   size;
    AVDictionary *metadata;
    AVBufferRef *buf;
} AVFrameSideData;

/**
 * Structure describing a single Region Of Interest.
 *
 * When multiple regions are defined in a single side-data block, they
 * should be ordered from most to least important - some encoders are only
 * capable of supporting a limited number of distinct regions, so will have
 * to truncate the list.
 *
 * When overlapping regions are defined, the first region containing a given
 * area of the frame applies.
 */
typedef struct AVRegionOfInterest {
    /**
     * Must be set to the size of this data structure (that is,
     * sizeof(AVRegionOfInterest)).
     */
    uint32_t self_size;
    /**
     * Distance in pixels from the top edge of the frame to the top and
     * bottom edges and from the left edge of the frame to the left and
     * right edges of the rectangle defining this region of interest.
     *
     * The constraints on a region are encoder dependent, so the region
     * actually affected may be slightly larger for alignment or other
     * reasons.
     */
    int top;
    int bottom;
    int left;
    int right;
    /**
     * Quantisation offset.
     *
     * Must be in the range -1 to +1.  A value of zero indicates no quality
     * change.  A negative value asks for better quality (less quantisation),
     * while a positive value asks for worse quality (greater quantisation).
     *
     * The range is calibrated so that the extreme values indicate the
     * largest possible offset - if the rest of the frame is encoded with the
     * worst possible quality, an offset of -1 indicates that this region
     * should be encoded with the best possible quality anyway.  Intermediate
     * values are then interpolated in some codec-dependent way.
     *
     * For example, in 10-bit H.264 the quantisation parameter varies between
     * -12 and 51.  A typical qoffset value of -1/10 therefore indicates that
     * this region should be encoded with a QP around one-tenth of the full
     * range better than the rest of the frame.  So, if most of the frame
     * were to be encoded with a QP of around 30, this region would get a QP
     * of around 24 (an offset of approximately -1/10 * (51 - -12) = -6.3).
     * An extreme value of -1 would indicate that this region should be
     * encoded with the best possible quality regardless of the treatment of
     * the rest of the frame - that is, should be encoded at a QP of -12.
     */
    AVRational qoffset;
} AVRegionOfInterest;

/**
 * 此结构描述解码（原始）音频或视频数据。
 *
 * AVFrame必须使用av_frame_alloc（）分配。
 * 注意，这只分配AVFrame本身，数据的缓冲区必须通过其他方式进行管理（见下文）。
 * 必须使用av_frame_free（）释放AVFrame。
 *
 * AVFrame通常分配一次，然后多次重复使用，以保存不同的数据（例如，单个AVFrame用于保存从解码器接收的帧）。
 * 在这种情况下，av_frame_unref（）将释放帧持有的所有引用，并将其重置为原始干净状态，然后再重新使用。
 *
 * AVFrame描述的数据通常通过AVBuffer API进行引用计数。
 * 底层缓冲区引用存储在AVFrame中。
 * buf / AVFrame.extended_buf。
 * 如果至少设置了一个引用，即如果AVFrame，则认为该AVFrame已被引用计数。
 * buf[0]! = NULL。在这种情况下，每个数据平面都必须包含在AVFrame中的一个缓冲区中。
 * 缓冲区或AVFrame.extended_buf。
 * 所有数据可能有一个缓冲区，或者每个平面有一个单独的缓冲区，或两者之间的任何缓冲区。
 *
 * sizeof(AVFrame) is not a part of the public ABI, so new fields may be added
 * to the end with a minor bump.
 *
 * Fields can be accessed through AVOptions, the name string used, matches the
 * C structure field name for fields accessible through AVOptions. The AVClass
 * for AVFrame can be obtained from avcodec_get_frame_class()
 */
typedef struct AVFrame {
#define AV_NUM_DATA_POINTERS 8
    /**
     * pointer to the picture/channel planes.
     * This might be different from the first allocated byte. For video,
     * it could even point to the end of the image data.
     *
     * All pointers in data and extended_data must point into one of the
     * AVBufferRef in buf or extended_buf.
     *
     * Some decoders access areas outside 0,0 - width,height, please
     * see avcodec_align_dimensions2(). Some filters and swscale can read
     * up to 16 bytes beyond the planes, if these filters are to be used,
     * then 16 extra bytes must be allocated.
     *
     * NOTE: Pointers not needed by the format MUST be set to NULL.
     *
     * @attention In case of video, the data[] pointers can point to the
     * end of image data in order to reverse line order, when used in
     * combination with negative values in the linesize[] array.
     */
    uint8_t *data[AV_NUM_DATA_POINTERS];

