frame.h

Go to the documentation of this file.

/*
 * 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,
    /**
     * Recommends 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.
     *
     * May be present multiple times, for example when there are multiple
     * alternative parameter sets for different video signal characteristics.
     * The user should select the most appropriate set for the application.
     */
    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,
 
    /**
     * Ambient viewing environment metadata, as defined by H.274.
     */
    AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT,
 
    /**
     * Provide encoder-specific hinting information about changed/unchanged
     * portions of a frame.  It can be used to pass information about which
     * macroblocks can be skipped because they didn't change from the
     * corresponding ones in the previous frame. This could be useful for
     * applications which know this information in advance to speed up
     * encoding.
     */
    AV_FRAME_DATA_VIDEO_HINT,
 
    /**
     * Raw LCEVC payload data, as a uint8_t array, with NAL emulation
     * bytes intact.
     */
    AV_FRAME_DATA_LCEVC,
 
    /**
     * This side data must be associated with a video frame.
     * The presence of this side data indicates that the video stream is
     * composed of multiple views (e.g. stereoscopic 3D content,
     * cf. H.264 Annex H or H.265 Annex G).
     * The data is an int storing the view ID.
     */
    AV_FRAME_DATA_VIEW_ID,
 
    /**
     * This side data contains information about the reference display width(s)
     * and reference viewing distance(s) as well as information about the
     * corresponding reference stereo pair(s), i.e., the pair(s) of views to be
     * displayed for the viewer's left and right eyes on the reference display
     * at the reference viewing distance.
     * The payload is the AV3DReferenceDisplaysInfo struct defined in
     * libavutil/tdrdi.h.
     */
    AV_FRAME_DATA_3D_REFERENCE_DISPLAYS,
 
    /**
     * Extensible image file format metadata. The payload is a buffer containing
     * EXIF metadata, starting with either 49 49 2a 00, or 4d 4d 00 2a.
     */
     AV_FRAME_DATA_EXIF,
};
 
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;
 
enum AVSideDataProps {
    /**
     * The side data type can be used in stream-global structures.
     * Side data types without this property are only meaningful on per-frame
     * basis.
     */
    AV_SIDE_DATA_PROP_GLOBAL = (1 << 0),
 
    /**
     * Multiple instances of this side data type can be meaningfully present in
     * a single side data array.
     */
    AV_SIDE_DATA_PROP_MULTI  = (1 << 1),
 
    /**
     * Side data depends on the video dimensions. Side data with this property
     * loses its meaning when rescaling or cropping the image, unless
     * either recomputed or adjusted to the new resolution.
     */
    AV_SIDE_DATA_PROP_SIZE_DEPENDENT = (1 << 2),
 
    /**
     * Side data depends on the video color space. Side data with this property
     * loses its meaning when changing the video color encoding, e.g. by
     * adapting to a different set of primaries or transfer characteristics.
     */
    AV_SIDE_DATA_PROP_COLOR_DEPENDENT = (1 << 3),
 
    /**
     * Side data depends on the channel layout. Side data with this property
     * loses its meaning when downmixing or upmixing, unless either recomputed
     * or adjusted to the new layout.
     */
    AV_SIDE_DATA_PROP_CHANNEL_DEPENDENT = (1 << 4),
};
 
/**
 * This struct describes the properties of a side data type. Its instance
 * corresponding to a given type can be obtained from av_frame_side_data_desc().
 */
typedef struct AVSideDataDescriptor {
    /**
     * Human-readable side data description.
     */
    const char      *name;
 
    /**
     * Side data property flags, a combination of AVSideDataProps values.
     */
    unsigned         props;
} AVSideDataDescriptor;
 
/**
 * 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;
 
