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

git clone https://github.com/havlenapetr/FFMpeg.git

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

$ndk/ndk-build

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

关于havlenapetr-FFMpeg在Android 4.0（ICS）的补充说明

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。

绿色的是新加入的文件

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。

java.lang.NoSuchFieldError: no field with name='mSurface' signature='I' in class Landroid/view/Surface;

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) 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/surface.h>#include <surfaceflinger/Surface.h>#include <utils/Log.h>#include <SkBitmap.h>#include <SkCanvas.h>#define TAG "SurfaceWrapper"using namespace android;static Surface*sSurface;static SkBitmapsBitmapClient;static SkBitmapsBitmapSurface;static Surface* getNativeSurface(JNIEnv* env, jobject jsurface) {jclass clazz = env->FindClass("android/view/Surface");jfieldID field_surface = env->GetFieldID(clazz, "mNativeSurface", "I");if(field_surface == NULL) {return NULL;}return (Surface *) env->GetIntField(jsurface, field_surface);}static int initBitmap(SkBitmap *bitmap, int format, int width, int height, bool allocPixels) {switch (format) {        case PIXEL_FORMAT_RGBA_8888:            bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);            break;        case PIXEL_FORMAT_RGBA_4444:            bitmap->setConfig(SkBitmap::kARGB_4444_Config, width, height);            break;        case PIXEL_FORMAT_RGB_565:            bitmap->setConfig(SkBitmap::kRGB_565_Config, width, height);            break;        case PIXEL_FORMAT_A_8:            bitmap->setConfig(SkBitmap::kA8_Config, width, height);            break;        default:            bitmap->setConfig(SkBitmap::kNo_Config, width, height);            break;    }if(allocPixels) {bitmap->setIsOpaque(true);//-- alloc array of pixelsif(!bitmap->allocPixels()) {return -1;}}return 0;}int AndroidSurface_register(JNIEnv* env, jobject jsurface) {__android_log_print(ANDROID_LOG_INFO, TAG, "registering video surface");sSurface = getNativeSurface(env, jsurface);if(sSurface == NULL) {     return ANDROID_SURFACE_RESULT_JNI_EXCEPTION;}__android_log_print(ANDROID_LOG_INFO, TAG, "registered");return ANDROID_SURFACE_RESULT_SUCCESS;}int AndroidSurface_getPixels(int width, int height, void** pixels) {__android_log_print(ANDROID_LOG_INFO, TAG, "getting surface's pixels %ix%i", width, height);if(sSurface == NULL) {return ANDROID_SURFACE_RESULT_JNI_EXCEPTION;}if(initBitmap(&sBitmapClient, PIXEL_FORMAT_RGB_565, width, height, true) < 0) {return ANDROID_SURFACE_RESULT_COULDNT_INIT_BITMAP_CLIENT;}*pixels = sBitmapClient.getPixels();__android_log_print(ANDROID_LOG_INFO, TAG, "getted");return ANDROID_SURFACE_RESULT_SUCCESS;}static void doUpdateSurface() {SkCanvascanvas(sBitmapSurface);SkRectsurface_sBitmapClient;SkRectsurface_sBitmapSurface;SkMatrixmatrix;surface_sBitmapSurface.set(0, 0, sBitmapSurface.width(), sBitmapSurface.height());surface_sBitmapClient.set(0, 0, sBitmapClient.width(), sBitmapClient.height());matrix.setRectToRect(surface_sBitmapClient, surface_sBitmapSurface, SkMatrix::kFill_ScaleToFit);canvas.drawBitmapMatrix(sBitmapClient, matrix);}static int prepareSurfaceBitmap(Surface::SurfaceInfo* info) {if(initBitmap(&sBitmapSurface, info->format, info->w, info->h, false) < 0) {return -1;}sBitmapSurface.setPixels(info->bits);return 0;}int AndroidSurface_updateSurface() {static Surface::SurfaceInfo surfaceInfo;if(sSurface == NULL) {return ANDROID_SURFACE_RESULT_JNI_EXCEPTION;}if (!Surface::isValid (sSurface)){return ANDROID_SURFACE_RESULT_NOT_VALID;}if (sSurface->lock(&surfaceInfo) < 0) {return ANDROID_SURFACE_RESULT_COULDNT_LOCK;}if(prepareSurfaceBitmap(&surfaceInfo) < 0) {return ANDROID_SURFACE_RESULT_COULDNT_INIT_BITMAP_SURFACE;}doUpdateSurface();if (sSurface->unlockAndPost() < 0) {return ANDROID_SURFACE_RESULT_COULDNT_UNLOCK_AND_POST;}return ANDROID_SURFACE_RESULT_SUCCESS;}int AndroidSurface_unregister() {__android_log_print(ANDROID_LOG_INFO, TAG, "unregistering video surface");__android_log_print(ANDROID_LOG_INFO, TAG, "unregistered");    return ANDROID_SURFACE_RESULT_SUCCESS;}

video/jni/Android.mk (注意目录结构)

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)# our source files#LOCAL_SRC_FILES:= \ surface.cppLOCAL_SHARED_LIBRARIES := \ libskia \  libsurfaceflinger_client \  libutils \ liblogLOCAL_C_INCLUDES += \ $(JNI_H_INCLUDE) \ external/skia/src/core \ external/skia/include/core \ frameworks/base/include \ frameworks/base/native/include# Optional tag would mean it doesn't get installed by defaultLOCAL_MODULE_TAGS := optionalLOCAL_PRELINK_MODULE := falseLOCAL_MODULE:= libjnivideoinclude $(BUILD_SHARED_LIBRARY)

/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 capacity  if ((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)

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)# our source files#LOCAL_SRC_FILES:= \ audiotrack.cppLOCAL_SHARED_LIBRARIES := \ libbinder \  libmedia \  libutils \ liblogLOCAL_C_INCLUDES += \ $(JNI_H_INCLUDE) \ frameworks/base/include \ frameworks/base/native/include# Optional tag would mean it doesn't get installed by defaultLOCAL_MODULE_TAGS := optionalLOCAL_PRELINK_MODULE := falseLOCAL_MODULE:= libjniaudioinclude $(BUILD_SHARED_LIBRARY)

关于havlenapetr-FFMpeg在Android 4.0（ICS）的补充说明

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