一、重采样流程
重采样(解码音频数据之后格式不可以直接播放，需要重采样，类似图像的像素转换)
1.分配上下文
2.设置参数（分为（前几个是）输出格式和（后几个）输入格式，两个相对应的） 可以通过改变样本率来改变音频的播放速度，但是会失帧。
3.初始化
4.开始转换
二、相关函数说明
1、 SwrContext *actx = swr_alloc(); //进行分配和初始化
2、 actx = swr_alloc_set_opts(actx,
av_get_default_channel_layout(2), //输出标准（左右声道)
AV_SAMPLE_FMT_S16, //样本格式：float 、s16、s24
ac->sample_rate,//样本率，一般使用原始的
av_get_default_channel_layout(ac->channels),
ac->sample_fmt,
ac->sample_rate,
0,0 );
3、 re = swr_init(actx);
4、 //将一帧一帧的音频进行重采样 （参数对应输入输出）
int len = swr_convert(actx, //重采样上下文
out, //输出的指针
frame->nb_samples, //样本数量：单声道的样本数量
(const uint8_t**)frame->data,//解码出来的data
frame->nb_samples);//单通的样本数量
代码说明：
#include <jni.h>
#include <string>
#include <android/log.h>
#include <android/native_window.h>
#include <android/native_window_jni.h>
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,"testff",__VA_ARGS__) extern "C"{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavcodec/jni.h>
#include <libswscale/swscale.h>
#include <libswresample/swresample.h>
}
#include<iostream>
using namespace std; static double r2d(AVRational r)
{
return r.num==||r.den == ? :(double)r.num/(double)r.den;
} //当前时间戳 clock
long long GetNowMs()
{
struct timeval tv;
gettimeofday(&tv,NULL);
int sec = tv.tv_sec%;
long long t = sec*+tv.tv_usec/;
return t;
}
extern "C"
JNIEXPORT
jint JNI_OnLoad(JavaVM *vm,void *res)
{
av_jni_set_java_vm(vm,);
return JNI_VERSION_1_4;
} extern "C"
JNIEXPORT jstring
JNICALL
Java_aplay_testffmpeg_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++ ";
// TODO
hello += avcodec_configuration();
return env->NewStringUTF(hello.c_str());
} extern "C"
JNIEXPORT void JNICALL
Java_aplay_testffmpeg_XPlay_Open(JNIEnv *env, jobject instance, jstring url_, jobject surface) {
const char *path = env->GetStringUTFChars(url_, ); //初始化解封装
av_register_all();
//初始化网络
avformat_network_init(); avcodec_register_all(); //打开文件
AVFormatContext *ic = NULL;
//char path[] = "/sdcard/video.flv";
int re = avformat_open_input(&ic,path,,);
if(re != )
{
LOGW("avformat_open_input failed!:%s",av_err2str(re));
return;
}
LOGW("avformat_open_input %s success!",path);
//获取流信息
re = avformat_find_stream_info(ic,);
if(re != )
{
LOGW("avformat_find_stream_info failed!");
}
LOGW("duration = %lld nb_streams = %d",ic->duration,ic->nb_streams); int fps = ;
int videoStream = ;
int audioStream = ; for(int i = ; i < ic->nb_streams; i++)
{
AVStream *as = ic->streams[i];
if(as->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
{
LOGW("视频数据");
videoStream = i;
fps = r2d(as->avg_frame_rate); LOGW("fps = %d,width=%d height=%d codeid=%d pixformat=%d",fps,
as->codecpar->width,
as->codecpar->height,
as->codecpar->codec_id,
as->codecpar->format
);
}
else if(as->codecpar->codec_type ==AVMEDIA_TYPE_AUDIO )
{
LOGW("音频数据");
audioStream = i;
LOGW("sample_rate=%d channels=%d sample_format=%d",
as->codecpar->sample_rate,
as->codecpar->channels,
as->codecpar->format
);
}
}
//ic->streams[videoStream];
//获取音频流信息
audioStream = av_find_best_stream(ic,AVMEDIA_TYPE_AUDIO,-,-,NULL,);
LOGW("av_find_best_stream audioStream = %d",audioStream);
//////////////////////////////////////////////////////////
//打开视频解码器
//软解码器
AVCodec *codec = avcodec_find_decoder(ic->streams[videoStream]->codecpar->codec_id);
//硬解码
codec = avcodec_find_decoder_by_name("h264_mediacodec");
if(!codec)
{
LOGW("avcodec_find failed!");
return;
}
//解码器初始化