/**
 * This structure describes decoded (raw) audio or video data.
 *
 * AVFrame must be allocated using av_frame_alloc(). Note that this only
 * allocates the AVFrame itself, the buffers for the data must be managed
 * through other means (see below).
 * AVFrame must be freed with av_frame_free().
 *
 * AVFrame is typically allocated once and then reused multiple times to hold
 * different data (e.g. a single AVFrame to hold frames received from a
 * decoder). In such a case, av_frame_unref() will free any references held by
 * the frame and reset it to its original clean state before it
 * is reused again.
 *
 * The data described by an AVFrame is usually reference counted through the
 * AVBuffer API. The underlying buffer references are stored in AVFrame.buf /
 * AVFrame.extended_buf. An AVFrame is considered to be reference counted if at
 * least one reference is set, i.e. if AVFrame.buf[0] != NULL. In such a case,
 * every single data plane must be contained in one of the buffers in
 * AVFrame.buf or AVFrame.extended_buf.
 * There may be a single buffer for all the data, or one separate buffer for
 * each plane, or anything in between.
 *
 * 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.
 */
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;
 
    /**
     * Picture type of the frame.
     */
    enum AVPictureType pict_type;
 
    /**
     * Sample aspect ratio for the video frame, 0/1 if unknown/unspecified.
     */
    AVRational sample_aspect_ratio;
 
    /**
     * Presentation timestamp in time_base units (time when frame should be shown to user).
     */
    int64_t pts;
 
    /**
     * DTS copied from the AVPacket that triggered returning this frame. (if frame threading isn't used)
     * This is also the Presentation time of this AVFrame calculated from
     * only AVPacket.dts values without pts values.
     */
    int64_t pkt_dts;
 
    /**
     * Time base for the timestamps in this frame.
     * In the future, this field may be set on frames output by decoders or
     * filters, but its value will be by default ignored on input to encoders
     * or filters.
     */
    AVRational time_base;
 
    /**
     * quality (between 1 (good) and FF_LAMBDA_MAX (bad))
     */
    int quality;
 
    /**
     * Frame owner's private data.
     *
     * This field may be set by the code that allocates/owns the frame data.
     * It is then not touched by any library functions, except:
     * - it is copied to other references by av_frame_copy_props() (and hence by
     *   av_frame_ref());
     * - it is set to NULL when the frame is cleared by av_frame_unref()
     * - on the caller's explicit request. E.g. libavcodec encoders/decoders
     *   will copy this field to/from @ref AVPacket "AVPackets" if the caller sets
     *   @ref AV_CODEC_FLAG_COPY_OPAQUE.
     *
     * @see opaque_ref the reference-counted analogue
     */
    void *opaque;
 
    /**
     * Number of fields in this frame which should be repeated, i.e. the total
     * duration of this frame should be repeat_pict + 2 normal field durations.
     *
     * For interlaced frames this field may be set to 1, which signals that this
     * frame should be presented as 3 fields: beginning with the first field (as
     * determined by AV_FRAME_FLAG_TOP_FIELD_FIRST being set or not), followed
     * by the second field, and then the first field again.
     *
     * For progressive frames this field may be set to a multiple of 2, which
     * signals that this frame's duration should be (repeat_pict + 2) / 2
     * normal frame durations.
     *
     * @note This field is computed from MPEG2 repeat_first_field flag and its
     * associated flags, H.264 pic_struct from picture timing SEI, and
     * their analogues in other codecs. Typically it should only be used when
     * higher-layer timing information is not available.
     */
    int repeat_pict;
 
    /**
     * Sample rate of the audio data.
     */
    int sample_rate;
 
    /**
     * 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 frames that are keyframes.
 */
#define AV_FRAME_FLAG_KEY (1 << 1)
/**
 * A flag to mark the frames which need to be decoded, but shouldn't be output.
 */
#define AV_FRAME_FLAG_DISCARD   (1 << 2)
/**
 * A flag to mark frames whose content is interlaced.
 */
#define AV_FRAME_FLAG_INTERLACED (1 << 3)
/**
 * A flag to mark frames where the top field is displayed first if the content
 * is interlaced.
 */
#define AV_FRAME_FLAG_TOP_FIELD_FIRST (1 << 4)
/**
 * A decoder can use this flag to mark frames which were originally encoded losslessly.
 *
 * For coding bitstream formats which support both lossless and lossy
 * encoding, it is sometimes possible for a decoder to determine which method
 * was used when the bitstream was encoded.
 */
#define AV_FRAME_FLAG_LOSSLESS        (1 << 5)
/**
 * @}
 */
 
    /**
     * 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;
 
    /**
     * 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
 
    /**
     * For hwaccel-format frames, this should be a reference to the
     * AVHWFramesContext describing the frame.
     */
    AVBufferRef *hw_frames_ctx;
 
