首先感谢 Logan_iOS 大神
1.头文件和参数类型
#import <VideoToolbox/VideoToolbox.h>
VTDecompressionSessionRef _deocderSession; // 解码 session
CMVideoFormatDescriptionRef _decoderFormatDescription; // 解码 format 封装了sps和pps
//sps & pps
uint8_t *_sps;
NSInteger _spsSize;
uint8_t *_pps;
NSInteger _ppsSize;
2.调用解码方法 采集sps pps 关键帧 其他帧数据
// 解码操作
- (void)decodeNalu:(uint8_t *)frame size:(uint32_t) frameSize{
int nalu_type = (frame[4] & 0x1F);
CVPixelBufferRef pixelBuffer = NULL;
uint32_t nalSize = (uint32_t)(frameSize - 4);
uint8_t *pNalSize = (uint8_t*)(&nalSize);
frame[0] = *(pNalSize + 3);
frame[1] = *(pNalSize + 2);
frame[2] = *(pNalSize + 1);
frame[3] = *(pNalSize);
//传输的时候。关键帧不能丢数据 否则绿屏 B/P可以丢 这样会卡顿
switch (nalu_type)
{
case 0x05:
// 关键帧
if([self initH264Decoder])
{
pixelBuffer = [self decode:frame withSize:frameSize];
}
break;
case 0x07:
// sps
_spsSize = frameSize - 4;
_sps = malloc(_spsSize);
memcpy(_sps, &frame[4], _spsSize);
break;
case 0x08:
{
// pps
_ppsSize = frameSize - 4;
_pps = malloc(_ppsSize);
memcpy(_pps, &frame[4], _ppsSize);
break;
}
default:
{
// B/P其他帧
if([self initH264Decoder]){
pixelBuffer = [self decode:frame withSize:frameSize];
}
break;
}
}
}
3.初始化解码器
注意调用次数和位置
1.读取H264格式信息
2.设置解码参数NSDictionary类型
3.设置callBack 类和回调函数
4.创建解压会话，这时候只是创建了并未开始解压工作
5.设置解压会话属性
// 初始化解码器
- (BOOL)initH264Decoder {
if(_deocderSession) {
return YES;
}
const uint8_t* const parameterSetPointers[2] = { _sps, _pps };
const size_t parameterSetSizes[2] = { _spsSize, _ppsSize };
// 1.获取H264视频格式描述信息
// 参数1 alloc方式
// 参数2 参数集合数量
// parameterSetCount This parameter must be at least 2.可能和parameterSetPointers、parameterSetSizes有关系
// 参数3 parameterSetPointers
// 参数4 parameterSetSizes
// 参数5 NALU 标识StartCode的长度
// 参数6 CMVideoFormatDescriptionRef 视频格式描述容器 H264读取出来的信息放在这里面
OSStatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kCFAllocatorDefault,
2, //param count
parameterSetPointers,
parameterSetSizes,
4, //nal start code size
&_decoderFormatDescription);
if(status == noErr) {
// 2.设置解压会话参数值
NSDictionary* destinationPixelBufferAttributes = @{
(id)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange], //硬解必须是 kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange 或者是kCVPixelFormatType_420YpCbCr8Planar
//这里款高和编码反的
(id)kCVPixelBufferOpenGLCompatibilityKey : [NSNumber numberWithBool:YES]
};
// 3.设置回调方法
VTDecompressionOutputCallbackRecord callBackRecord;
// 回调函数
callBackRecord.decompressionOutputCallback = didDecompress;
// 输出的类
callBackRecord.decompressionOutputRefCon = (__bridge void *)self;
// 4.创建解压会话，这时候只是创建了并未开始解压工作
// 参数1 session alloc方式
// 参数2 CMVideoFormatDescriptionRef 视频格式描述信息 上面读取的
// 参数3 特殊的decoder NULL-> VideoToolbox自行选择
// 参数4 解压参数设置
// 参数5 回调地址
// 参数6 会话地址
status = VTDecompressionSessionCreate(kCFAllocatorDefault,
_decoderFormatDescription,
NULL,
