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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title><![CDATA[Chih Sheng Huang's Blog]]></title>
<link href="http://pedoe.github.io/atom.xml" rel="self"/>
<link href="http://pedoe.github.io/"/>
<updated>2016-05-27T15:02:54+08:00</updated>
<id>http://pedoe.github.io/</id>
<author>
<name><![CDATA[Chih Sheng Huang]]></name>
</author>
<generator uri="http://octopress.org/">Octopress</generator>
<entry>
<title type="html"><![CDATA[How to run java on Mac]]></title>
<link href="http://pedoe.github.io/blog/2016/05/27/how-to-run-java-on-mac/"/>
<updated>2016-05-27T14:07:18+08:00</updated>
<id>http://pedoe.github.io/blog/2016/05/27/how-to-run-java-on-mac</id>
<content type="html"><![CDATA[<h2>How to run the java code on the Mac</h2>
<h2>前言</h2>
<p>最近要開始學java, 本來想說要找個IDE來做開發練習, 但是又有點懶, 也想繼續多多練習使用vim。 就google了一下怎麼在mac上build java code, 畢竟跟C或C++不太一樣不能用gcc。接著以最常見的hello world當作範例。</p>
<h2>Step1</h2>
<p>寫一個印出hello world的程式</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>class HelloWorld{
</span><span class='line'> public static void main(String[] args)
</span><span class='line'> {
</span><span class='line'> System.out.println("hello world");
</span><span class='line'> }
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<h2>Step2</h2>
<p>使用javac指令做編譯</p>
<p> <img src="http://pedoe.github.io/images/HowToBuildJavaOnMac/compile.png" alt="compile" /></p>
<h2>Step3</h2>
<p>輸入java HelloWorld, 就可以看到結果了!</p>
<p> <img src="http://pedoe.github.io/images/HowToBuildJavaOnMac/execute.png" alt="execute" /></p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[iOS H264 Hardware Encode]]></title>
<link href="http://pedoe.github.io/blog/2016/04/13/ios-h264-hardware-encode/"/>
<updated>2016-04-13T16:33:42+08:00</updated>
<id>http://pedoe.github.io/blog/2016/04/13/ios-h264-hardware-encode</id>
<content type="html"><![CDATA[<h2>How to encode h264 file on iPhone by hardware encoding</h2>
<h2>前言</h2>
<p>最近工作上需要在iPhone上處理影音方面的codec, 花了不少時間去study跟找資料, 所以想把過程記錄下來, 怕以後自己忘掉可以很快回想起來。也希望可以幫到有需要的人,如果有許多錯誤還請多包涵, 畢竟小弟我只是個寫程式的新手。</p>
<p>要做到視訊影音的傳輸, 大概可以分成四個部分</p>
<ol>
<li>影像encode</li>
<li>影像decode</li>
<li>聲音播放</li>
<li>聲音錄製</li>
</ol>
<p>這篇就先記錄影像encode的部分, 為了達到encode出 h264 file的目的, 這邊的例子為用iPhone錄製影像, 並將影像encode成h264 file再輸出, 大概可以分成錄製影像流程跟硬體encode流程這兩個部分做說明。</p>
<h2>錄製影像</h2>
<p>這部分網路上資料很多, google就有很多答案, 主要的流程可以分為</p>
<ol>
<li>選擇輸入來源(相機, 麥克風, 耳機等等)</li>
<li>選擇前鏡頭後鏡頭</li>
<li>建立data output buffer</li>
<li>建立AVCaptrueSession</li>
<li>設定session相關參數</li>
</ol>
<p>這裡主要提一下AVCaptureSession, 根據Apple官方文件的說明, AVCaptureSession用來控制聲音或影像的輸入與輸出。就是先建立AVCaptureSession後, 加入輸入源例如AVCaptureDevieInput以及輸出源例如AVCaptureMovieFileOutput, 參考Apple官方的sample code如下:</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
</span><span class='line'>AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
</span><span class='line'>NSError *error = nil;
</span><span class='line'>AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error];
</span><span class='line'>if (audioInput) {
</span><span class='line'> [captureSession addInput:audioInput];
</span><span class='line'>}
</span><span class='line'>else {
</span><span class='line'> // Handle the failure.
