ffmpeg实战教程（六）Android CMake实现解码（MP4转YUV）

在前面的文章中我们用ffmpeg在windows上实现了多种功能，下面系列的文章我们将移植到Android系统上实现。

我们将使用最新版：

最新版ffmpeg ffmpeg3.3
新版Android studio Android studio2.3
新版JNI编译方式 CMake

对于Android开发者或许对C/C++/JNI知识不够了解。

可以先看这里：

C语言小结 ：http://blog.csdn.net/king1425/article/details/70256764
C++小结（一） ： http://blog.csdn.net/king1425/article/details/70260091
JNI高阶知识总结 ： http://blog.csdn.net/king1425/article/details/71405131

下面我们开始实现今天的功能：

1.编译Android版ffmpeg并移植到Android studio中

看这里：
windows下编译最新版ffmpeg3.3-android，并通过CMake方式移植到Android studio2.3中
http://blog.csdn.net/king1425/article/details/70338674

2.复制一份第一步移植成功的的代码命名为：ffmpegandroiddecoder

3.删减部分代码验证无误，然后编写布局代码逻辑代码

点击codec按钮出现如上图列表界面则无误
下面是相关代码：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin">    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <Button            android:id="@+id/btn_codec"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_margin="2dp"            android:text="Codec"            android:textAllCaps="false" />    </LinearLayout>    <EditText        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_margin="12dp"        android:text="ws2.mp4"        android:id="@+id/editText1" />    <EditText        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_margin="12dp"        android:text="ws2.yuv"        android:id="@+id/editText2" />    <Button        android:text="开始解码为YUV"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/button" />    <ScrollView        android:layout_width="match_parent"        android:layout_height="wrap_content">        <TextView            android:id="@+id/tv_info"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:text="Hello World!" />    </ScrollView></LinearLayout>

package com.ws.ffmpegandroiddecoder;import android.os.Bundle;import android.os.Environment;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    // Used to load the 'native-lib' library on application startup.    static {        System.loadLibrary("native-lib");    }    private Button codec;    private TextView tv_info;    private EditText editText1,editText2;    private Button btnDecoder;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        init();    }    private void init() {        codec = (Button) findViewById(R.id.btn_codec);        tv_info= (TextView) findViewById(R.id.tv_info);        editText1 = (EditText) findViewById(R.id.editText1);        editText2 = (EditText) findViewById(R.id.editText2);        btnDecoder= (Button) findViewById(R.id.button);        codec.setOnClickListener(this);        btnDecoder.setOnClickListener(this);    }    @Override    public void onClick(View view) {        switch (view.getId()) {            case R.id.btn_codec:                tv_info.setText(avcodecinfo());                break;            case R.id.button:               startDecode();                break;            default:                break;        }    }    private void startDecode() {        String folderurl= Environment.getExternalStorageDirectory().getPath();        String inputurl=folderurl+"/"+editText1.getText().toString();        String outputurl=folderurl+"/"+editText2.getText().toString();        Log.e("ws-----------inputurl",inputurl);        Log.e("ws------------outputurl",outputurl);        decode(inputurl,outputurl);    }    public native String decode(String inputurl, String outputurl);    public native String avcodecinfo();}

4.实现native方法 decode(String inputurl, String outputurl)

对ffmeg API不了解的同学先看这里： ffmpeg源码简析（一）结构总览:http://blog.csdn.net/king1425/article/details/70597642

