2016.5.7:
使用AVAssetWriterInputPixelBufferAdaptor来创建、写入CVPixelBuffer后，可以成功录制视频了，下面的这个错误没有再出现
不过，在iPhone6上又遇到一个新的问题（5c、5s上没有），图像出现了变形……

原问题：
在使用AVAssetWriter录制视频，调用AVAssetWriterInput的appendSampleBuffer方法时，返回失败，error信息如下：

Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x1b83f490 {Error Domain=NSOSStatusErrorDomain Code=-12780 "(null)"}, NSLocalizedFailureReason=An unknown error occurred (-12780)}

文档里也查不到……如果有人遇到过类似问题，或是对这方面有所了解，还请不吝赐教，非常感谢。下面我会给出一些详细信息：

由于某些原因，sampleBuffer并没有直接使用AVCaptureSession和AVCaptureVideoDataOutput的组合得到的数据，或是AVAssetReader。而是通过其它途径创建出CGImageRef，再创建CVPixelBufferRef，最后得到CMSampleBufferRef。可以通过Xcode的调试预览看到正确的CGImageRef图像，CVPixelBufferRef的信息如下：

<CVPixelBuffer 0x13fc8f3e0 width=375 height=667 bytesPerRow=1536 pixelFormat=BGRA iosurface=0x0 
    attributes=<CFBasicHash 0x13fc12130 [0x19e5bcb68]> {
        type = immutable dict, count = 3, entries =>
            0 : <CFString 0x19a067ad8 [0x19e5bcb68]>{contents = "CGImageCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
            1 : <CFString 0x19a067c98 [0x19e5bcb68]>{contents = "PixelFormatDescription"} = <CFBasicHash 0x13dee97d0 [0x19e5bcb68]> {
                type = immutable dict, count = 15, entries =>
                    1 : <CFString 0x19a067ad8 [0x19e5bcb68]>{contents = "CGImageCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    2 : <CFString 0x19a068198 [0x19e5bcb68]>{contents = "FillExtendedPixelsCallback"} = <CFData 0x1418176b0 [0x19e5bcb68]>{length = 24, capacity = 24, bytes = 0x0000000000000000dc0cbc82010000000000000000000000}
                    5 : <CFString 0x19a067ed8 [0x19e5bcb68]>{contents = "ContainsAlpha"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    6 : <CFString 0x19a067ab8 [0x19e5bcb68]>{contents = "CGBitmapContextCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    7 : <CFString 0x19a067f98 [0x19e5bcb68]>{contents = "BitsPerBlock"} = <CFNumber 0xb000000000000202 [0x19e5bcb68]>{value = +32, type = kCFNumberSInt32Type}
                    8 : <CFString 0x19a067fb8 [0x19e5bcb68]>{contents = "BlackBlock"} = <CFData 0x141817500 [0x19e5bcb68]>{length = 4, capacity = 4, bytes = 0x000000ff}
                    9 : <CFString 0x19a067bb8 [0x19e5bcb68]>{contents = "IOSurfaceOpenGLESTextureCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    10 : <CFString 0x19a067bf8 [0x19e5bcb68]>{contents = "OpenGLESCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    11 : <CFString 0x19a068078 [0x19e5bcb68]>{contents = "CGBitmapInfo"} = <CFNumber 0xb000000000020042 [0x19e5bcb68]>{value = +8196, type = kCFNumberSInt32Type}
                    12 : <CFString 0x19a067b98 [0x19e5bcb68]>{contents = "IOSurfaceCoreAnimationCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    13 : <CFString 0x19a067bd8 [0x19e5bcb68]>{contents = "IOSurfaceOpenGLESFBOCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
                    14 : <CFString 0x19a068098 [0x19e5bcb68]>{contents = "ContainsYCbCr"} = <CFBoolean 0x19e5bd0b0 [0x19e5bcb68]>{value = false}
                    15 : <CFString 0x19a067e78 [0x19e5bcb68]>{contents = "PixelFormat"} = <CFNumber 0xb000000424752412 [0x19e5bcb68]>{value = +1111970369, type = kCFNumberSInt32Type}
                    16 : <CFString 0x19a0680f8 [0x19e5bcb68]>{contents = "ComponentRange"} = <CFString 0x19a068138 [0x19e5bcb68]>{contents = "FullRange"}
                    21 : <CFString 0x19a0680b8 [0x19e5bcb68]>{contents = "ContainsRGB"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
            }

            2 : <CFString 0x19a067ab8 [0x19e5bcb68]>{contents = "CGBitmapContextCompatibility"} = <CFBoolean 0x19e5bd0a0 [0x19e5bcb68]>{value = true}
    }
    propagatedAttachments=<CFBasicHash 0x13fcbdd40 [0x19e5bcb68]>{type = mutable dict, count = 0, entries => }
    nonPropagatedAttachments=<CFBasicHash 0x13fca58f0 [0x19e5bcb68]>{type = mutable dict, count = 0, entries => }
>

CMSampleBufferRef信息：

CMSampleBuffer 0x1418db960 retainCount: 1 allocator: 0x19e5bcb68
    invalid = NO
    dataReady = YES
    makeDataReadyCallback = 0x0
    makeDataReadyRefcon = 0x0
    formatDescription = <CMVideoFormatDescription 0x14181e0a0 [0x19e5bcb68]> {
        mediaType:'vide' 
        mediaSubType:'BGRA' 
        mediaSpecific: {
            codecType: 'BGRA'       dimensions: 375 x 667 
        } 
        extensions: {(null)}
    }
    sbufToTrackReadiness = 0x0
    numSamples = 1
    sampleTimingArray[1] = {
        {PTS = {0/1 = 0.000}, DTS = {INVALID}, duration = {INVALID}},
    }
    imageBuffer = 0x13fc8f3e0

另外，AVAssetWriterInput的outputSettings如下：

{
    AVVideoCodecKey = avc1;
    AVVideoCompressionPropertiesKey =     {
        AverageBitRate = "4.05";
        ExpectedFrameRate = 30;
        MaxKeyFrameInterval = 30;
    };
    AVVideoHeightKey = 667;
    AVVideoWidthKey = 375;
}

sourceFormatHint：

<CMVideoFormatDescription 0x152156900 [0x19e5bcb68]> {
    mediaType:'vide' 
    mediaSubType:'BGRA' 
    mediaSpecific: {
        codecType: 'BGRA'        dimensions: 375 x 667 
    } 
    extensions: {(null)}
}

如果还需要其它信息我再贴上来～万分感谢！