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>其他設定相機錄製等等就到後面直接看程式碼說明會比較清楚。</p>
<h2>Hardware Encode 流程</h2>
<p>在以前蘋果是沒有開放hardware codec給開發者使用的, 到了iOS8.0後才推出了VideoToolbox這個framework來讓開發者使用, 藉由硬體將需要大量運算的影像編解碼處理掉, 可以省下不少運算資源留給其他功能。為了使用硬體進行encode, 我們可以先參考蘋果在WWDC14中session513(Direct Access to Video Encoding and Decoding)中對encode流程的示意圖如下:</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/CompressFlow.png" alt="compress flow" /></p>
<p>這張圖要描述一開始iPhone鏡頭(最左邊)開啟後開始拍攝, 資料流開始讀入, 並假設現在在拍那隻貓, 貓的影像就會一張一張存到Buffer中(此時是為壓縮的原始檔)。</p>
<p>再來中間是AVAssetWriter, 這部分將未壓縮的frame丟到Video Encoder中轉成H.246的格式再輸出成file。這個部分可以再拆更細來看如下圖:</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/CompressionSession.png" alt="compression session" /></p>
<p>為了使用video encoder, 我們必須創建VTCompressionSession這個物件, 其中VTCompressionSession這個物件必須給定部分條件或值才能成功建立, 條件如下</p>
<ol>
<li>Dimenssions for compressed output</li>
<li>Format for compression</li>
<li>PixelBufferAttributes describing source buffer requirements (optional)</li>
<li>A callback for VTCompresssionSession output</li>
</ol>
<p>第一個就是你必須告知encoder你想要壓縮的frame大小, 大小單位為pixel; 第二個是則是你想壓縮成的格式, 在Apple官方提供的framework中有幾種格式可以選, 不過這裡格式就用H.264;
第三個為看你要不要建立buffer pool來存放你的source frame, 這部分我沒有用到就不是非常清楚; 第四個為必須給一個callback讓encoder處理完後呼叫, callback的機制可以參考下圖</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/CompressionCallback.png" alt="compression callback" /></p>
<p>可以看出來我們必須要將壓縮後存有h.264 frame的CMSampleBuffer傳入callback, 並在callback中進行h.264 frame的解析處理(關於sps, pps ,i-frame etc.), 若在中間錯誤callback則會有
error code等相關處理。</p>
<p>創建完VTCompressionSession這個物件後, 可以對該encoder給定一些描述, 例如壓縮的bitrate, 畫素等等如下圖:</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/CompressionConfiguring.png" alt="compression configuring" /></p>
<p>整個流程可以總結如下</p>
<ol>
<li>準備一個裝有未壓縮frame的Buffer</li>
<li>建立encoder(前面提到的VTCompressionSession物件)</li>
<li>設定encoder相關參數, 特性</li>
<li>開始錄影後把得到的CVPixelBuffer送進encoder內, 再把encode出來的frame放入CMSampleBuffer做後續的處理(看要存成檔案還是透過網路傳出去等等)</li>
</ol>
<h2>實作錄製影像並encode成h264檔案</h2>
<h3>開啟錄影等功能</h3>
<p>首先開啟一個新的專案</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/CreateProject.png" alt="create project" /></p>
<p>建立一個Button跟UIView, Button用來開始錄製和結束錄製, UIView則用來呈現出鏡頭拍攝到的即時影像。</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/UIView.png" alt="set view and button on storyboard" /></p>
<p>接下來加入VideoToolBox的framework和把UIView跟ViewController做連結</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/myView_VideoToolBox.png" alt="videoToolBox" /></p>
<p>接著先處理相機相關的部分, 根據上面介紹的流程, 我們先建立物件如下, 並且使class符合<AVCaptureVideoDataOutputSampleBufferDelegate> 這個協定的規範</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>@interface ViewController ()<AVCaptureVideoDataOutputSampleBufferDelegate>
</span><span class='line'>{
</span><span class='line'> AVCaptureSession *captureSession; //根據前面說明captureSession負責處理資料的輸入輸出
</span><span class='line'> AVCaptureVideoPreviewLayer *previewLayer; //到時候將鏡頭拍攝到的影像在此view上作呈現
</span><span class='line'> AVCaptureConnection *connection; //負責資料流的開關與建立captureSession後和capture到的output, input資料做連結
</span><span class='line'> bool isStart; //開啟和關閉影像錄製, 初始值給定true
</span><span class='line'>}
</span><span class='line'>@end</span></code></pre></td></tr></table></div></figure>
<p>再來建立Button觸發後的行為</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>- (IBAction)actionStartStop:(id)sender {
</span><span class='line'> if (isStart) {
</span><span class='line'> [self startCamera];
</span><span class='line'> isStart = false;
</span><span class='line'> [_startButton setTitle:@"Stop" forState:UIControlStateNormal];
</span><span class='line'> }
</span><span class='line'> else{
</span><span class='line'> isStart = true;
</span><span class='line'> [self stopCamera];
</span><span class='line'> [_startButton setTitle:@"Start" forState:UIControlStateNormal];
</span><span class='line'> }
</span><span class='line'>}
</span><span class='line'>
</span><span class='line'>- (void)startCamera
</span><span class='line'>{
</span><span class='line'>
</span><span class='line'>}
</span><span class='line'>
</span><span class='line'>- (void)stopCamera
</span><span class='line'>{
</span><span class='line'>
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>接下來處理button觸發後startCamera的行為, 首先建立輸入來源, 在這邊我們選擇前鏡頭, 方便自拍</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>NSError *deviceError;
</span><span class='line'>AVCaptureDeviceInput *inputDevice;
</span><span class='line'>for (AVCaptureDevice *device in [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]) {
</span><span class='line'> if ([device position] == AVCaptureDevicePositionFront) {
</span><span class='line'> inputDevice = [AVCaptureDeviceInput deviceInputWithDevice:device error:&deviceError];
</span><span class='line'> }
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>處理輸出源, 這邊使用了AVCaptureVideoDataOutput這個類別, 因為它提供我們去access得到的未壓縮frame, 可以呼叫 captureOutput:didOutputSampleBuffer:fromConnection:
這個delegate method來對frame做後續處理製作成h264的frame。除了選定輸出源, 我們還可以對輸出源做參數上的設定, iOS對kCVPixelBufferPixelFormatTypeKey支援三種format分別是</p>
<pre><code>kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
kCVPixelFormatType_420YpCbCr8BiPlanarFullRange
kCVPixelFormatType_32BGRA.
