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=====AVCodecContext=====
Defined in ''avcodec.h''

<code c>
/**
 * main external API structure
 */
typedef struct AVCodecContext {
    /**
     * information on struct for av_log
     * - set by avcodec_alloc_context
     */
    AVClass *av_class;
    /**
     * the average bitrate
     * - encoding: Set by user; unused for constant quantizer encoding.
     * - decoding: Set by libavcodec. 0 or some bitrate if this info is available in the stream.
     */
    int bit_rate;

    /**
     * number of bits the bitstream is allowed to diverge from the reference.
     *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
     * - encoding: Set by user; unused for constant quantizer encoding.
     * - decoding: unused
     */
    int bit_rate_tolerance;

    /**
     * CODEC_FLAG_*.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int flags;

    /**
     * Some codecs need additional format info. It is stored here.
     * If any muxer uses this then ALL demuxers/parsers AND encoders for the
     * specific codec MUST set it correctly otherwise stream copy breaks.
     * In general use of this field by muxers is not recommanded.
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec. (FIXME: Is this OK?)
     */
    int sub_id;

    /**
     * Motion estimation algorithm used for video coding.
     * 1 (zero), 2 (full), 3 (log), 4 (phods), 5 (epzs), 6 (x1), 7 (hex),
     * 8 (umh), 9 (iter) [7, 8 are x264 specific, 9 is snow specific]
     * - encoding: MUST be set by user.
     * - decoding: unused
     */
    int me_method;

    /**
     * some codecs need / can use extradata like Huffman tables.
     * mjpeg: Huffman tables
     * rv10: additional flags
     * mpeg4: global headers (they can be in the bitstream or here)
     * The allocated memory should be FF_INPUT_BUFFER_PADDING_SIZE bytes larger
     * than extradata_size to avoid prolems if it is read with the bitstream reader.
     * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
     * - encoding: Set/allocated/freed by libavcodec.
     * - decoding: Set/allocated/freed by user.
     */
    uint8_t *extradata;
    int extradata_size;

    /**
     * This is the fundamental unit of time (in seconds) in terms
     * of which frame timestamps are represented. For fixed-fps content,
     * timebase should be 1/framerate and timestamp increments should be
     * identically 1.
     * - encoding: MUST be set by user.
     * - decoding: Set by libavcodec.
     */
    AVRational time_base;

    /* video only */
    /**
     * picture width / height.
     * - encoding: MUST be set by user.
     * - decoding: Set by libavcodec.
     * Note: For compatibility it is possible to set this instead of
     * coded_width/height before decoding.
     */
    int width, height;

#define FF_ASPECT_EXTENDED 15

    /**
     * the number of pictures in a group of pictures, or 0 for intra_only
     * - encoding: Set by user.
     * - decoding: unused
     */
    int gop_size;

    /**
     * Pixel format, see PIX_FMT_xxx.
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    enum PixelFormat pix_fmt;

    /**
     * Frame rate emulation. If not zero, the lower layer (i.e. format handler)
     * has to read frames at native frame rate.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rate_emu;

    /**
     * If non NULL, 'draw_horiz_band' is called by the libavcodec
     * decoder to draw a horizontal band. It improves cache usage. Not
     * all codecs can do that. You must check the codec capabilities
     * beforehand.
     * - encoding: unused
     * - decoding: Set by user.
     * @param height the height of the slice
     * @param y the y position of the slice
     * @param type 1->top field, 2->bottom field, 3->frame
     * @param offset offset into the AVFrame.data from which the slice should be read
     */
    void (*draw_horiz_band)(struct AVCodecContext *s,
                            const AVFrame *src, int offset[4],
                            int y, int type, int height);

    /* audio only */
    int sample_rate; ///< samples per second
    int channels;

    /**
     * audio sample format
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    enum SampleFormat sample_fmt;  ///< sample format, currently unused

    /* The following data should not be initialized. */
    /**
     * Samples per packet, initialized when calling 'init'.
     */
    int frame_size;
    int frame_number;   ///< audio or video frame number
    int real_pict_num;  ///< Returns the real picture number of previous encoded frame.

