蘋果在iOS 8.0系統之前若要做音視訊開發需使用第三方軟體進行編解碼(FFmpeg軟解碼H264視訊流可看到這裡)，學習成本較大，項目開發進度也可能超出預期。在iOS 8.0之後開放了視訊編解碼架構VideoToolbox，在此之後對于音視訊開發變得相對簡單。

一、硬解碼名詞(結構)解釋

1、VTDecompressionSessionRef：解碼器對象資料結構；

2、CMVideoFormatDescriptionRef：圖形解碼相關格式及描述；

3、CVPixelBufferRef：編碼前和解碼後的圖像資料結構；

4、CMBlockBufferRef：存在解碼前圖像資料記憶體結構；

5、CMSampleBufferRef：存放解碼前的視訊圖像的容器資料結構；

6、AVSampleBufferDisplayLayer：以CMSampleBufferRef進行解碼并顯示Layer圖層；

7、SPS、PPS：h.264解碼參數資訊；IDR：h.264視訊流I幀；

二、H264硬解碼流程圖

iOS硬解碼H264視訊流一、硬解碼名詞(結構)解釋二、H264硬解碼流程圖三：IDR(I幀)網絡裸流資料結構四、硬解碼相關接口五、完整H264解碼代碼

三：IDR(I幀)網絡裸流資料結構

一般情況下網絡視訊裸流I幀中基本會包含SPS、PPS、SEI、IDR幀資料，如下圖所示，但是部分隻含有IDR幀資料，其他解碼參數資訊被單獨已Slice擷取。

iOS硬解碼H264視訊流一、硬解碼名詞(結構)解釋二、H264硬解碼流程圖三：IDR(I幀)網絡裸流資料結構四、硬解碼相關接口五、完整H264解碼代碼

四、硬解碼相關接口

1、初始化H264硬解解碼器

1）使用CMVideoFormatDescriptionCreateFromH264ParameterSets函數建構解碼描述結構CMVideoFormatDescriptionRef：

const uint8_t *const parameterSetPointers[2] = {pSPS,pPPS};
    const size_t parameterSetSizes[2] = {mSpsSize, mPpsSize};
    
    OSStatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kCFAllocatorDefault,
                                                                          2,    //參數個數，主要包含SPS、PPS
                                                                          parameterSetPointers,
                                                                          parameterSetSizes,
                                                                          4,    //NALU起始位個數
                                                                          &mDecoderFormatDescription);

2）使用VTDecompressionSessionCreate函數建構解碼器結構VTDecompressionSessionRef：

uint32_t pixelFormatType = kCVPixelFormatType_420YpCbCr8BiPlanarFullRange;  //NV12
    const void *keys[] = { kCVPixelBufferPixelFormatTypeKey };
    const void *values[] = { CFNumberCreate(NULL, kCFNumberSInt32Type, &pixelFormatType) };    //32位
    CFDictionaryRef attrs = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    
    VTDecompressionOutputCallbackRecord callBackRecord;
    callBackRecord.decompressionOutputCallback = didDecompress;    
    callBackRecord.decompressionOutputRefCon = NULL;
    
    status = VTDecompressionSessionCreate(kCFAllocatorDefault,
                                          mDecoderFormatDescription,
                                          NULL, attrs,
                                          &callBackRecord,
                                          &mDeocderSession);
    CFRelease(attrs);

2、H264硬體解碼

1）将視訊裸流資料建構成CMBlockBufferRef，主要目的是進一步轉換為CMSampleBufferRef：

    CMBlockBufferRef blockBuffer = NULL;
    OSStatus status  = CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, (void *)videoBuffer, videoBufferSize, kCFAllocatorNull, NULL, 0, videoBufferSize, 0, &blockBuffer);

CMSampleBufferRef sampleBuffer = NULL;
    const size_t sampleSizeArray[] = { videoBufferSize };
    OSStatus status = CMSampleBufferCreateReady(kCFAllocatorDefault, blockBuffer, mDecoderFormatDescription , 1, 0, NULL, 1, sampleSizeArray, &sampleBuffer);