</code></pre>
<p>詳細差異我就不是很清楚了</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>AVCaptureVideoDataOutput *outputDevice = [[AVCaptureVideoDataOutput alloc]init];
</span><span class='line'>NSString *key = (NSString *)kCVPixelBufferPixelFormatTypeKey;
</span><span class='line'>NSNumber *val = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange];
</span><span class='line'>NSDictionary *videoSettings = [NSDictionary dictionaryWithObject:val forKey:key];
</span><span class='line'>outputDevice.videoSettings = videoSettings;
</span><span class='line'>[outputDevice setSampleBufferDelegate:self queue:dispatch_get_main_queue()];</span></code></pre></td></tr></table></div></figure>
<p></p>
<p>allocate AVCaptureSession, 接著加入output與input, 再呼叫begingConfiguring為後續調整output做準備。
這邊我們設定畫素為640x480, 並將connection設為連接output與video, 最後commit我們的配置。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>captureSession = [[AVCaptureSession alloc]init];
</span><span class='line'>[captureSession addInput:inputDevice];
</span><span class='line'>[captureSession addOutput:outputDevice];
</span><span class='line'>[captureSession beginConfiguration];
</span><span class='line'>captureSession.sessionPrest = AVCaptureSessionPreset640x480;
</span><span class='line'>connection = [outputDevice connectionWithMediaType:AVMediaTypeVideo];
</span><span class='line'>[connection commitConfiguration];</span></code></pre></td></tr></table></div></figure>
<p>最後把擷取到的影像放到previewLayer上做呈現, 並startRunning!</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>previewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:captureSession];
</span><span class='line'>previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
</span><span class='line'>[self.myView.layer addSublayer:previewLayer];
</span><span class='line'>previewLayer.frame = self.myView.bounds;
</span><span class='line'>[captureSession startRunning];</span></code></pre></td></tr></table></div></figure>
<p>停止的部分比較簡單, 呼叫stopRunning即可</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>- (void)stopCamera
</span><span class='line'>{
</span><span class='line'> [captureSession stopRunning];
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>到這邊應該就可以試看看簡單的攝影功能了, 按下button相機鏡頭拍攝到的影像就會呈現在preView上。</p>
<h3>Encoder建立</h3>
<p>先新增一個名為VideoEncode的class, 再VideoEncode.h檔中, 我們建立兩個method與新增一個delegate 的portocol協定
initEncode:width:height是用來初始化一個encoder, 並給定要encode的影像畫素大小; encode:則是把未壓縮的frame做encode, 需要傳入一裝有未壓縮frame的sampleBuffer
這邊則創建一個新的portocol協定取名為H264HwEncoderDelegate, 裡面含有兩個實作方法, 分別是取得sps, pps frame還有keyframe的方法。接下來只要在ViewController中實作該方法就可以得到
影像再存入檔案中了。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>#import <Foundation/Foundation.h>
</span><span class='line'>#import <AVFoundation/AVFoundation.h>
</span><span class='line'>#import <VideoToolbox/VideoToolbox.h>
</span><span class='line'>
</span><span class='line'>@protocol H264HwEncoderDelegate <NSObject>
</span><span class='line'>
</span><span class='line'>- (void)gotSpsPps:(NSData*)sps pps:(NSData*)pps;
</span><span class='line'>- (void)gotEncodedData:(NSData*)data isKeyFrame:(BOOL)isKeyFrame;
</span><span class='line'>
</span><span class='line'>@end
</span><span class='line'>
</span><span class='line'>@interface VideoEncode : NSObject
</span><span class='line'>- (void) initEncode:(int)width height:(int)height;
</span><span class='line'>- (void) encode:(CMSampleBufferRef )sampleBuffer;
</span><span class='line'>
</span><span class='line'>@property (weak, nonatomic) id<H264HwEncoderDelegate> delegate;
</span><span class='line'>
</span><span class='line'>@end</span></code></pre></td></tr></table></div></figure>
<p>接下來宣告相關變數, VTCompressionSessionRef就是前面提到的VideoToolbox提供的壓縮session物件, encodeQueue則是要將encode frame丟到queue裡面照順序處理, 得到的file時間順序才會對。
CMFormatDescriptionRef是用來設定壓縮的format;</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>@implementation VideoEncode
</span><span class='line'>{
</span><span class='line'> NSString *error;
</span><span class='line'> VTCompressionSessionRef *encodeSession;
</span><span class='line'> dispatch_queue_t encodeQueue;
</span><span class='line'> CMFormatDescriptionRef format;