AVCodecContext *vc = avcodec_alloc_context3(codec);
avcodec_parameters_to_context(vc,ic->streams[videoStream]->codecpar); vc->thread_count = ;
//打开解码器
re = avcodec_open2(vc,,);
//vc->time_base = ic->streams[videoStream]->time_base;
LOGW("vc timebase = %d/ %d",vc->time_base.num,vc->time_base.den);
if(re != )
{
LOGW("avcodec_open2 video failed!");
return;
} //////////////////////////////////////////////////////////
//打开音频解码器
//软解码器
AVCodec *acodec = avcodec_find_decoder(ic->streams[audioStream]->codecpar->codec_id);
//硬解码
//codec = avcodec_find_decoder_by_name("h264_mediacodec");
if(!acodec)
{
LOGW("avcodec_find failed!");
return;
}
//音频解码器初始化
AVCodecContext *ac = avcodec_alloc_context3(acodec);
avcodec_parameters_to_context(ac,ic->streams[audioStream]->codecpar);
ac->thread_count = ;
//打开解码器
re = avcodec_open2(ac,,);
if(re != )
{
LOGW("avcodec_open2 audio failed!");
return;
}
//读取帧数据
AVPacket *pkt = av_packet_alloc();
AVFrame *frame = av_frame_alloc();
long long start = GetNowMs();
int frameCount = ; //初始化像素格式转换的上下文
SwsContext *vctx = NULL;
int outWidth = ;
int outHeight = ;
char *rgb = new char[**];
char *pcm = new char[**]; //音频重采样上下文初始化
SwrContext *actx = swr_alloc();
actx = swr_alloc_set_opts(actx,
av_get_default_channel_layout(),
AV_SAMPLE_FMT_S16,ac->sample_rate,
av_get_default_channel_layout(ac->channels),
ac->sample_fmt,ac->sample_rate,
, );
re = swr_init(actx);
if(re != )
{
LOGW("swr_init failed!");
}
else
{
LOGW("swr_init success!");
} //显示窗口初始化
ANativeWindow *nwin = ANativeWindow_fromSurface(env,surface);
ANativeWindow_setBuffersGeometry(nwin,outWidth,outHeight,WINDOW_FORMAT_RGBA_8888);
ANativeWindow_Buffer wbuf; for(;;)
{
//超过三秒
if(GetNowMs() - start >= )
{
LOGW("now decode fps is %d",frameCount/);
start = GetNowMs();
frameCount = ;
} int re = av_read_frame(ic,pkt);
if(re != )
{ LOGW("读取到结尾处!");
int pos = * r2d(ic->streams[videoStream]->time_base);
av_seek_frame(ic,videoStream,pos,AVSEEK_FLAG_BACKWARD|AVSEEK_FLAG_FRAME );
continue;
} AVCodecContext *cc = vc;
if(pkt->stream_index == audioStream)
cc=ac; //发送到线程中解码
re = avcodec_send_packet(cc,pkt);
//清理
int p = pkt->pts;
av_packet_unref(pkt); if(re != )
{
LOGW("avcodec_send_packet failed!");
continue;
} for(;;)
{
re = avcodec_receive_frame(cc,frame);
if(re !=)
{
//LOGW("avcodec_receive_frame failed!");
break;
}
//LOGW("avcodec_receive_frame %lld",frame->pts);
//如果是视频帧
if(cc == vc)
{
frameCount++;
vctx = sws_getCachedContext(vctx,
frame->width,
frame->height,
(AVPixelFormat)frame->format,
outWidth,
outHeight,
AV_PIX_FMT_RGBA,
SWS_FAST_BILINEAR,
,,
);
if(!vctx)
{
LOGW("sws_getCachedContext failed!");
}
else
{
uint8_t *data[AV_NUM_DATA_POINTERS] = {};
data[] =(uint8_t *)rgb;
int lines[AV_NUM_DATA_POINTERS] = {};
lines[] = outWidth * ;
int h = sws_scale(vctx,
(const uint8_t **)frame->data,
frame->linesize,,
frame->height,
data,lines);
LOGW("sws_scale = %d",h);
if(h > )
{
ANativeWindow_lock(nwin,&wbuf,);
uint8_t *dst = (uint8_t*)wbuf.bits;
memcpy(dst,rgb,outWidth*outHeight*);
ANativeWindow_unlockAndPost(nwin);
}
} }
else //音频
{
uint8_t *out[] = {};
out[] = (uint8_t*) pcm; //音频重采样
int len = swr_convert(actx,out,
frame->nb_samples,
(const uint8_t**)frame->data,
frame->nb_samples);
LOGW("swr_convert = %d",len);
} } ////////////////////// }
delete rgb;
delete pcm; //关闭上下文
avformat_close_input(&ic); env->ReleaseStringUTFChars(url_, path);
}