模拟器一样是模拟ARM指令的,不像Symbian模拟器一样执行的是本地代码,所以在模拟器上模拟出来的效率会比真实手机上的效率要低,之前这款解码器已经优化到在nokia
6600(相当低端的一款手机,CPU主频才120Hz)上做到在线播放。
假定前提
1)熟悉Java/C/C++语言;
2)熟悉Java的JNI技术;
3)有一定的跨手机平台移植经验;
4)有一套可供移植的源代码库,这里以H.264解码库为例,为了保护我们的知识版权,这里只能够公开头文件:
- #ifndef __H264DECODE_H__
- #define __H264DECODE_H__
- #
if
defined(__SYMBIAN32__)
//S602rd/3rd/UIQ
- #include <e32base.h>
- #include <libc/stdio.h>
- #include <libc/stdlib.h>
- #include <libc/string.h>
- #
else
//Windows/Mobile/MTK/OPhone
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #endif
- class
H264Decode - {
- public
:
-
/***************************************************************************/
-
/* 构造解码器 */
-
/* @return H264Decode解码器实例 */
-
/***************************************************************************/
-
static
H264Decode *H264DecodeConstruct();
-
/***************************************************************************/
-
/* 解码一帧 */
-
/* @pInBuffer 指向H264的视频流 */
-
/* @iInSize H264视频流的大小 */
-
/* @pOutBuffer 解码后的视频视频 */
-
/* @iOutSize 解码后的视频大小 */
-
/* @return 已解码的H264视频流的尺寸 */
-
/***************************************************************************/
-
int
DecodeOneFrame(unsigned
char
*pInBuffer,unsigned
int
iInSize,unsigned
char
*pOutBuffer,unsigned
int
&iOutSize); - ~H264Decode();
- };
- #endif
// __H264DECODE_H__
你不用熟悉Android平台,一切从零开始,因为在此之前,我也不熟悉
封装Java接口
在“假定前提”中提到了要移植的函数,接下来会编写这些 函数的Java Native
Interface。
- package
ophone.streaming.video.h264;
- import
java.nio.ByteBuffer; - public
class
H264decode { -
- //H264解码库指针,因为Java没有指针一说,所以这里用一个32位的数来存放指针的值
-
private
long
H264decode =
0
; -
-
static
{ - System.loadLibrary(
"H264Decode"
); - }
-
public
H264decode() { -
this
.H264decode = Initialize(); - }
-
-
public
void
Cleanup() { - Destroy(H264decode);
- }
-
-
public
int
DecodeOneFrame(ByteBuffer pInBuffer,ByteBuffer pOutBuffer) {
-
return
DecodeOneFrame(H264decode, pInBuffer, pOutBuffer);
- }
-
private
native
static
int
DecodeOneFrame(
long
H264decode,ByteBuffer pInBuffer,ByteBuffer pOutBuffer);
-
private
native
static
long
Initialize(); -
private
native
static
void
Destroy(
long
H264decode); - }
- #include <jni.h>
- #ifndef _Included_ophone_streaming_video_h264_H264decode
- #define _Included_ophone_streaming_video_h264_H264decode
- #ifdef __cplusplus
- extern
"C"
{
- #endif
- JNIEXPORT jint JNICALL Java_ophone_streaming_video_h264_H264decode_DecodeOneFrame
- (JNIEnv *, jclass, jlong, jobject, jobject);
- JNIEXPORT jlong JNICALL Java_ophone_streaming_video_h264_H264decode_Initialize
- (JNIEnv *, jclass);
- JNIEXPORT
void
JNICALL Java_ophone_streaming_video_h264_H264decode_Destroy
- (JNIEnv *, jclass, jlong);
- #ifdef __cplusplus
- }
- #endif
- #endif
之前已经生成了JNI头文件,接下来只需要实现这个头文件的几个导出函数,这里以H264解码器的实现为例:
- #include
"ophone_streaming_video_h264_H264decode.h"
- #include
"H264Decode.h"
- JNIEXPORT jint JNICALL Java_ophone_streaming_video_h264_H264decode_DecodeOneFrame
- (JNIEnv * env, jclass obj, jlong decode, jobject pInBuffer, jobject pOutBuffer) {
- H264Decode *pDecode = (H264Decode *)decode;
- unsigned
char
*In = NULL;unsigned
char
*Out = NULL; - unsigned
int
InPosition =
0
;unsigned
int
InRemaining =
0
;unsigned
int
InSize =
0
; - unsigned
int
OutSize =
0
; - jint DecodeSize = -
1
; - jbyte *InJbyte =
0
; - jbyte *OutJbyte =
0
; - jbyteArray InByteArrary =
0
; - jbyteArray OutByteArrary =
0
; -
//获取Input/Out ByteBuffer相关属性
- {
-
//Input
- {
- jclass ByteBufferClass = env->GetObjectClass(pInBuffer);
- jmethodID PositionMethodId = env->GetMethodID(ByteBufferClass,
"position"
,
"()I"
); - jmethodID RemainingMethodId = env->GetMethodID(ByteBufferClass,
"remaining"
,
"()I"
); - jmethodID ArraryMethodId = env->GetMethodID(ByteBufferClass,
"array"
,
"()[B"
); - InPosition = env->CallIntMethod(pInBuffer,PositionMethodId);
