本例需求：使用H264, H265實現視頻數據的編碼并錄制開始200幀存為文件.
原理：比如做直播功能，需要將客戶端的視頻數據傳給服務器，如果分辨率過大如2K,4K則傳輸壓力太大，所以需要對視頻數據進行編碼，傳給服務器后再解碼以實現大數據量的視頻數據的傳輸，而利用硬件編碼則可以極大限度減小CPU壓力，
H264進行編碼，iOS 11 之后，iPhone 7以上的設備可以支持新的編碼器H265編碼器，使得同等質量視頻占用的存儲空間更小。所以本例中可以使用兩種方式實現視頻數據的編碼
最終效果如下 ： h264
h265 :
GitHub地址(附代碼) : H264,H265Encode
簡書地址 : H264,H265Encode
博客地址 : H264,H265Encode
掘金地址 : H264,H265Encode
實現方式：
1. H264 : H264是當前主流編碼標準，以高壓縮高質量和支持多種網絡的流媒體傳輸著稱
2. H265 ：H264編碼器的下一代，它的主要優點提供的壓縮比高，相同質量的視頻是H264的兩倍。
一.本文需要基本知識點
注意:可以先通過H264,H265編碼器介紹, H.264 Data Structure了解預備知識。
1. 軟編與硬編概念
- 軟編碼：使用CPU進行編碼。
- 硬編碼：不使用CPU進行編碼，使用顯卡GPU,專用的DSP、FPGA、ASIC芯片等硬件進行編碼。
- 比較
- 軟編碼：實現直接、簡單，參數調整方便，升級易，但CPU負載重，性能較硬編碼低，低碼率下質量通常比硬編碼要好一點。
- 性能高，低碼率下通常質量低于軟編碼器，但部分產品在GPU硬件平臺移植了優秀的軟編碼算法（如X264）的，質量基本等同于軟編碼。
- 蘋果在iOS 8.0系統之前，沒有開放系統的硬件編碼解碼功能，不過Mac OS系統一直有，被稱為Video ToolBox的框架來處理硬件的編碼和解碼，終于在iOS 8.0后，蘋果將該框架引入iOS系統
2.H265優點
- 壓縮比高，在相同圖片質量情況下，比JPEG高兩倍
- 能增加如圖片的深度信息，透明通道等輔助圖片。
- 支持存放多張圖片，類似相冊和集合。(實現多重曝光的效果)
- 支持多張圖片實現GIF和livePhoto的動畫效果。
- 無類似JPEG的最大像素限制
- 支持透明像素
- 分塊加載機制
- 支持縮略圖
二.代碼解析
1.實現流程
- 初始化相機參數，設置相機代理，這里就固定只有豎屏模式。
- 初始化編碼器參數，并啟動編碼器
- 在編碼成功的回調中從開始錄制200幀(文件大小可自行修改)的視頻，存到沙盒中，可以通過連接數據線到電腦從itunes中將文件(test0.asf)提取出來
2.編碼器實現流程
- 創建編碼器需要的session (h264, h265 或同時創建)
- 設置session屬性,如實時編碼，碼率，fps, 編碼的分辨率的寬高，相鄰I幀的最大間隔等等
- 當相機回調AVCaptureVideoDataOutputSampleBufferDelegate采集到一幀數據的時候則使用H264/H265編碼器對每一幀數據進行編碼。
- 若編碼成功會觸發回調，回調函數首先檢測是否有I幀出現，如果有I幀出現則將sps,pps信息寫入否則遍歷NALU碼流并將startCode替換成{0x00, 0x00, 0x00, 0x01}
3.主要方法解析
- 初始化編碼器 首先選擇使用哪種方式實現，在本例中可以設置[XDXHardwareEncoder getInstance].enableH264 = YES 或者 [XDXHardwareEncoder getInstance].enableH265 = YES，也可以同時設置，如果同時設置需要將其中一個回調函數中的writeFile的方法屏蔽掉，并且只有較新的iPhone(> iPhone8 穩定)才支持同時打開兩個session。
判斷當前設備是否支持H265編碼，必須滿足兩個條件，一是iPhone 7 以上設備，二是版本大于iOS 11
if (@available(iOS 11.0, *)) {BOOL hardwareDecodeSupported = VTIsHardwareDecodeSupported(kCMVideoCodecType_HEVC);
if (hardwareDecodeSupported) {_deviceSupportH265 = YES;NSLog(@
"XDXHardwareEncoder : Support H265 Encode/Decode!");}}
else {_deviceSupportH265 = NO;NSLog(@
"XDXHardwareEncoder : Not support H265 Encode/Decode!");}
復制代碼系統已經提供VTIsHardwareDecodeSupported判斷當前設備是否支持H265編碼
初始化編碼器操作
- (void)prepareForEncode {
if(self.width == 0 || self.height == 0) {NSLog(@
"XDXHardwareEncoder : VTSession need with and height for init,with = %d,height = %d",self.width, self.height);
return;}
if(g_isSupportRealTimeEncoder) NSLog(@
"XDXHardwareEncoder : Device processor is 64 bit");
else NSLog(@
"XDXHardwareEncoder : Device processor is not 64 bit");NSLog(@
"XDXHardwareEncoder : Current h264 open state : %d, h265 open state : %d",self.enableH264, self.enableH265);OSStatus h264Status,h265Status;BOOL isRestart = NO;
if (self.enableH264) {
if (h264CompressionSession != NULL) {NSLog(@
