avcodec.h

ffmpeg源码分析

     * - decoding: set by lavc\
     */\
    int coded_picture_number;\
    /**\
     * picture number in display order.\
     * - encoding: set by\
     * - decoding: set by lavc\
     */\
    int display_picture_number;\
\
    /**\
     * quality (between 1 (good) and FF_LAMBDA_MAX (bad)) \
     * - encoding: set by lavc for coded_picture (and set by user for input)\
     * - decoding: set by lavc\
     */\
    int quality; \
\
    /**\
     * buffer age (1->was last buffer and dint change, 2->..., ...).\
     * set to INT_MAX if the buffer has not been used yet \
     * - encoding: unused\
     * - decoding: MUST be set by get_buffer()\
     */\
    int age;\
\
    /**\
     * is this picture used as reference\
     * - encoding: unused\
     * - decoding: set by lavc (before get_buffer() call))\
     */\
    int reference;\
\
    /**\
     * QP table\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    int8_t *qscale_table;\
    /**\
     * QP store stride\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    int qstride;\
\
    /**\
     * mbskip_table[mb]>=1 if MB didnt change\
     * stride= mb_width = (width+15)>>4\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    uint8_t *mbskip_table;\
\
    /**\
     * Motion vector table.\
     * @code\
     * example:\
     * int mv_sample_log2= 4 - motion_subsample_log2;\
     * int mb_width= (width+15)>>4;\
     * int mv_stride= (mb_width << mv_sample_log2) + 1;\
     * motion_val[direction][x + y*mv_stride][0->mv_x, 1->mv_y];\
     * @endcode\
     * - encoding: set by user\
     * - decoding: set by lavc\
     */\
    int16_t (*motion_val[2])[2];\
\
    /**\
     * Macroblock type table\
     * mb_type_base + mb_width + 2\
     * - encoding: set by user\
     * - decoding: set by lavc\
     */\
    uint32_t *mb_type;\
\
    /**\
     * log2 of the size of the block which a single vector in motion_val represents: \
     * (4->16x16, 3->8x8, 2-> 4x4, 1-> 2x2)\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    uint8_t motion_subsample_log2;\
\
    /**\
     * for some private data of the user\
     * - encoding: unused\
     * - decoding: set by user\
     */\
    void *opaque;\
\
    /**\
     * error\
     * - encoding: set by lavc if flags&CODEC_FLAG_PSNR\
     * - decoding: unused\
     */\
    uint64_t error[4];\
\
    /**\
     * type of the buffer (to keep track of who has to dealloc data[*])\
     * - encoding: set by the one who allocs it\
     * - decoding: set by the one who allocs it\
     * Note: user allocated (direct rendering) & internal buffers can not coexist currently\
     */\
    int type;\
    \
    /**\
     * when decoding, this signal how much the picture must be delayed.\
     * extra_delay = repeat_pict / (2*fps)\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    int repeat_pict;\
    \
    /**\
     * \
     */\
    int qscale_type;\
    \
    /**\
     * The content of the picture is interlaced.\
     * - encoding: set by user\
     * - decoding: set by lavc (default 0)\
     */\
    int interlaced_frame;\
    \
    /**\
     * if the content is interlaced, is top field displayed first.\
     * - encoding: set by user\
     * - decoding: set by lavc\
     */\
    int top_field_first;\
    \
    /**\
     * Pan scan.\
     * - encoding: set by user\
     * - decoding: set by lavc\
     */\
    AVPanScan *pan_scan;\
    \
    /**\
     * tell user application that palette has changed from previous frame.\
     * - encoding: ??? (no palette-enabled encoder yet)\
     * - decoding: set by lavc (default 0)\
     */\
    int palette_has_changed;\
    \
    /**\
     * Codec suggestion on buffer type if != 0\
     * - encoding: unused\
     * - decoding: set by lavc (before get_buffer() call))\
     */\
    int buffer_hints;\
\
    /**\
     * DCT coeffitients\
     * - encoding: unused\
     * - decoding: set by lavc\
     */\
    short *dct_coeff;\
\
    /**\
     * Motion referece frame index\
     * - encoding: set by user\
     * - decoding: set by lavc\
     */\
    int8_t *ref_index[2];