2）将CMSampleBufferRef結構送入VTDecompressionSessionDecodeFrame函數進行解碼處理：

VTDecodeFrameFlags flags = 0;
    VTDecodeInfoFlags flagOut = 0;
    CVPixelBufferRef outputPixelBuffer = NULL;
    OSStatus decodeStatus = VTDecompressionSessionDecodeFrame(mDeocderSession, sampleBuffer, flags, &outputPixelBuffer, &flagOut);

3）若使用AVSampleBufferDisplayLayer圖層進行直接顯示，可忽略上一步的還行，直接将CMSampleBufferRef送入AVSampleBufferDisplayLayer進行顯示：

CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, YES);
    CFMutableDictionaryRef dict = (CFMutableDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);
    CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanTrue);
    if ([self.displayLayer isReadyForMoreMediaData]) {
        @weakify(self);
        dispatch_sync(dispatch_get_main_queue(),^{
            @strongify(self);
            [self.displayLayer enqueueSampleBuffer:sampleBuffer];
        });
    }

3、解碼之後的資料顯示

在本文中支援3種顯示方式：UIImage、CVPixelBufferRef、AVSampleBufferDisplayLayer，因在項目中需要UIImage，是以被預設轉化模式。

CVPixelBufferRef：即不進行UIImage轉換而直接輸出的方式；

AVSampleBufferDisplayLayer：不進行代碼邏輯解碼，被Layer層自行解碼和顯示；

UIImage：通過CVPixelBufferRef進一步轉化所得(提供了2種轉化方法，可在後面代碼中檢視)：

CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
    CIContext *temporaryContext = [CIContext contextWithOptions:nil];
    CGImageRef videoImage = [temporaryContext createCGImage:ciImage fromRect:CGRectMake(0, 0, CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer))];
    image = [[UIImage alloc] initWithCGImage:videoImage];
    CGImageRelease(videoImage);

五、完整H264解碼代碼

本人原則上主張自主編寫相關代碼并學習相應的知識，在此貼出iOS對H264視訊裸流硬解碼的完整代碼，各位可進行參考或學習，若存在問題或者疑問歡迎留言。代碼中關于CLog接口為列印輸出，可自行屏蔽。

//
//  H264HwDecoder.h
//  IOTCamera
//
//  Created by lzj<[email protected]> on 2017/2/18.
//  Copyright (c) 2017 LZJ. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <VideoToolbox/VideoToolbox.h>
#import <AVFoundation/AVSampleBufferDisplayLayer.h>

typedef enum : NSUInteger {
    H264HWDataType_Image = 0,
    H264HWDataType_Pixel,
    H264HWDataType_Layer,
} H264HWDataType;

@interface H264HwDecoder : NSObject

@property (nonatomic,assign) H264HWDataType showType;    //顯示類型
@property (nonatomic,strong) UIImage *image;            //解碼成RGB資料時的IMG
@property (nonatomic,assign) CVPixelBufferRef pixelBuffer;    //解碼成YUV資料時的解碼BUF
@property (nonatomic,strong) AVSampleBufferDisplayLayer *displayLayer;  //顯示圖層

@property (nonatomic,assign) BOOL isNeedPerfectImg;    //是否讀取完整UIImage圖形(showType為0時才有效)

- (instancetype)init;

/**
 H264視訊流解碼

 @param videoData 視訊幀資料
 @param videoSize 視訊幀大小
 @return 視圖的寬高(width, height)，當為接收為AVSampleBufferDisplayLayer時傳回接口是無效的
 */
- (CGSize)decodeH264VideoData:(uint8_t *)videoData videoSize:(NSInteger)videoSize;

/**
 釋放解碼器
 */
- (void)releaseH264HwDecoder;

/**
 視訊截圖

 @return IMG
 */
- (UIImage *)snapshot;

@end

//
//  H264HwDecoder.m
//  IOTCamera
//
//  Created by lzj<[email protected]> on 2017/2/18.
//  Copyright (c) 2017 LZJ. All rights reserved.
//

#import "H264HwDecoder.h"