    /**
     * Frame owner's private data.
     *
     * This field may be set by the code that allocates/owns the frame data.
     * It is then not touched by any library functions, except:
     * - a new reference to the underlying buffer is propagated by
     *   av_frame_copy_props() (and hence by av_frame_ref());
     * - it is unreferenced in av_frame_unref();
     * - on the caller's explicit request. E.g. libavcodec encoders/decoders
     *   will propagate a new reference to/from @ref AVPacket "AVPackets" if the
     *   caller sets @ref AV_CODEC_FLAG_COPY_OPAQUE.
     *
     * @see opaque the plain pointer analogue
     */
    AVBufferRef *opaque_ref;
 
    /**
     * @anchor cropping
     * @name Cropping
     * Video frames only. The number of pixels to discard from 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;
    /**
     * @}
     */
 
    /**
     * RefStruct reference 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 must never check or change private_ref.
     */
    void *private_ref;
 
    /**
     * Channel layout of the audio data.
     */
    AVChannelLayout ch_layout;
 
    /**
     * Duration of the frame, in the same units as pts. 0 if unknown.
     */
    int64_t duration;
 
    /**
     * Indicates how the alpha channel of the video is to be handled.
     * - encoding: Set by user
     * - decoding: Set by libavcodec
     */
    enum AVAlphaMode alpha_mode;
} AVFrame;
 
 
/**
 * Allocate an AVFrame and set its fields to default values.  The resulting
 * struct must be freed using av_frame_free().
 *
 * @return An AVFrame filled with default values or NULL on failure.
 *
 * @note this only allocates the AVFrame itself, not the data buffers. Those
 * must be allocated through other means, e.g. with av_frame_get_buffer() or
 * manually.
 */
AVFrame *av_frame_alloc(void);
 
/**
 * Free the frame and any dynamically allocated objects in it,
 * e.g. extended_data. If the frame is reference counted, it will be
 * unreferenced first.
 *
 * @param frame frame to be freed. The pointer will be set to 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);
 
/**
 * Ensure the destination frame refers to the same data described by the source
 * frame, either by creating a new reference for each AVBufferRef from src if
 * they differ from those in dst, by allocating new buffers and copying data if
 * src is not reference counted, or by unreferencing it if src is empty.
 *
 * Frame properties on dst will be replaced by those from src.
 *
 * @return 0 on success, a negative AVERROR on error. On error, dst is
 *         unreferenced.
 */
int av_frame_replace(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);
 
/**
 * Unreference all the buffers referenced by frame and reset the frame fields.
 */
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 and data pointer 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. Non-refcounted frames behave as non-writable, i.e. a copy
 * is always made.
 *
 * @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);
 
/**
 * Copy only "metadata" fields from src to dst.
 *
 * Metadata for the purpose of this function are those fields that do not affect
 * the data layout in the buffers.  E.g. pts, sample rate (for audio) or sample
 * aspect ratio (for video), but not width/height or channel layout.
 * Side data is also copied.
 */
int av_frame_copy_props(AVFrame *dst, const AVFrame *src);
 
/**
 * Get the buffer reference a given data plane is stored in.
 *
 * @param frame the frame to get the plane's buffer from
 * @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(const 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);
 
/**
 * @return side data descriptor corresponding to a given side data type, NULL
 *         when not available.
 */
const AVSideDataDescriptor *av_frame_side_data_desc(enum AVFrameSideDataType type);
 
/**
 * Free all side data entries and their contents, then zeroes out the
 * values which the pointers are pointing to.
 *
 * @param sd    pointer to array of side data to free. Will be set to NULL
 *              upon return.
 * @param nb_sd pointer to an integer containing the number of entries in
 *              the array. Will be set to 0 upon return.
 */
void av_frame_side_data_free(AVFrameSideData ***sd, int *nb_sd);
 
/**
 * Remove existing entries before adding new ones.
 */
#define AV_FRAME_SIDE_DATA_FLAG_UNIQUE (1 << 0)
/**
 * Don't add a new entry if another of the same type exists.
 * Applies only for side data types without the AV_SIDE_DATA_PROP_MULTI prop.
 */
#define AV_FRAME_SIDE_DATA_FLAG_REPLACE (1 << 1)
/**
 * Create a new reference to the passed in buffer instead of taking ownership
 * of it.
 */
#define AV_FRAME_SIDE_DATA_FLAG_NEW_REF (1 << 2)
 