</span><span class='line'> BOOL initialized;
</span><span class='line'> int frameCount;
</span><span class='line'> NSData *sps;
</span><span class='line'> NSData *pps;
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>進行初始化</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>- (id)init
</span><span class='line'>{
</span><span class='line'> self = [super init];
</span><span class='line'> if(self) {
</span><span class='line'> [self initVariables];
</span><span class='line'> }
</span><span class='line'> return self;
</span><span class='line'>}
</span><span class='line'>
</span><span class='line'>- (void)initVariables
</span><span class='line'>{
</span><span class='line'> encodeSession = nil;
</span><span class='line'> initialized = true;
</span><span class='line'> encodeQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
</span><span class='line'> frameCount = 0;
</span><span class='line'> sps = NULL;
</span><span class='line'> pps = NULL;
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>初始化encoder內容, 先將初始化的過程丟到sync Queue內保護起來照順序做。接著建立Compression Session, VTCompressionSessionCreate這個API有許多東西要給入, 例如畫素大小,
callbalck(didCompressH264), 還有最一開始宣告的encodeSession位置等等。而VTCompressionSessionCreate這個API會回傳一個error code, 正常的話會傳回0, 方便我們檢驗。
VTSessionSetProperty有很多參數可以設定, 這裏設定了realtime的encode, I frame到下一張I frame的間隔, 以及選定compression bitstream的profile level。
最後告知encoder準備好了。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>- (void)initEncode:(int)width height:(int)height
</span><span class='line'>{
</span><span class='line'> dispatch_sync(encodeQueue, ^{
</span><span class='line'> // Create the compression session
</span><span class='line'> OSStatus status = VTCompressionSessionCreate(NULL, width, height, kCMVideoCodecType_H264, NULL, NULL, NULL, didCompressH264, (__bridge void *)(self), &encodeSession);
</span><span class='line'> NSLog(@"H264: VTCompressionSessionCreate %d", (int)status);
</span><span class='line'>
</span><span class='line'> if (status != 0) {
</span><span class='line'> NSLog(@"H264: Unable to create H264 session");
</span><span class='line'> error = @"H264: Unable to create H264 session";
</span><span class='line'>
</span><span class='line'> return;
</span><span class='line'> }
</span><span class='line'>
</span><span class='line'> // Set the properties
</span><span class='line'> VTSessionSetProperty(encodeSession, kVTCompressionPropertyKey_RealTime, kCFBooleanTrue);
</span><span class='line'> VTSessionSetProperty(encodeSession, kVTCompressionPropertyKey_MaxKeyFrameInterval, (__bridge CFNumberRef)@(10.0)); // change the frame number between 2 I frame
</span><span class='line'> VTSessionSetProperty(encodeSession, kVTCompressionPropertyKey_ProfileLevel, kVTProfileLevel_H264_Main_AutoLevel);
</span><span class='line'>
</span><span class='line'> // Tell the encoder to start encoding
</span><span class='line'> vVTCompressionSessionPrepareToEncodeFrames(encodeSession);
</span><span class='line'> });
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>處理encode frame部分, 前面init時不丟到queue裡面還行, 這裏注意一定要丟到sync queue裡, 確保frame的順序正確。
使用CMSampleBufferGetImageBuffer來取得buffer內的影像資料, 存到imageBuffer內; VTCompressionSessionEncodeFrame, 這個function就是負責壓縮frame的function, 所以有一些參數必須設置
以及傳入。一些重要一定得傳入的有先前創建的encodeSession, 還有存有未壓縮frame的imageBuffer, 最後則是當error發生時要進行的處理。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>- (void)encode:(CMSampleBufferRef)sampleBuffer
</span><span class='line'>{
</span><span class='line'> dispatch_sync(encodeQueue, ^{
</span><span class='line'> frameCount++;
</span><span class='line'> // Get the CV Image buffer
</span><span class='line'> CVImageBufferRef imageBuffer = (CVImageBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);
</span><span class='line'> // Create properties
</span><span class='line'> CMTime presentationTimeStamp = CMTimeMake(frameCount, 1000);
</span><span class='line'> //CMTime duration = CMTimeMake(1, DURATION);
</span><span class='line'> VTEncodeInfoFlags flags;
</span><span class='line'> // Pass it to the encoder
</span><span class='line'> OSStatus statusCode = VTCompressionSessionEncodeFrame(encodeSession,
</span><span class='line'> imageBuffer,
