X264编码流程

参数的初始化

1.opt，param根据输入的参数和标准的规定，进行初始化设置。

Opt的说明如下：

Opt->hin用于给出读入的yuv文件的指针地址

Opt->hout给出了输出的文件的指针地址

Opt->i_seek给出了起始编码帧的帧数，是由编码时的seek命令参数决定的

如：

X264 -seek 10 -o foreman.cif test.264 352x288

i_seek 设为10，表示起始编码的帧为元序列的第十帧

Opt->qpfile按照说明，为qp值文件输入进行定义这种方式的接口，可以通过读入标准的文件格式，对编码时的qp值进行定义。

Param的说明：

typedef struct

{

/* CPU flags */

unsigned int cpu;

int         i_threads;  /* divide each frame into multiple slices, encode in parallel */线程数，用于多线程并行编码

/* Video Properties */

int         i_width;                               图像的宽度

int         i_height;                               图像的高度

int         i_csp;  /* CSP of encoded bitstream, only i420 supported */    色彩空间的设置

int         i_level_idc;             level 值的设置

int         i_frame_total; /* number of frames to encode if known, else 0 */  总共需要编码的帧数，由--frames设置

Vui参数集

struct

{

/* they will be reduced to be 0 < x <= 65535 and prime */

int         i_sar_height;

int         i_sar_width;

int         i_overscan;    /* 0=undef, 1=no overscan, 2=overscan */

/* see h264 annex E for the values of the following */

int         i_vidformat;

int         b_fullrange;

int         i_colorprim;

int         i_transfer;

int         i_colmatrix;

int         i_chroma_loc;    /* both top & bottom */

} vui;

int         i_fps_num;

int         i_fps_den;

这两个参数是由fps帧率确定的，赋值的过程见下：

{

float fps;

if( sscanf( value, "%d/%d", &p->i_fps_num, &p->i_fps_den ) == 2 )

;

else if( sscanf( value, "%f", &fps ) )

{

p->i_fps_num = (int)(fps * 1000 + .5);

p->i_fps_den = 1000;

}

else

b_error = 1;

}

Value的值就是fps。

/* Bitstream parameters */

int         i_frame_reference;  /* Maximum number of reference frames */

int         i_keyint_max;       /* Force an IDR keyframe at this interval */

int         i_keyint_min;       /* Scenecuts closer together than this are coded as I, not IDR. */

int         i_scenecut_threshold; /* how aggressively to insert extra I frames */

int         i_bframe;   /* how many b-frame between 2 references pictures */

int         b_bframe_adaptive;

int         i_bframe_bias;

int         b_bframe_pyramid;   /* Keep some B-frames as references */

去块滤波器需要的参数

int         b_deblocking_filter;

int         i_deblocking_filter_alphac0;    /* [-6, 6] -6 light filter, 6 strong */

int         i_deblocking_filter_beta;       /* [-6, 6]  idem */

熵编码

int         b_cabac;

int         i_cabac_init_idc;

量化

int         i_cqm_preset;

char        *psz_cqm_file;      /* JM format */

uint8_t     cqm_4iy[16];        /* used only if i_cqm_preset == X264_CQM_CUSTOM */

uint8_t     cqm_4ic[16];

uint8_t     cqm_4py[16];

uint8_t     cqm_4pc[16];

uint8_t     cqm_8iy[64];

uint8_t     cqm_8py[64];

/* Log */

void        (*pf_log)( void *, int i_level, const char *psz, va_list );

void        *p_log_private;

int         i_log_level;

int         b_visualize;

/* Encoder analyser parameters */

struct

{

unsigned int intra;     /* intra partitions */

unsigned int inter;     /* inter partitions */

int          b_transform_8x8;

int          b_weighted_bipred; /* implicit weighting for B-frames */

int          i_direct_mv_pred; /* spatial vs temporal mv prediction */

int          i_chroma_qp_offset;

int          i_me_method; /* motion estimation algorithm to use (X264_ME_*) */

int          i_me_range; /* integer pixel motion estimation search range (from predicted mv) */

int          i_mv_range; /* maximum length of a mv (in pixels) */

int          i_subpel_refine; /* subpixel motion estimation quality */

int          b_bidir_me; /* jointly optimize both MVs in B-frames */

int          b_chroma_me; /* chroma ME for subpel and mode decision in P-frames */

int          b_bframe_rdo; /* RD based mode decision for B-frames */

int          b_mixed_references; /* allow each mb partition in P-frames to have it's own reference number */

int          i_trellis;  /* trellis RD quantization */

int          b_fast_pskip; /* early SKIP detection on P-frames */

int          b_dct_decimate; /* transform coefficient thresholding on P-frames */

int          i_noise_reduction; /* adaptive pseudo-deadzone */

int          b_psnr;    /* Do we compute PSNR stats (save a few % of cpu) */

} analyse;

/* Rate control parameters */

struct

{

int         i_rc_method;    /* X264_RC_* */

int         i_qp_constant;  /* 0-51 */

int         i_qp_min;       /* min allowed QP value */

int         i_qp_max;       /* max allowed QP value */

int         i_qp_step;      /* max QP step between frames */

int         i_bitrate;              比特率 --bitrate控制

int         i_rf_constant;  /* 1pass VBR, nominal QP */

float       f_rate_tolerance;

int         i_vbv_max_bitrate;

int         i_vbv_buffer_size;

float       f_vbv_buffer_init;

float       f_ip_factor;

float       f_pb_factor;

/* 2pass */

int         b_stat_write;   /* Enable stat writing in psz_stat_out */

char        *psz_stat_out;

int         b_stat_read;    /* Read stat from psz_stat_in and use it */

char        *psz_stat_in;

/* 2pass params (same as ffmpeg ones) */

char        *psz_rc_eq;     /* 2 pass rate control equation */

float       f_qcompress;    /* 0.0 => cbr, 1.0 => constant qp */

float       f_qblur;        /* temporally blur quants */

float       f_complexity_blur; /* temporally blur complexity */

x264_zone_t *zones;         /* ratecontrol overrides */

int         i_zones;        /* sumber of zone_t's */

char        *psz_zones;     /* alternate method of specifying zones */

} rc;

/* Muxing parameters */

int b_aud;                  /* generate access unit delimiters */

int b_repeat_headers;       /* put SPS/PPS before each keyframe */

int i_sps_id;               /* SPS and PPS id number */

} x264_param_t;