/**
 * Add new side data entry to an array.
 *
 * @param sd    pointer to array of side data to which to add another entry,
 *              or to NULL in order to start a new array.
 * @param nb_sd pointer to an integer containing the number of entries in
 *              the array.
 * @param type  type of the added side data
 * @param size  size of the side data
 * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
 *
 * @return newly added side data on success, NULL on error.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of
 *       matching AVFrameSideDataType will be removed before the addition
 *       is attempted.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_REPLACE being set, if an
 *       entry of the same type already exists, it will be replaced instead.
 */
AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
                                        enum AVFrameSideDataType type,
                                        size_t size, unsigned int flags);
 
/**
 * Add a new side data entry to an array from an existing AVBufferRef.
 *
 * @param sd    pointer to array of side data to which to add another entry,
 *              or to NULL in order to start a new array.
 * @param nb_sd pointer to an integer containing the number of entries in
 *              the array.
 * @param type  type of the added side data
 * @param buf   Pointer to AVBufferRef to add to the array. On success,
 *              the function takes ownership of the AVBufferRef and *buf is
 *              set to NULL, unless AV_FRAME_SIDE_DATA_FLAG_NEW_REF is set
 *              in which case the ownership will remain with the caller.
 * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
 *
 * @return newly added side data on success, NULL on error.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of
 *       matching AVFrameSideDataType will be removed before the addition
 *       is attempted.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_REPLACE being set, if an
 *       entry of the same type already exists, it will be replaced instead.
 *
 */
AVFrameSideData *av_frame_side_data_add(AVFrameSideData ***sd, int *nb_sd,
                                        enum AVFrameSideDataType type,
                                        AVBufferRef **buf, unsigned int flags);
 
/**
 * Add a new side data entry to an array based on existing side data, taking
 * a reference towards the contained AVBufferRef.
 *
 * @param sd    pointer to array of side data to which to add another entry,
 *              or to NULL in order to start a new array.
 * @param nb_sd pointer to an integer containing the number of entries in
 *              the array.
 * @param src   side data to be cloned, with a new reference utilized
 *              for the buffer.
 * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
 *
 * @return negative error code on failure, >=0 on success.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of
 *       matching AVFrameSideDataType will be removed before the addition
 *       is attempted.
 * @note In case of AV_FRAME_SIDE_DATA_FLAG_REPLACE being set, if an
 *       entry of the same type already exists, it will be replaced instead.
 */
int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
                             const AVFrameSideData *src, unsigned int flags);
 
/**
 * Get a side data entry of a specific type from an array.
 *
 * @param sd    array of side data.
 * @param nb_sd integer containing the number of entries in the array.
 * @param type  type of side data to be queried
 *
 * @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 set.
 */
const AVFrameSideData *av_frame_side_data_get_c(const AVFrameSideData * const *sd,
                                                const int nb_sd,
                                                enum AVFrameSideDataType type);
 
/**
 * Wrapper around av_frame_side_data_get_c() to workaround the limitation
 * that for any type T the conversion from T * const * to const T * const *
 * is not performed automatically in C.
 * @see av_frame_side_data_get_c()
 */
static inline
const AVFrameSideData *av_frame_side_data_get(AVFrameSideData * const *sd,
                                              const int nb_sd,
                                              enum AVFrameSideDataType type)
{
    return av_frame_side_data_get_c((const AVFrameSideData * const *)sd,
                                    nb_sd, type);
}
 
/**
 * Remove and free all side data instances of the given type from an array.
 */
void av_frame_side_data_remove(AVFrameSideData ***sd, int *nb_sd,
                               enum AVFrameSideDataType type);
 
/**
 * Remove and free all side data instances that match any of the given
 * side data properties. (See enum AVSideDataProps)
 */
void av_frame_side_data_remove_by_props(AVFrameSideData ***sd, int *nb_sd,
                                        int props);
 
/**
 * @}
 */
 
#endif /* AVUTIL_FRAME_H */