Android多媒体开发（3）————使用Android(安卓)NKD编译havlenapetr-FFMpeg-7c27aa2

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1、

使用NDK去编译官方的FFmpeg原版的话，还得自己实现JNI层与java层，工程量比较大。所以移植FFmpeg到Android平台时，可以移植一些已经实现JNI与JAVA层的开源项目，毕竟软件行业从来都是站在巨人肩膀上发展的。

2、移植havlenapetr/FFMpeg

havlenapetr的开源项目是比较出名的一个FFmpeg工程，很多Android多媒体项目都是在此基础上面修改的。

下载地址：https://github.com/havlenapetr/FFMpeg

可以直接ZIP包：https://github.com/havlenapetr/FFMpeg/zipball/debug

或者通过git方式下载，新建一个目录，然后在linux的终端下执行，当然了，你要事情安装git的相关工具

3、利用NDK编译生成so库

下载后直接在havlenapetr-FFMpeg-7c27aa2的顶级目录下执行

是可以编译通过的，不会提示任何error。

关于如何利用NDK编译，可以参考我之前的博文：http://blog.csdn.net/conowen/article/details/7518870

4、导入java工程，实现播放

然后把在eclipse里面，把havlenapetr-FFMpeg-7c27aa2这个项目import进来，就可以播放视频了。

4.1、需要注意的是：这个版本的havlenapetr FFmpeg工程只能在Android 2.2上面运行，因为havlenapetr采用的是音视频直接在JNI层输入。可以注意到havlenapetr-FFMpeg-7c27aa2目录下有prebuilt这样一个目录，此目录下有Android 2.2版本的libjniaudio.so和libjnivideo.so两个库文件。

4.2、Android版本不同导致不能播放：

havlenapetr的FFmpeg项目音视频输出如下

音频：采用Android底层的audiotrack输出。

视频：在FFmpeg解码之后，得到YUV信号，然后转换成RGB信号，最终通过Android底层的surface输出。

提示：可以移植SDL开源库实现音视频输出，因为SDL的视频输出机制是通过OPenGL呈现画面，这样就可以兼容所有的Android平台。

但是问题就来了，Android每个版本的framework都是不大一样的，所以要在底层使用Android的audiotrack和surface来输入音视频信号，就要在相应版本的Android源代码中，重新编译生成libjniaudio.so和libjnivideo.so两个库文件了。

5、编译havlenapetr FFmpeg工程Android 2.3版本的libjniaudio.so和libjnivideo.so

首先要明白一点，Android的官方源代码编译之后，是不会生成libjniaudio.so和libjnivideo.so的。所以要自己添加audiotrack.cpp、surface.cpp和Android.mk文件到Android源代码里面编译生成。（每次编译libjniaudio.so和libjnivideo.so都要重新编译这个Android源代码，时间比较长。）

5.1下载audio与video文件夹

可以在https://github.com/havlenapetr/android_frameworks_base下载audiotrack.cpp、surface.cpp和Android.mk，注意要选择正确的branch（分支）

froyo---->Android 2.2

gingerbread---->Android 2.3

ICS---->Android 4.0

5.2、编译Android系统源代码

下载之后，然后找到里面的native文件夹，把里面的audio和video文件夹拖进Android源代码的frameworks/base/native目录下。

需要注意的一点是：

gingerbread下载之后，里面是没有audio和video文件夹的，但是可以用froyo版本的audio和video文件夹。（也就是下载gingerbread感觉也没啥用Orz~~~）

但是我们可以使用froyo的audio和video文件夹，编译Android源代码是可以成功通过的，ndk-build也可以通过，但是在Android的java工程里面使用就会有以下错误信息。

加载库时，找不到mSruface类
修改方法是：
将surface.cpp中mSurface改为 mNativeSurface ,然后重新编译即可。当然了，你也可以用ICS的surface.cpp文件，这个版本是没有问题的。

另外编译havlenapetr FFmpeg工程Android 4.0版本的libjniaudio.so和libjnivideo.so与上面步骤差不多。

/************************************************************************/

附上我所使用的audio与video(来源havlenapetr的项目)

video/jni/surface.cpp(注意目录结构)

