x264_param_t各项意义--------x264学习笔记ByMK

typedef struct x264_param_t

{

/* CPU flags */

unsigned int cpu;

int i_threads; /* encode multiple frames in parallel //并行编码多帧 */

int b_deterministic; /* whether to allow non-deterministic optimizations when threaded //是否允许非确定性时线程优化*/

int i_sync_lookahead; /* threaded lookahead buffer //线程超前缓冲*/

/* Video Properties */

int i_width;

int i_height;

int i_csp; /* CSP of encoded bitstream, only i420 supported //csp比特流编码，只支持i420（即YUV标准格式4：2：0）*/

int i_level_idc;//编码复杂度

int i_frame_total; /* number of frames to encode if known, else 0 //如果已知则为需要编码的帧数，否则为0*/

struct /*Vui参数集视频可用性信息视频标准化选项 */

{

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

int i_sar_height;

int i_sar_width;/* 设置长宽比 */

int i_overscan; /* 0=undef, 1=no overscan, 2=overscan *//*过扫描线，默认"undef"(不设置)，可选项：show(观看)/crop(去除)*/

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

int i_vidformat;/* 视频格式，默认"undef"，component/pal/ntsc/secam/mac/undef*/

int b_fullrange;//表示黑电平和亮度与色度信号的范围由E’Y, E’PB, 和E’PR 或 E’R, E’G, 和 E’B模拟信号分量得到。

int i_colorprim;//表示最初的原色的色度坐标

int i_transfer;//表示源图像的光电转换特性

int i_colmatrix;//描述用于根据红、绿、蓝三原色得到亮度和色度信号的矩阵系数

int i_chroma_loc; /* both top & bottom 等于1 表示hroma_sample_loc_type_top_field 和chroma_sample_loc_type_bottom_field 存在。

chroma_loc_info_present_flag 等于0 表示hroma_sample_loc_type_top_field 和chroma_sample_loc_type_bottom_field不存在。*/

} 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 参考帧最大数目*/

int i_keyint_max; /* Force an IDR keyframe at this interval 最大IDR关键帧间隔*/

int i_keyint_min; /* Scenecuts closer together than this are coded as I, not IDR. 场景切换少于次值编码位I，而不是IDR*/

int i_scenecut_threshold; /* how aggressively to insert extra I frames 如何积极的插入额外的I帧*/

int i_bframe; /* how many b-frame between 2 references pictures 两个相关图像间b帧数量*/

int i_bframe_adaptive;//自适应b帧判定

int i_bframe_bias;//控制插入b帧判定，范围-100~100，越高越容易插入b帧，默认为0

int b_bframe_pyramid; /* Keep some B-frames as references 允许部分b帧作为参考帧*/

//下面是去块滤波需要的参数

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;

int b_interlaced;//隔行扫描

int i_cqm_preset; //自定义量化矩阵（CQM），初始化量化模式为flat

char *psz_cqm_file; /* JM format 读取jm格式的外部量化矩阵文件，自动忽略其他--cqm选项*/

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;

char *psz_dump_yuv; /* filename for reconstructed frames */

/* Encoder analyser parameters 编码分析参数*/

struct

{

unsigned int intra; /* intra partitions 帧内分区*/

unsigned int inter; /* inter partitions 帧间分区*/

int b_transform_8x8;

int b_weighted_bipred; /* implicit weighting for B-frames 为B帧隐式加权*/

int i_direct_mv_pred; /* spatial vs temporal mv prediction 时间空间队列运动预测*/

int i_chroma_qp_offset;//色度量化步长偏移量

int i_me_method; /* motion estimation algorithm to use (X264_ME_*) 运动估计算法（X264_ME_*）*/

int i_me_range; /* integer pixel motion estimation search range (from predicted mv) 整像素运动估计范围*/

int i_mv_range; /* maximum length of a mv (in pixels). -1 = auto, based on level 运动矢量最大长度，-1为自动设置*/

int i_mv_range_thread; /* minimum space between threads. -1 = auto, based on number of threads. 线程之间最小空间*/