"XDXHardwareEncoder : H264 session not NULL");
return;}[m_h264_lock lock];NSLog(@
"XDXHardwareEncoder : Prepare H264 hardware encoder");//[self.delegate willEncoderStart];self.h264ErrCount = 0;h264Status = VTCompressionSessionCreate(NULL, self.width, self.height, kCMVideoCodecType_H264, NULL, NULL, NULL, vtCallBack,(__bridge void *)self, &h264CompressionSession);
if (h264Status != noErr) {self.h265ErrCount++;NSLog(@
"XDXHardwareEncoder : H264 VTCompressionSessionCreate Failed, status = %d",h264Status);}[self getSupportedPropertyFlags];[self applyAllSessionProperty:h264CompressionSession propertyArr:self.h264propertyFlags];h264Status = VTCompressionSessionPrepareToEncodeFrames(h264CompressionSession);
if(h264Status != noErr) {NSLog(@
"XDXHardwareEncoder : H264 VTCompressionSessionPrepareToEncodeFrames Failed, status = %d",h264Status);}
else {initializedH264 =
true;NSLog(@
"XDXHardwareEncoder : H264 VTSession create success, with = %d, height = %d, framerate = %d",self.width,self.height,self.fps);}
if(h264Status != noErr && self.h264ErrCount != 0) isRestart = YES;[m_h264_lock unlock];}
if (self.enableH265) {
if (h265CompressionSession != NULL) {NSLog(@
"XDXHardwareEncoder : H265 session not NULL");
return;}[m_h265_lock lock];NSLog(@
"XDXHardwareEncoder : Prepare h265 hardware encoder");// [self.delegate willEncoderStart];self.h265ErrCount = 0;h265Status = VTCompressionSessionCreate(NULL, self.width, self.height, kCMVideoCodecType_HEVC, NULL, NULL, NULL, vtH265CallBack,(__bridge void *)self, &h265CompressionSession);
if (h265Status != noErr) {self.h265ErrCount++;NSLog(@
"XDXHardwareEncoder : H265 VTCompressionSessionCreate Failed, status = %d",h265Status);}[self getSupportedPropertyFlags];[self applyAllSessionProperty:h265CompressionSession propertyArr:self.h265PropertyFlags];h265Status = VTCompressionSessionPrepareToEncodeFrames(h265CompressionSession);
if(h265Status != noErr) {NSLog(@
"XDXHardwareEncoder : H265 VTCompressionSessionPrepareToEncodeFrames Failed, status = %d",h265Status);}
else {initializedH265 =
true;NSLog(@
"XDXHardwareEncoder : H265 VTSession create success, with = %d, height = %d, framerate = %d",self.width,self.height,self.fps);}
if(h265Status != noErr && self.h265ErrCount != 0) isRestart = YES;[m_h265_lock unlock];}
if (isRestart) {NSLog(@
"XDXHardwareEncoder : VTSession create failured!");static int count = 0;count ++;
if (count == 3) {NSLog(@
"TVUEncoder ： restart 5 times failured! exit!");
return;}sleep(1);NSLog(@
"TVUEncoder ： try to restart after 1 second!");NSLog(@
"TVUEncoder ： vtsession error occured!,resetart encoder width: %d, height %d, times %d",self.width,self.height,count);[self tearDownSession];[self prepareForEncode];}
}
