Android FFmpeg视频播放
本文介绍了使用Native Window和FFmpeg在Android平台上实现音频解码播放功能的方法。
Native Window简介
从Android API level 9开始，Android NDK支持native代码直接操控native window的像素缓存。这无疑方便了我们直接在native层操控界面显示。
准备工作
- 搭建Android Studio NDK开发环境
- 编译FFmpeg库并将之集成到Android Studio中
- 在工程的AndroidManifest中加入权限
<!-- RECORD_AUDIO is needed to create an audio recorder -->
<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<!-- MODIFY_AUDIO_SETTINGS is needed to use audio effects such as environmental reverb -->
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
<!-- INTERNET is needed to use a URI-based audio player, depending on the URI -->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
FFmpeg视频解码播放
- 在native-lib中加入相关的库
extern "C"{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libswresample/swresample.h"
#include "libavutil/opt.h"
#include "libavutil/imgutils.h"
};
- 声明变量
static AVPacket *vPacket;
static AVFrame *vFrame, *pFrameRGBA;
static AVCodecContext *vCodecCtx;
struct SwsContext *img_convert_ctx;
static AVFormatContext *pFormatCtx;
ANativeWindow* nativeWindow;
ANativeWindow_Buffer windowBuffer;
uint8_t *v_out_buffer;
- 初始化FFmpeg，读取音频文件，创建解码器并解码播放
extern "C"
int
Java_cn_jx_audiotest_MainActivity_play(JNIEnv* env, jclass clazz, jstring url, jobject surface) {
int i;
AVCodec *vCodec;
char input_str[500]={0};
//读取输入的视频频文件地址
sprintf(input_str, "%s", env->GetStringUTFChars(url, NULL));
//初始化
av_register_all();
//分配一个AVFormatContext结构
pFormatCtx = avformat_alloc_context();
//打开文件
if(avformat_open_input(&pFormatCtx,input_str,NULL,NULL)!=0){
LOGD("Couldn't open input stream.\n");
return -1;
}
//查找文件的流信息
if(avformat_find_stream_info(pFormatCtx,NULL)<0){
LOGD("Couldn't find stream information.\n");
return -1;
}
//在流信息中找到视频流
int videoindex = -1;
for(i=0; i<pFormatCtx->nb_streams; i++) {
if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
videoindex = i;
break;
}
}
if(videoindex == -1){
LOGD("Couldn't find a video stream.\n");
return -1;
}
//获取相应视频流的解码器
vCodecCtx=pFormatCtx->streams[videoindex]->codec;
vCodec = avcodec_find_decoder(vCodecCtx->codec_id);
assert(vCodec != NULL);
//打开解码器
if(avcodec_open2(vCodecCtx, vCodec,NULL)<0){
LOGD("Couldn't open codec.\n");
return -1;
}
//获取界面传下来的surface
nativeWindow = ANativeWindow_fromSurface(env, surface);
if (0 == nativeWindow){
LOGD("Couldn't get native window from surface.\n");
return -1;
}
int width = vCodecCtx->width;
int height = vCodecCtx->height;
//分配一个帧指针，指向解码后的原始帧
vFrame = av_frame_alloc();
vPacket = (AVPacket *)av_malloc(sizeof(AVPacket));
pFrameRGBA = av_frame_alloc();
//绑定输出buffer
int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, width, height, 1);
v_out_buffer = (uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, v_out_buffer, AV_PIX_FMT_RGBA, width, height, 1);
img_convert_ctx = sws_getContext(width, height, vCodecCtx->pix_fmt,
width, height, AV_PIX_FMT_RGBA, SWS_BICUBIC, NULL, NULL, NULL);
if (0 > ANativeWindow_setBuffersGeometry(nativeWindow,width,height,WINDOW_FORMAT_RGBA_8888)){
LOGD("Couldn't set buffers geometry.\n");
ANativeWindow_release(nativeWindow);
return -1;
}
//读取帧
while(av_read_frame(pFormatCtx, vPacket)>=0){
if(vPacket->stream_index==videoindex){
//视频解码
int ret = avcodec_send_packet(vCodecCtx, vPacket);
if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
return -1;
ret = avcodec_receive_frame(vCodecCtx, vFrame);
if (ret < 0 && ret != AVERROR_EOF)
return -1;
//转化格式
sws_scale(img_convert_ctx, (const uint8_t* const*)vFrame->data, vFrame->linesize, 0, vCodecCtx->height,
pFrameRGBA->data, pFrameRGBA->linesize);
if (ANativeWindow_lock(nativeWindow, &windowBuffer, NULL) < 0) {
LOGD("cannot lock window");
} else {
//将图像绘制到界面上，注意这里pFrameRGBA一行的像素和windowBuffer一行的像素长度可能不一致
//需要转换好，否则可能花屏
uint8_t *dst = (uint8_t *) windowBuffer.bits;
for (int h = 0; h < height; h++)
{
memcpy(dst + h * windowBuffer.stride * 4,
v_out_buffer + h * pFrameRGBA->linesize[0],
pFrameRGBA->linesize[0]);
}
ANativeWindow_unlockAndPost(nativeWindow);
}
}
av_packet_unref(vPacket);
}
//释放内存
sws_freeContext(img_convert_ctx);
av_free(vPacket);
av_free(pFrameRGBA);
avcodec_close(vCodecCtx);
avformat_close_input(&pFormatCtx);
return 0;
}
JAVA层调用
我们在JAVA层定义好JNI接口，并按照顺序调用即可开始播放视频文件了。
- 加载so库，定义JNI接口
static {
System.loadLibrary("native-lib");
}
public native void play(String url, Surface surface);
- 界面创建一个SurfaceView，当界面准备好时传到native层供播放使用
surfaceView = (SurfaceView) findViewById(R.id.surface);
surfaceViewHolder = surfaceView.getHolder();
surfaceViewHolder.addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
//获取文件路径，这里将文件放置在手机根目录下
String folderurl = Environment.getExternalStorageDirectory().getPath();
String inputurl = folderurl+"/someVideo.mp4";
play(inputurl, surfaceViewHolder.getSurface());
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { }
@Override
public void surfaceDestroyed(SurfaceHolder holder) { }
});
注意点
- 将图像绘制到界面上时，pFrameRGBA一行的像素和windowBuffer一行的像素长度可能不一致，需要一行一行的复制，否则会花屏或者显示多个重叠的图像。