/* * Copyright (C) 2012 Havlena Petr * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */#define LOG_TAG "ASurface"#include <utils/Log.h>#include <surfaceflinger/Surface.h>#include <SkCanvas.h>#include <SkBitmap.h>#include <SkMatrix.h>#include <SkRect.h>#include "surface.h"#define CHECK(val) \    if(!val) { \        LOGE("%s [%i]: NULL pointer exception!", __func__, __LINE__); \        return -1; \    }#define SDK_VERSION_FROYO 8using namespace android;typedef struct ASurface {    /* our private members here */    Surface* surface;    SkCanvas canvas;} ASurface;static Surface* getNativeSurface(JNIEnv* env, jobject jsurface, int sdkVersion) {    /* we know jsurface is a valid local ref, so use it */    jclass clazz = env->GetObjectClass(jsurface);    if(clazz == NULL) {        LOGE("Can't find surface class!");        return NULL;    }    jfieldID field_surface = env->GetFieldID(clazz,                                             sdkVersion > SDK_VERSION_FROYO ? "mNativeSurface" : "mSurface",                                             "I");    if(field_surface == NULL) {        LOGE("Can't find native surface field!");        return NULL;    }    return (Surface *) env->GetIntField(jsurface, field_surface);}int ASurface_init(JNIEnv* env, jobject jsurface, int sdkVersion, ASurface** aSurface) {    if(!env || jsurface == NULL) {        LOGE("JNIEnv or jsurface obj is NULL!");        return -1;    }    Surface* surface = getNativeSurface(env, jsurface, sdkVersion);    if(!surface) {        LOGE("Can't obtain native surface!");        return -1;    }    *aSurface = (ASurface *) malloc(sizeof(ASurface));    (*aSurface)->surface = surface;    return 0;}void ASurface_deinit(ASurface** aSurface) {    free(*aSurface);    *aSurface = NULL;}int ASurface_lock(ASurface* aSurface, AndroidSurfaceInfo* info) {    static Surface::SurfaceInfo surfaceInfo;    CHECK(aSurface);    CHECK(aSurface->surface);    Surface* surface = aSurface->surface;    if (!surface->isValid()) {        LOGE("Native surface isn't valid!");        return -1;    }    int res = surface->lock(&surfaceInfo);    if(res < 0) {        LOGE("Can't lock native surface!");        return res;    }    info->w = surfaceInfo.w;    info->h = surfaceInfo.h;    info->s = surfaceInfo.s;    info->usage = surfaceInfo.usage;    info->format = surfaceInfo.format;    info->bits = surfaceInfo.bits;    return 0;}static SkBitmap::ConfigconvertPixelFormat(APixelFormat format) {    switch(format) {        case ANDROID_PIXEL_FORMAT_RGBX_8888:        case ANDROID_PIXEL_FORMAT_RGBA_8888:            return SkBitmap::kARGB_8888_Config;        case ANDROID_PIXEL_FORMAT_RGB_565:            return SkBitmap::kRGB_565_Config;    }    return SkBitmap::kNo_Config;}static voidinitBitmap(SkBitmap& bitmap, AndroidSurfaceInfo* info) {    bitmap.setConfig(convertPixelFormat(info->format), info->w, info->h);    if (info->format == ANDROID_PIXEL_FORMAT_RGBX_8888) {        bitmap.setIsOpaque(true);    }    if (info->w > 0 && info->h > 0) {        bitmap.setPixels(info->bits);    } else {        // be safe with an empty bitmap.        bitmap.setPixels(NULL);    }}void ASurface_scaleToFullScreen(ASurface* aSurface, AndroidSurfaceInfo* src, AndroidSurfaceInfo* dst) {    SkBitmap    srcBitmap;    SkBitmap    dstBitmap;    SkMatrix    matrix;    initBitmap(srcBitmap, src);    initBitmap(dstBitmap, dst);    matrix.setRectToRect(SkRect::MakeWH(srcBitmap.width(), srcBitmap.height()),                         SkRect::MakeWH(dstBitmap.width(), dstBitmap.height()),                         SkMatrix::kFill_ScaleToFit);    aSurface->canvas.setBitmapDevice(dstBitmap);    aSurface->canvas.drawBitmapMatrix(srcBitmap, matrix);}int ASurface_rotate(ASurface* aSurface, AndroidSurfaceInfo* src, uint32_t degrees) {    SkBitmap    bitmap;    CHECK(aSurface);    CHECK(src);    initBitmap(bitmap, src);    aSurface->canvas.setBitmapDevice(bitmap);    return aSurface->canvas.rotate(SkScalar(degrees)) ? 0 : -1;}int ASurface_unlockAndPost(ASurface* aSurface) {    CHECK(aSurface);    CHECK(aSurface->surface);    return aSurface->surface->unlockAndPost();}

video/jni/Android.mk(注意目录结构)

