解读x264_param_default

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#C #x264 #视频编码

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本文详细介绍了x264编码器的参数配置过程，包括内存分配、CPU检测、视频属性设置、编码参数调整、码率控制策略及日志记录等。通过对这些参数的理解与设置，可以帮助开发者更好地优化视频编码效果。

from:http://blog.youkuaiyun.com/maopig/article/details/6702656

void    x264_param_default( x264_param_t *param ) 
{

    /* 开辟内存空间*/

    memset( param, 0, sizeof( x264_param_t ) );      

 

    /* CPU自动检测 */

    param->cpu = x264_cpu_detect();

    param->i_threads = X264_THREADS_AUTO; /* 并行编码线程为0 */

    param->b_deterministic = 1; /*允许非确定性时线程优化*/

    param->i_sync_lookahead = X264_SYNC_LOOKAHEAD_AUTO;/* 自动选择线程超前缓冲大小-1 */

 

    /* 视频属性 */

    param->i_csp           = X264_CSP_I420; /*设置输入的视频采样的格式0x0001yuv 4:2:0 planar*/

    param->i_width         = 0; /* 宽度*/

    param->i_height        = 0; /* 高度*/

    param->vui.i_sar_width = 0;

    param->vui.i_sar_height= 0; /* 设置长宽比 */

    param->vui.i_overscan  = 0;  /* 过扫描线，默认undef(不设置)，可选：show(观看)crop(去除) */

    param->vui.i_vidformat = 5;  /* undef视频格式 */

    param->vui.b_fullrange = 0;  /* off */

    param->vui.i_colorprim = 2;  /* undef原始色度格式*/

    param->vui.i_transfer  = 2;  /* undef 转换方式*/

    param->vui.i_colmatrix = 2;  /* undef 色度矩阵设置*/

    param->vui.i_chroma_loc= 0;  /* left center 色度样本指定，范围0~5，默认0*/

    param->i_fps_num       = 25; /*帧率*/

    param->i_fps_den       = 1; /*用两个整型的数的比值，来表示帧率*/

    param->i_level_idc     = -1; /* level值的设置*/

    param->i_slice_max_size = 0; /* 每片字节的最大数，包括预计的NAL开销. */

    param->i_slice_max_mbs = 0; /* 每片宏块的最大数，重写 i_slice_count */

    param->i_slice_count = 0; /* 每帧的像条数目: 设置矩形像条. */

 

    /* 编码参数 */

    param->i_frame_reference = 3; /*参考帧的最大帧数。*/

    param->i_keyint_max = 250; /* 在此间隔设置IDR关键帧 */

    param->i_keyint_min = 25; /* 场景切换少于次值编码位I, 而不是 IDR. */

    param->i_bframe = 3; /*两个参考帧之间的B帧数目*/

    param->i_scenecut_threshold = 40; /*如何积极地插入额外的I帧 */

    param->i_bframe_adaptive = X264_B_ADAPT_FAST; /*自适应B帧判定1*/

    param->i_bframe_bias = 0; /*控制插入B帧判定，范围-100~+100，越高越容易插入B帧*/

    param->b_bframe_pyramid = 0; /*允许部分B为参考帧 */

 

    param->b_deblocking_filter = 1; /*去块效应相关*/

    param->i_deblocking_filter_alphac0 = 0; /* [-6, 6] -6 亮度滤波器, 6 强 */

    param->i_deblocking_filter_beta = 0; /* [-6, 6]  同上 */

 

    param->b_cabac = 1; /*cabac的开关*/

    param->i_cabac_init_idc = 0;

   

/*码率控制*/

    param->rc.i_rc_method = X264_RC_CRF;;/*恒定码率*/

    param->rc.i_bitrate = 0;/*设置平均码率大小*/

    param->rc.f_rate_tolerance = 1.0;

    param->rc.i_vbv_max_bitrate = 0; /*平均码率模式下，最大瞬时码率，默认0(与-B设置相同) */

    param->rc.i_vbv_buffer_size = 0; /*码率控制缓冲区的大小，单位kbit，默认0 */

    param->rc.f_vbv_buffer_init = 0.9; /* <=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*/

    param->rc.i_qp_constant = 23;;/*最小qp值*/

    param->rc.f_rf_constant = 23;

    param->rc.i_qp_min = 10; /*允许的最小量化值 */

    param->rc.i_qp_max = 51; /*允许的最大量化值*/

    param->rc.i_qp_step = 4; /*帧间最大量化步长 */

    param->rc.f_ip_factor = 1.4;

    param->rc.f_pb_factor = 1.3;

    param->rc.i_aq_mode = X264_AQ_VARIANCE; /* psy adaptive QP. (X264_AQ_*) *//通过减少色度量化偏移量的方法来提高亮度的总体质量。adaptive QP.