    /**
     * Number of frames the decoded output will be delayed relative to
     * the encoded input.
     * - encoding: Set by libavcodec.
     * - decoding: unused
     */
    int delay;

    /* - encoding parameters */
    float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
    float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)

    /**
     * minimum quantizer
     * - encoding: Set by user.
     * - decoding: unused
     */
    int qmin;

    /**
     * maximum quantizer
     * - encoding: Set by user.
     * - decoding: unused
     */
    int qmax;

    /**
     * maximum quantizer difference between frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_qdiff;

    /**
     * maximum number of B-frames between non-B-frames
     * Note: The output will be delayed by max_b_frames+1 relative to the input.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_b_frames;

    /**
     * qscale factor between IP and B-frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    float b_quant_factor;

    /** obsolete FIXME remove */
    int rc_strategy;
#define FF_RC_STRATEGY_XVID 1

    int b_frame_strategy;

    /**
     * hurry up amount
     * - encoding: unused
     * - decoding: Set by user. 1-> Skip B-frames, 2-> Skip IDCT/dequant too, 5-> Skip everything except header
     * @deprecated Deprecated in favor of skip_idct and skip_frame.
     */
    int hurry_up;

    struct AVCodec *codec;

    void *priv_data;

#if LIBAVCODEC_VERSION_INT < ((52<<16)+(0<<8)+0)
    /* unused, FIXME remove*/
    int rtp_mode;
#endif

    int rtp_payload_size;   /* The size of the RTP payload: the coder will  */
                            /* do its best to deliver a chunk with size     */
                            /* below rtp_payload_size, the chunk will start */
                            /* with a start code on some codecs like H.263. */
                            /* This doesn't take account of any particular  */
                            /* headers inside the transmitted RTP payload.  */


    /* The RTP callback: This function is called    */
    /* every time the encoder has a packet to send. */
    /* It depends on the encoder if the data starts */
    /* with a Start Code (it should). H.263 does.   */
    /* mb_nb contains the number of macroblocks     */
    /* encoded in the RTP payload.                  */
    void (*rtp_callback)(struct AVCodecContext *avctx, void *data, int size, int mb_nb);

    /* statistics, used for 2-pass encoding */
    int mv_bits;
    int header_bits;
    int i_tex_bits;
    int p_tex_bits;
    int i_count;
    int p_count;
    int skip_count;
    int misc_bits;

    /**
     * number of bits used for the previously encoded frame
     * - encoding: Set by libavcodec.
     * - decoding: unused
     */
    int frame_bits;

    /**
     * Private data of the user, can be used to carry app specific stuff.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    void *opaque;

    char codec_name[32];
    enum CodecType codec_type; /* see CODEC_TYPE_xxx */
    enum CodecID codec_id; /* see CODEC_ID_xxx */

    /**
     * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
     * This is used to work around some encoder bugs.
     * A demuxer should set this to what is stored in the field used to identify the codec.
     * If there are multiple such fields in a container then the demuxer should choose the one
     * which maximizes the information about the used codec.
     * If the codec tag field in a container is larger then 32 bits then the demuxer should
     * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
     * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
     * first.
     * - encoding: Set by user, if not then the default based on codec_id will be used.
     * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
     */
    unsigned int codec_tag;

    /**
     * Work around bugs in encoders which sometimes cannot be detected automatically.
     * - encoding: Set by user
     * - decoding: Set by user
     */
    int workaround_bugs;
#define FF_BUG_AUTODETECT       1  ///< autodetection
#define FF_BUG_OLD_MSMPEG4      2
#define FF_BUG_XVID_ILACE       4
#define FF_BUG_UMP4             8
#define FF_BUG_NO_PADDING       16
#define FF_BUG_AMV              32
#define FF_BUG_AC_VLC           0  ///< Will be removed, libavcodec can now handle these non-compliant files by default.
#define FF_BUG_QPEL_CHROMA      64
#define FF_BUG_STD_QPEL         128
#define FF_BUG_QPEL_CHROMA2     256
#define FF_BUG_DIRECT_BLOCKSIZE 512
#define FF_BUG_EDGE             1024
#define FF_BUG_HPEL_CHROMA      2048
#define FF_BUG_DC_CLIP          4096
#define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
//#define FF_BUG_FAKE_SCALABILITY 16 //Autodetection should work 100%.