    /**
     * For video, a positive or negative value, which is typically indicating
     * the size in bytes of each picture line, but it can also be:
     * - the negative byte size of lines for vertical flipping
     *   (with data[n] pointing to the end of the data
     * - a positive or negative multiple of the byte size as for accessing
     *   even and odd fields of a frame (possibly flipped)
     *
     * For audio, only linesize[0] may be set. For planar audio, each channel
     * plane must be the same size.
     *
     * For video the linesizes should be multiples of the CPUs alignment
     * preference, this is 16 or 32 for modern desktop CPUs.
     * Some code requires such alignment other code can be slower without
     * correct alignment, for yet other it makes no difference.
     *
     * @note The linesize may be larger than the size of usable data -- there
     * may be extra padding present for performance reasons.
     *
     * @attention In case of video, line size values can be negative to achieve
     * a vertically inverted iteration over image lines.
     */
    int linesize[AV_NUM_DATA_POINTERS];

    /**
     * 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 should always be set in a valid frame,
     * 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;

    /**
     * @name Video dimensions
     * Video frames only. The coded dimensions (in pixels) of the video frame,
     * i.e. the size of the rectangle that contains some well-defined values.
     *
     * @note The part of the frame intended for display/presentation is further
     * restricted by the @ref cropping "Cropping rectangle".
     * @{
     */
    int width, height;
    /**
     * @}
     */

    /**
     * number of audio samples (per channel) described by this frame
     */
    int nb_samples;

    /**
     * format of the frame, -1 if unknown or unset
     * Values correspond to enum AVPixelFormat for video frames,
     * enum AVSampleFormat for audio)
     */
    int format;

    /**
     * 1 -> keyframe, 0-> not
     */
    int key_frame;

    /**
     * 框架的图片类型。
     */
    enum AVPictureType pict_type;

    /**
     * 视频帧的采样纵横比，如果未知/未指定，则为0/1。
     */
    AVRational sample_aspect_ratio;

    /**
     * 以time_base单元表示的时间戳(帧应该显示给用户的时间)。
     */
    int64_t pts;

    /**
     * 从触发返回此帧的AVPacket中复制DTS。(如果不使用帧线程)
     * 这也是该AVFrame的呈现时间，仅从AVPacket计算。没有PTS值的DTS值。
     */
    int64_t pkt_dts;

    /**
     * 此帧中时间戳的时间基数。
     * 将来，这个字段可能在解码器或过滤器输出的帧上设置，但在默认情况下，它的值将在编码器或过滤器的输入上被忽略。
     */
    AVRational time_base;

    /**
     * picture number in bitstream order
     */
    int coded_picture_number;
    /**
     * picture number in display order
     */
    int display_picture_number;

    /**
     * quality (between 1 (good) and FF_LAMBDA_MAX (bad))
     */
    int quality;

    /**
     * for some private data of the user
     */
    void *opaque;

    /**
     * When decoding, this signals how much the picture must be delayed.
     * extra_delay = repeat_pict / (2*fps)
     */
    int repeat_pict;

    /**
     * The content of the picture is interlaced.
     */
    int interlaced_frame;

    /**
     * If the content is interlaced, is top field displayed first.
     */
    int top_field_first;

    /**
     * Tell user application that palette has changed from previous frame.
     */
    int palette_has_changed;

    /**
     * reordered opaque 64 bits (generally an integer or a double precision float
     * PTS but can be anything).
     * The user sets AVCodecContext.reordered_opaque to represent the input at
     * that time,
     * the decoder reorders values as needed and sets AVFrame.reordered_opaque
     * to exactly one of the values provided by the user through AVCodecContext.reordered_opaque
     */
    int64_t reordered_opaque;

    /**
     * Sample rate of the audio data.
     */
    int sample_rate;

#if FF_API_OLD_CHANNEL_LAYOUT
    /**
     * Channel layout of the audio data.
     * @deprecated use ch_layout instead
     */
    attribute_deprecated
    uint64_t channel_layout;
#endif