#ifndef FreeCharP
#define FreeCharP(p) if (p) {free(p); p = NULL;}
#endif

typedef enum : NSUInteger {
    HWVideoFrameType_UNKNOWN = 0,
    HWVideoFrameType_I,
    HWVideoFrameType_P,
    HWVideoFrameType_B,
    HWVideoFrameType_SPS,
    HWVideoFrameType_PPS,
    HWVideoFrameType_SEI,
} HWVideoFrameType;

@interface H264HwDecoder ()
{
    VTDecompressionSessionRef mDeocderSession;
    CMVideoFormatDescriptionRef mDecoderFormatDescription;
    
    uint8_t *pSPS;
    uint8_t *pPPS;
    uint8_t *pSEI;
    NSInteger mSpsSize;
    NSInteger mPpsSize;
    NSInteger mSeiSize;
    
    NSInteger mINalCount;        //I幀起始碼個數
    NSInteger mPBNalCount;       //P、B幀起始碼個數
    NSInteger mINalIndex;       //I幀起始碼開始位
    
    BOOL mIsNeedReinit;         //需要重置解碼器
}

@end

static void didDecompress(void *decompressionOutputRefCon, void *sourceFrameRefCon, OSStatus status, VTDecodeInfoFlags infoFlags, CVImageBufferRef pixelBuffer, CMTime presentationTimeStamp, CMTime presentationDuration )
{
    CVPixelBufferRef *outputPixelBuffer = (CVPixelBufferRef *)sourceFrameRefCon;
    *outputPixelBuffer = CVPixelBufferRetain(pixelBuffer);
}

@implementation H264HwDecoder

- (instancetype)init
{
    if (self = [super init]) {
        pSPS = pPPS = pSEI = NULL;
        mSpsSize = mPpsSize = mSeiSize = 0;
        mINalCount = mPBNalCount = mINalIndex = 0;
        mIsNeedReinit = NO;
        
        _showType = H264HWDataType_Image;
        _isNeedPerfectImg = NO;
        _pixelBuffer = NULL;
    }
    
    return self;
}

- (void)dealloc
{
    [self releaseH264HwDecoder];
}

- (BOOL)initH264HwDecoder
{
    if (mDeocderSession) {
        return YES;
    }
    
    const uint8_t *const parameterSetPointers[2] = {pSPS,pPPS};
    const size_t parameterSetSizes[2] = {mSpsSize, mPpsSize};
    
    OSStatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kCFAllocatorDefault, 2, parameterSetPointers, parameterSetSizes, 4, &mDecoderFormatDescription);
    
    if (status == noErr) {
        //      kCVPixelFormatType_420YpCbCr8Planar is YUV420
        //      kCVPixelFormatType_420YpCbCr8BiPlanarFullRange is NV12
        //      kCVPixelFormatType_24RGB    //使用24位bitsPerPixel
        //      kCVPixelFormatType_32BGRA   //使用32位bitsPerPixel，kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst
    uint32_t pixelFormatType = kCVPixelFormatType_420YpCbCr8BiPlanarFullRange;  //NV12
    if (self.showType == H264HWDataType_Pixel) {
        pixelFormatType = kCVPixelFormatType_420YpCbCr8Planar;
    }
    const void *keys[] = { kCVPixelBufferPixelFormatTypeKey };
    const void *values[] = { CFNumberCreate(NULL, kCFNumberSInt32Type, &pixelFormatType) };
    CFDictionaryRef attrs = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    
    VTDecompressionOutputCallbackRecord callBackRecord;
    callBackRecord.decompressionOutputCallback = didDecompress;
    callBackRecord.decompressionOutputRefCon = NULL;
    
    status = VTDecompressionSessionCreate(kCFAllocatorDefault,
                                          mDecoderFormatDescription,
                                          NULL, attrs,
                                          &callBackRecord,
                                          &mDeocderSession);
    CFRelease(attrs);
        CLog(@"Init H264 hardware decoder success");
    } else {
        CLog([NSString stringWithFormat:@"Init H264 hardware decoder fail: %d", (int)status]);
        return NO;
    }
    
    return YES;
}

- (void)removeH264HwDecoder
{
    if(mDeocderSession) {
        VTDecompressionSessionInvalidate(mDeocderSession);
        CFRelease(mDeocderSession);
        mDeocderSession = NULL;
    }
    
    if(mDecoderFormatDescription) {
        CFRelease(mDecoderFormatDescription);
        mDecoderFormatDescription = NULL;
    }
}

