資源簡介
將G711轉化為PCM，然后再采用CDL2播放，在VS2010下測試通過，并附帶G711音頻測試文件
代碼片段和文件信息
/**
?*?最簡單的SDL2播放音頻的例子（SDL2播放PCM）
?*?Simplest?Audio?Play?SDL2?（SDL2?play?PCM）?
?*
?*?雷霄驊?Lei?Xiaohua
?*?leixiaohua1020@126.com
?*?中國傳媒大學/數字電視技術
?*?Communication?University?of?China?/?Digital?TV?Technology
?*?http://blog.csdn.net/leixiaohua1020
?*
?*?本程序使用SDL2播放PCM音頻采樣數據。SDL實際上是對底層繪圖
?*?API（Direct3D，OpenGL）的封裝，使用起來明顯簡單于直接調用底層
?*?API。
?*
?*?函數調用步驟如下：
?*
?*?[初始化]
?*?SDL_Init（）：初始化SDL。
?*?SDL_OpenAudio（）：根據參數（存儲于SDL_AudioSpec）打開音頻設備。
?*
?*?[循環播放數據]
?*?SDL_PauseAudio（）：播放音頻數據。
?*?SDL_Delay（）：延時等待播放完成。
?*
?*?This?software?plays?PCM?raw?audio?data?using?SDL2.
?*?SDL?is?a?wrapper?of?low-level?API?（DirectSound）.
?*?Use?SDL?is?much?easier?than?directly?call?these?low-level?API.
?*
?*?The?process?is?shown?as?follows:
?*
?*?[Init]
?*?SDL_Init（）:?Init?SDL.
?*?SDL_OpenAudio（）:?Opens?the?audio?device?with?the?desired?
?* parameters?（In?SDL_AudioSpec）.
?*
?*?[Loop?to?play?data]
?*?SDL_PauseAudio（）:?Play?Audio.
?*?SDL_Delay（）:?Wait?for?completetion?of?playback.
?*/
#include?
#include?
#include?
#include?
extern?“C“
{
#include?“sdl/SDL.h“
#include?
#include?
#include?
};
#define SIGN_BIT （0x80） /*?Sign?bit?for?a?A-law?byte.?*/
#define QUANT_MASK （0xf） /*?Quantization?field?mask.?*/
#define NSEGS （8） /*?Number?of?A-law?segments.?*/
#define SEG_SHIFT （4） /*?Left?shift?for?segment?number.?*/
#define SEG_MASK （0x70） /*?Segment?field?mask.?*/
#define BIAS （0x84） /*?Bias?for?linear?code.?*/
//Buffer:
//|-----------|-------------|
//chunk-------pos---len-----|
static??Uint8??*audio_chunk;?
static??Uint32??audio_len;?
static??Uint8??*audio_pos;?
int?ulaw2linear（?unsigned?char u_val）
{
int t;
/*?Complement?to?obtain?normal?u-law?value.?*/
u_val?=?~u_val;
/*
?*?Extract?and?bias?the?quantization?bits.?Then
?*?shift?up?by?the?segment?number?and?subtract?out?the?bias.
?*/
t?=?（（u_val?&?QUANT_MASK）?< t?<<=?（（unsigned）u_val?&?SEG_MASK）?>>?SEG_SHIFT;
return?（（u_val?&?SIGN_BIT）???（BIAS?-?t）?:?（t?-?BIAS））;
}
int?g711utoPCM（const?char*?g711file?const?char*?pcmfile）{
FILE?*?inpf;
FILE?*?outf;
inpf?=?fopen（g711file?“rb“）;
if（?inpf?==?NULL?）
{
printf（“G.711?file?cant?open\n“）;
return?1?;
}
outf?=?fopen（pcmfile?“wb“）;
unsigned?char*?Buf;
Buf?=?（unsigned?char*）calloc（1024?sizeof（char））;
int?nalLen?=?0;
while（!feof（inpf））
{
nalLen?=fread（Buf11inpf）;
int?iLinear?=?ulaw2linear（Buf[0]）;
fwrite（&iLinear12outf）;//寫到文件
}
if（inpf）
fclose（inpf）;
if（outf）
fclose（outf）;
printf（“The?pcm?audio?file?is?end?!?\n“）;
return?0;
}
/*?Audio?Callback
?*?The?audio?function?callback?takes?the?following?parameters:?
?*?stream:?A?pointer?to?the?audio?buffer?to?be?filled?
?*?len:?The?length?（in?bytes）?of?the?audio?buffer?
?*?
*/?
void??fill_audio（void?*udataUint8?*streamint?len）{?
//SDL?2.0
SDL_mem?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????文件?????????25??2014-06-05?19:35??AudioDecode&play—G711播放DEMO_20150806\.gitignore
?????文件???22247936??2015-07-09?16:34??AudioDecode&play—G711播放DEMO_20150806\avcodec-56.dll
?????文件????1380352??2015-06-19?12:41??AudioDecode&play—G711播放DEMO_20150806\avdevice-56.dll
?????文件????2386432??2015-06-19?12:41??AudioDecode&play—G711播放DEMO_20150806\avfilter-5.dll
?????文件????6021632??2015-06-19?12:41??AudioDecode&play—G711播放DEMO_20150806\avformat-56.dll
?????文件?????495104??2015-07-09?16:34??AudioDecode&play—G711播放DEMO_20150806\avutil-54.dll
?????文件???????1698??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\cl.command.1.tlog
?????文件??????30292??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\CL.read.1.tlog
?????文件???????1130??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\CL.write.1.tlog
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件??????????2??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件???????4140??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件???????8032??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件???????2464??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\li
?????文件???????1070??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\mt.command.1.tlog
?????文件????????970??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\mt.read.1.tlog
?????文件????????776??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\mt.write.1.tlog
?????文件???????1594??2015-08-06?09:25??AudioDecode&play—G711播放DEMO_20150806\Debug\rc.command.1.tlog
?????文件????????914??2015-08-06?09:25??AudioDecode&play—G711播放DEMO_20150806\Debug\rc.read.1.tlog
?????文件????????930??2015-08-06?09:25??AudioDecode&play—G711播放DEMO_20150806\Debug\rc.write.1.tlog
?????文件??????31232??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.exe
?????文件????????658??2015-08-06?08:54??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.exe.em
?????文件????????724??2015-08-06?09:25??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.exe.em
?????文件????????616??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.exe.intermediate.manifest
?????文件?????385072??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.ilk
?????文件?????????73??2015-08-06?09:36??AudioDecode&play—G711播放DEMO_20150806\Debug\simplest_audio_play_sdl2.lastbuildstate
............此處省略205個文件信息
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