- InRemaining = env->CallIntMethod(pInBuffer,RemainingMethodId);
- InSize = InPosition + InRemaining;
- InByteArrary = (jbyteArray)env->CallObjectMethod(pInBuffer,ArraryMethodId);
- InJbyte = env->GetByteArrayElements(InByteArrary,
0
); - In = (unsigned
char
*)InJbyte + InPosition; - }
-
//Output
- {
- jclass ByteBufferClass = env->GetObjectClass(pOutBuffer);
- jmethodID ArraryMethodId = env->GetMethodID(ByteBufferClass,
"array"
,
"()[B"
); - jmethodID ClearMethodId = env->GetMethodID(ByteBufferClass,
"clear"
,
"()Ljava/nio/Buffer;"
); -
//清理输出缓存区
- env->CallObjectMethod(pOutBuffer,ClearMethodId);
- OutByteArrary = (jbyteArray)env->CallObjectMethod(pOutBuffer,ArraryMethodId);
- OutJbyte = env->GetByteArrayElements(OutByteArrary,
0
); - Out = (unsigned
char
*)OutJbyte; - }
- }
-
//解码
- DecodeSize = pDecode->DecodeOneFrame(In,InRemaining,Out,OutSize);
-
//设置Input/Output ByteBuffer相关属性
- {
-
//Input
- {
- jclass ByteBufferClass = env->GetObjectClass(pInBuffer);
- jmethodID SetPositionMethodId = env->GetMethodID(ByteBufferClass,
"position"
,
"(I)Ljava/nio/Buffer;"
); -
//设置输入缓冲区偏移
- env->CallObjectMethod(pInBuffer,SetPositionMethodId,InPosition + DecodeSize);
- }
-
//Output
- {
- jclass ByteBufferClass = env->GetObjectClass(pOutBuffer);
- jmethodID SetPositionMethodId = env->GetMethodID(ByteBufferClass,
"position"
,
"(I)Ljava/nio/Buffer;"
); -
//设置输出缓冲区偏移
- env->CallObjectMethod(pOutBuffer,SetPositionMethodId,OutSize);
- }
- }
-
//清理
- env->ReleaseByteArrayElements(InByteArrary,InJbyte,
0
); - env->ReleaseByteArrayElements(OutByteArrary,OutJbyte,
0
); -
return
DecodeSize; - }
- JNIEXPORT jlong JNICALL Java_ophone_streaming_video_h264_H264decode_Initialize
- (JNIEnv * env, jclass obj) {
- H264Decode *pDecode = H264Decode::H264DecodeConstruct();
-
return
(jlong)pDecode; - }
- JNIEXPORT
void
JNICALL Java_ophone_streaming_video_h264_H264decode_Destroy
- (JNIEnv * env, jclass obj, jlong decode) {
- H264Decode *pDecode = (H264Decode *)decode;
-
if
(pDecode) - {
- delete pDecode;
- pDecode = NULL;
- }
- }
5.3.3 编译本地方法
接下来,只需要把用C实现的本地方法编译为动态链接库,如果之前你用于移植的那个库曾经移植到Symbian上过,那么编译会相当简单,因为NDK的编译器和Symbian的编译器一样,都是采用GCC做交叉编译器。
首先,需要在$NDK/apps目录下,创建一个项目目录,这里创建了一个H264Decode目录,在H264Decode目录中,创建一个Android.mk文件:
- APP_PROJECT_PATH := $(call my-dir)
- APP_MODULES := H264Decode
接下来,需要在$NDK/source目录下,创建源代码目录(这里的目录名要和上面创建的项目目录文件名相同),这里创建一个H264Decode目录,然后把之前生成的JNI头文件和你实现的本地方法相关头文件和源代码,都拷贝到
这个目录下面。
编写库测试程序
/**
* @author ophone
* @email 3751624@qq.com
*/
package ophone.streaming.video.h264;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.nio.ByteBuffer;
import OPhone.app.Activity;
import OPhone.graphics.BitmapFactory;
import OPhone.os.Bundle;
import OPhone.os.Handler;
import OPhone.os.Message;
import OPhone.widget.ImageView;
import OPhone.widget.TextView;
public class H264Example extends Activity {
private static final int VideoWidth = 352;
private static final int VideoHeight = 288;
private ImageView ImageLayout = null;
private TextView FPSLayout = null;
private H264decode Decode = null;
private Handler H = null;
private byte[] Buffer = null;
private int DecodeCount = 0;
private long StartTime = 0;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ImageLayout = (ImageView) findViewById(R.id.ImageView);
FPSLayout = (TextView) findViewById(R.id.TextView);
Decode = new H264decode();
StartTime = System.currentTimeMillis();
new Thread(new Runnable(){
public void run() {
StartDecode();
}
}).start();
H = new Handler(){
public void handleMessage(Message msg) {
ImageLayout.invalidate();
ImageLayout.setImageBitmap(BitmapFactory.decodeByteArray(Buffer, 0, Buffer.length));
long Time = (System.currentTimeMillis()-StartTime)/1000;
if(Time > 0){
FPSLayout.setText("花费时间:" + Time + "秒 解码帧数:" + DecodeCount + " FPS:" + (DecodeCount/Time) );