#define FF_QSCALE_TYPE_MPEG1 0
#define FF_QSCALE_TYPE_MPEG2 1
#define FF_QSCALE_TYPE_H264  2

#define FF_BUFFER_TYPE_INTERNAL 1
#define FF_BUFFER_TYPE_USER     2 ///< Direct rendering buffers (image is (de)allocated by user)
#define FF_BUFFER_TYPE_SHARED   4 ///< buffer from somewhere else, don't dealloc image (data/base), all other tables are not shared
#define FF_BUFFER_TYPE_COPY     8 ///< just a (modified) copy of some other buffer, don't dealloc anything


#define FF_I_TYPE 1 // Intra
#define FF_P_TYPE 2 // Predicted
#define FF_B_TYPE 3 // Bi-dir predicted
#define FF_S_TYPE 4 // S(GMC)-VOP MPEG4
#define FF_SI_TYPE 5
#define FF_SP_TYPE 6

#define FF_BUFFER_HINTS_VALID    0x01 // Buffer hints value is meaningful (if 0 ignore)
#define FF_BUFFER_HINTS_READABLE 0x02 // Codec will read from buffer
#define FF_BUFFER_HINTS_PRESERVE 0x04 // User must not alter buffer content
#define FF_BUFFER_HINTS_REUSABLE 0x08 // Codec will reuse the buffer (update)

/**
 * Audio Video Frame.
 */
typedef struct AVFrame {
    FF_COMMON_FRAME
} AVFrame;

#define DEFAULT_FRAME_RATE_BASE 1001000

/**
 * Used by av_log
 */
typedef struct AVCLASS AVClass;
struct AVCLASS {
    const char* class_name;
    const char* (*item_name)(void*); /* actually passing a pointer to an AVCodecContext
                                        or AVFormatContext, which begin with an AVClass.
                                        Needed because av_log is in libavcodec and has no visibility
                                        of AVIn/OutputFormat */
    struct AVOption *option;
};

/**
 * main external api structure.
 */
typedef struct AVCodecContext {
    /**
     * Info 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 lavc. 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 needs additionnal format info. It is stored here
     * - encoding: set by user.
     * - decoding: set by lavc. (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 extra-data 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
     * then extradata_size to avoid prolems if its read with the bitstream reader
     * the bytewise contents of extradata must not depend on the architecture or cpu endianness
     * - encoding: set/allocated/freed by lavc.
     * - decoding: set/allocated/freed by user.
     */
    void *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 lavc.
     */
    AVRational time_base;

    /* video only */
    /**
     * picture width / height.
     * - encoding: MUST be set by user.
     * - decoding: set by lavc.
     * Note, for compatibility its 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 pitures, 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 lavc.
     */
    enum PixelFormat pix_fmt;

    /**
     * Frame rate emulation. If not zero 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 an horizontal band. It improve cache usage. Not
     * all codecs can do that. You must check the codec capabilities
     * before
     * - 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 sec
    int channels;

    /**
     * audio sample format.
     * - encoding: set by user.
     * - decoding: set by lavc.
     */
    enum SampleFormat sample_fmt;  ///< sample format, currenly 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 lavc.
     * - 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 etween 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.
     * deprecated in favor of skip_idct and skip_frame
     * - encoding: unused
     * - decoding: set by user. 1-> skip b frames, 2-> skip idct/dequant too, 5-> skip everything except header
     */
    int hurry_up;

    struct AVCodec *codec;

    void *priv_data;

    /* unused, FIXME remove*/
    int rtp_mode;

    int rtp_payload_size;   /* The size of the RTP payload: the coder will  */
                            /* do it's 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 transmited RTP payload    */


    /* The RTP callback: This function is called   */
    /* every time the encoder has a packet to send */
    /* 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 lavc
     * - 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];