</span><span class='line'> presentationTimeStamp,
</span><span class='line'> kCMTimeInvalid,
</span><span class='line'> NULL, NULL, &flags);
</span><span class='line'> // Check for error
</span><span class='line'> if (statusCode != noErr) {
</span><span class='line'> NSLog(@"H264: VTCompressionSessionEncodeFrame failed with %d", (int)statusCode);
</span><span class='line'> error = @"H264: VTCompressionSessionEncodeFrame failed ";
</span><span class='line'>
</span><span class='line'> // End the session
</span><span class='line'> VTCompressionSessionInvalidate(encodeSession);
</span><span class='line'> CFRelease(encodeSession);
</span><span class='line'> encodeSession = NULL;
</span><span class='line'> error = NULL;
</span><span class='line'>
</span><span class='line'> return;
</span><span class='line'> }
</span><span class='line'>
</span><span class='line'> NSLog(@"H264: VTCompressionSessionEncodeFrame Success");
</span><span class='line'> });
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>關於callback比較特別, 進去看VTCompressionCreate這個API裡面的Callback是一個C語言的function pointer type, 所以要做一些轉換。要宣告該callback函數讓其他method能夠呼叫,
再實作該callbackvoid。callback要處理的事情有點多就分段記錄下來, 首先是檢查呼叫callback時傳入的狀態與資料是否正確以及是否有key frame等等, 再來是因為在C語言的寫法下我們沒辦法像[self function]這樣呼叫, C語言看不懂self, 所以在呼叫callback時要把整個class傳入再做casting的轉換。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>void didCompressH264(void *outputCallbackRefCon, void *sourceFrameRefCon, OSStatus status, VTEncodeInfoFlags infoFlags,CMSampleBufferRef sampleBuffer );
</span><span class='line'>
</span><span class='line'>void didCompressH264(void *outputCallbackRefCon, void *sourceFrameRefCon, OSStatus status, VTEncodeInfoFlags infoFlags,CMSampleBufferRef sampleBuffer )
</span><span class='line'>{
</span><span class='line'> if (status != 0) {
</span><span class='line'> assert(status == 0);
</span><span class='line'> return;
</span><span class='line'> }
</span><span class='line'>
</span><span class='line'> if (!CMSampleBufferDataIsReady(sampleBuffer)) {
</span><span class='line'> NSLog(@"didCompressH264 data is not ready");
</span><span class='line'> }
</span><span class='line'>
</span><span class='line'> VideoEncode *THIS = (__bridge VideoEncode*)outputCallbackRefCon;
</span><span class='line'>
</span><span class='line'> //Check if we have got a key frame first
</span><span class='line'> bool keyframe = !CFDictionaryContainsKey((CFArrayGetValueAtIndex(CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, true), 0)), kCMSampleAttachmentKey_NotSync);
</span></code></pre></td></tr></table></div></figure>
<p>若成功得到key frame後, 依照h264的格式先後得到sps, pps, i-frame。根據官方提供的資料, 在錄製影像時未壓縮的檔案是以MP4的格式header用AVCC呈現。可以看下圖會比比較清楚的了解,
可以看到下圖中MP4的sps, pps可以直接利用CMVideoFormatDescriptionGetH264ParameterSetAtIndex這個method來取得。</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/H264_sps_pps.png" alt="H264 sps pps format" /></p>
<p>知道如何取得sps, pps後先宣告frame的資料大小以及存放frame raw data的變數, 接下來呼叫CMVideoFormatDescriptionGetH264ParameterSetAtIndex時
將宣告的變數位址傳入。得到sps, pps frame後就可以將資料丟到有實作前面定義portocol協定的class中, 在這邊是ViewController, 因此ViewController那邊就可以得到sps, pps frame的資料。</p>
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</pre></td><td class='code'><pre><code class=''><span class='line'>if (keyframe) {
</span><span class='line'> CMFormatDescriptionRef format = CMSampleBufferGetFormatDescription(sampleBuffer);
</span><span class='line'> size_t sparameterSetSize, sparameterSetCount;
</span><span class='line'> const uint8_t *sparameterSet;
</span><span class='line'> OSStatus statusCode = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format,0,&sparameterSet,&sparameterSetSize,&sparameterSetCount, 0);
</span><span class='line'>
</span><span class='line'> if (statusCode == noErr) {
</span><span class='line'> assert(status == 0);
</span><span class='line'> // Found sps and now check the pps
</span><span class='line'> size_t pparameterSetSize, pparameterSetCount;
</span><span class='line'> const uint8_t *pparameterSet;
</span><span class='line'> OSStatus statusCode = CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format,1,&pparameterSet,&pparameterSetSize,&pparameterSetCount, 0);
