Android音视频-FFmpeg视频解码

我们这一篇主要了解FFmpeg的解码API，把Mp4解码出yuv视频数据格式。其中的主要C代码参考自雷神查看，本实例的功能在上一节的一个应用里面。

在Java层声明native方法并调用

我这里第一次把在res/raw下面的mp4文件拷贝到了存储卡上面去然后调用native方法：

package com.lyman.ffmpeg_cmake;

import android.content.Context;
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.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class DecodeActivity extends AppCompatActivity {
    private static final String TAG = "DecodeActivity";
    private TextView mDecodeFilePathTV;
    private String mDecodeFilePath;
    private ProgressBar mProgressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_decode);
        if (!getMoveFile().exists()) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    copyFilesFromRaw(DecodeActivity.this, R.raw.i_am_you,
                            "i_am_you.mp4",
                            getExternalFilesDir(Environment.DIRECTORY_MOVIES).getAbsolutePath());
                }
            }).start();
        }
        mDecodeFilePathTV = findViewById(R.id.textView);
        mProgressBar = findViewById(R.id.progressBar);
    }

    public void onClickDecode(View view) {
        if (!getMoveFile().exists()) {
            Toast.makeText(this, "source file not exist", Toast.LENGTH_SHORT).show();
            return;
        }

        if (mDecodeFilePath == null) {
            mDecodeFilePath = getExternalFilesDir(Environment.DIRECTORY_MOVIES).getAbsolutePath()
                    + File.separator + "i_am_you.yuv";
        }

        mProgressBar.setVisibility(View.VISIBLE);
        new Thread(new Runnable() {
            @Override
            public void run() {
                decode(getMoveFile().getAbsolutePath(), mDecodeFilePath);
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        mProgressBar.setVisibility(View.GONE);
                        mDecodeFilePathTV.setText(mDecodeFilePath);
                    }
                });
            }
        }).start();

    }

    public native int decode(String inputUrl, String outputUrl);

    static {
//        System.loadLibrary("avutil-55");
//        System.loadLibrary("swresample-2");
//        System.loadLibrary("swscale-4");
//        System.loadLibrary("postproc-54");
//        System.loadLibrary("avcodec-57");
//        System.loadLibrary("avformat-57");
//        System.loadLibrary("avfilter-6");
//        System.loadLibrary("avdevice-57");
        System.loadLibrary("decode-lib");
    }

    private File getMoveFile() {
        File rootFile = getExternalFilesDir(Environment.DIRECTORY_MOVIES);
        // Create the storage directory if it does not exist
        if (!rootFile.exists()) {
            if (!rootFile.mkdirs()) {
                Log.d(TAG, "failed to create directory");
                return null;
            }
        }

        String fileName = "i_am_you.mp4";
        String path = rootFile.getAbsolutePath() + File.separator + fileName;
        return new File(path);
    }


    private void copyFilesFromRaw(Context context, int id, String fileName, String storagePath) {
        InputStream inputStream = context.getResources().openRawResource(id);
        File file = new File(storagePath);
        if (!file.exists()) {//如果文件夹不存在，则创建新的文件夹
            file.mkdirs();
        }
        readInputStream(storagePath + File.separator + fileName, inputStream);
    }

    /**
     * 读取输入流中的数据写入输出流
     *
     * @param storagePath 目标文件路径
     * @param inputStream 输入流
     */
    private void readInputStream(String storagePath, InputStream inputStream) {
        File file = new File(storagePath);
        try {
            if (!file.exists()) {
                // 1.建立通道对象
                FileOutputStream fos = new FileOutputStream(file);
                // 2.定义存储空间
                byte[] buffer = new byte[inputStream.available()];
                // 3.开始读文件
                int lenght = 0;
                while ((lenght = inputStream.read(buffer)) != -1) {// 循环从输入流读取buffer字节
                    // 将Buffer中的数据写到outputStream对象中
                    fos.write(buffer, 0, lenght);
                }
                fos.flush();// 刷新缓冲区
                // 4.关闭流
                fos.close();
                inputStream.close();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

实现底层c代码

这个c文件和native-lib.c处于同一个目录下面，命名为decode-lib.c

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
#include <stdio.h>

#include "include/libavcodec/avcodec.h"
#include "include/libavformat/avformat.h"
#include "include/libswscale/swscale.h"
#include "include/libavutil/log.h"

#include <libavutil/imgutils.h>


#ifdef ANDROID

#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__)
#else
#define LOGE(format, ...)  printf("(>_<) " format "\n", ##__VA_ARGS__)
#define LOGI(format, ...)  printf("(^_^) " format "\n", ##__VA_ARGS__)
#endif

/* Header for class com_lyman_ffmpeg_cmake_DecodeActivity */

#ifndef _Included_com_lyman_ffmpeg_cmake_DecodeActivity
#define _Included_com_lyman_ffmpeg_cmake_DecodeActivity
#ifdef __cplusplus
extern "C" {
#endif

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);
    }
}
/*
 * Class:     com_lyman_ffmpeg_cmake_DecodeActivity
 * Method:    decode
 * Signature: (Ljava/lang/String;Ljava/lang/String;)I
 */
JNIEXPORT jint JNICALL Java_com_lyman_ffmpeg_1cmake_DecodeActivity_decode
        (JNIEnv *env, jobject object, 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(env, input_jstr, NULL));
    sprintf(output_str, "%s", (*env)->GetStringUTFChars(env, 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;

}

#ifdef __cplusplus
}
#endif
#endif

配置CmakeLists.txt 文件

这里接着上一章节的配置下面进行配置，添加的配置代码如下：

add_library( # Sets the name of the library.
             decode-lib
             # Sets the library as a shared library.
             SHARED
             # Provides a relative path to your source file(s).
             src/main/cpp/decode-lib.c)
target_link_libraries(
                       native-lib
                       libavcodec-57
                       libavdevice-57
                       libavfilter-6
                       libavformat-57
                       libavutil-55
                       libpostproc-54
                       libswresample-2
                       libswscale-4
                       ${log-lib})

target_link_libraries(
                       decode-lib
                       libavcodec-57
                       libavdevice-57
                       libavfilter-6
                       libavformat-57
                       libavutil-55
                       libpostproc-54
                       libswresample-2
                       libswscale-4
                       ${log-lib})

这里趟了一个坑，刚开始的时候把新的decode-lib添加到了native-lib一起，对于target_link_libraries的理解错误了，以为是所有的so链接进来到这里配置，并不是这样，它是把第一个例如native-lib这个target链接可以使用的库文件，后面都是可以链接使用的库文件：详细参考：查看

---

OK到这里运行项目一起OK并且也和雷神一样解码出了yuv格式的视频数据。
项目完整代码：查看

参考链接：查看