- (void)releaseH264HwDecoder
{
    [self removeH264HwDecoder];
    [self releaseSliceInfo];
    
    if (_pixelBuffer) {
        CVPixelBufferRelease(_pixelBuffer);
        _pixelBuffer = NULL;
    }
}

- (void)releaseSliceInfo
{
    FreeCharP(pSPS);
    FreeCharP(pPPS);
    FreeCharP(pSEI);
    
    mSpsSize = 0;
    mPpsSize = 0;
    mSeiSize = 0;
}

//将視訊資料封裝成CMSampleBufferRef進行解碼
- (CVPixelBufferRef)decode:(uint8_t *)videoBuffer videoSize:(NSInteger)videoBufferSize
{
    CVPixelBufferRef outputPixelBuffer = NULL;
    CMBlockBufferRef blockBuffer = NULL;
    OSStatus status  = CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, (void *)videoBuffer, videoBufferSize, kCFAllocatorNull, NULL, 0, videoBufferSize, 0, &blockBuffer);
    if (status == kCMBlockBufferNoErr) {
        CMSampleBufferRef sampleBuffer = NULL;
        const size_t sampleSizeArray[] = { videoBufferSize };
        status = CMSampleBufferCreateReady(kCFAllocatorDefault, blockBuffer, mDecoderFormatDescription , 1, 0, NULL, 1, sampleSizeArray, &sampleBuffer);
        
        if (status == kCMBlockBufferNoErr && sampleBuffer) {
            if (self.showType == H264HWDataType_Layer && _displayLayer) {
                CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, YES);
                CFMutableDictionaryRef dict = (CFMutableDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);
                CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanTrue);
                if ([self.displayLayer isReadyForMoreMediaData]) {
                    @weakify(self);
                    dispatch_sync(dispatch_get_main_queue(),^{
                        @strongify(self);
                        [self.displayLayer enqueueSampleBuffer:sampleBuffer];
                    });
                }
                
                CFRelease(sampleBuffer);
            } else {
                VTDecodeFrameFlags flags = 0;
                VTDecodeInfoFlags flagOut = 0;
                OSStatus decodeStatus = VTDecompressionSessionDecodeFrame(mDeocderSession, sampleBuffer, flags, &outputPixelBuffer, &flagOut);
                CFRelease(sampleBuffer);
                if (decodeStatus == kVTVideoDecoderMalfunctionErr) {
                    CLog(@"Decode failed status: kVTVideoDecoderMalfunctionErr");
                    CVPixelBufferRelease(outputPixelBuffer);
                    outputPixelBuffer = NULL;
                } else if(decodeStatus == kVTInvalidSessionErr) {
                    CLog(@"Invalid session, reset decoder session");
                    [self removeH264HwDecoder];
                } else if(decodeStatus == kVTVideoDecoderBadDataErr) {
                    CLog([NSString stringWithFormat:@"Decode failed status=%d(Bad data)", (int)decodeStatus]);
                } else if(decodeStatus != noErr) {
                    CLog([NSString stringWithFormat:@"Decode failed status=%d", (int)decodeStatus]);
                }
            }
        }
        
        CFRelease(blockBuffer);
    }
    
    return outputPixelBuffer;
}

- (CGSize)decodeH264VideoData:(uint8_t *)videoData videoSize:(NSInteger)videoSize
{
    CGSize imageSize = CGSizeMake(0, 0);
    if (videoData && videoSize > 0) {
        HWVideoFrameType frameFlag = [self analyticalData:videoData size:videoSize];
        if (mIsNeedReinit) {
            mIsNeedReinit = NO;
            [self removeH264HwDecoder];
        }
        