    /**
     * luma single coefficient elimination threshold
     * - encoding: Set by user.
     * - decoding: unused
     */
    int luma_elim_threshold;

    /**
     * chroma single coeff elimination threshold
     * - encoding: Set by user.
     * - decoding: unused
     */
    int chroma_elim_threshold;

    /**
     * strictly follow the standard (MPEG4, ...).
     * - encoding: Set by user.
     * - decoding: unused
     */
    int strict_std_compliance;
#define FF_COMPLIANCE_VERY_STRICT   2 ///< Strictly conform to a older more strict version of the spec or reference software.
#define FF_COMPLIANCE_STRICT        1 ///< Strictly conform to all the things in the spec no matter what consequences.
#define FF_COMPLIANCE_NORMAL        0
#define FF_COMPLIANCE_INOFFICIAL   -1 ///< Allow inofficial extensions.
#define FF_COMPLIANCE_EXPERIMENTAL -2 ///< Allow nonstandardized experimental things.

    /**
     * qscale offset between IP and B-frames
     * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
     * - encoding: Set by user.
     * - decoding: unused
     */
    float b_quant_offset;

    /**
     * Error resilience; higher values will detect more errors but may
     * misdetect some more or less valid parts as errors.
     * - encoding: unused
     * - decoding: Set by user.
     */
    int error_resilience;
#define FF_ER_CAREFUL         1
#define FF_ER_COMPLIANT       2
#define FF_ER_AGGRESSIVE      3
#define FF_ER_VERY_AGGRESSIVE 4

    /**
     * Called at the beginning of each frame to get a buffer for it.
     * If pic.reference is set then the frame will be read later by libavcodec.
     * avcodec_align_dimensions() should be used to find the required width and
     * height, as they normally need to be rounded up to the next multiple of 16.
     * - encoding: unused
     * - decoding: Set by libavcodec., user can override.
     */
    int (*get_buffer)(struct AVCodecContext *c, AVFrame *pic);

    /**
     * Called to release buffers which where allocated with get_buffer.
     * A released buffer can be reused in get_buffer().
     * pic.data[*] must be set to NULL.
     * - encoding: unused
     * - decoding: Set by libavcodec., user can override.
     */
    void (*release_buffer)(struct AVCodecContext *c, AVFrame *pic);

    /**
     * If 1 the stream has a 1 frame delay during decoding.
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec.
     */
    int has_b_frames;

    /**
     * number of bytes per packet if constant and known or 0
     * Used by some WAV based audio codecs.
     */
    int block_align;

    int parse_only; /* - decoding only: If true, only parsing is done
                       (function avcodec_parse_frame()). The frame
                       data is returned. Only MPEG codecs support this now. */

    /**
     * 0-> h263 quant 1-> mpeg quant
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mpeg_quant;

    /**
     * pass1 encoding statistics output buffer
     * - encoding: Set by libavcodec.
     * - decoding: unused
     */
    char *stats_out;

    /**
     * pass2 encoding statistics input buffer
     * Concatenated stuff from stats_out of pass1 should be placed here.
     * - encoding: Allocated/set/freed by user.
     * - decoding: unused
     */
    char *stats_in;

    /**
     * ratecontrol qmin qmax limiting method
     * 0-> clipping, 1-> use a nice continous function to limit qscale wthin qmin/qmax.
     * - encoding: Set by user.
     * - decoding: unused
     */
    float rc_qsquish;

    float rc_qmod_amp;
    int rc_qmod_freq;

    /**
     * ratecontrol override, see RcOverride
     * - encoding: Allocated/set/freed by user.
     * - decoding: unused
     */
    RcOverride *rc_override;
    int rc_override_count;

    /**
     * rate control equation
     * - encoding: Set by user
     * - decoding: unused
     */
    char *rc_eq;

    /**
     * maximum bitrate
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_max_rate;

    /**
     * minimum bitrate
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_min_rate;

    /**
     * decoder bitstream buffer size
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_buffer_size;
    float rc_buffer_aggressivity;

    /**
     * qscale factor between P and I-frames
     * If > 0 then the last p frame quantizer will be used (q= lastp_q*factor+offset).
     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
     * - encoding: Set by user.
     * - decoding: unused
     */
    float i_quant_factor;