</span><span class='line'>
</span><span class='line'> if (statusCode == noErr) {
</span><span class='line'> assert(status == 0);
</span><span class='line'> // Found pps
</span><span class='line'> THIS->sps = [NSData dataWithBytes:sparameterSet length:sparameterSetSize];
</span><span class='line'> THIS->pps = [NSData dataWithBytes:pparameterSet length:pparameterSetSize];
</span><span class='line'>
</span><span class='line'> if (THIS->_delegate) {
</span><span class='line'> [THIS->_delegate gotSpsPps:THIS->sps pps:THIS->pps];
</span><span class='line'> }
</span><span class='line'> }
</span><span class='line'> }
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>處理完sps, pps frame後進行i-frame的處理。i-frame跟sps, pps frame比起來就需要做一些轉換, MP4的前四個byte代表該筆資料的長度, 第五個byte開始才是影像資料。
所以我們需要另外處理一下, 而且前四個byte是以big-endian呈現資料長度, 需要轉成low-endian。剩下的就是不斷的把位置移到下一個NALU開頭, 找到之後再把資料依序處理。
這部分可以參考下圖</p>
<p> <img src="http://pedoe.github.io/images/iOS_H264_HardwareEncode/H264_iFrame.png" alt="h264 i frame" /></p>
<p>因為i-frame不確定長度會有多長, 有可能會比較大的長度才得到完整的i-frame, 這裏用CMBlockBufferGetDataPointer去取得資料。一樣把要存放資料與資料的大小長度等變數位址傳入。</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>CMBlockBufferRef dataBuffer = CMSampleBufferGetDataBuffer(sampleBuffer);
</span><span class='line'>size_t length, totalLength;
</span><span class='line'>char *dataPointer;
</span><span class='line'>OSStatus statusCodeRet = CMBlockBufferGetDataPointer(dataBuffer, 0, &length, &totalLength, &dataPointer);
</span><span class='line'>if (statusCodeRet == noErr) {
</span><span class='line'> assert(statusCodeRet == 0);
</span><span class='line'> size_t bufferOffset = 0;
</span><span class='line'> static const int AVCCHeaderLength = 4;
</span><span class='line'> while (bufferOffset < totalLength - AVCCHeaderLength) {
</span><span class='line'> // Read the NAL unit length
</span><span class='line'> uint32_t NALUnitLength = 0;
</span><span class='line'> memcpy(&NALUnitLength, dataPointer + bufferOffset, AVCCHeaderLength);
</span><span class='line'>
</span><span class='line'> // Convert the length value from Big-endian to Little-endian
</span><span class='line'> // After converting the length value, the start 4 byte will present the NALUnitLength
</span><span class='line'>
</span><span class='line'> NALUnitLength = CFSwapInt32BigToHost(NALUnitLength);
</span><span class='line'> NSData *data = [[NSData alloc]initWithBytes:(dataPointer + bufferOffset + AVCCHeaderLength) length:NALUnitLength];
</span><span class='line'>
</span><span class='line'> if (THIS->_delegate) {
</span><span class='line'> [THIS->_delegate gotEncodedData:data isKeyFrame:keyframe];
</span><span class='line'> }
</span><span class='line'>
</span><span class='line'> // Move to the next NAL unit in the block buffer
</span><span class='line'> bufferOffset += AVCCHeaderLength + NALUnitLength;
</span><span class='line'> }
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>回到ViewController來看, 將宣告的變數補齊以及實作delegate</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>@interface ViewController ()<AVCaptureVideoDataOutputSampleBufferDelegate, H264HwEncoderDelegate>
</span><span class='line'>{
</span><span class='line'> AVCaptureSession *captureSession;
</span><span class='line'> AVCaptureVideoPreviewLayer *previewLayer;
</span><span class='line'> AVCaptureConnection *connection;
</span><span class='line'> bool isStart;
</span><span class='line'> VideoEncode *videoEncode;
</span><span class='line'> NSFileHandle *fileHandle;
</span><span class='line'> NSString *h264File;
</span><span class='line'>}
</span><span class='line'>@property (weak, nonatomic) IBOutlet UIButton *startButton;
</span><span class='line'>@end</span></code></pre></td></tr></table></div></figure>
<p>接著透過delegate取得資料後寫入檔案, 在前面有用到AVCaptureVideoDataOutput並實作該協定, 所以加上該協定下的delegate method。
這個method會在有資料進到buffer內時被呼叫, 我們再將buffer傳給繼承VideoEncode的物件videoEncode去做影像的encode。</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>-(void) captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
</span><span class='line'>{
</span><span class='line'> [videoEncode encode:sampleBuffer];