復制代碼1> g_isSupportRealTimeEncoder = (is64Bit == 8) ? true : false;用來判斷當前設備是32位還是64位
2> 創建H264/H265Session 區別僅僅為參數的不同，h264為kCMVideoCodecType_H264。 h265為kCMVideoCodecType_HEVC，在創建Session指定了回調函數后，當編碼成功一幀就會調用相應的回調函數。
3> 通過[self getSupportedPropertyFlags];獲取當前編碼器支持設置的屬性，經過測試，H265不支持碼率的限制。目前暫時得不到解決。等待蘋果后續處理。
4> 之后設置編碼器相關屬性，下面會具體介紹，設置完成后則調用VTCompressionSessionPrepareToEncodeFrames準備編碼。
- (OSStatus)
setSessionProperty:(VTCompressionSessionRef)session key:(CFStringRef)key value:(CFTypeRef)value {OSStatus status = VTSessionSetProperty(session, key, value);
if (status != noErr) {NSString *sessionStr;
if (session == h264CompressionSession) {sessionStr = @
"h264 Session";self.h264ErrCount++;}
else if (session == h265CompressionSession) {sessionStr = @
"h265 Session";self.h265ErrCount++;}NSLog(@
"XDXHardwareEncoder : Set %s of %s Failed, status = %d",CFStringGetCStringPtr(key, kCFStringEncodingUTF8),sessionStr.UTF8String,status);}
return status;
}- (void)applyAllSessionProperty:(VTCompressionSessionRef)session propertyArr:(NSArray *)propertyArr {OSStatus status;
if(!g_isSupportRealTimeEncoder) {/* increase max frame delay from 3 to 6 to reduce encoder pressure*/int value = 3;CFNumberRef ref = CFNumberCreate(NULL, kCFNumberSInt32Type, &value);[self
setSessionProperty:session key:kVTCompressionPropertyKey_MaxFrameDelayCount value:ref];CFRelease(ref);}
if(self.fps) {
if([self isSupportPropertyWithKey:Key_ExpectedFrameRate
inArray:propertyArr]) {int value = self.fps;CFNumberRef ref = CFNumberCreate(NULL, kCFNumberSInt32Type, &value);[self
setSessionProperty:session key:kVTCompressionPropertyKey_ExpectedFrameRate value:ref];CFRelease(ref);}}
else {NSLog(@
"XDXHardwareEncoder : Current fps is 0");}
if(self.bitrate) {
if([self isSupportPropertyWithKey:Key_AverageBitRate
inArray:propertyArr]) {int value = self.bitrate;
if (session == h265CompressionSession) value = 2*1000; //
if current session is h265, Set birate 2M.CFNumberRef ref = CFNumberCreate(NULL, kCFNumberSInt32Type, &value);[self
setSessionProperty:session key:kVTCompressionPropertyKey_AverageBitRate value:ref];CFRelease(ref);}}
else {NSLog(@
"XDXHardwareEncoder : Current bitrate is 0");}/*2016-11-15,@gang, iphone7/7plus
do not support realtime encoding, so
disable itotherwize ,we can not control encoding bit rate*/
if (![[self deviceVersion] isEqualToString:@
"iPhone9,1"] && ![[self deviceVersion] isEqualToString:@
"iPhone9,2"]) {
if(g_isSupportRealTimeEncoder) {
if([self isSupportPropertyWithKey:Key_RealTime
inArray:propertyArr]) {NSLog(@
"use RealTimeEncoder");NSLog(@
"XDXHardwareEncoder : use realTimeEncoder");[self
setSessionProperty:session key:kVTCompressionPropertyKey_RealTime value:kCFBooleanTrue];}}}