    param->rc.f_aq_strength = 1.0;

    param->rc.i_lookahead = 40;

 

    param->rc.b_stat_write = 0; /* Enable stat writing in psz_stat_out */

    param->rc.psz_stat_out = "x264_2pass.log";

    param->rc.b_stat_read = 0;

    param->rc.psz_stat_in = "x264_2pass.log";

param->rc.f_qcompress = 0.6; /* 0.0 => cbr, 1.0 => constant qp */  

 param->rc.f_qblur = 0.5;   /*时间上模糊量化 */

    param->rc.f_complexity_blur = 20; /* 时间上模糊复杂性 */

    param->rc.i_zones = 0; /* number of zone_t's */

    param->rc.b_mb_tree = 1; /* Macroblock-tree ratecontrol. */

 

    /* 日志 */

    param->pf_log = x264_log_default;

    param->p_log_private = NULL;

    param->i_log_level = X264_LOG_INFO;/*默认为“Info”*/

 

    /*分析 */

    param->analyse.intra = X264_ANALYSE_I4x4 | X264_ANALYSE_I8x8;

    param->analyse.inter = X264_ANALYSE_I4x4 | X264_ANALYSE_I8x8

                         | X264_ANALYSE_PSUB16x16 | X264_ANALYSE_BSUB16x16;

    param->analyse.i_direct_mv_pred = X264_DIRECT_PRED_SPATIAL;/*空间预测模式*/

    param->analyse.i_me_method = X264_ME_HEX;/*运动估计算法HEX*/

    param->analyse.f_psy_rd = 1.0;

    param->analyse.b_psy = 1;

    param->analyse.f_psy_trellis = 0;

    param->analyse.i_me_range = 16;/*运动估计范围*/

    param->analyse.i_subpel_refine = 7; /* 亚像素运动估计质量 */

    param->analyse.b_mixed_references = 1; /*允许每个宏块的分区在P帧有它自己的参考号*/

    param->analyse.b_chroma_me = 1; /* 亚像素色度运动估计和P帧的模式选择 */

    param->analyse.i_mv_range_thread = -1; /* 线程之间的最小空间. -1 = auto, based on number of threads. */

    param->analyse.i_mv_range = -1; /*运动矢量最大长度set from level_idc*/

    param->analyse.i_chroma_qp_offset = 0; /*色度量化步长偏移量 */

    param->analyse.b_fast_pskip = 1; /*快速P帧跳过检测*/

    param->analyse.b_weighted_bipred = 1; /*为b帧隐式加权 */

    param->analyse.b_dct_decimate = 1; /* 在P-frames转换参数域 */

    param->analyse.b_transform_8x8 = 1; /* 帧间分区*/

    param->analyse.i_trellis = 1; /* 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*/

    param->analyse.i_luma_deadzone[0] = 21; /*帧间亮度量化中使用的无效区大小*/

    param->analyse.i_luma_deadzone[1] = 11; /*帧内亮度量化中使用的无效区大小*/

    param->analyse.b_psnr = 0;/*是否显示PSNR*/

    param->analyse.b_ssim = 0;/*是否显示SSIM*/

 

/*量化*/

    param->i_cqm_preset = X264_CQM_FLAT; /*自定义量化矩阵(CQM),初始化量化模式为flat 0*/

    memset( param->cqm_4iy, 16, 16 );

    memset( param->cqm_4ic, 16, 16 );

    memset( param->cqm_4py, 16, 16 );

    memset( param->cqm_4pc, 16, 16 );

    memset( param->cqm_8iy, 16, 64 );

    memset( param->cqm_8py, 16, 64 );/*开辟空间*/

    /*muxing*/

    param->b_repeat_headers = 1; /* 在每个关键帧前放置SPS/PPS*/

param->b_aud = 0; /*生成访问单元分隔符*/

}