(__bridge CFDictionaryRef)destinationPixelBufferAttributes,
&callBackRecord,
&_deocderSession);
// 5.设置解压属性
VTSessionSetProperty(_deocderSession, kVTDecompressionPropertyKey_ThreadCount, (__bridge CFTypeRef)[NSNumber numberWithInt:1]);
VTSessionSetProperty(_deocderSession, kVTDecompressionPropertyKey_RealTime, kCFBooleanTrue);
} else {
NSLog(@"IOS8VT: reset decoder session failed status=%d", (int)status);
}
return YES;
}
4.开始解码
// 开始解压
// 1.根据帧信息获取编码后的CMBlockBuffer
// 2.创建 CMSampleBuffer
// 3.解压
// 4.返回解压后的信息CVPixelBufferRef
- (CVPixelBufferRef)decode:(uint8_t *)frame withSize:(uint32_t)frameSize{
CVPixelBufferRef outputPixelBuffer = NULL;
//1.根据帧信息获取编码后的CMBlockBuffer
// 参数1 alloc方式
// 参数2 frame
// 参数3 frameSize
// 参数4 blockAllocator NULL ->default
// 参数5
// 参数6
CMBlockBufferRef blockBuffer = NULL;
OSStatus status = CMBlockBufferCreateWithMemoryBlock(NULL,
(void *)frame,
frameSize,
kCFAllocatorNull,
NULL,
0,
frameSize,
FALSE,
&blockBuffer);
if(status == kCMBlockBufferNoErr) {
CMSampleBufferRef sampleBuffer = NULL;
const size_t sampleSizeArray[] = {frameSize};
// 2.创建 CMSampleBuffer
// 参数1 alloc方式
// 参数2 CMBlockBufferRef 编码后的视频数据信息
// 参数3 视频格式描述
status = CMSampleBufferCreateReady(kCFAllocatorDefault,
blockBuffer,
_decoderFormatDescription ,
1, 0, NULL, 1, sampleSizeArray,
&sampleBuffer);
if (status == kCMBlockBufferNoErr && sampleBuffer) {
VTDecodeFrameFlags flags = 0;
VTDecodeInfoFlags flagOut = 0;
OSStatus decodeStatus = VTDecompressionSessionDecodeFrame(_deocderSession,
sampleBuffer,
flags,
&outputPixelBuffer,
&flagOut);
if(decodeStatus == kVTInvalidSessionErr) {
NSLog(@"IOS8VT: Invalid session, reset decoder session");
} else if(decodeStatus == kVTVideoDecoderBadDataErr) {
NSLog(@"IOS8VT: decode failed status=%d(Bad data)", (int)decodeStatus);
} else if(decodeStatus != noErr) {
NSLog(@"IOS8VT: decode failed status=%d", (int)decodeStatus);
}
CFRelease(sampleBuffer);
}
CFRelease(blockBuffer);
}
return outputPixelBuffer;
}
5.解码后回调方法
// 解码回调函数
static void didDecompress( void *decompressionOutputRefCon, void *sourceFrameRefCon, OSStatus status, VTDecodeInfoFlags infoFlags, CVImageBufferRef pixelBuffer, CMTime presentationTimeStamp, CMTime presentationDuration ){
CVPixelBufferRef *outputPixelBuffer = (CVPixelBufferRef *)sourceFrameRefCon;
*outputPixelBuffer = CVPixelBufferRetain(pixelBuffer);
VideoH264Decoder *decoder = (__bridge VideoH264Decoder *)decompressionOutputRefCon;
if ([decoder.delegate respondsToSelector:@selector(decoder:didDecodingFrame:)]) {
[decoder.delegate decoder: decoder didDecodingFrame:pixelBuffer];
}
}
6.解码调用
编码成功后，模拟客户端进行解码调用
// 获取数据进行解码
- (void)didReadData:(NSData *)data{
[self.h264Decoder decodeNalu:(uint8_t *)[data bytes] size:(uint32_t)data.length];
}
7.视频H264编码前后CMSampleBuffer结构示意图
视频H264编码后-解压后数据结构图.png