if([self isSupportPropertyWithKey:Key_AllowFrameReordering
inArray:propertyArr]) {[self
setSessionProperty:session key:kVTCompressionPropertyKey_AllowFrameReordering value:kCFBooleanFalse];}
if(g_isSupportRealTimeEncoder) {
if([self isSupportPropertyWithKey:Key_ProfileLevel
inArray:propertyArr]) {[self
setSessionProperty:session key:kVTCompressionPropertyKey_ProfileLevel value:self.enableH264 ? kVTProfileLevel_H264_Main_AutoLevel : kVTProfileLevel_HEVC_Main_AutoLevel];}}
else {
if([self isSupportPropertyWithKey:Key_ProfileLevel
inArray:propertyArr]) {[self
setSessionProperty:session key:kVTCompressionPropertyKey_ProfileLevel value:self.enableH264 ? kVTProfileLevel_H264_Baseline_AutoLevel : kVTProfileLevel_HEVC_Main_AutoLevel];}
if (self.enableH264) {
if([self isSupportPropertyWithKey:Key_H264EntropyMode
inArray:propertyArr]) {[self
setSessionProperty:session key:kVTCompressionPropertyKey_H264EntropyMode value:kVTH264EntropyMode_CAVLC];}}}
if([self isSupportPropertyWithKey:Key_MaxKeyFrameIntervalDuration
inArray:propertyArr]) {int value = 1;CFNumberRef ref = CFNumberCreate(NULL, kCFNumberSInt32Type, &value);[self
setSessionProperty:session key:kVTCompressionPropertyKey_MaxKeyFrameIntervalDuration value:ref];CFRelease(ref);}
}
復制代碼上述方法主要設置啟動編碼器所需的各個參數
1> kVTCompressionPropertyKey_MaxFrameDelayCount : 壓縮器被允許保持的最大幀數在輸出一個壓縮幀之前。例如如果最大幀延遲數是M,那么在編碼幀N返回的調用之前，幀N-M必須被排出。
2> kVTCompressionPropertyKey_ExpectedFrameRate : 設置fps
3> kVTCompressionPropertyKey_AverageBitRate : 它不是強制的限制，bit rate可能會超出峰值
4> kVTCompressionPropertyKey_RealTime : 設置編碼器是否實時編碼，如果設置為False則不是實時編碼，視頻效果會更好一點。
5> kVTCompressionPropertyKey_AllowFrameReordering : 是否讓幀進行重新排序。為了編碼B幀，編碼器必須對幀重新排序，這將意味著解碼的順序與顯示的順序不同。將其設置為false以防止幀重新排序。
6> kVTCompressionPropertyKey_ProfileLevel : 指定編碼比特流的配置文件和級別
7> kVTCompressionPropertyKey_H264EntropyMode ：如果支持h264該屬性設置編碼器是否應該使用基于CAVLC 還是 CABAC
8> kVTCompressionPropertyKey_MaxKeyFrameIntervalDuration : 兩個I幀之間最大持續時間，該屬性特別有用當frame rate是可變
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
if( !CMSampleBufferDataIsReady(sampleBuffer)) {NSLog( @
"sample buffer is not ready. Skipping sample" );
return;}
if([XDXHardwareEncoder getInstance] != NULL) {[[XDXHardwareEncoder getInstance] encode:sampleBuffer];}
}
復制代碼以上方法在每采集到一幀視頻數據后會調用一次，我們將拿到的每一幀數據進行編碼。
-(void)encode:(CMSampleBufferRef)sampleBuffer {
if (self.enableH264) {[m_h264_lock lock];
if(h264CompressionSession == NULL) {[m_h264_lock unlock];
return;}
if(initializedH264 ==
false) {NSLog(@
"TVUEncoder : h264 encoder is not ready\n");
return;}}
if (self.enableH265) {[m_h265_lock lock];
if(h265CompressionSession == NULL) {[m_h265_lock unlock];
return;}
if(initializedH265 ==
false) {NSLog(@
"TVUEncoder : h265 encoder is not ready\n");