        if (pSPS && pPPS && (frameFlag == HWVideoFrameType_I || frameFlag == HWVideoFrameType_P || frameFlag == HWVideoFrameType_B)) {
            uint8_t *buffer = NULL;
            if (frameFlag == HWVideoFrameType_I) {
                int nalExtra = (mINalCount==3?1:0);      //如果是3位的起始碼，轉為大端時需要增加1位
                videoSize -= mINalIndex;
                buffer = (uint8_t *)malloc(videoSize + nalExtra);
                memcpy(buffer + nalExtra, videoData + mINalIndex, videoSize);
                videoSize += nalExtra;
            } else {
                int nalExtra = (mPBNalCount==3?1:0);
                buffer = (uint8_t *)malloc(videoSize + nalExtra);
                memcpy(buffer + nalExtra, videoData, videoSize);
                videoSize += nalExtra;
            }
            
            uint32_t nalSize = (uint32_t)(videoSize - 4);
            uint32_t *pNalSize = (uint32_t *)buffer;
            *pNalSize = CFSwapInt32HostToBig(nalSize);
            
            CVPixelBufferRef pixelBuffer = NULL;
            if ([self initH264HwDecoder]) {
                pixelBuffer = [self decode:buffer videoSize:videoSize];
                
                if(pixelBuffer) {
                    NSInteger width = CVPixelBufferGetWidth(pixelBuffer);
                    NSInteger height = CVPixelBufferGetHeight(pixelBuffer);
                    imageSize = CGSizeMake(width, height);
                    
                    if (self.showType == H264HWDataType_Pixel) {
                        if (_pixelBuffer) {
                            CVPixelBufferRelease(_pixelBuffer);
                        }
                        self.pixelBuffer = CVPixelBufferRetain(pixelBuffer);
                    } else {
                        if (frameFlag == HWVideoFrameType_B) {  //若B幀未進行亂序解碼，順序播放，則在此需要去除，否則解碼圖形則是灰色。
                            size_t planeCount = CVPixelBufferGetPlaneCount(pixelBuffer);
                            if (planeCount >= 2 && planeCount <= 3) {
                                CVPixelBufferLockBaseAddress(pixelBuffer, 0);
                                u_char *yDestPlane = (u_char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
                                if (planeCount == 2) {
                                    u_char *uvDestPlane = (u_char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
                                    if (yDestPlane[0] == 0x80 && uvDestPlane[0] == 0x80 && uvDestPlane[1] == 0x80) {
                                        frameFlag = HWVideoFrameType_UNKNOWN;
                                        NSLog(@"Video YUV data parse error: Y=%02x U=%02x V=%02x", yDestPlane[0], uvDestPlane[0], uvDestPlane[1]);
                                    }
                                } else if (planeCount == 3) {
                                    u_char *uDestPlane = (u_char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
                                    u_char *vDestPlane = (u_char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 2);
                                    if (yDestPlane[0] == 0x80 && uDestPlane[0] == 0x80 && vDestPlane[0] == 0x80) {
                                        frameFlag = HWVideoFrameType_UNKNOWN;
                                        NSLog(@"Video YUV data parse error: Y=%02x U=%02x V=%02x", yDestPlane[0], uDestPlane[0], vDestPlane[0]);
                                    }
                                }
                                CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
                            }
                        }
                        
                        if (frameFlag != HWVideoFrameType_UNKNOWN) {
                            self.image = [self pixelBufferToImage:pixelBuffer];
                        }
                    }
                    
                    CVPixelBufferRelease(pixelBuffer);
                }
            }
            
            FreeCharP(buffer);
        }
    }
    
    return imageSize;
}

- (UIImage *)pixelBufferToImage:(CVPixelBufferRef)pixelBuffer
{
    UIImage *image = nil;
    if (!self.isNeedPerfectImg) {
        //第1種繪制（可直接顯示，不可儲存為檔案(無效缺少圖像描述參數)）
        CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
        image = [UIImage imageWithCIImage:ciImage];
    } else {
        //第2種繪制（可直接顯示，可直接儲存為檔案，相對第一種性能消耗略大）
    CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
    CIContext *temporaryContext = [CIContext contextWithOptions:nil];
    CGImageRef videoImage = [temporaryContext createCGImage:ciImage fromRect:CGRectMake(0, 0, CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer))];
    image = [[UIImage alloc] initWithCGImage:videoImage];
    CGImageRelease(videoImage);
    }
    
