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

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/King1425/article/details/71440809

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 JNICALL
Java_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;
}


jstring
Java_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