return;}}CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);CMTime duration = CMSampleBufferGetOutputDuration(sampleBuffer);frameID++;CMTime presentationTimeStamp = CMTimeMake(frameID, 1000);[self
doSetBitrate];OSStatus status;VTEncodeInfoFlags flags;
if (self.enableH264) {status = VTCompressionSessionEncodeFrame(h264CompressionSession, imageBuffer, presentationTimeStamp, duration, NULL, imageBuffer, &flags);
if(status != noErr) NSLog(@
"TVUEncoder : H264 VTCompressionSessionEncodeFrame failed");[m_h264_lock unlock];
if (status != noErr) {NSLog(@
"TVUEncoder : VTCompressionSessionEncodeFrame failed");VTCompressionSessionCompleteFrames(h264CompressionSession, kCMTimeInvalid);VTCompressionSessionInvalidate(h264CompressionSession);CFRelease(h264CompressionSession);h264CompressionSession = NULL;}
else {// NSLog(@
"TVUEncoder : Success VTCompressionSessionCompleteFrames");}}
if (self.enableH265) {status = VTCompressionSessionEncodeFrame(h265CompressionSession, imageBuffer, presentationTimeStamp, duration, NULL, imageBuffer, &flags);
if(status != noErr) NSLog(@
"TVUEncoder : H265 VTCompressionSessionEncodeFrame failed");[m_h265_lock unlock];
if (status != noErr) {NSLog(@
"TVUEncoder : VTCompressionSessionEncodeFrame failed");VTCompressionSessionCompleteFrames(h265CompressionSession, kCMTimeInvalid);VTCompressionSessionInvalidate(h265CompressionSession);CFRelease(h265CompressionSession);h265CompressionSession = NULL;}
else {NSLog(@
"TVUEncoder : Success VTCompressionSessionCompleteFrames");}}}
復制代碼1> 通過frameID的遞增構造時間戳為了使編碼后的每一幀數據連續
2> 設置最大碼率的限制，注意：H265目前不支持設置碼率的限制，等待官方后續通知。可以對H264進行碼率限制
3> kVTCompressionPropertyKey_DataRateLimits : 將數據的bytes和duration封裝到CFMutableArrayRef傳給API進行調用
4> VTCompressionSessionEncodeFrame : 調用此方法成功后觸發回調函數完成編碼。
static void vtCallBack(void *outputCallbackRefCon,void *souceFrameRefCon,OSStatus status,VTEncodeInfoFlags infoFlags, CMSampleBufferRef sampleBuffer) {XDXHardwareEncoder *encoder = (__bridge XDXHardwareEncoder*)outputCallbackRefCon;
if(status != noErr) {NSError *error = [NSError errorWithDomain:NSOSStatusErrorDomain code:status userInfo:nil];NSLog(@
"H264: vtCallBack failed with %@", error);NSLog(@
"XDXHardwareEncoder : encode frame failured! %s" ,error.debugDescription.UTF8String);
return;}
if (!CMSampleBufferDataIsReady(sampleBuffer)) {NSLog(@
"didCompressH265 data is not ready ");
return;}
if (infoFlags == kVTEncodeInfo_FrameDropped) {NSLog(@
"%s with frame dropped.", __FUNCTION__);
return;}CMBlockBufferRef block = CMSampleBufferGetDataBuffer(sampleBuffer);BOOL isKeyframe =
false;CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer,
false);
