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question:数组元素怎么算出来的
answer:i_mb_b_cost_table数组元素的值是根据编码器对不同预测方式的分析和试验,通过经验法则或者统计计算得出的,数值大小与预测方式的编码难度和效果有关。在实际编码中,计算每种预测方式的编码代价时,会将其它编码参数和压缩模式一起考虑,确保选择的预测方式具有最小的编码代价和最佳的视频质量。通常情况下,预测方式的编码代价越小,则压缩效果越好,码率越低,但编码代价与编码速度之间通常是一种牺牲和平衡。
question:解析下面结构体的每个变量 typedef struct { x264_me_t me16x16; x264_me_t bi16x16; /* for b16x16 BI mode, since MVs can differ from l0/l1 */ x264_me_t me8x8[4]; x264_me_t me4x4[4][4]; x264_me_t me8x4[4][2]; x264_me_t me4x8[4][2]; x264_me_t me16x8[2]; x264_me_t me8x16[2]; int i_rd16x16; int i_cost8x8; int i_cost4x4[4]; /* cost per 8x8 partition */ int i_cost8x4[4]; /* cost per 8x8 partition */ int i_cost4x8[4]; /* cost per 8x8 partition */ int i_cost16x8; int i_cost8x16; /* [ref][0] is 16x16 mv, [ref][1..4] are 8x8 mv from partition [0..3] */ ALIGNED_4( int16_t mvc[32][5][2] ); } x264_mb_analysis_list_t;
answer:这个结构体是x264视频编码器中的宏块分析列表(MB Analysis List),用于保存对预测模式和运动向量的分析结果和计算代价,用于后续的编码操作。 具体解析每个变量如下: - x264_me_t me16x16表示16x16块的运动估计结果; - x264_me_t bi16x16表示双向16x16块的运动估计结果,由于参考帧的不同,需单独计算; - x264_me_t me8x8[4]表示4个8x8块(4x4的4个子块)的运动估计结果; - x264_me_t me4x4[4][4]表示4个8x8块(4x4的16个子块)的运动估计结果; - x264_me_t me8x4[4][2]表示4个8x4块(4x4的8个子块)的运动估计结果; - x264_me_t me4x8[4][2]表示4个4x8块(4x4的8个子块)的运动估计结果; - x264_me_t me16x8[2]表示2个16x8块的运动估计结果; - x264_me_t me8x16[2]表示2个8x16块的运动估计结果; - int i_rd16x16表示16x16块的编码难度,用于快速计算最优运动估计(Motion Estimation); - int i_cost8x8表示8x8块的编码代价,用于计算最优编码方式; - int i_cost4x4[4]表示4个8x8块(4x4的16个子块)的编码代价,用于计算最优编码方式; - int i_cost8x4[4]表示4个8x4块(4x4的8个子块)的编码代价,用于计算最优编码方式; - int i_cost4x8[4]表示4个4x8块(4x4的8个子块)的编码代价,用于计算最优编码方式; - int i_cost16x8表示16x8块的编码代价,用于计算最优编码方式; - int i_cost8x16表示8x16块的编码代价,用于计算最优编码方式; - ALIGNED_4(int16_t mvc[32][5][2])表示运动向量(Motion Vector)缓存,用于存储每个宏块各自的运动向量。 需要注意的是,这个结构体中包含多个运动估计结果和编码代价,用于不同分辨率和块大小的视频编码,以及单/双向预测和双向16x16预测的情况。每个变量的含义和作用在不同情况下有所不同。
question:详细解释int16_t mvc[32][5][2]
answer:int16_t mvc[32][5][2]是x264_mb_analysis_list_t结构体中的一个二维数组,用于存储各个宏块的运动向量信息。这个数组的第一维大小为32,表示一个宏块指向32个参考帧之一的运动向量。其中,0表示当前帧本身,1-15表示之前的15个P帧(正向预测),16-31表示之前的15个B帧(双向预测)。 第二维大小为5,表示一个宏块在当前参考帧下的运动向量。第一项表示16x16的运动向量,剩余4项表示对应的8x8块的运动向量(如下图)。 ``` 0 1 2 3 4 +--------+-------+-------+-------+-------+ | | | 16x16 MV 8x8 partitions | | | V V V 5 +---+---+ 6 +---+---+ 7 +---+---+ 8 +---+---+ | 1 | 2 | | 9 |10 | |17 |18 | |25 |26 | +---+---+ +---+---+ +---+---+ +---+---+ | 3 | 4 | |11 |12 | |19 |20 | |27 |28 | +---+---+ +---+---+ +---+---+ +---+---+ | | | 8x8 partitions 8x8 partitions | | | V V V 13 +---+---+ 14 +---+---+ 15 +---+---+ 16 +---+---+ |21 |22 | |29 |30 | | 1 | 2 | | 9 |10 | +---+---+ +---+---+ +---+---+ +---+---+ |23 |24 | |31 |32 | | 3 | 4 | |11 |12 | +---+---+ +---+---+ +---+---+ +---+---+ | | | 8x8 partitions 8x8 partitions | | | V V V 21 +---+---+ 22 +---+---+ 23 +---+---+ 24 +---+---+ | 5 | 6 | |13 |14 | |21 |22 | |29 |30 | +---+---+ +---+---+ +---+---+ +---+---+ | 7 | 8 | |15 |16 | |23 |24 | |31 |32 | +---+---+ +---+---+ +---+---+ +---+---+ 8x8 partitions | V 25 +---+---+ 26 +---+---+ |17 |18 | |25 |26 | +---+---+ +---+---+ |19 |20 | |27 |28 | +---+---+ +---+---+ ``` 第三维大小为2,表示运动向量的x和y分量。每个元素都是一个16位整数(int16_t类型),表示运动向量在像素坐标系下的位移。 mvc数组用于记录运动估计的结果,包括各个参考帧各个块的运动向量,以便进行后续的运动补偿和重构。它的大小与编码器的配置有关,可以根据需求进行调整和优化。
question:What is power? What are three kinds of power postulated by Robert A Dahl? Please answer it with the know ledge of public administration and Please give concise answers
answer:Power is the ability to influence or control the behavior of others. It is often exercised in politics, public administration, and other spheres of social life. Robert A Dahl, a noted political scientist, postulated three kinds of power: 1. Coercive power: This is power that is exercised through the use of force or the threat of force. It is often associated with authoritarian regimes or situations of extreme conflict. 2. Economic power: This is power that is based on control over resources or wealth. It can be exercised by large corporations, wealthy individuals, or governments that control the economy. 3. Institutional power: This is power that is based on the ability to influence or control the workings of institutions such as governments, bureaucracies, or other formal organizations. It is often exercised through authority or rules and regulations.