    /**
     * AVBuffer references backing the data for this frame. All the pointers in
     * data and extended_data must point inside one of the buffers in buf or
     * extended_buf. This array must be filled contiguously -- if buf[i] is
     * non-NULL then buf[j] must also be non-NULL for all j < i.
     *
     * There may be at most one AVBuffer per data plane, so for video this array
     * always contains all the references. For planar audio with more than
     * AV_NUM_DATA_POINTERS channels, there may be more buffers than can fit in
     * this array. Then the extra AVBufferRef pointers are stored in the
     * extended_buf array.
     */
    AVBufferRef *buf[AV_NUM_DATA_POINTERS];

    /**
     * For planar audio which requires more than AV_NUM_DATA_POINTERS
     * AVBufferRef pointers, this array will hold all the references which
     * cannot fit into AVFrame.buf.
     *
     * Note that this is different from AVFrame.extended_data, which always
     * contains all the pointers. This array only contains the extra pointers,
     * which cannot fit into AVFrame.buf.
     *
     * This array is always allocated using av_malloc() by whoever constructs
     * the frame. It is freed in av_frame_unref().
     */
    AVBufferRef **extended_buf;
    /**
     * Number of elements in extended_buf.
     */
    int        nb_extended_buf;

    AVFrameSideData **side_data;
    int            nb_side_data;

/**
 * @defgroup lavu_frame_flags AV_FRAME_FLAGS
 * @ingroup lavu_frame
 * Flags describing additional frame properties.
 *
 * @{
 */

/**
 * The frame data may be corrupted, e.g. due to decoding errors.
 */
#define AV_FRAME_FLAG_CORRUPT       (1 << 0)
/**
 * A flag to mark the frames which need to be decoded, but shouldn't be output.
 */
#define AV_FRAME_FLAG_DISCARD   (1 << 2)
/**
 * @}
 */

    /**
     * Frame flags, a combination of @ref lavu_frame_flags
     */
    int flags;

    /**
     * MPEG vs JPEG YUV range.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorRange color_range;

    enum AVColorPrimaries color_primaries;

    enum AVColorTransferCharacteristic color_trc;

    /**
     * YUV colorspace type.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVColorSpace colorspace;

    enum AVChromaLocation chroma_location;

    /**
     * frame timestamp estimated using various heuristics, in stream time base
     * - encoding: unused
     * - decoding: set by libavcodec, read by user.
     */
    int64_t best_effort_timestamp;

    /**
     * 从已输入到解码器的最后一个AVPacket中重新排序的pos
     * - encoding: unused
     * - decoding: Read by user.
     */
    int64_t pkt_pos;

    /**
     * 相应数据包的持续时间，以AVStream->time_base单位表示，如果未知，则为0。
     * - encoding: unused
     * - decoding: Read by user.
     */
    int64_t pkt_duration;

    /**
     * metadata.
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    AVDictionary *metadata;

    /**
     * decode error flags of the frame, set to a combination of
     * FF_DECODE_ERROR_xxx flags if the decoder produced a frame, but there
     * were errors during the decoding.
     * - encoding: unused
     * - decoding: set by libavcodec, read by user.
     */
    int decode_error_flags;
#define FF_DECODE_ERROR_INVALID_BITSTREAM   1
#define FF_DECODE_ERROR_MISSING_REFERENCE   2
#define FF_DECODE_ERROR_CONCEALMENT_ACTIVE  4
#define FF_DECODE_ERROR_DECODE_SLICES       8

#if FF_API_OLD_CHANNEL_LAYOUT
    /**
     * number of audio channels, only used for audio.
     * - encoding: unused
     * - decoding: Read by user.
     * @deprecated use ch_layout instead
     */
    attribute_deprecated
    int channels;
#endif

    /**
     * 包含压缩帧的相应数据包的大小。
     * 如果未知，则将其设置为负值。
     * - encoding: unused
     * - decoding: set by libavcodec, read by user.
     */
    int pkt_size;

    /**
     * For hwaccel-format frames, this should be a reference to the
     * AVHWFramesContext describing the frame.
     */
    AVBufferRef *hw_frames_ctx;

    /**
     * AVBufferRef for free use by the API user. FFmpeg will never check the
     * contents of the buffer ref. FFmpeg calls av_buffer_unref() on it when
     * the frame is unreferenced. av_frame_copy_props() calls create a new
     * reference with av_buffer_ref() for the target frame's opaque_ref field.
     *
     * This is unrelated to the opaque field, although it serves a similar
     * purpose.
     */
    AVBufferRef *opaque_ref;