    return image;
}

- (UIImage *)snapshot
{
    UIImage *img = nil;
    if (self.displayLayer) {
        UIGraphicsBeginImageContext(self.displayLayer.bounds.size);
        [self.displayLayer renderInContext:UIGraphicsGetCurrentContext()];
        img = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    } else {
        if (self.showType == H264HWDataType_Pixel) {
            if (self.pixelBuffer) {
                img = [self pixelBufferToImage:self.pixelBuffer];
            }
        } else {
            img = self.image;
        }
        
        if (!self.isNeedPerfectImg) {
            UIGraphicsBeginImageContext(CGSizeMake(img.size.width, img.size.height));
            [img drawInRect:CGRectMake(0, 0, img.size.width, img.size.height)];
            img = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
        }
    }
    
    return img;
}


//從起始位開始查詢SPS、PPS、SEI、I、B、P幀起始碼，遇到I、P、B幀則退出
//存在多種情況：
//1、起始碼是0x0 0x0 0x0 0x01 或 0x0 0x0 0x1
//2、每個SPS、PPS、SEI、I、B、P幀為單獨的Slice
//3、I幀中包含SPS、PPS、I資料Slice
//4、I幀中包含第3點的資料之外還包含SEI，順序：SPS、PPS、SEI、I
//5、起始位是AVCC協定格式的大端資料(不支援多Slice的視訊幀)
- (HWVideoFrameType)analyticalData:(const uint8_t *)buffer size:(NSInteger)size
{
    NSInteger preIndex = 0;
    HWVideoFrameType preFrameType = HWVideoFrameType_UNKNOWN;
    HWVideoFrameType curFrameType = HWVideoFrameType_UNKNOWN;
    for (int i=0; i<size && i<300; i++) {       //一般第四種情況下的幀起始資訊不會超過(32+256+12)位，可适當增大，為了不循環整個幀片資料
        int nalSize = [self getNALHeaderLen:(buffer + i) size:size-i];
        if (nalSize == 0 && i == 0) {   //當每個Slice起始位開始若使用AVCC協定則判斷幀大小是否一緻
            uint32_t *pNalSize = (uint32_t *)(buffer);
            uint32_t videoSize = CFSwapInt32BigToHost(*pNalSize);    //大端模式轉為系統端模式
            if (videoSize == size - 4) {     //是大端模式(AVCC)
                nalSize = 4;
            }
        }
        
        if (nalSize && i + nalSize + 1 < size) {
            int sliceType = buffer[i + nalSize] & 0x1F;
            
            if (sliceType == 0x1) {
                mPBNalCount = nalSize;
                if (buffer[i + nalSize] == 0x1) {   //B幀
                    curFrameType = HWVideoFrameType_B;
                } else {    //P幀
                    curFrameType = HWVideoFrameType_P;
                }
                break;
            } else if (sliceType == 0x5) {     //IDR(I幀)
                if (preFrameType == HWVideoFrameType_PPS) {
                    mIsNeedReinit = [self getSliceInfo:buffer slice:&pPPS size:&mPpsSize start:preIndex end:i];
                } else if (preFrameType == HWVideoFrameType_SEI)  {
                    [self getSliceInfo:buffer slice:&pSEI size:&mSeiSize start:preIndex end:i];
                }
                
                mINalCount = nalSize;
                mINalIndex = i;
                curFrameType = HWVideoFrameType_I;
                goto Goto_Exit;
            } else if (sliceType == 0x7) {      //SPS
                preFrameType = HWVideoFrameType_SPS;
                preIndex = i + nalSize;
                i += nalSize;
            } else if (sliceType == 0x8) {      //PPS
                if (preFrameType == HWVideoFrameType_SPS) {
                    mIsNeedReinit = [self getSliceInfo:buffer slice:&pSPS size:&mSpsSize start:preIndex end:i];
                }
                
                preFrameType = HWVideoFrameType_PPS;
                preIndex = i + nalSize;
                i += nalSize;
            } else if (sliceType == 0x6) {      //SEI
                if (preFrameType == HWVideoFrameType_PPS) {
                    mIsNeedReinit = [self getSliceInfo:buffer slice:&pPPS size:&mPpsSize start:preIndex end:i];
                }
                
                preFrameType = HWVideoFrameType_SEI;
                preIndex = i + nalSize;
                i += nalSize;
            }
        }
    }
    