#include <jni.h>#include <string>extern "C"{#include <libavutil/log.h>#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libswscale/swscale.h>#include <libavutil/imgutils.h>#include <android/log.h>#define LOGE(format, ...)  __android_log_print(ANDROID_LOG_ERROR, "(>_<)", format, ##__VA_ARGS__)#define LOGI(format, ...)  __android_log_print(ANDROID_LOG_INFO,  "(^_^)", format, ##__VA_ARGS__)//Output FFmpeg's av_log()void custom_log(void *ptr, int level, const char* fmt, va_list vl){    FILE *fp=fopen("/storage/emulated/0/av_log.txt","a+");    if(fp){        vfprintf(fp,fmt,vl);        fflush(fp);        fclose(fp);    }}JNIEXPORT jint JNICALLJava_com_ws_ffmpegandroiddecoder_MainActivity_decode(        JNIEnv *env,        jobject , jstring input_jstr, jstring output_jstr) {    AVFormatContext *pFormatCtx;    int             i, videoindex;    AVCodecContext  *pCodecCtx;    AVCodec         *pCodec;    AVFrame *pFrame,*pFrameYUV;    uint8_t *out_buffer;    AVPacket *packet;    int y_size;    int ret, got_picture;    struct SwsContext *img_convert_ctx;    FILE *fp_yuv;    int frame_cnt;    clock_t time_start, time_finish;    double  time_duration = 0.0;    char input_str[500]={0};    char output_str[500]={0};    char info[1000]={0};    sprintf(input_str,"%s",env->GetStringUTFChars(input_jstr, NULL));    sprintf(output_str,"%s",env->GetStringUTFChars(output_jstr, NULL));    //FFmpeg av_log() callback    av_log_set_callback(custom_log);    av_register_all();    avformat_network_init();    pFormatCtx = avformat_alloc_context();    if(avformat_open_input(&pFormatCtx,input_str,NULL,NULL)!=0){        LOGE("Couldn't open input stream.\n");        return -1;    }    if(avformat_find_stream_info(pFormatCtx,NULL)<0){        LOGE("Couldn't find stream information.\n");        return -1;    }    videoindex=-1;    for(i=0; i<pFormatCtx->nb_streams; i++)        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){            videoindex=i;            break;        }    if(videoindex==-1){        LOGE("Couldn't find a video stream.\n");        return -1;    }    pCodecCtx=pFormatCtx->streams[videoindex]->codec;    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);    if(pCodec==NULL){        LOGE("Couldn't find Codec.\n");        return -1;    }    if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){        LOGE("Couldn't open codec.\n");        return -1;    }    pFrame=av_frame_alloc();    pFrameYUV=av_frame_alloc();    out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P,  pCodecCtx->width, pCodecCtx->height,1));    av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize,out_buffer,                         AV_PIX_FMT_YUV420P,pCodecCtx->width, pCodecCtx->height,1);    packet=(AVPacket *)av_malloc(sizeof(AVPacket));    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,                                     pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);    sprintf(info,   "[Input     ]%s\n", input_str);    sprintf(info, "%s[Output    ]%s\n",info,output_str);    sprintf(info, "%s[Format    ]%s\n",info, pFormatCtx->iformat->name);    sprintf(info, "%s[Codec     ]%s\n",info, pCodecCtx->codec->name);    sprintf(info, "%s[Resolution]%dx%d\n",info, pCodecCtx->width,pCodecCtx->height);    fp_yuv=fopen(output_str,"wb+");    if(fp_yuv==NULL){        printf("Cannot open output file.\n");        return -1;    }    frame_cnt=0;    time_start = clock();    while(av_read_frame(pFormatCtx, packet)>=0){        if(packet->stream_index==videoindex){            ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);            if(ret < 0){                LOGE("Decode Error.\n");                return -1;            }            if(got_picture){                sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,                          pFrameYUV->data, pFrameYUV->linesize);                y_size=pCodecCtx->width*pCodecCtx->height;                fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y                fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U                fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V                //Output info                char pictype_str[10]={0};                switch(pFrame->pict_type){                    case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;                    case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;                    case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;                    default:sprintf(pictype_str,"Other");break;                }                LOGI("Frame Index: %5d. Type:%s",frame_cnt,pictype_str);                frame_cnt++;            }        }        av_free_packet(packet);    }    //flush decoder    //FIX: Flush Frames remained in Codec    while (1) {        ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);        if (ret < 0)            break;        if (!got_picture)            break;        sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,                  pFrameYUV->data, pFrameYUV->linesize);        int y_size=pCodecCtx->width*pCodecCtx->height;        fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y        fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U        fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V        //Output info        char pictype_str[10]={0};        switch(pFrame->pict_type){            case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;            case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;            case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;            default:sprintf(pictype_str,"Other");break;        }        LOGI("Frame Index: %5d. Type:%s",frame_cnt,pictype_str);        frame_cnt++;    }    time_finish = clock();    time_duration=(double)(time_finish - time_start);    sprintf(info, "%s[Time      ]%fms\n",info,time_duration);    sprintf(info, "%s[Count     ]%d\n",info,frame_cnt);    sws_freeContext(img_convert_ctx);    fclose(fp_yuv);    av_frame_free(&pFrameYUV);    av_frame_free(&pFrame);    avcodec_close(pCodecCtx);    avformat_close_input(&pFormatCtx);    return 0;}jstringJava_com_ws_ffmpegandroiddecoder_MainActivity_avcodecinfo(        JNIEnv *env, jobject) {    char info[40000] = {0};    av_register_all();    AVCodec *c_temp = av_codec_next(NULL);    while (c_temp != NULL) {        if (c_temp->decode != NULL) {            sprintf(info, "%sdecode:", info);        } else {            sprintf(info, "%sencode:", info);        }        switch (c_temp->type) {            case AVMEDIA_TYPE_VIDEO:                sprintf(info, "%s(video):", info);                break;            case AVMEDIA_TYPE_AUDIO:                sprintf(info, "%s(audio):", info);                break;            default:                sprintf(info, "%s(other):", info);                break;        }        sprintf(info, "%s[%10s]\n", info, c_temp->name);        c_temp = c_temp->next;    }    return env->NewStringUTF(info);}}

5.拷贝ws.mp4到ＳＤ卡根目录，编译运行

GG编译报错(⊙o⊙)，不慌不慌，链接库报错，应该是CMakeLists.txt配置问题。

在之前一章配置的target_link_libraries基础上，更改如下即可

target_link_libraries( native-lib avutil-55 swresample-2 avcodec-57 avfilter-6 swscale-4 avdevice-57 avformat-57                       ${log-lib} )

6.点击开始解码按钮，然后看SD卡跟目录是否多了一个ws.yuv文件

OK~success
请大家务必对着源码观看博文，否则如盲人摸象(⊙o⊙)

源码：https://github.com/WangShuo1143368701/FFmpegAndroid/tree/master/ffmpegandroiddecoder