if(attachments != NULL) {CFDictionaryRef attachment =(CFDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);CFBooleanRef dependsOnOthers = (CFBooleanRef)CFDictionaryGetValue(attachment, kCMSampleAttachmentKey_DependsOnOthers);isKeyframe = (dependsOnOthers == kCFBooleanFalse);}
if(isKeyframe) {CMFormatDescriptionRef format = CMSampleBufferGetFormatDescription(sampleBuffer);static uint8_t *spsppsNALBuff = NULL;static size_t spsSize, ppsSize;size_t parmCount;const uint8_t*sps, *pps;int NALUnitHeaderLengthOut;CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format, 0, &sps, &spsSize, &parmCount, &NALUnitHeaderLengthOut );CMVideoFormatDescriptionGetH264ParameterSetAtIndex(format, 1, &pps, &ppsSize, &parmCount, &NALUnitHeaderLengthOut );spsppsNALBuff = (uint8_t*)malloc(spsSize+4+ppsSize+4);memcpy(spsppsNALBuff,
"\x00\x00\x00\x01", 4);memcpy(&spsppsNALBuff[4], sps, spsSize);memcpy(&spsppsNALBuff[4+spsSize],
"\x00\x00\x00\x01", 4);memcpy(&spsppsNALBuff[4+spsSize+4], pps, ppsSize);NSLog(@
"XDXHardwareEncoder : H264 spsSize : %zu, ppsSize : %zu",spsSize, ppsSize);writeFile(spsppsNALBuff,spsSize+4+ppsSize+4,encoder->_videoFile, 200);}size_t blockBufferLength;uint8_t *bufferDataPointer = NULL;CMBlockBufferGetDataPointer(block, 0, NULL, &blockBufferLength, (char **)&bufferDataPointer);size_t bufferOffset = 0;
while (bufferOffset < blockBufferLength - startCodeLength) {uint32_t NALUnitLength = 0;memcpy(&NALUnitLength, bufferDataPointer+bufferOffset, startCodeLength);NALUnitLength = CFSwapInt32BigToHost(NALUnitLength);memcpy(bufferDataPointer+bufferOffset, startCode, startCodeLength);bufferOffset += startCodeLength + NALUnitLength;}writeFile(bufferDataPointer, blockBufferLength,encoder->_videoFile, 200);
}
static void vtH265CallBack(void *outputCallbackRefCon,void *souceFrameRefCon,OSStatus status,VTEncodeInfoFlags infoFlags, CMSampleBufferRef sampleBuffer) {XDXHardwareEncoder *encoder = (__bridge XDXHardwareEncoder*)outputCallbackRefCon;
if(status != noErr) {NSError *error = [NSError errorWithDomain:NSOSStatusErrorDomain code:status userInfo:nil];NSLog(@
"H264: H265 vtH265CallBack failed with %@", error);NSLog(@
"XDXHardwareEncoder : H265 encode frame failured! %s" ,error.debugDescription.UTF8String);
return;}
if (!CMSampleBufferDataIsReady(sampleBuffer)) {NSLog(@
"didCompressH265 data is not ready ");
return;}
if (infoFlags == kVTEncodeInfo_FrameDropped) {NSLog(@
"%s with frame dropped.", __FUNCTION__);
return;}CMBlockBufferRef block = CMSampleBufferGetDataBuffer(sampleBuffer);BOOL isKeyframe =
false;CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer,
false);
if(attachments != NULL) {CFDictionaryRef attachment =(CFDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);CFBooleanRef dependsOnOthers = (CFBooleanRef)CFDictionaryGetValue(attachment, kCMSampleAttachmentKey_DependsOnOthers);isKeyframe = (dependsOnOthers == kCFBooleanFalse);}