    /**
     * @anchor cropping
     * @name Cropping
     * Video frames only. The number of pixels to discard from the the
     * top/bottom/left/right border of the frame to obtain the sub-rectangle of
     * the frame intended for presentation.
     * @{
     */
    size_t crop_top;
    size_t crop_bottom;
    size_t crop_left;
    size_t crop_right;
    /**
     * @}
     */

    /**
     * AVBufferRef for internal use by a single libav* library.
     * Must not be used to transfer data between libraries.
     * Has to be NULL when ownership of the frame leaves the respective library.
     *
     * Code outside the FFmpeg libs should never check or change the contents of the buffer ref.
     *
     * FFmpeg calls av_buffer_unref() on it when the frame is unreferenced.
     * av_frame_copy_props() calls create a new reference with av_buffer_ref()
     * for the target frame's private_ref field.
     */
    AVBufferRef *private_ref;

    /**
     * Channel layout of the audio data.
     */
    AVChannelLayout ch_layout;
} AVFrame;


#if FF_API_COLORSPACE_NAME
/**
 * Get the name of a colorspace.
 * @return a static string identifying the colorspace; can be NULL.
 * @deprecated use av_color_space_name()
 */
attribute_deprecated
const char *av_get_colorspace_name(enum AVColorSpace val);
#endif
/**
 * 分配AVFrame并将其字段设置为默认值。必须使用av_frame_free（）释放生成的结构。
 *
 * @return AVFrame填充了默认值或失败时为NULL。
 *
 * @note 这只分配AVFrame本身，而不是数据缓冲区。
 *       这些必须通过其他方式分配，例如使用av_frame_get_buffer（）或手动分配。
 */
AVFrame *av_frame_alloc(void);

/**
 * 释放帧和其中任何动态分配的对象，
 * e.g.扩展数据。如果帧是引用计数的，则首先将取消引用。
 * @param 要释放的帧帧。指针将设置为NULL。
 */
void av_frame_free(AVFrame **frame);

/**
 * Set up a new reference to the data described by the source frame.
 *
 * Copy frame properties from src to dst and create a new reference for each
 * AVBufferRef from src.
 *
 * If src is not reference counted, new buffers are allocated and the data is
 * copied.
 *
 * @warning: dst MUST have been either unreferenced with av_frame_unref(dst),
 *           or newly allocated with av_frame_alloc() before calling this
 *           function, or undefined behavior will occur.
 *
 * @return 0 on success, a negative AVERROR on error
 */
int av_frame_ref(AVFrame *dst, const AVFrame *src);

/**
 * Create a new frame that references the same data as src.
 *
 * This is a shortcut for av_frame_alloc()+av_frame_ref().
 *
 * @return newly created AVFrame on success, NULL on error.
 */
AVFrame *av_frame_clone(const AVFrame *src);

/**
 * 取消引用帧引用的所有缓冲区并重置帧字段。
 */
void av_frame_unref(AVFrame *frame);

/**
 * Move everything contained in src to dst and reset src.
 *
 * @warning: dst is not unreferenced, but directly overwritten without reading
 *           or deallocating its contents. Call av_frame_unref(dst) manually
 *           before calling this function to ensure that no memory is leaked.
 */
void av_frame_move_ref(AVFrame *dst, AVFrame *src);

/**
 * Allocate new buffer(s) for audio or video data.
 *
 * The following fields must be set on frame before calling this function:
 * - format (pixel format for video, sample format for audio)
 * - width and height for video
 * - nb_samples and ch_layout for audio
 *
 * This function will fill AVFrame.data and AVFrame.buf arrays and, if
 * necessary, allocate and fill AVFrame.extended_data and AVFrame.extended_buf.
 * For planar formats, one buffer will be allocated for each plane.
 *
 * @warning: if frame already has been allocated, calling this function will
 *           leak memory. In addition, undefined behavior can occur in certain
 *           cases.
 *
 * @param frame frame in which to store the new buffers.
 * @param align Required buffer size alignment. If equal to 0, alignment will be
 *              chosen automatically for the current CPU. It is highly
 *              recommended to pass 0 here unless you know what you are doing.
 *
 * @return 0 on success, a negative AVERROR on error.
 */
int av_frame_get_buffer(AVFrame *frame, int align);

/**
 * Check if the frame data is writable.
 *
 * @return A positive value if the frame data is writable (which is true if and
 * only if each of the underlying buffers has only one reference, namely the one
 * stored in this frame). Return 0 otherwise.
 *
 * If 1 is returned the answer is valid until av_buffer_ref() is called on any
 * of the underlying AVBufferRefs (e.g. through av_frame_ref() or directly).
 *
 * @see av_frame_make_writable(), av_buffer_is_writable()
 */
int av_frame_is_writable(AVFrame *frame);

