ffmpeg重采样中swr_convert和swr_get_out

ffmpeg重采样中swr_convert和swr_get_out_samples的用法

在做mux的时候关于重采样可以用fifo，或者audiofifo做缓存处理，当做demux的时候关于重采样就可以用到上面的swr_convert和swr_get_out_samples做配合处理。先看下这两个函数的注释：

[cpp] view plain copy

/** Convert audio.
*
* in and in_count can be set to 0 to flush the last few samples out at the
* end.
*
* If more input is provided than output space, then the input will be buffered.
* You can avoid this buffering by using swr_get_out_samples() to retrieve an
* upper bound on the required number of output samples for the given number of
* input samples. Conversion will run directly without copying whenever possible.
*
* @param s allocated Swr context, with parameters set
* @param out output buffers, only the first one need be set in case of packed audio
* @param out_count amount of space available for output in samples per channel
* @param in input buffers, only the first one need to be set in case of packed audio
* @param in_count number of input samples available in one channel
*
* @return number of samples output per channel, negative value on error
*/
int swr_convert(struct SwrContext *s, uint8_t **out, int out_count,
const uint8_t **in , int in_count);

[cpp] view plain copy

/**
* Find an upper bound on the number of samples that the next swr_convert
* call will output, if called with in_samples of input samples. This
* depends on the internal state, and anything changing the internal state
* (like further swr_convert() calls) will may change the number of samples
* swr_get_out_samples() returns for the same number of input samples.
*
* @param in_samples number of input samples.
* @note any call to swr_inject_silence(), swr_convert(), swr_next_pts()
* or swr_set_compensation() invalidates this limit
* @note it is recommended to pass the correct available buffer size
* to all functions like swr_convert() even if swr_get_out_samples()
* indicates that less would be used.
* @returns an upper bound on the number of samples that the next swr_convert
* will output or a negative value to indicate an error
*/
int swr_get_out_samples(struct SwrContext *s, int in_samples);

就说如果传入的nb_samles大于了传出的nb_samplse则SwrContext中会有缓存，会导致内存一直暴涨，解决方法，可以看如下代码：

没有缓存的重采样这么处理：

[cpp] view plain copy

ret = swr_convert(swrcontext, pOutputFrame->data,pOutputFrame->nb_samples,
(const uint8_t**)pInputFrame->data,pInputFrame->nb_samples);

有缓存的代码这么处理：

[cpp] view plain copy

//如果还有缓存在swrcontext中,第二个参数要填写0才能获取到，缓存数据
int fifo_size = swr_get_out_samples(swrcontext,0);
if ( fifo_size >= pOutputFrame->nb_samples)
{
ret = swr_convert(swrcontext, pOutputFrame->data,pOutputFrame->nb_samples,
NULL,0);
}

即如果有缓存则先判断是否有缓存在里面，如果有则传入数据为空取出缓存。

ffmpeg重采样中swr_convert和swr_get_out_samples的用法相关推荐

@ini_get php,php中get_cfg_var()和ini_get()的用法及区别_php技巧_脚本之家
本文实例讲述了php中get_cfg_var()和ini_get()的用法及区别.分享给大家供大家参考.具体分析如下: php里get_cfg_var()和ini_get()都是取得配置值的函数,当你 ...
java7 javascript引擎_Java7中脚本引擎的一般用法，共三种方法获得JavaScript引擎：名称、文件扩展名、MIME类型 | 学步园...
package com.sino.java7; import javax.script.ScriptEngine; import javax.script.ScriptEngineManager; i ...
Oracle中INSTR和SUBSTR的用法
2019独角兽企业重金招聘Python工程师标准>>> Oracle中INSTR和SUBSTR的用法 Oracle中INSTR的用法: INSTR方法的格式为 INSTR(源字符串, ...
python threading join_Python中threading模块join函数用法实例分析
本文实例讲述了Python中threading模块join函数用法.分享给大家供大家参考.具体分析如下: join的作用是众所周知的,阻塞进程直到线程执行完毕.通用的做法是我们启动一批线程,最后joi ...
sklearn中cross_val_score、cross_val_predict的用法比较
sklearn中cross_val_score.cross_val_predict的用法比较_程大海的博客-CSDN博客_cross_val_predict
MapInfo中常用查询函数及用法
MapInfo中常用查询函数及用法: 函数用途语法备注图层中选点 Str$(obj)="point": Str(String)表示字符串:point表示点: 图层中选线 St ...
【Java学习笔记之二十九】Java中的equals和==的用法及区别
Java中的"equals"和"=="的用法及区别在初学Java时,可能会经常碰到下面的代码: 1 String str1 = new String(&quo ...
jquery中this与$(this)的用法区别.
2019独角兽企业重金招聘Python工程师标准>>> jquery中this与$(this)的用法区别.先看以下代码: $("#textbox").hover( ...
C#中static静态变量的用法
原文:C#中static静态变量的用法使用 static 修饰符声明属于类型本身而不是属于特定对象的静态成员static修饰符可用于类.字段.方法.属性.运算符.事件和构造函数,但不能用于索引器.析 ...

ffmpeg重采样中swr_convert和swr_get_out_samples的用法

ffmpeg重采样中swr_convert和swr_get_out_samples的用法相关推荐

最新文章

热门文章