x264中几个重要结构体的说明
看代码，虽说不一定非得把每一个变量的含义都弄得一清二楚，但是对于比较重要的变量参数，你不了解的话那看起程序来会特别吃力，故这里先开个头，给出x264中几个重要结构体的说明，主要以注释的形式给出。
typedef struct x264_param_t
{
/* CPU flags */
unsigned int cpu;
int i_threads; /* encode multiple frames in parallel */
int b_deterministic; /* whether to allow non-deterministic optimizations when threaded */
/* 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 */
int i_level_idc; //!< level值的设置
int i_frame_total; /* number of frames to encode if known, else 0 */
//! Video Usability Information (VUI) 视频可用性信息
struct
{
/* they will be reduced to be 0 < x <= 65535 and prime */
int i_sar_height;
int i_sar_width; //!< 设置宽高比
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;
//! 帧率
int i_fps_num; //!< 分子
int i_fps_den; //!< 分母
/* 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 b_pre_scenecut; /* compute scenecut on lowres frames */
int i_bframe; /* how many b-frame between 2 references pictures */
int i_bframe_adaptive; //!< B帧数目自适应
int i_bframe_bias;
int b_bframe_pyramid; /* Keep some B-frames as references */
int b_deblocking_filter; //!< 设置去方波滤波
int i_deblocking_filter_alphac0; /* [-6, 6] -6 light filter, 6 strong */
int i_deblocking_filter_beta; /* [-6, 6] idem */
int b_cabac; //!< 设置CABAC
int i_cabac_init_idc;
int b_interlaced;
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;
char *psz_dump_yuv; /* filename for reconstructed frames */
/* Encoder analyser parameters */
struct
{
unsigned int intra; /* intra partitions */
unsigned int inter; /* inter partitions */
int b_transform_8x8; //!< 设置8x8变换
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). -1 = auto, based on level */
int i_mv_range_thread; /* minimum space between threads. -1 = auto, based on number of threads. */
int i_subpel_refine; /* subpixel motion estimation quality */
int b_chroma_me; /* chroma ME for subpel and mode decision in P-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 */
float f_psy_rd; /* Psy RD strength */
float f_psy_trellis; /* Psy trellis strength */
/* the deadzone size that will be used in luma quantization */
int i_luma_deadzone[2]; /* {inter, intra} */
int b_psnr; /* compute and print PSNR stats */
int b_ssim; /* compute and print SSIM stats */
} 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;
float f_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; /* <=1: fraction of buffer_size. >1: kbit */
float f_ip_factor;
float f_pb_factor;
int i_aq_mode; /* psy adaptive QP. (X264_AQ_*) */
float f_aq_strength;
/* 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 */
float f_complexity_blur; /* temporally blur complexity */
x264_zone_t *zones; /* ratecontrol overrides */
int i_zones; /* number 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;
typedef struct
{
int i_csp; //!< Color Space Parameter，色彩空间参数，实际上仅支持I420格式
int i_plane; //!< 色彩空间的色彩分量数
int i_stride[4]; //!< 对应于各个色彩分量的跨度
uint8_t *plane[4]; //!< 对应于各个色彩分量的数据
} x264_image_t;
typedef struct
{
/* In: force picture type (if not auto)
* If x264 encoding parameters are violated in the forcing of picture types,
* x264 will correct the input picture type and log a warning.
* The quality of frametype decisions may suffer if a great deal of fine-grained
* mixing of auto and forced frametypes is done.
* Out: type of the picture encoded */
int i_type; //!<指明帧的类型，有X264_TYPE_AUTO，X264_TYPE_IDR，X264_TYPE_I，X264_TYPE_P，X264_TYPE_B，X264_TYPE_BREF几种类型
/* In: force quantizer for > 0 */
int i_qpplus1; //!< 帧的量化参数值减1
/* In: user pts, Out: pts of encoded picture (user)*/
int64_t i_pts; //!< Presentation Time Stamp
/* In: raw data */
x264_image_t img; //!< 用于维护原始图像数据的结构体
} x264_picture_t;
typedef struct
{
int i_ref_idc; /* nal_priority_e */ //!< nal 的优先级
int i_type; /* nal_unit_type_e */ //!< nal 的类型
/* This data are raw payload */
int i_payload; //!< nal 载荷的长度
uint8_t *p_payload; //!< nal 载荷的数据
} x264_nal_t;