    /**
     * qscale offset between P and I-frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    float i_quant_offset;

    /**
     * initial complexity for pass1 ratecontrol
     * - encoding: Set by user.
     * - decoding: unused
     */
    float rc_initial_cplx;

    /**
     * DCT algorithm, see FF_DCT_* below
     * - encoding: Set by user.
     * - decoding: unused
     */
    int dct_algo;
#define FF_DCT_AUTO    0
#define FF_DCT_FASTINT 1
#define FF_DCT_INT     2
#define FF_DCT_MMX     3
#define FF_DCT_MLIB    4
#define FF_DCT_ALTIVEC 5
#define FF_DCT_FAAN    6

    /**
     * luminance masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float lumi_masking;

    /**
     * temporary complexity masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float temporal_cplx_masking;

    /**
     * spatial complexity masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float spatial_cplx_masking;

    /**
     * p block masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float p_masking;

    /**
     * darkness masking (0-> disabled)
     * - encoding: Set by user.
     * - decoding: unused
     */
    float dark_masking;


    /* for binary compatibility */
    int unused;

    /**
     * IDCT algorithm, see FF_IDCT_* below.
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int idct_algo;
#define FF_IDCT_AUTO         0
#define FF_IDCT_INT          1
#define FF_IDCT_SIMPLE       2
#define FF_IDCT_SIMPLEMMX    3
#define FF_IDCT_LIBMPEG2MMX  4
#define FF_IDCT_PS2          5
#define FF_IDCT_MLIB         6
#define FF_IDCT_ARM          7
#define FF_IDCT_ALTIVEC      8
#define FF_IDCT_SH4          9
#define FF_IDCT_SIMPLEARM    10
#define FF_IDCT_H264         11
#define FF_IDCT_VP3          12
#define FF_IDCT_IPP          13
#define FF_IDCT_XVIDMMX      14
#define FF_IDCT_CAVS         15
#define FF_IDCT_SIMPLEARMV5TE 16
#define FF_IDCT_SIMPLEARMV6  17

    /**
     * slice count
     * - encoding: Set by libavcodec.
     * - decoding: Set by user (or 0).
     */
    int slice_count;
    /**
     * slice offsets in the frame in bytes
     * - encoding: Set/allocated by libavcodec.
     * - decoding: Set/allocated by user (or NULL).
     */
    int *slice_offset;

    /**
     * error concealment flags
     * - encoding: unused
     * - decoding: Set by user.
     */
    int error_concealment;
#define FF_EC_GUESS_MVS   1
#define FF_EC_DEBLOCK     2

    /**
     * dsp_mask could be add used to disable unwanted CPU features
     * CPU features (i.e. MMX, SSE. ...)
     *
     * With the FORCE flag you may instead enable given CPU features.
     * (Dangerous: Usable in case of misdetection, improper usage however will
     * result into program crash.)
     */
    unsigned dsp_mask;
#define FF_MM_FORCE    0x80000000 /* Force usage of selected flags (OR) */
    /* lower 16 bits - CPU features */
#define FF_MM_MMX      0x0001 /* standard MMX */
#define FF_MM_3DNOW    0x0004 /* AMD 3DNOW */
#define FF_MM_MMXEXT   0x0002 /* SSE integer functions or AMD MMX ext */
#define FF_MM_SSE      0x0008 /* SSE functions */
#define FF_MM_SSE2     0x0010 /* PIV SSE2 functions */
#define FF_MM_3DNOWEXT 0x0020 /* AMD 3DNowExt */
#define FF_MM_SSE3     0x0040 /* Prescott SSE3 functions */
#define FF_MM_SSSE3    0x0080 /* Conroe SSSE3 functions */
#define FF_MM_IWMMXT   0x0100 /* XScale IWMMXT */

    /**
     * bits per sample/pixel from the demuxer (needed for huffyuv).
     * - encoding: Set by libavcodec.
     * - decoding: Set by user.
     */
     int bits_per_sample;

    /**
     * prediction method (needed for huffyuv)
     * - encoding: Set by user.
     * - decoding: unused
     */
     int prediction_method;
#define FF_PRED_LEFT   0
#define FF_PRED_PLANE  1
#define FF_PRED_MEDIAN 2