/audio/jni/audiotrack.cpp(注意目录结构)

/* * Copyright (C) 2009 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */#include <android/audiotrack.h>#include <utils/Log.h>#include <media/AudioTrack.h>#include <media/AudioSystem.h>#include <utils/Errors.h>#include <binder/MemoryHeapBase.h>#include <binder/MemoryBase.h>#define TAG "AudioTrackWrapper"using namespace android;//struct audiotrack_fields_t {static AudioTrack*track;//sp<MemoryHeapBase>memHeap;//sp<MemoryBase>memBase;//};//static struct audiotrack_fields_t audio;static AudioTrack* getNativeAudioTrack(JNIEnv* env, jobject jaudioTrack) {jclass clazz = env->FindClass("android/media/AudioTrack");jfieldID field_track = env->GetFieldID(clazz, "mNativeTrackInJavaObj", "I");if(field_track == NULL) {return NULL;}return (AudioTrack *) env->GetIntField(jaudioTrack, field_track);}/*static bool allocSharedMem(int sizeInBytes) {memHeap = new MemoryHeapBase(sizeInBytes);if (memHeap->getHeapID() < 0) {return false;}memBase = new MemoryBase(memHeap, 0, sizeInBytes);return true;}*/int AndroidAudioTrack_register() {__android_log_print(ANDROID_LOG_INFO, TAG, "registering audio track");track = new AudioTrack();if(track == NULL) {     return ANDROID_AUDIOTRACK_RESULT_JNI_EXCEPTION;}__android_log_print(ANDROID_LOG_INFO, TAG, "registered");return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_start() {//__android_log_print(ANDROID_LOG_INFO, TAG, "starting audio track");    if(track == NULL) {        return ANDROID_AUDIOTRACK_RESULT_ALLOCATION_FAILED;    }track->start();    return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_set(int streamType,  uint32_t sampleRate,  int format,  int channels) {if(track == NULL) {        return ANDROID_AUDIOTRACK_RESULT_ALLOCATION_FAILED;    }__android_log_print(ANDROID_LOG_INFO, TAG, "setting audio track");status_t ret = track->set(streamType,   sampleRate,   format,   channels,   0,   0,  0,   0,  false);if (ret != NO_ERROR) {return ANDROID_AUDIOTRACK_RESULT_ERRNO;}return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_flush() {    if(track == NULL) {        return ANDROID_AUDIOTRACK_RESULT_ALLOCATION_FAILED;    }track->flush();    return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_stop() {    if(track == NULL) {        return ANDROID_AUDIOTRACK_RESULT_ALLOCATION_FAILED;    }track->stop();    return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_reload() {    if(track == NULL) {        return ANDROID_AUDIOTRACK_RESULT_ALLOCATION_FAILED;    }if(track->reload() != NO_ERROR) {return ANDROID_AUDIOTRACK_RESULT_ERRNO;}    return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_unregister() {__android_log_print(ANDROID_LOG_INFO, TAG, "unregistering audio track");    if(!track->stopped()) {        track->stop();    }//memBase.clear();//memHeap.clear();free(track);//track = NULL;__android_log_print(ANDROID_LOG_INFO, TAG, "unregistered");    return ANDROID_AUDIOTRACK_RESULT_SUCCESS;}int AndroidAudioTrack_write(void *buffer, int buffer_size) {// give the data to the native AudioTrack object (the data starts at the offset)    ssize_t written = 0;    // regular write() or copy the data to the AudioTrack's shared memory?    if (track->sharedBuffer() == 0) {        written = track->write(buffer, buffer_size);    } else {// writing to shared memory, check for capacityif ((size_t)buffer_size > track->sharedBuffer()->size()) {__android_log_print(ANDROID_LOG_INFO, TAG, "buffer size was too small");buffer_size = track->sharedBuffer()->size();}memcpy(track->sharedBuffer()->pointer(), buffer, buffer_size);written = buffer_size;}return written;}

/audio/jni/Android.mk(注意目录结构)

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