1.命令行播放
songlin@feng-sl ~/audio/pcm_to_wav master ± ffplay 44100-2-f32le.wav
ffplay version 4.3.2 Copyright (c) 2003-2021 the FFmpeg developers
built with Apple clang version 12.0.0 (clang-1200.0.32.29)
configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.2_4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
Input #0, wav, from '44100-2-f32le.wav':
Duration: 00:00:17.36, bitrate: 2822 kb/s
Stream #0:0: Audio: pcm_f32le ([3][0][0][0] / 0x0003), 44100 Hz, 2 channels, flt, 2822 kb/s
5.56 M-A: 0.000 fd= 0 aq= 356KB vq= 0KB sq= 0B f=0/0
从终端输出可以看到已经成功播放了。从前面得知WAV文件是对PCM文件的深一层封装，里面已经包含了声道数，采样率，采样格式等参数，所以可以直接使用ffplay命令播放，不需要想PCM 这样的裸数据增加额外的参数
2.程序代码播放
- mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include
#include "playthread.h"
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
PlayThread *_playThread = nullptr;
};
#endif // MAINWINDOW_H
- mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include
#include
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow) {
ui->setupUi(this);
}
MainWindow::~MainWindow() {
delete ui;
}
void showVersion() {
SDL_version version;
SDL_VERSION(&version);
qDebug() << version.major << version.minor << version.patch;
}
void MainWindow::on_playButton_clicked() {
if (_playThread) { // 停止播放
_playThread->requestInterruption();
_playThread = nullptr;
ui->playButton->setText("开始播放");
} else { // 开始播放
_playThread = new PlayThread(this);
_playThread->start();
// 监听线程的结束
connect(_playThread, &PlayThread::finished,
[this]() {
_playThread = nullptr;
ui->playButton->setText("开始播放");
});
ui->playButton->setText("停止播放");
}
}
- playthread.h
#ifndef PLAYTHREAD_H
#define PLAYTHREAD_H
#include
class PlayThread : public QThread
{
public:
explicit PlayThread(QObject *parent = nullptr);
~PlayThread();
private:
void run();
};
#endif // PLAYTHREAD_H
- playthread.cpp
#include "playthread.h"
#include
#include
#include
#define FILENAME "/Users/songlin/audio/pcm_to_wav/44100-2-f32le.wav"
typedef struct{
int len = 0;
int pullLen = 0;
Uint8 *data = nullptr;
} AudioBuffer;
PlayThread::PlayThread(QObject *parent) : QThread(parent){
connect(this,&PlayThread::finished,
this,&PlayThread::deleteLater);
}
PlayThread::~PlayThread(){
disconnect();
requestInterruption();
quit();
wait();
qDebug() << this << "析构了";
}
/*音频回调方法，会多次回调
* *
* userdata:需要往stream中填充PCM数据
* stream 流数据
* len 希望填充的大小(samples * format *channels / 8)
**/
void pull_audio_data(void *userdata,Uint8 *stream,int len){
qDebug() << "pull_audio_data" << len;
//清空stream(静音处理)
SDL_memset(stream,0,len);
//取出AudioBuffer
AudioBuffer *buffer = (AudioBuffer *)userdata;
//文件数据还没有准备好
if(buffer->len <= 0) return;
//获取len，bufferLen的最小值(确保获取到数据完整和安全)
buffer->pullLen = (len > buffer->len) ? buffer->len : len;
//填充数据
SDL_MixAudio(stream,buffer->data,buffer->pullLen,SDL_MIX_MAXVOLUME);
buffer->data += buffer->pullLen;
buffer->len -= buffer->pullLen;
}
/*
* SDL 播放音频有两种模式
