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

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* author：conowen@大钟
* E-mail：[e-mail]
* http://blog.csdn.net/conowen
* 注：本文为原创，仅作为学习交流使用，转载请标明作者及出处。

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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

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。

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 SkBitmap  sBitmapClient;
static SkBitmap  sBitmapSurface;

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 pixels
  if(!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() {
 SkCanvas canvas(sBitmapSurface);
 SkRect  surface_sBitmapClient;
 SkRect  surface_sBitmapSurface;
 SkMatrix matrix;
 
 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 (!sSurface->isValid()) {
  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.cpp

LOCAL_SHARED_LIBRARIES := \
 libskia \
  libsurfaceflinger_client \
  libutils \
 liblog

LOCAL_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 default
LOCAL_MODULE_TAGS := optional

LOCAL_PRELINK_MODULE := false

LOCAL_MODULE:= libjnivideo

include $(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.cpp

LOCAL_SHARED_LIBRARIES := \
 libbinder \
  libmedia \
  libutils \
 liblog

LOCAL_C_INCLUDES += \
 $(JNI_H_INCLUDE) \
 frameworks/base/include \
 frameworks/base/native/include

# Optional tag would mean it doesn't get installed by default
LOCAL_MODULE_TAGS := optional

LOCAL_PRELINK_MODULE := false

LOCAL_MODULE:= libjniaudio

include $(BUILD_SHARED_LIBRARY)