if(isKeyframe) {CMFormatDescriptionRef format = CMSampleBufferGetFormatDescription(sampleBuffer);static uint8_t *vpsspsppsNALBuff = NULL;static size_t vpsSize, spsSize, ppsSize;size_t parmCount;const uint8_t *vps, *sps, *pps;
if (encoder.deviceSupportH265) { // >= iPhone 7 && support ios11CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 0, &vps, &vpsSize, &parmCount, 0);CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 1, &sps, &spsSize, &parmCount, 0);CMVideoFormatDescriptionGetHEVCParameterSetAtIndex(format, 2, &pps, &ppsSize, &parmCount, 0);vpsspsppsNALBuff = (uint8_t*)malloc(vpsSize+4+spsSize+4+ppsSize+4);memcpy(vpsspsppsNALBuff,
"\x00\x00\x00\x01", 4);memcpy(&vpsspsppsNALBuff[4], vps, vpsSize);memcpy(&vpsspsppsNALBuff[4+vpsSize],
"\x00\x00\x00\x01", 4);memcpy(&vpsspsppsNALBuff[4+vpsSize+4], sps, spsSize);memcpy(&vpsspsppsNALBuff[4+vpsSize+4+spsSize],
"\x00\x00\x00\x01", 4);memcpy(&vpsspsppsNALBuff[4+vpsSize+4+spsSize+4], pps, ppsSize);NSLog(@
"XDXHardwareEncoder : H265 vpsSize : %zu, spsSize : %zu, ppsSize : %zu",vpsSize,spsSize, ppsSize);}writeFile(vpsspsppsNALBuff, vpsSize+4+spsSize+4+ppsSize+4,encoder->_videoFile, 200);}size_t blockBufferLength;uint8_t *bufferDataPointer = NULL;CMBlockBufferGetDataPointer(block, 0, NULL, &blockBufferLength, (char **)&bufferDataPointer);size_t bufferOffset = 0;
while (bufferOffset < blockBufferLength - startCodeLength) {uint32_t NALUnitLength = 0;memcpy(&NALUnitLength, bufferDataPointer+bufferOffset, startCodeLength);NALUnitLength = CFSwapInt32BigToHost(NALUnitLength);memcpy(bufferDataPointer+bufferOffset, startCode, startCodeLength);bufferOffset += startCodeLength + NALUnitLength;}writeFile(bufferDataPointer, blockBufferLength,encoder->_videoFile, 200);
}
復制代碼1> 首先在回調函數中截取到I幀，從I幀中提取到(h265中新增vps),sps,pps信息并寫入文件 2> 遍歷其他幀將頭信息0000,0001寫入每個頭信息中，再將該數據寫入文件即可
二.碼流數據結構介紹
這里我們簡單介紹一下H264,H265碼流信息
H264流數據是由一系列NAL單元(NAL Unit)組成的。
一個NALU可能包含：視頻幀，視頻幀也就是視頻片段，具體有I,P,B幀
H.264屬性合集-FormatDesc(包含 SPS和PPS) 注意在H265流數據中新增vps在最前。
- H.264屬性合集-FormatDesc(包含 SPS和PPS)
流數據中，屬性集合可能是這樣的：
經過處理之后，在Format Description中則是:
- NALU header 對于流數據來說，一個NALU的Header中，可能是0x00 00 01或者是0x00 00 00 01作為開頭(兩者都有可能，下面以0x00 00 01作為例子)。0x00 00 01因此被稱為開始碼(Start code).所以我們需要在提取的數據中用0x00 00 00 01對數據內容進行替換
總結以上知識，我們知道H264的碼流由NALU單元組成，NALU單元包含視頻圖像數據和H264的參數信息。其中視頻圖像數據就是CMBlockBuffer，而H264的參數信息則可以組合成FormatDesc。具體來說參數信息包含SPS（Sequence Parameter Set）和PPS（Picture Parameter Set）.如下圖顯示了一個H.264碼流結構：
根據上述得到CMVideoFormatDescriptionRef、CMBlockBufferRef和可選的時間信息，使用CMSampleBufferCreate接口得到CMSampleBuffer數據這個待解碼的原始的數據。如下圖所示的H264數據轉換示意圖。
編碼器知識可參考:H264,H265編碼器介紹
總結
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