* Push 推：【程序】主动推送数据给音频设备
* Pull 拉：【音频设备】主动向【程序】拉去数据
* */
void PlayThread::run(){
//初始化Audio子系统
if(SDL_Init(SDL_INIT_AUDIO)){
qDebug() << "SDL_Init error" << SDL_GetError();
return;
}
//加载wav文件
SDL_AudioSpec spec;
//指向PCM数据
Uint8 *data = nullptr;
//PCM数据的长度
Uint32 len = 0;
if(!SDL_LoadWAV(FILENAME,&spec,&data,&len)){
qDebug() << "SDL_LoadWAV error" << SDL_GetError();
//清除所有的子系统
SDL_Quit();
return;
}
//音频缓冲区的样本数量
spec.samples = 1024;
//设置回调
spec.callback = pull_audio_data;
//设置userdata
AudioBuffer buffer;
buffer.data = data;
buffer.len = len;
spec.userdata = &buffer;
//打开设备
if(SDL_OpenAudio(&spec,nullptr)){
qDebug() << "SDL_OpenAudio error" << SDL_GetError();
//清除所有的子系统
SDL_Quit();
return;
}
//开始播放(0是取消暂停)
SDL_PauseAudio(0);
//配置初始化参数
int sampleSize = SDL_AUDIO_BITSIZE(spec.format);
int bytesPerSample = (sampleSize * spec.channels) >> 3;
//存放从文件中读取的数据
while (!isInterruptionRequested()) {
//主要从文件中读取的音频数据还没有填充完毕，则跳过
if(buffer.len > 0) continue;
//来到这里说明文件数据已经读取完毕
if(buffer.len <= 0){
//剩余的样本数量
int samples = buffer.pullLen / bytesPerSample;
int ms = samples * 1000 / spec.freq;
SDL_Delay(ms);
break;
}
}
//释放WAV文件数据
SDL_FreeWAV(data);
//关闭设备
SDL_CloseAudio();
//清除所有的子系统
SDL_Quit();
}
2.1 方法解说
初始化子系统
// 初始化Audio子系统
if (SDL_Init(SDL_INIT_AUDIO)) {
qDebug() << "SDL_Init error:" << SDL_GetError();
return;
}
加载WAV
// 存放WAV的PCM数据和数据长度
typedef struct {
Uint32 len = 0;
int pullLen = 0;
Uint8 *data = nullptr;
} AudioBuffer;
// WAV中的PCM数据
Uint8 *data;
// WAV中的PCM数据大小（字节）
Uint32 len;
// 音频参数
SDL_AudioSpec spec;
// 加载wav文件
if (!SDL_LoadWAV(FILENAME, &spec, &data, &len)) {
qDebug() << "SDL_LoadWAV error:" << SDL_GetError();
// 清除所有的子系统
SDL_Quit();
return;
}
// 回调
spec.callback = pull_audio_data;
// 传递给回调函数的userdata
AudioBuffer buffer;
buffer.len = len;
buffer.data = data;
spec.userdata = &buffer;
打开音频设备
// 打开设备
if (SDL_OpenAudio(&spec, nullptr)) {
qDebug() << "SDL_OpenAudio error:" << SDL_GetError();
// 释放文件数据
SDL_FreeWAV(data);
// 清除所有的子系统
SDL_Quit();
return;
}
播放音乐
// 开始播放（0是取消暂停）
SDL_PauseAudio(0);
while (!isInterruptionRequested()) {
if (buffer.len > 0) continue;
// 每一个样本的大小
int size = spec.channels * SDL_AUDIO_BITSIZE(spec.format) / 8;
// 最后一次播放的样本数量
int samples = buffer.pullLen / size;
// 最后一次播放的时长
int ms = samples * 1000 / spec.freq;
SDL_Delay(ms);
break;
}
播放回调函数
// 等待音频设备回调(会回调多次)
void pull_audio_data(void *userdata,
// 需要往stream中填充PCM数据
Uint8 *stream,
// 希望填充的大小(samples * format * channels / 8)
int len
) {
// 清空stream
SDL_memset(stream, 0, len);
AudioBuffer *buffer = (AudioBuffer *) userdata;
// 文件数据还没准备好
if (buffer->len <= 0) return;
// 取len、bufferLen的最小值
buffer->pullLen = (len > (int) buffer->len) ? buffer->len : len;
// 填充数据
SDL_MixAudio(stream,
buffer->data,
buffer->pullLen,
SDL_MIX_MAXVOLUME);
buffer->data += buffer->pullLen;
buffer->len -= buffer->pullLen;
}
释放内存资源
// 释放WAV文件数据
SDL_FreeWAV(data);
// 关闭设备
SDL_CloseAudio();
// 清除所有的子系统
SDL_Quit();