rate_ctl.c
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上传用户:hxb_1234
上传日期:2010-03-30
资源大小:8328k
文件大小:3k
源码类别:
VC书籍
开发平台:
Visual C++
- #include "stdio.h"
- extern FILE *ftrace;
- extern int max_quantizer, min_quantizer;
- typedef struct _rc_param_ {
- double quant;
- int rc_period;
- double target_rate;
- double average_rate;
- double reaction_rate;
- double average_delta;
- double reaction_delta;
- double reaction_ratio;
- } RC_Param;
- static RC_Param rc_param;
- void RateCtlInit(double quant, double target_rate,
- long rc_period, long rc_reaction_period, long rc_reaction_ratio)
- {
- #ifdef _RC_
- fprintf(ftrace, "Initializing Rate Control module:n");
- fprintf(ftrace, "Initial quantizer is %f.n", quant);
- fprintf(ftrace, "Target rate is %f bits per frame.n", target_rate);
- fprintf(ftrace, "RC averaging period is %d.n", rc_period);
- fprintf(ftrace, "RC reaction period is %d.n", rc_reaction_period);
- fprintf(ftrace, "RC reaction ratio is %d.n", rc_reaction_ratio);
- #endif
- rc_param.quant = quant;
- rc_param.rc_period = rc_period;
- rc_param.target_rate = target_rate;
- rc_param.reaction_ratio = rc_reaction_ratio;
- rc_param.average_delta = 1. / rc_period;
- rc_param.reaction_delta = 1. / rc_reaction_period;
- rc_param.average_rate = target_rate;
- rc_param.reaction_rate = target_rate;
- return;
- }
- int RateCtlGetQ(double MAD)
- {
- double quant;
- quant = rc_param.quant;
- return (int)(quant + 0.5);
- }
- void RateCtlUpdate(int current_frame)
- {
- double rate, delta, decay;
- double target, current_target;
- double median_quant;
- #ifdef _RC_
- fprintf(ftrace, "Quantizer is currently %f.n", rc_param.quant);
- fprintf(ftrace, "Current frame is %d bits long.n", current_frame);
- #endif
- rate = rc_param.average_rate;
- delta = rc_param.average_delta;
- decay = 1 - delta;
- rate = rate * decay + current_frame * delta;
- rc_param.average_rate = rate;
- target = rc_param.target_rate;
- if (rate > target) {
- current_target = target - (rate - target);
- if (current_target < target * 0.75) current_target = target * 0.75;
- } else {
- current_target = target;
- }
- #ifdef _RC_
- fprintf(ftrace, "Target rate is %f.n", target);
- fprintf(ftrace, "Average rate is %f.n", rate);
- fprintf(ftrace, "Target rate for current frame is %f.n", current_target);
- #endif
- rate = rc_param.reaction_rate;
- delta = rc_param.reaction_delta;
- decay = 1 - delta;
- rate = rate * decay + current_frame * delta;
- rc_param.reaction_rate = rate;
- median_quant = min_quantizer + (max_quantizer - min_quantizer) / 2;
- if (rate < current_target) rc_param.quant *=
- (1 - rc_param.reaction_delta * ((current_target - rate) / current_target / 0.20) );
- if (rc_param.quant < min_quantizer) rc_param.quant = min_quantizer;
- if (rate > current_target) {
- if (rc_param.quant > median_quant)
- rc_param.quant *= (1 + rc_param.reaction_delta / rc_param.reaction_ratio);
- else if (rate > current_target * 1.20) rc_param.quant *=
- (1 + rc_param.reaction_delta);
- else rc_param.quant *=
- (1 + rc_param.reaction_delta * ((rate - current_target) / current_target / 0.20) );
- }
- if (rc_param.quant > max_quantizer) rc_param.quant = max_quantizer;
- #ifdef _RC_
- fprintf(ftrace, "Reaction rate is %f.n", rate);
- fprintf(ftrace, "Quantizer is updated to %f.n", rc_param.quant);
- #endif
- return;
- }