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>接著在ViewController內實作H264HwEncoderDelegate的方法來取得sps, pps, i-frame, 記得要在寫入file前將frame的資料加上h264的header byte(0x00, 0x00, 0x00, 0x01)
因為MP4 AVCC下沒有h264的header, 要自己加上去。</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>- (void)gotSpsPps:(NSData*)sps pps:(NSData*)pps
</span><span class='line'>{
</span><span class='line'> NSLog(@"gotSpsPps %d %d", (int)[sps length], (int)[pps length]);
</span><span class='line'> const char bytes[] = "\x00\x00\x00\x01";
</span><span class='line'> size_t length = (sizeof bytes) - 1; //string literals have implicit trailing '\0'
</span><span class='line'> NSData *ByteHeader = [NSData dataWithBytes:bytes length:length];
</span><span class='line'> [fileHandle writeData:ByteHeader];
</span><span class='line'> [fileHandle writeData:sps];
</span><span class='line'> [fileHandle writeData:ByteHeader];
</span><span class='line'> [fileHandle writeData:pps];
</span><span class='line'>}
</span><span class='line'>
</span><span class='line'>- (void)gotEncodedData:(NSData*)data isKeyFrame:(BOOL)isKeyFrame
</span><span class='line'>{
</span><span class='line'> NSLog(@"gotEncodedData %d", (int)[data length]);
</span><span class='line'> if (fileHandle != NULL)
</span><span class='line'> {
</span><span class='line'> const char bytes[] = "\x00\x00\x00\x01";
</span><span class='line'> size_t length = (sizeof bytes) - 1; //string literals have implicit trailing '\0'
</span><span class='line'> NSData *ByteHeader = [NSData dataWithBytes:bytes length:length];
</span><span class='line'> [fileHandle writeData:ByteHeader];
</span><span class='line'> [fileHandle writeData:data];
</span><span class='line'> }
</span><span class='line'>}</span></code></pre></td></tr></table></div></figure>
<p>到這邊應該就差不多完成了, 可以簡單的錄製影像成h264 file, 再找個可以播放h264的播放器驗證看看。我是用VLC或是用自己寫的另一個專案做h264 decoder,
這部分找機會會在記錄一下, 畢竟打一篇網誌真的要好久好久…</p>
<p>可能有部分小細節沒有提到, 所以我將這部分的代碼放在我的GitHub上: <a href="https://github.com/pedoe/iOS_h264_hardware_encode">https://github.com/pedoe/iOS_h264_hardware_encode</a></p>
<p>有問題的地方還請告知~</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[How to separate storyboard for iPhone and iPad]]></title>
<link href="http://pedoe.github.io/blog/2016/03/17/how-to-separate-storyboard-for-iphone-and-ipad/"/>
<updated>2016-03-17T19:29:51+08:00</updated>
<id>http://pedoe.github.io/blog/2016/03/17/how-to-separate-storyboard-for-iphone-and-ipad</id>
<content type="html"><![CDATA[<h2>Storyboard for iPhone and iPad</h2>
<p>在Xocde6時Apple提供了Universal Storyboard的選項讓一個storyboard可以適應任何size的裝置。但有時候還是會因為iPhone與iPad的大小不同來呈現不同的效果, 在Standford CS193 Class11中的例子就使用iPad額外添加splitView的效果。</p>
<p>1.增加iPad的Storyboard</p>
<p> <img src="http://pedoe.github.io/images/CreateStoryboard.png" alt="Create Storyboard" /></p>
<p>2.取名(這裏我用<code>Main_iPad</code>)</p>
<p> <img src="http://pedoe.github.io/images/GiveName.png" alt="Give Name" /></p>
<p>3.在Project setting中選擇Info</p>
<p> <img src="http://pedoe.github.io/images/Info.png" alt="Info" /></p>
<p>4.右鍵新增並取名為的Main storyboard file base name (iPad)</p>
<p> <img src="http://pedoe.github.io/images/AddNewStoryboardfile.png" alt="Add New Storyboard File" /></p>
<p>5.Value中給定你在步驟3中設定iPad storyboard的名字(這裏我的是<code>Main_iPad</code>)</p>
<p>6.別忘了開啟iPad Storyboard設定Initial view, 才找得到你的Viewcontroller</p>
<p> <img src="http://pedoe.github.io/images/AddInitialView.png" alt="AddInitialView" /></p>
<h2>Reference</h2>
<p>1.<a href="https://irawd.wordpress.com/2014/10/21/xcode-6-separate-storyboard-for-ipad-and-iphone/">https://irawd.wordpress.com/2014/10/21/xcode-6-separate-storyboard-for-ipad-and-iphone/</a></p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[How to Update Locate Database on OS X]]></title>
<link href="http://pedoe.github.io/blog/2016/03/17/update-locate-database/"/>
<updated>2016-03-17T09:51:29+08:00</updated>
<id>http://pedoe.github.io/blog/2016/03/17/update-locate-database</id>
<content type="html"><![CDATA[<h2>在Mac上使用locate指令尋找檔案</h2>
<p>最近開始學在Mac上用Terminal做事情, ㄧ直不知道怎樣找檔案最快, 直到讀到了locate這個指令。</p>
<p>但是第一次使用locate前需要update database, 若是沒有更新會遇到以下問題:</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>WARNING: The locate database (/var/db/locate.database) does not exist.
