avcodec.h

ffmpeg源码分析

    int dia_size;

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

    /**
     * pre pass for motion estimation.
     * - encoding: set by user.
     * - decoding: unused
     */
    int pre_me;

    /**
     * motion estimation pre pass compare function.
     * - encoding: set by user.
     * - decoding: unused
     */
    int me_pre_cmp;

    /**
     * ME pre pass 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,
     * its terminated by -1 as 0 is a valid format, the formats are ordered by quality
     * the first is allways the native one
     * @return the choosen format
     * - encoding: unused
     * - decoding: set by user, if not set then the native format will always be choosen
     */
    enum PixelFormat (*get_format)(struct AVCodecContext *s, const enum PixelFormat * fmt);

    /**
     * DTG active format information (additionnal aspect ratio
     * information only used in DVB MPEG2 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
     *             table have to be stored somewhere FIXME
     */
    int color_table_id;

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

    /**
     * internal_buffers.
     * Don't touch, used by lavc 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 MPEG1/2/4 qscale.
     * - encoding: set by user.
     * - decoding: unused
     */
    int global_quality;

#define FF_CODER_TYPE_VLC   0
#define FF_CODER_TYPE_AC    1
    /**
     * 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 lavc
     */
    uint16_t *intra_matrix;

    /**
     * custom inter quantization matrix
     * - encoding: set by user, can be NULL
     * - decoding: set by lavc
     */
    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 workaround some encoder bugs
     * - encoding: unused
     * - decoding: set by user, will be converted to upper case by lavc 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. lavc won't check it.
     * lavc 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 lavc, 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 independant 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 independant 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 lavc, user can override
     * - decoding: set by lavc, 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. under 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. under 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 lavc
     */
     int profile;
#define FF_PROFILE_UNKNOWN -99

    /**
     * level
     * - encoding: set by user
     * - decoding: set by lavc
     */
     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;

    /**
     * bitsream 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 comparission 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;

    /**