x264 struct 學習

x264_t結構體維護著CODEC的諸多重要信息

其中成員frames是一個指示和控制幀編碼過程的結構。其中current是已經準備就緒可以編碼的幀，其類型已經確定；next是尚未確定類型的幀；unused用于回收不使用的frame結構體以備今后再次使用。

structx264_t?????????????????????????????????

{

???

???unsigned int??cpu;

???

???struct

???{

???????int????????i_nal;????????//定義一個網絡提取層//

???????x264_nal_t?nal[3];????????

???????int????????i_bitstream;???

???????uint8_t????*p_bitstream;??

???????bs_t???????bs;

???} out;

???

???x264_param_t???param;

???

???int????????????i_frame;???????????//一個指示和控制幀編碼過程的結構

???int????????????i_poc;

???int????????????i_frame_offset;

???int????????????i_frame_num;???

???int????????????i_poc_msb;?????

???int????????????i_poc_lsb;?????

???

???x264_sps_t?????sps_array[32];

???x264_sps_t?????*sps;

???x264_pps_t?????pps_array[256];

???x264_pps_t?????*pps;

???int????????????i_idr_pic_id;

???

???x264_slice_header_t sh;
???

???x264_cabac_t???cabac;

???

???x264_picture_t? *picture;

???

???x264_frame_t???*bframe_current[X264_BFRAME_MAX];

???x264_frame_t???*frame_next[X264_BFRAME_MAX+1];??這個是定義下一個幀,但不一定是B幀

???x264_frame_t???*frame_unused[X264_BFRAME_MAX+1];

???

???x264_frame_t???*fdec;

???

???struct

???{

???????DECLARE_ALIGNED( int, luma16×16_dc[16], 16 );

???????DECLARE_ALIGNED( int, chroma_dc[2][4], 16 );//色度

???????struct

???????{

???????????DECLARE_ALIGNED( int, residual_ac[15], 16 );

???????????DECLARE_ALIGNED( int, luma4×4[16], 16 );

???????} block[16+8];16*8的宏快的取用情況

???} dct;離散余弦變換

???

???struct

???{

???????

???????int????i_mb_stride;

???????

???????int????i_mb_x;

???????int????i_mb_y;

???????int????i_mb_xy;

???????unsigned int i_neighbour;

???????

???????int8_t?*type;?????????????????????

???????int8_t?*qp;???????????????????????

???????int16_t*cbp;??????？???????????????

???????int8_t?(*intra4×4_pred_mode)[7];??

???????uint8_t (*non_zero_count)[16+4+4];?

???????int8_t?*chroma_pred_mode;?????????

???????int16_t(*mv[2])[2];???????????????

???????int16_t(*mvd[2])[2];??????????????

???????int8_t??*ref[2];??????????????????

???????

???????int????i_type;

???????int???i_partition;

???????int????i_sub_partition[4];

???????int????i_cbp_luma;

???????int????i_cbp_chroma;

???????int????i_intra16×16_pred_mode;

???????int????i_chroma_pred_mode;

???????struct

???????{

???????????

???????????uint8_t *p_img[3];

???????????int?????i_img[3];

???????????

???????????uint8_t *p_fdec[3];

???????????uint8_t*p_fref[2][16][3];

???????????int????i_fdec[3];

???????} pic;

???????

???????struct

???????{

???????????

???????????int????intra4×4_pred_mode[X264_SCAN8_SIZE];色度預測模式

???????????

???????????int????non_zero_count[X264_SCAN8_SIZE];

???????????

???????????int8_t ref[2][X264_SCAN8_SIZE];

???????????

???????????int16_t mv[2][X264_SCAN8_SIZE][2];

???????????int16_t mvd[2][X264_SCAN8_SIZE][2];運動矢量與真實值之間的差

???????} cache;

???????

???????int????i_last_qp;

???????int????i_last_dqp;

?
???} mb;宏快的預測以及運動補償和運動估計

???