}
}
};
}
private void StartDecode(){
File h264file = new File("/tmp/Demo.264");
InputStream h264stream = null;
try {
h264stream = new FileInputStream(h264file);
ByteBuffer pInBuffer = ByteBuffer.allocate(51200);//分配50k的缓存
ByteBuffer pRGBBuffer = ByteBuffer.allocate(VideoWidth*VideoHeight*3);
while (h264stream.read(pInBuffer.array(), pInBuffer.position(), pInBuffer.remaining()) >= 0) {
pInBuffer.position(0);
do{
int DecodeLength = Decode.DecodeOneFrame(pInBuffer, pRGBBuffer);
//如果解码成功,把解码出来的图片显示出来
if(DecodeLength > 0 && pRGBBuffer.position() > 0){
//转换RGB字节为BMP
BMPImage bmp = new BMPImage(pRGBBuffer.array(),VideoWidth,VideoHeight);
Buffer = bmp.getByte();
H.sendMessage(H.obtainMessage());
Thread.sleep(1);
DecodeCount ++;
}
}while(pInBuffer.remaining() > 10240);//确保缓存区里面的数据始终大于10k
//清理已解码缓冲区
int Remaining = pInBuffer.remaining();
System.arraycopy(pInBuffer.array(), pInBuffer.position(), pInBuffer.array(), 0, Remaining);
pInBuffer.position(Remaining);
}
} catch (Exception e1) {
e1.printStackTrace();
} finally {
try{h264stream.close();} catch(Exception e){}
}
}
protected void onDestroy() {
super.onDestroy();
Decode.Cleanup();
}
}
BMPImage是一个工具类,主要用于把RGB序列,转换为BMP图象用于显示:
@author ophone
* @email 3751624@qq.com
*/
package ophone.streaming.video.h264;
import java.nio.ByteBuffer;
public class BMPImage {
// --- 私有常量
private final static int BITMAPFILEHEADER_SIZE = 14;
private final static int BITMAPINFOHEADER_SIZE = 40;
// --- 位图文件标头
private byte bfType[] = { 'B', 'M' };
private int bfSize = 0;
private int bfReserved1 = 0;
private int bfReserved2 = 0;
private int bfOffBits = BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE;
// --- 位图信息标头
private int biSize = BITMAPINFOHEADER_SIZE;
private int biWidth = 176;
private int biHeight = 144;
private int biPlanes = 1;
private int biBitCount = 24;
private int biCompression = 0;
private int biSizeImage = biWidth*biHeight*3;
private int biXPelsPerMeter = 0x0;
private int biYPelsPerMeter = 0x0;
private int biClrUsed = 0;
private int biClrImportant = 0;
ByteBuffer bmpBuffer = null;
public BMPImage(byte[] Data,int Width,int Height){
biWidth = Width;
biHeight = Height;
biSizeImage = biWidth*biHeight*3;
bfSize = BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE + biWidth*biHeight*3;
bmpBuffer = ByteBuffer.allocate(BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE + biWidth*biHeight*3);
writeBitmapFileHeader();
writeBitmapInfoHeader();
bmpBuffer.put(Data);
}
public byte[] getByte(){
return bmpBuffer.array();
}
private byte[] intToWord(int parValue) {
byte retValue[] = new byte[2];
retValue[0] = (byte) (parValue & 0x00FF);
retValue[1] = (byte) ((parValue >> 8) & 0x00FF);
return (retValue);
}
private byte[] intToDWord(int parValue) {
byte retValue[] = new byte[4];
retValue[0] = (byte) (parValue & 0x00FF);
retValue[1] = (byte) ((parValue >> 8) & 0x000000FF);
retValue[2] = (byte) ((parValue >> 16) & 0x000000FF);
retValue[3] = (byte) ((parValue >> 24) & 0x000000FF);
return (retValue);
}
private void writeBitmapFileHeader () {
bmpBuffer.put(bfType);
bmpBuffer.put(intToDWord (bfSize));
bmpBuffer.put(intToWord (bfReserved1));
bmpBuffer.put(intToWord (bfReserved2));
bmpBuffer.put(intToDWord (bfOffBits));
}
private void writeBitmapInfoHeader () {
bmpBuffer.put(intToDWord (biSize));
bmpBuffer.put(intToDWord (biWidth));
bmpBuffer.put(intToDWord (biHeight));
bmpBuffer.put(intToWord (biPlanes));
bmpBuffer.put(intToWord (biBitCount));
bmpBuffer.put(intToDWord (biCompression));
bmpBuffer.put(intToDWord (biSizeImage));
bmpBuffer.put(intToDWord (biXPelsPerMeter));
bmpBuffer.put(intToDWord (biYPelsPerMeter));
bmpBuffer.put(intToDWord (biClrUsed));
bmpBuffer.put(intToDWord (biClrImportant));
}
}
来自:http://www.ophonesdn.com/article/show/45