    /**
     * sample aspect ratio (0 if unknown)
     * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
    AVRational sample_aspect_ratio;

    /**
     * the picture in the bitstream
     * - encoding: Set by libavcodec.
     * - decoding: Set by libavcodec.
     */
    AVFrame *coded_frame;

    /**
     * debug
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int debug;
#define FF_DEBUG_PICT_INFO 1
#define FF_DEBUG_RC        2
#define FF_DEBUG_BITSTREAM 4
#define FF_DEBUG_MB_TYPE   8
#define FF_DEBUG_QP        16
#define FF_DEBUG_MV        32
#define FF_DEBUG_DCT_COEFF 0x00000040
#define FF_DEBUG_SKIP      0x00000080
#define FF_DEBUG_STARTCODE 0x00000100
#define FF_DEBUG_PTS       0x00000200
#define FF_DEBUG_ER        0x00000400
#define FF_DEBUG_MMCO      0x00000800
#define FF_DEBUG_BUGS      0x00001000
#define FF_DEBUG_VIS_QP    0x00002000
#define FF_DEBUG_VIS_MB_TYPE 0x00004000

    /**
     * debug
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int debug_mv;
#define FF_DEBUG_VIS_MV_P_FOR  0x00000001 //visualize forward predicted MVs of P frames
#define FF_DEBUG_VIS_MV_B_FOR  0x00000002 //visualize forward predicted MVs of B frames
#define FF_DEBUG_VIS_MV_B_BACK 0x00000004 //visualize backward predicted MVs of B frames

    /**
     * error
     * - encoding: Set by libavcodec if flags&CODEC_FLAG_PSNR.
     * - decoding: unused
     */
    uint64_t error[4];

    /**
     * minimum MB quantizer
     * - encoding: unused
     * - decoding: unused
     */
    int mb_qmin;

    /**
     * maximum MB quantizer
     * - encoding: unused
     * - decoding: unused
     */
    int mb_qmax;

    /**
     * motion estimation comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_cmp;
    /**
     * subpixel motion estimation comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_sub_cmp;
    /**
     * macroblock comparison function (not supported yet)
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_cmp;
    /**
     * interlaced DCT comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int ildct_cmp;
#define FF_CMP_SAD  0
#define FF_CMP_SSE  1
#define FF_CMP_SATD 2
#define FF_CMP_DCT  3
#define FF_CMP_PSNR 4
#define FF_CMP_BIT  5
#define FF_CMP_RD   6
#define FF_CMP_ZERO 7
#define FF_CMP_VSAD 8
#define FF_CMP_VSSE 9
#define FF_CMP_NSSE 10
#define FF_CMP_W53  11
#define FF_CMP_W97  12
#define FF_CMP_DCTMAX 13
#define FF_CMP_DCT264 14
#define FF_CMP_CHROMA 256

    /**
     * ME diamond size & shape
     * - encoding: Set by user.
     * - decoding: unused
     */
    int dia_size;

    /**
     * amount of previous MV predictors (2a+1 x 2a+1 square)
     * - encoding: Set by user.
     * - decoding: unused
     */
    int last_predictor_count;

    /**
     * prepass for motion estimation
     * - encoding: Set by user.
     * - decoding: unused
     */
    int pre_me;

    /**
     * motion estimation prepass comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_pre_cmp;

    /**
     * ME prepass diamond size & shape
     * - encoding: Set by user.
     * - decoding: unused
     */
    int pre_dia_size;

    /**
     * subpel ME quality
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_subpel_quality;

    /**
     * callback to negotiate the pixelFormat
     * @param fmt is the list of formats which are supported by the codec,
     * it is terminated by -1 as 0 is a valid format, the formats are ordered by quality.
     * The first is always the native one.
     * @return the chosen format
     * - encoding: unused
     * - decoding: Set by user, if not set the native format will be chosen.
     */
    enum PixelFormat (*get_format)(struct AVCodecContext *s, const enum PixelFormat * fmt);

    /**
     * DTG active format information (additional aspect ratio
     * information only used in DVB MPEG-2 transport streams)
     * 0 if not set.
     *
     * - encoding: unused
     * - decoding: Set by decoder.
     */
    int dtg_active_format;
#define FF_DTG_AFD_SAME         8
#define FF_DTG_AFD_4_3          9
#define FF_DTG_AFD_16_9         10
#define FF_DTG_AFD_14_9         11
#define FF_DTG_AFD_4_3_SP_14_9  13
#define FF_DTG_AFD_16_9_SP_14_9 14
#define FF_DTG_AFD_SP_4_3       15