/**
 * Ensure that the frame data is writable, avoiding data copy if possible.
 *
 * Do nothing if the frame is writable, allocate new buffers and copy the data
 * if it is not.
 *
 * @return 0 on success, a negative AVERROR on error.
 *
 * @see av_frame_is_writable(), av_buffer_is_writable(),
 * av_buffer_make_writable()
 */
int av_frame_make_writable(AVFrame *frame);

/**
 * Copy the frame data from src to dst.
 *
 * This function does not allocate anything, dst must be already initialized and
 * allocated with the same parameters as src.
 *
 * This function only copies the frame data (i.e. the contents of the data /
 * extended data arrays), not any other properties.
 *
 * @return >= 0 on success, a negative AVERROR on error.
 */
int av_frame_copy(AVFrame *dst, const AVFrame *src);

/**
 * 仅将“metadata”字段从src复制到dst。
 *
 * 用于此函数的元数据是那些不影响缓冲区中的数据布局的字段。
 * 例如，pts，采样率(音频)或采样长宽比(视频)，但不是宽度/高度或频道布局。
 * 侧数据也会被复制。
 */
int av_frame_copy_props(AVFrame *dst, const AVFrame *src);

/**
 * Get the buffer reference a given data plane is stored in.
 *
 * @param plane index of the data plane of interest in frame->extended_data.
 *
 * @return the buffer reference that contains the plane or NULL if the input
 * frame is not valid.
 */
AVBufferRef *av_frame_get_plane_buffer(AVFrame *frame, int plane);

/**
 * Add a new side data to a frame.
 *
 * @param frame a frame to which the side data should be added
 * @param type type of the added side data
 * @param size size of the side data
 *
 * @return newly added side data on success, NULL on error
 */
AVFrameSideData *av_frame_new_side_data(AVFrame *frame,
                                        enum AVFrameSideDataType type,
                                        size_t size);

/**
 * Add a new side data to a frame from an existing AVBufferRef
 *
 * @param frame a frame to which the side data should be added
 * @param type  the type of the added side data
 * @param buf   an AVBufferRef to add as side data. The ownership of
 *              the reference is transferred to the frame.
 *
 * @return newly added side data on success, NULL on error. On failure
 *         the frame is unchanged and the AVBufferRef remains owned by
 *         the caller.
 */
AVFrameSideData *av_frame_new_side_data_from_buf(AVFrame *frame,
                                                 enum AVFrameSideDataType type,
                                                 AVBufferRef *buf);

/**
 * @return a pointer to the side data of a given type on success, NULL if there
 * is no side data with such type in this frame.
 */
AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
                                        enum AVFrameSideDataType type);

/**
 * Remove and free all side data instances of the given type.
 */
void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);


/**
 * Flags for frame cropping.
 */
enum {
    /**
     * Apply the maximum possible cropping, even if it requires setting the
     * AVFrame.data[] entries to unaligned pointers. Passing unaligned data
     * to FFmpeg API is generally not allowed, and causes undefined behavior
     * (such as crashes). You can pass unaligned data only to FFmpeg APIs that
     * are explicitly documented to accept it. Use this flag only if you
     * absolutely know what you are doing.
     */
    AV_FRAME_CROP_UNALIGNED     = 1 << 0,
};

/**
 * Crop the given video AVFrame according to its crop_left/crop_top/crop_right/
 * crop_bottom fields. If cropping is successful, the function will adjust the
 * data pointers and the width/height fields, and set the crop fields to 0.
 *
 * In all cases, the cropping boundaries will be rounded to the inherent
 * alignment of the pixel format. In some cases, such as for opaque hwaccel
 * formats, the left/top cropping is ignored. The crop fields are set to 0 even
 * if the cropping was rounded or ignored.
 *
 * @param frame the frame which should be cropped
 * @param flags Some combination of AV_FRAME_CROP_* flags, or 0.
 *
 * @return >= 0 on success, a negative AVERROR on error. If the cropping fields
 * were invalid, AVERROR(ERANGE) is returned, and nothing is changed.
 */
int av_frame_apply_cropping(AVFrame *frame, int flags);

/**
 * @return a string identifying the side data type
 */
const char *av_frame_side_data_name(enum AVFrameSideDataType type);

/**
 * @}
 */

#endif /* AVUTIL_FRAME_H */