    //SPS、PPS、SEI為單獨的Slice幀片
    if (curFrameType == HWVideoFrameType_UNKNOWN && preIndex != 0) {
        if (preFrameType == HWVideoFrameType_SPS) {
            mIsNeedReinit = [self getSliceInfo:buffer slice:&pSPS size:&mSpsSize start:preIndex end:size];
            curFrameType = HWVideoFrameType_SPS;
        } else if (preFrameType == HWVideoFrameType_PPS) {
             mIsNeedReinit = [self getSliceInfo:buffer slice:&pPPS size:&mPpsSize start:preIndex end:size];
            curFrameType = HWVideoFrameType_PPS;
        } else if (preFrameType == HWVideoFrameType_SEI)  {
            [self getSliceInfo:buffer slice:&pSEI size:&mSeiSize start:preIndex end:size];
            curFrameType = HWVideoFrameType_SEI;
        }
    }
    
Goto_Exit:
    return curFrameType;
}

//擷取NAL的起始碼長度是3還4
- (int)getNALHeaderLen:(const uint8_t *)buffer size:(NSInteger)size
{
    if (size >= 4 && buffer[0] == 0x0 && buffer[1] == 0x0 && buffer[2] == 0x0 && buffer[3] == 0x1) {
        return 4;
    } else if (size >= 3 && buffer[0] == 0x0 && buffer[1] == 0x0 && buffer[2] == 0x1) {
        return 3;
    }
    
    return 0;
}

//給SPS、PPS、SEI的Buf指派，傳回YES表示不同于之前的值
- (BOOL)getSliceInfo:(const uint8_t *)videoBuf slice:(uint8_t **)sliceBuf size:(NSInteger *)size start:(NSInteger)start end:(NSInteger)end
{
    BOOL isDif = NO;
    
    NSInteger len = end - start;
    uint8_t *tempBuf = (uint8_t *)(*sliceBuf);
    if (tempBuf) {
        if (len != *size || memcmp(tempBuf, videoBuf + start, len) != 0) {
            free(tempBuf);
            tempBuf = (uint8_t *)malloc(len);
            memcpy(tempBuf, videoBuf + start, len);
            
            *sliceBuf = tempBuf;
            *size = len;
            
            isDif = YES;
        }
    } else {
        tempBuf = (uint8_t *)malloc(len);
        memcpy(tempBuf, videoBuf + start, len);
        
        *sliceBuf = tempBuf;
        *size = len;
    }
    
    return isDif;
}

@end

iOS硬解碼H264視訊流一、硬解碼名詞(結構)解釋二、H264硬解碼流程圖三：IDR(I幀)網絡裸流資料結構四、硬解碼相關接口五、完整H264解碼代碼

一、硬解碼名詞(結構)解釋

二、H264硬解碼流程圖

三：IDR(I幀)網絡裸流資料結構

四、硬解碼相關接口

1、初始化H264硬解解碼器

2、H264硬體解碼

3、解碼之後的資料顯示

五、完整H264解碼代碼

繼續閱讀

二、主流視訊編碼标準的發展：H.261\H.263\MPEG-1\MPEG-2\MPEG-4一、發展曆程：二、H.261标準三、H.263标準四、MPEG-1标準五、MPEG-2标準六、MPEG-4标準

PAT (Advanced Level) Practise 1083 List Grades (25)

PAT (Advanced Level) Practise 1135 Is It A Red-Black Tree (30)

UVA 348 Optimal Array Multiplication Sequence

PAT (Advanced Level) Practise 1066 Root of AVL Tree (25)

CSU 1806 Toll

CodeChef PALPROB Palindromeness

ZOJ 1032 Area 2

UVA 590 Always on the run

FZU 1978 Repair the brackets

UVA 10344- 23 out of 5

POJ 2115 C Looooops

ZOJ 3700 Ever Dream

UVA 620 Cellular Structure

swift資料合集

蘋果稽核 Guideline 2.1 - Information Needed