videoToolBox 硬解码 VTDecompressionSessionRef 创建失败 求解答

const uint8_t* const parameterSetPointers[2] = {_sps, _pps};
const size_t parameterSetSizes[2] = {_spsSize, _ppsSize};



OSStatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kCFAllocatorDefault,
2, //param count
parameterSetPointers,
parameterSetSizes,
4, //nal start code size
&_decoderFormatDescription);

if(status == noErr) {
NSDictionary* destinationPixelBufferAttributes = @{
(id)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange],
//硬解必须是 kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
// 或者是 kCVPixelFormatType_420YpCbCr8Planar
//因为 iOS 是 nv12 其他是 nv21
(id)kCVPixelBufferWidthKey : [NSNumber numberWithInt:347],
(id)kCVPixelBufferHeightKey : [NSNumber numberWithInt:666]
//这里宽高和编码反的
// (id)kCVPixelBufferOpenGLCompatibilityKey : [NSNumber numberWithBool:YES]
};


VTDecompressionOutputCallbackRecord callBackRecord;
callBackRecord.decompressionOutputCallback = didDecompress;
callBackRecord.decompressionOutputRefCon = (__bridge void *)self;
OSStatus status = VTDecompressionSessionCreate(kCFAllocatorDefault,
_decoderFormatDescription,
NULL,
(__bridge CFDictionaryRef)destinationPixelBufferAttributes,
&callBackRecord,
&_deocderSession);
NSLog(@"%d",status);
// VTSessionSetProperty(_deocderSession, kVTDecompressionPropertyKey_ThreadCount, (__bridge CFTypeRef)[NSNumber numberWithInt:1]);
// VTSessionSetProperty(_deocderSession, kVTDecompressionPropertyKey_RealTime, kCFBooleanTrue);
} else {
NSLog(@"IOS8VT: reset decoder session failed status=%d", status);
}



这里 VTDecompressionSessionCreate 执行后 返回-5 _deocderSession nil 有大神知道怎么解么