    /**
     * maximum motion estimation search range in subpel units
     * If 0 then no limit.
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_range;

    /**
     * intra quantizer bias
     * - encoding: Set by user.
     * - decoding: unused
     */
    int intra_quant_bias;
#define FF_DEFAULT_QUANT_BIAS 999999

    /**
     * inter quantizer bias
     * - encoding: Set by user.
     * - decoding: unused
     */
    int inter_quant_bias;

    /**
     * color table ID
     * - encoding: unused
     * - decoding: Which clrtable should be used for 8bit RGB images.
     *             Tables have to be stored somewhere. FIXME
     */
    int color_table_id;

    /**
     * internal_buffer count
     * Don't touch, used by libavcodec default_get_buffer().
     */
    int internal_buffer_count;

    /**
     * internal_buffers
     * Don't touch, used by libavcodec default_get_buffer().
     */
    void *internal_buffer;

#define FF_LAMBDA_SHIFT 7
#define FF_LAMBDA_SCALE (1<<FF_LAMBDA_SHIFT)
#define FF_QP2LAMBDA 118 ///< factor to convert from H.263 QP to lambda
#define FF_LAMBDA_MAX (256*128-1)

#define FF_QUALITY_SCALE FF_LAMBDA_SCALE //FIXME maybe remove
    /**
     * Global quality for codecs which cannot change it per frame.
     * This should be proportional to MPEG-1/2/4 qscale.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int global_quality;

#define FF_CODER_TYPE_VLC       0
#define FF_CODER_TYPE_AC        1
#define FF_CODER_TYPE_RAW       2
#define FF_CODER_TYPE_RLE       3
#define FF_CODER_TYPE_DEFLATE   4
    /**
     * coder type
     * - encoding: Set by user.
     * - decoding: unused
     */
    int coder_type;

    /**
     * context model
     * - encoding: Set by user.
     * - decoding: unused
     */
    int context_model;
#if 0
    /**
     *
     * - encoding: unused
     * - decoding: Set by user.
     */
    uint8_t * (*realloc)(struct AVCodecContext *s, uint8_t *buf, int buf_size);
#endif

    /**
     * slice flags
     * - encoding: unused
     * - decoding: Set by user.
     */
    int slice_flags;
#define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
#define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG2 field pics)
#define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)

    /**
     * XVideo Motion Acceleration
     * - encoding: forbidden
     * - decoding: set by decoder
     */
    int xvmc_acceleration;

    /**
     * macroblock decision mode
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_decision;
#define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
#define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
#define FF_MB_DECISION_RD     2        ///< rate distoration

    /**
     * custom intra quantization matrix
     * - encoding: Set by user, can be NULL.
     * - decoding: Set by libavcodec.
     */
    uint16_t *intra_matrix;

    /**
     * custom inter quantization matrix
     * - encoding: Set by user, can be NULL.
     * - decoding: Set by libavcodec.
     */
    uint16_t *inter_matrix;

    /**
     * fourcc from the AVI stream header (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
     * This is used to work around some encoder bugs.
     * - encoding: unused
     * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
     */
    unsigned int stream_codec_tag;

    /**
     * scene change detection threshold
     * 0 is default, larger means fewer detected scene changes.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int scenechange_threshold;

    /**
     * minimum Lagrange multipler
     * - encoding: Set by user.
     * - decoding: unused
     */
    int lmin;

    /**
     * maximum Lagrange multipler
     * - encoding: Set by user.
     * - decoding: unused
     */
    int lmax;

    /**
     * palette control structure
     * - encoding: ??? (no palette-enabled encoder yet)
     * - decoding: Set by user.
     */
    struct AVPaletteControl *palctrl;

    /**
     * noise reduction strength
     * - encoding: Set by user.
     * - decoding: unused
     */
    int noise_reduction;