???x264_frame_t?????*freference[16+1];?

???int??????????????i_ref0; 參考幀列表一（定義為lsit0意為向前預測編碼）

???x264_frame_t?????*fref0[16];??????

???int??????????????i_ref1;參考幀列表二（定義為lsit1意為向后預測編碼）

???x264_frame_t?????*fref1[16];??????

???

???x264_ratecontrol_t *rc;

???

???struct

???{

???????

???????int??i_slice_count[5];

???????int??i_slice_size[5];

???????float f_psnr_y[5];

???????float f_psnr_u[5];

???????float f_psnr_v[5];

???????int??i_mb_count[5][18];

???} stat;聲明每一片的參數變量

???

???x264_predict_t?????predict_16×16[4+3];

???x264_predict_t?????predict_8×8[4+3];

???x264_predict_t?????predict_4×4[9+3];

???x264_pixel_function_t pixf;

???x264_mc_function_t???mc[2];

???x264_dct_function_t??dctf;

???

???x264_vlc_table_t *x264_coeff_token_lookup[5];

???x264_vlc_table_t *x264_level_prefix_lookup;

???x264_vlc_table_t *x264_total_zeros_lookup[15];

???x264_vlc_table_t *x264_total_zeros_dc_lookup[3];

???x264_vlc_table_t *x264_run_before_lookup[7];

};

#endif

給出編碼過程中的各個參數的初始化

x264_param_t

typedef struct

{

???

???unsigned int cpu;

???

???int????????i_width;

???int????????i_height;

???struct

???{

???????

???????int????????i_sar_height;

???????int????????i_sar_width;

???} vui;？

???float??????f_fps;

???

???int????????i_frame_reference;?

???int????????i_idrframe;

???int????????i_iframe;??

???int????????i_bframe;??

???int????????b_deblocking_filter;

???int????????b_cabac;

???int????????i_cabac_init_idc;給出熵編碼初始化時表格的選擇

???int????????i_qp_constant;?

???int????????i_bitrate;?????

???

???struct

???{

???????unsigned intintra;???

???????unsigned intinter;???

???} analyse;

}
x264_param_t給出編碼過程中的各個參數的初始化

sps序列參數集

typedef struct

{

???int i_id;
?
???int i_profile_idc;指明所用profile

???int i_level_idc; 指明所用level

????int b_constraint_set0;

???int b_constraint_set1;

???int b_constraint_set2; 當他們值等于1時，表示必須遵守某些制約條件

???int i_log2_max_frame_num;表示圖像解碼順序的最大取值
?
???inti_poc_type;???

???inti_log2_max_poc_lsb;???

???intb_delta_pic_order_always_zero;其值等于一時句法元素delta_pic_order_cnt[0]和delta_pic_order_cnt[1]不再片頭出現，且他們的默認值都為0。為0時上述則出現。

???int i_offset_for_non_ref_pic;用來計算非參考幀或場的picture order count,其值應在[-2e31,2e31-1]

???int i_offset_for_top_to_bottom_field; 用來計算幀的底場的picture order count其值應在[-2e31,2e31-1]

???int i_num_ref_frames_in_poc_cycle;用來解碼picture order count取值應在[0，255]之間

???int i_offset_for_ref_frame[256]; 當picture order counttype=1時用來解碼poc，這句語法對循環num_ref_frames_in_poc_cycle中的每一個元素指定了一個偏移
?
???int i_num_ref_frames;指定參考幀隊列的最大長度 h264規定最多可為16個參考幀

???int b_gaps_in_frame_num_value_allowed;值為1時表示允許句法frame_num可以不連續

???int i_mb_width;

???int i_mb_height;

???int b_frame_mbs_only;

???int b_mb_adaptive_frame_field;

???int b_direct8×8_inference;指明b片的直接和skip模式下運動矢量的預測方法
???
???int b_crop;

???struct

???{

???????int i_left;

???????int i_right;

???????int i_top;

???????int i_bottom;