android studio 2.2 cmake ffmpeg 簡單的播放器（這裡只有視頻解碼）

背景

在上一次的初次使用cmake編譯jni後，這次cmake文件再次升級。利用網上的代碼來編譯一個簡單的播放器。在cmake下重新編譯。特將過程分享給大家。

gradle 配置

apply plugin: 'com.android.application'

android {
    compileSdkVersion 22
    buildToolsVersion "23.0.1"

    //sourceSets.main.jni.srcDirs = ['jniLibs']

    defaultConfig {
        applicationId "jonesx.videoplayer"
        minSdkVersion 9
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        ndk {
            abiFilters 'armeabi'
        }
        externalNativeBuild {
            cmake {
                arguments '-DANDROID_TOOLCHAIN=clang','-DANDROID_STL=gnustl_static'
            }
        }


    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    externalNativeBuild {
        cmake {
            path "src/main/cpp/CMakeLists.txt"
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.android.support:design:22.2.1'
}

cmake 配置

整個工程的層級。
框架.png
cmake配置文件
CMakeLists.txt

cmake_minimum_required(VERSION 3.4.1)
set(lib_src_DIR ${CMAKE_SOURCE_DIR}/../jniLibs/${ANDROID_ABI})
include_directories(
        ${CMAKE_SOURCE_DIR}/include
)

add_library(avcodec-57_lib SHARED IMPORTED)
set_target_properties(avcodec-57_lib PROPERTIES IMPORTED_LOCATION
                             ${lib_src_DIR}/libavcodec-57.so)


add_library(avformat-57_lib SHARED IMPORTED)
set_target_properties(avformat-57_lib PROPERTIES IMPORTED_LOCATION
                        ${lib_src_DIR}/libavformat-57.so)

add_library(avutil-55_lib SHARED IMPORTED)
set_target_properties(avutil-55_lib PROPERTIES IMPORTED_LOCATION
                        ${lib_src_DIR}/libavutil-55.so)

add_library(swresample-2_lib SHARED IMPORTED)
set_target_properties(swresample-2_lib PROPERTIES IMPORTED_LOCATION
                        ${lib_src_DIR}/libswresample-2.so)

add_library(swscale-4_lib SHARED IMPORTED)
set_target_properties(swscale-4_lib PROPERTIES IMPORTED_LOCATION
                        ${lib_src_DIR}/libswscale-4.so)


# build application's shared lib
add_library(VideoPlayer SHARED
            VideoPlayer.cpp)

# Include libraries needed for VideoPlayer lib
target_link_libraries(VideoPlayer
log
android
avcodec-57_lib
avformat-57_lib
avutil-55_lib
swresample-2_lib
swscale-4_lib)

解釋下，這裡添加了依賴的so庫，注意路徑呀，我在這裡坑了半天，還有同事拯救了我。
add_library(swscale-4_lib SHARED IMPORTED)
set_target_properties(swscale-4_lib PROPERTIES IMPORTED_LOCATION
${lib_src_DIR}/libswscale-4.so)
最後，不要忘了，target_link_libraries中添加對應的庫。

VideoPlayer.cpp

//
// Created by Jonesx on 2016/3/20.
//

#include 
#include "VideoPlayer.h"
#include 
#include 
#include 

extern "C"{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};


#define  LOG_TAG    "videoplayer"
#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)

 JNIEXPORT jint JNICALL Java_jonesx_videoplayer_VideoPlayer_play
        (JNIEnv *env, jclass clazz, jobject surface) {
    LOGD("play");

    // sd卡中的視頻文件地址,可自行修改或者通過jni傳入
    char *file_name = "/sdcard/test.mp4";

    av_register_all();

    AVFormatContext *pFormatCtx = avformat_alloc_context();

    // Open video file
    if (avformat_open_input(&pFormatCtx, file_name, NULL, NULL) != 0) {

        LOGD("Couldn't open file:%s\n", file_name);
        return -1; // Couldn't open file
    }

    // Retrieve stream information
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        LOGD("Couldn't find stream information.");
        return -1;
    }

    // Find the first video stream
    int videoStream = -1, i;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO
            && videoStream < 0) {
            videoStream = i;
        }
    }
    if (videoStream == -1) {
        LOGD("Didn't find a video stream.");
        return -1; // Didn't find a video stream
    }