    /**
     * Called at the beginning of a frame to get cr buffer for it.
     * Buffer type (size, hints) must be the same. libavcodec won't check it.
     * libavcodec will pass previous buffer in pic, function should return
     * same buffer or new buffer with old frame "painted" into it.
     * If pic.data[0] == NULL must behave like get_buffer().
     * - encoding: unused
     * - decoding: Set by libavcodec., user can override
     */
    int (*reget_buffer)(struct AVCodecContext *c, AVFrame *pic);

    /**
     * Number of bits which should be loaded into the rc buffer before decoding starts.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int rc_initial_buffer_occupancy;

    /**
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int inter_threshold;

    /**
     * CODEC_FLAG2_*
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int flags2;

    /**
     * Simulates errors in the bitstream to test error concealment.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int error_rate;

    /**
     * MP3 antialias algorithm, see FF_AA_* below.
     * - encoding: unused
     * - decoding: Set by user.
     */
    int antialias_algo;
#define FF_AA_AUTO    0
#define FF_AA_FASTINT 1 //not implemented yet
#define FF_AA_INT     2
#define FF_AA_FLOAT   3
    /**
     * quantizer noise shaping
     * - encoding: Set by user.
     * - decoding: unused
     */
    int quantizer_noise_shaping;

    /**
     * thread count
     * is used to decide how many independent tasks should be passed to execute()
     * - encoding: Set by user.
     * - decoding: Set by user.
     */
    int thread_count;

    /**
     * The codec may call this to execute several independent things.
     * It will return only after finishing all tasks.
     * The user may replace this with some multithreaded implementation,
     * the default implementation will execute the parts serially.
     * @param count the number of things to execute
     * - encoding: Set by libavcodec, user can override.
     * - decoding: Set by libavcodec, user can override.
     */
    int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void **arg2, int *ret, int count);

    /**
     * thread opaque
     * Can be used by execute() to store some per AVCodecContext stuff.
     * - encoding: set by execute()
     * - decoding: set by execute()
     */
    void *thread_opaque;

    /**
     * Motion estimation threshold below which no motion estimation is
     * performed, but instead the user specified motion vectors are used.
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
     int me_threshold;

    /**
     * Macroblock threshold below which the user specified macroblock types will be used.
     * - encoding: Set by user.
     * - decoding: unused
     */
     int mb_threshold;

    /**
     * precision of the intra DC coefficient - 8
     * - encoding: Set by user.
     * - decoding: unused
     */
     int intra_dc_precision;

    /**
     * noise vs. sse weight for the nsse comparsion function
     * - encoding: Set by user.
     * - decoding: unused
     */
     int nsse_weight;

    /**
     * Number of macroblock rows at the top which are skipped.
     * - encoding: unused
     * - decoding: Set by user.
     */
     int skip_top;

    /**
     * Number of macroblock rows at the bottom which are skipped.
     * - encoding: unused
     * - decoding: Set by user.
     */
     int skip_bottom;

    /**
     * profile
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
     int profile;
#define FF_PROFILE_UNKNOWN -99
#define FF_PROFILE_AAC_MAIN 0
#define FF_PROFILE_AAC_LOW 1
#define FF_PROFILE_AAC_SSR 2
#define FF_PROFILE_AAC_LTP 3

    /**
     * level
     * - encoding: Set by user.
     * - decoding: Set by libavcodec.
     */
     int level;
#define FF_LEVEL_UNKNOWN -99

    /**
     * low resolution decoding, 1-> 1/2 size, 2->1/4 size
     * - encoding: unused
     * - decoding: Set by user.
     */
     int lowres;

    /**
     * Bitstream width / height, may be different from width/height if lowres
     * or other things are used.
     * - encoding: unused
     * - decoding: Set by user before init if known. Codec should override / dynamically change if needed.
     */
    int coded_width, coded_height;

    /**
     * frame skip threshold
     * - encoding: Set by user.
     * - decoding: unused
     */
    int frame_skip_threshold;

    /**
     * frame skip factor
     * - encoding: Set by user.
     * - decoding: unused
     */
    int frame_skip_factor;

    /**
     * frame skip exponent
     * - encoding: Set by user.
     * - decoding: unused
     */
    int frame_skip_exp;

    /**
     * frame skip comparison function
     * - encoding: Set by user.
     * - decoding: unused
     */
    int frame_skip_cmp;