</span><span class='line'>To create the database, run the following command:
</span><span class='line'>
</span><span class='line'> sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.locate.plist
</span><span class='line'>
</span><span class='line'> Please be aware that the database can take some time to generate; once
</span><span class='line'> the database has been created, this message will no longer appear.</span></code></pre></td></tr></table></div></figure>
<p>而怎麼更新database在"Learning Unix for OS X" 這本書上並沒有講得很清楚, 因此上網google了一下。</p>
<p>需要執行<code>$sudo /usr/libexec/locate.updatedb</code></p>
<p>讓你的Mac做第一次更新, 第一次會花些時間來建立你的database。</p>
<p>成功後就可以使用locate查詢, ex: <code>$locate test</code></p>
<p>但是接下來每次更新都需要下相同指令<code>$sudo /usr/libexec/locate.updatedb</code>,</p>
<p>變得稍嫌麻煩, 可以做一些更改將指令簡化成updatedb(跟linux上相同的指令)。</p>
<p><code>cd /usr/local/bin</code></p>
<p><code>ln -s /usr/libexec/locate.updatedb updatedb</code></p>
<p>接下來每次更新database只需要下<code>updatedb</code>就可以了。</p>
<h2>Referrence</h2>
<p>1.<a href="http://aross.se/2015/07/19/how-to-update-locate-database-on-osx.html">http://aross.se/2015/07/19/how-to-update-locate-database-on-osx.html</a></p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Post Article]]></title>
<link href="http://pedoe.github.io/blog/2016/03/03/post-article/"/>
<updated>2016-03-03T21:28:18+08:00</updated>
<id>http://pedoe.github.io/blog/2016/03/03/post-article</id>
<content type="html"><![CDATA[<h2>前言</h2>
<p> 成功架好blog後要做的第一件事, 就是來發表一篇文章充充版面。這篇文章中會教大家如何發表文章以及基礎的排版編輯。首先要來談談使用Octopress+Github Pages架設網頁的主要優點。</p>
<ol>
<li><p>GitHub是一使用Git版本控制並且提供存放軟體代碼與內容服務的平台。而Git是一免費的分散式版本控制系統, 由Linus Torvalds(Linux Kernel的創作者)在2005年左右所創造出來的, 目前是被廣泛應用的版本控制系統之一。Git的好處是可以在本機端就有一儲存庫(Repository)可進行修改編輯並運作版本控制, 不必連線到主機端取得資料, 使得開發非常快速且方便。因此使用Github來存放blog好處是可以用強大的git進行blog內容的控制, 也容易讓多個作者維護同一個blog。最棒的是可以學習熟悉目前世界上最潮的版本控制系統。</p></li>
<li><p>Octopress支援markdown語法來進行編輯, 大大簡化編寫網頁的過程。Markdown是一種輕量級的標記式語言, 目的為好讀好寫, 讓使用者免去學習HTML複雜繁長的語法由靠編寫markdown文件再轉換成HTML文件來產生網頁。這篇文章將會介紹一些常用的語法並舉簡單的例子實作markdown語法。而使用Octopress還有一個好處是內部一些方便的指令, 例如幫助你把網頁部署到github pages與local端預覽blog呈現效果等等。</p></li>
</ol>
<h2>發表你第一篇文章</h2>
<ol>
<li><p>進到你的Octopress資料夾內</p>
<p><code>$cd octopress</code></p></li>
<li><p>產生一篇名為'title'的文章</p>
<p><code>$rake new_post['title']</code></p></li>
<li><p>接下來你就會看到產生一個名字為時間與title的markdown文件, 類似下方的訊息</p>
<p><code>Creating new post: source/_posts/2016-03-04-title.markdown</code></p></li>
<li><p>產生文章後我們來預覽看看</p>
<p><code>$rake preview</code></p>
<p><img src="http://pedoe.github.io/images/new_post_article.png" alt="Alt Text" /></p>
<p>有沒有看到上面一篇名為'Title'的文章？恭喜你!在blog上發表了第一篇文章。</p></li>
</ol>
<h2>編輯文章內容</h2>
<p>要開始編輯文章, 我們必須進到文章所在的資料夾去開始編輯。</p>
<ol>
<li><p>預設中是放在/octopress/source/_posts</p>
<p><code>$cd octopress/source/_posts</code></p></li>
<li><p>檢查文章是否存在, 輸入ls來觀看資料夾內所有內容</p>
<p><code>$ls</code></p>
<p>此時你應該會看到剛剛所建立的文章, 在本文的例子中是'2016-03-04-title.markdown'這篇文章</p>
<p><img src="http://pedoe.github.io/images/ls.png" alt="Alt Text" /></p></li>
<li><p>由於我是用vim進行文章編輯, 網路上也有許多方便好用的markdwon編輯軟體, 就依照個人喜好囉。首先開啟文章進行編輯</p>
<p><code>$vim 2016-03-04-title.markdown</code></p>
<p>開啟後你應該會看到如下的畫面</p>
<p><img src="http://pedoe.github.io/images/content.png" alt="Alt Text" /></p>
<p>title這行就是顯示你這篇文章的title</p>
<p>data就是你產生文章的時間</p>
<p>comment則是你可以選擇這篇文章是否允許評論(要能成功使別人留言還需做點額外努力, 可以自行google或是以後有機會談到blog設定時再分享給大家)</p>
<p>categories則是可以添加你希望支援的語法, 例如CSS3, Sass等等</p></li>
<li><p>接下來隨意輸入內容進行測試</p>