    // Get a pointer to the codec context for the video stream
    AVCodecContext *pCodecCtx = pFormatCtx->streams[videoStream]->codec;

    // Find the decoder for the video stream
    AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        LOGD("Codec not found.");
        return -1; // Codec not found
    }

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // 獲取native window
    ANativeWindow *nativeWindow = ANativeWindow_fromSurface(env, surface);

    // 獲取視頻寬高
    int videoWidth = pCodecCtx->width;
    int videoHeight = pCodecCtx->height;

    // 設置native window的buffer大小,可自動拉伸
    ANativeWindow_setBuffersGeometry(nativeWindow, videoWidth, videoHeight,
                                     WINDOW_FORMAT_RGBA_8888);
    ANativeWindow_Buffer windowBuffer;

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // Allocate video frame
    AVFrame *pFrame = av_frame_alloc();

    // 用於渲染
    AVFrame *pFrameRGBA = av_frame_alloc();
    if (pFrameRGBA == NULL || pFrame == NULL) {
        LOGD("Could not allocate video frame.");
        return -1;
    }

    // Determine required buffer size and allocate buffer
    // buffer中數據就是用於渲染的,且格式為RGBA
    int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height,
                                            1);
    uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, buffer, AV_PIX_FMT_RGBA,
                         pCodecCtx->width, pCodecCtx->height, 1);

    // 由於解碼出來的幀格式不是RGBA的,在渲染之前需要進行格式轉換
    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,
                                                pCodecCtx->height,
                                                pCodecCtx->pix_fmt,
                                                pCodecCtx->width,
                                                pCodecCtx->height,
                                                AV_PIX_FMT_RGBA,
                                                SWS_BILINEAR,
                                                NULL,
                                                NULL,
                                                NULL);

    int frameFinished;
    AVPacket packet;
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        // Is this a packet from the video stream?
        if (packet.stream_index == videoStream) {

            // Decode video frame
            avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);

            // 並不是decode一次就可解碼出一幀
            if (frameFinished) {

                // lock native window buffer
                ANativeWindow_lock(nativeWindow, &windowBuffer, 0);

                // 格式轉換
                sws_scale(sws_ctx, (uint8_t const *const *) pFrame->data,
                          pFrame->linesize, 0, pCodecCtx->height,
                          pFrameRGBA->data, pFrameRGBA->linesize);

                // 獲取stride
                uint8_t *dst = (uint8_t *) windowBuffer.bits;
                int dstStride = windowBuffer.stride * 4;
                uint8_t *src = (pFrameRGBA->data[0]);
                int srcStride = pFrameRGBA->linesize[0];

                // 由於window的stride和幀的stride不同,因此需要逐行復制
                int h;
                for (h = 0; h < videoHeight; h++) {
                    memcpy(dst + h * dstStride, src + h * srcStride, srcStride);
                }

                ANativeWindow_unlockAndPost(nativeWindow);
            }

        }
        av_packet_unref(&packet);
    }

    av_free(buffer);
    av_free(pFrameRGBA);

    // Free the YUV frame
    av_free(pFrame);

    // Close the codecs
    avcodec_close(pCodecCtx);

    // Close the video file
    avformat_close_input(&pFormatCtx);
    return 0;
}

這裡是正常的ffmpeg編解碼流程。參見雷神
這裡又有一個坑點，由於我使用的是c++ 編譯器clang，而ffmpeg的so庫均為c語言的，故需添加

extern "C"{

include "libavcodec/avcodec.h"

include "libavformat/avformat.h"

include "libswscale/swscale.h"

include "libavutil/imgutils.h"

};

如果這裡沒添加extern "C"{}，即不是按C語言編譯，就會存在undefined reference錯誤。下面是使用

VideoPlayer.java

package jonesx.videoplayer;

/**
 * Created by Jonesx on 2016/3/12.
 */
public class VideoPlayer {

    static {
        System.loadLibrary("VideoPlayer");
    }

    public static native int play(Object surface);
}

MainActivity.java

這裡使用的SufaceView來進行播放。

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    SurfaceHolder surfaceHolder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SurfaceView surfaceView = (SurfaceView) findViewById(R.id.surface_view);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);
    }


    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                VideoPlayer.play(surfaceHolder.getSurface());
            }
        }).start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }
}