    /**
     * Border processing masking, raises the quantizer for mbs on the borders
     * of the picture.
     * - encoding: Set by user.
     * - decoding: unused
     */
    float border_masking;

    /**
     * minimum MB lagrange multipler
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_lmin;

    /**
     * maximum MB lagrange multipler
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mb_lmax;

    /**
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int me_penalty_compensation;

    /**
     *
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_loop_filter;

    /**
     *
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_idct;

    /**
     *
     * - encoding: unused
     * - decoding: Set by user.
     */
    enum AVDiscard skip_frame;

    /**
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int bidir_refine;

    /**
     *
     * - encoding: Set by user.
     * - decoding: unused
     */
    int brd_scale;

    /**
     * constant rate factor - quality-based VBR - values ~correspond to qps
     * - encoding: Set by user.
     * - decoding: unused
     */
    float crf;

    /**
     * constant quantization parameter rate control method
     * - encoding: Set by user.
     * - decoding: unused
     */
    int cqp;

    /**
     * minimum GOP size
     * - encoding: Set by user.
     * - decoding: unused
     */
    int keyint_min;

    /**
     * number of reference frames
     * - encoding: Set by user.
     * - decoding: unused
     */
    int refs;

    /**
     * chroma qp offset from luma
     * - encoding: Set by user.
     * - decoding: unused
     */
    int chromaoffset;

    /**
     * Influences how often B-frames are used.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int bframebias;

    /**
     * trellis RD quantization
     * - encoding: Set by user.
     * - decoding: unused
     */
    int trellis;

    /**
     * Reduce fluctuations in qp (before curve compression).
     * - encoding: Set by user.
     * - decoding: unused
     */
    float complexityblur;

    /**
     * in-loop deblocking filter alphac0 parameter
     * alpha is in the range -6...6
     * - encoding: Set by user.
     * - decoding: unused
     */
    int deblockalpha;

    /**
     * in-loop deblocking filter beta parameter
     * beta is in the range -6...6
     * - encoding: Set by user.
     * - decoding: unused
     */
    int deblockbeta;

    /**
     * macroblock subpartition sizes to consider - p8x8, p4x4, b8x8, i8x8, i4x4
     * - encoding: Set by user.
     * - decoding: unused
     */
    int partitions;
#define X264_PART_I4X4 0x001  /* Analyse i4x4 */
#define X264_PART_I8X8 0x002  /* Analyse i8x8 (requires 8x8 transform) */
#define X264_PART_P8X8 0x010  /* Analyse p16x8, p8x16 and p8x8 */
#define X264_PART_P4X4 0x020  /* Analyse p8x4, p4x8, p4x4 */
#define X264_PART_B8X8 0x100  /* Analyse b16x8, b8x16 and b8x8 */

    /**
     * direct MV prediction mode - 0 (none), 1 (spatial), 2 (temporal)
     * - encoding: Set by user.
     * - decoding: unused
     */
    int directpred;

    /**
     * Audio cutoff bandwidth (0 means "automatic"), currently used only by FAAC.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int cutoff;

    /**
     * Multiplied by qscale for each frame and added to scene_change_score.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int scenechange_factor;

    /**
     *
     * Note: Value depends upon the compare function used for fullpel ME.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int mv0_threshold;

    /**
     * Adjusts sensitivity of b_frame_strategy 1.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int b_sensitivity;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int compression_level;
#define FF_COMPRESSION_DEFAULT -1

    /**
     * Sets whether to use LPC mode - used by FLAC encoder.
     * - encoding: Set by user.
     * - decoding: unused
     */
    int use_lpc;

    /**
     * LPC coefficient precision - used by FLAC encoder
     * - encoding: Set by user.
     * - decoding: unused
     */
    int lpc_coeff_precision;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int min_prediction_order;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_prediction_order;

    /**
     * search method for selecting prediction order
     * - encoding: Set by user.
     * - decoding: unused
     */
    int prediction_order_method;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int min_partition_order;

    /**
     * - encoding: Set by user.
     * - decoding: unused
     */
    int max_partition_order;

    /**
     * GOP timecode frame start number, in non drop frame format
     * - encoding: Set by user.
     * - decoding: unused
     */
    int64_t timecode_frame_start;
} AVCodecContext;
</code>

----
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