int i_subpel_refine; /* subpixel motion estimation quality 亚像素运动估计质量*/

int b_chroma_me; /* chroma ME for subpel and mode decision in P-frames 亚像素色度运动估计和P帧的模式选择*/

int b_mixed_references; /* allow each mb partition in P-frames to have it's own reference number 允许每个宏块的分区在P帧有它自己的参考号*/

int i_trellis; /* trellis RD quantization-- Trellis量化，对每个8x8的块寻找合适的量化值，需要CABAC，默认0 0：关闭1：只在最后编码时使用2：一直使用*/

int b_fast_pskip; /* early SKIP detection on P-frames 快速P帧跳过检测*/

int b_dct_decimate; /* transform coefficient thresholding on P-frames 在P帧转换参数域*/

int i_noise_reduction; /* adaptive pseudo-deadzone 自适应伪盲区*/

float f_psy_rd; /* Psy RD strength */

float f_psy_trellis; /* Psy trellis strength */

int b_psy; /* Toggle all psy optimizations */

/* the deadzone size that will be used in luma quantization */

/*，亮度量化中使用的无效区大小*/

int i_luma_deadzone[2]; /* {inter, intra} {帧间，帧内}*/

int b_psnr; /* compute and print PSNR stats 计算打印PSNR信息*/

int b_ssim; /* compute and print SSIM stats 计算打印SSIM信息*/

} analyse;

/* Rate control parameters 码率控制参数*/

struct

{

int i_rc_method; /* X264_RC_* */

int i_qp_constant; /* 0-51 */

int i_qp_min; /* min allowed QP value 允许最小量化值*/

int i_qp_max; /* max allowed QP value 允许最大量化值*/

int i_qp_step; /* max QP step between frames 帧间最大量化步长*/

int i_bitrate; //平均码率

float f_rf_constant; /* 1pass VBR, nominal QP */

float f_rate_tolerance;

int i_vbv_max_bitrate;//平均码率模式下，最大瞬间码率，默认0（与-B设置相同）

int i_vbv_buffer_size;//码率控制缓冲区的大小，单位kbit，默认0

float f_vbv_buffer_init; /* <=1: fraction of buffer_size. >1: kbit 码率控制缓冲区数据保留的最大数据量与缓冲区大小之比，范围0~1.0，默认0.9*/

float f_ip_factor;

float f_pb_factor;

int i_aq_mode; /* psy adaptive QP. (X264_AQ_*) */

float f_aq_strength;

int b_mb_tree; /* Macroblock-tree ratecontrol. */

int i_lookahead;

/* 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) */

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

float f_qblur; /* temporally blur quants 时间上模糊量化*/

float f_complexity_blur; /* temporally blur complexity 时间上模糊复杂性*/

x264_zone_t *zones; /* ratecontrol overrides 码率控制覆盖*/

int i_zones; /* number of zone_t's --zones数量*/

char *psz_zones; /* alternate method of specifying zones 指定区的另一种方法*/

} rc;

/* Muxing parameters */

int b_aud; /* generate access unit delimiters 生成访问单元分隔符*/

int b_repeat_headers; /* put SPS/PPS before each keyframe 在每个关键帧前放置SPS/PPS*/

int b_annexb; /* if set, place start codes (4 bytes) before NAL units,

* otherwise place size (4 bytes) before NAL units. 如果设置了该项，则在每个NAL单元前加一个四字节的前缀符*/

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

/* Slicing parameters */

int i_slice_max_size; /* Max size per slice in bytes; includes estimated NAL overhead. 每片字节最大数，包括预计的nal开销*/

int i_slice_max_mbs; /* Max number of MBs per slice; overrides i_slice_count. 每片宏块的最大数，重写i_slice_count*/

int i_slice_count; /* Number of slices per frame: forces rectangular slices. 每帧的像条数目：设置矩形像条*/

/* Optional callback for freeing this x264_param_t when it is done being used.

* Only used when the x264_param_t sits in memory for an indefinite period of time,

* i.e. when an x264_param_t is passed to x264_t in an x264_picture_t or in zones.

* Not used when x264_encoder_reconfig is called directly. */

void (*param_free)( void* );

} x264_param_t;