作物CMSampleBufferRef

我正在嘗試將CMSampleBufferRef中的圖像裁剪爲特定尺寸。我想提出5個步驟 - 1.獲取PixelBuffer從SampleBuffer 2.轉換到裁剪CIImage 4.渲染CIImage回到PixelBuffer 5.安裝PixelBuffer到SampleBuffer。到目前爲止，我有第4步 - 渲染圖像回PixelBuffer（無法檢查超出此點）的任何東西都呈現緩衝區（我檢查它使用相同CIImage imageWithCVPixelBuffer並獲得NULL作爲返回）的問題。將不勝感激任何提示或幫助。作物CMSampleBufferRef

CGRect cropRect = CGRectMake(0, 0, 640, 480); 

CIImage *ciImage = [CIImage imageWithCVPixelBuffer:(CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer)]; //options: [NSDictionary dictionaryWithObjectsAndKeys:[NSNull null], kCIImageColorSpace, nil]]; 
ciImage = [ciImage imageByCroppingToRect:cropRect];  

CVPixelBufferRef pixelBuffer; 
CVPixelBufferCreate(kCFAllocatorSystemDefault, 640, 480, kCVPixelFormatType_32BGRA, NULL, &pixelBuffer); 

CVPixelBufferLockBaseAddress(pixelBuffer, 0); 

CIContext * ciContext = [CIContext contextWithOptions: nil]; 
[ciContext render:ciImage toCVPixelBuffer:pixelBuffer]; 
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0); 

CMSampleTimingInfo sampleTime = { 
    .duration = CMSampleBufferGetDuration(sampleBuffer), 
    .presentationTimeStamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer), 
    .decodeTimeStamp = CMSampleBufferGetDecodeTimeStamp(sampleBuffer) 
}; 

CMVideoFormatDescriptionRef videoInfo = NULL; 
CMVideoFormatDescriptionCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, &videoInfo); 

CMSampleBufferRef oBuf; 
CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, true, NULL, NULL, videoInfo, &sampleTime, &oBuf);

來源

2013-03-28 Laz

什麼是你的問題有？我在這裏沒有看到問題。 – Aurelius

ciContext不在緩衝區中呈現任何東西。我檢查它與相同的ciimage imageWithCVPixelBuffer並獲得NULL – Laz

嗨。我也卡住了一些喜歡你的地方。我使用AVFoundation捕捉視頻。我需要實現放大Avcapture委託「didOutputSampleBuffer」。請告訴我如何縮放和裁剪CMSampleBufferRef/CVImageBufferRef。 –

所以我找到了我有問題的原因。顯然，我必須在初始化像素緩衝區時添加kCVPixelBufferIOSurfacePropertiesKey鍵，方法是創建字典並將其傳遞給初始化程序。這裏有一個代碼，如果任何人絆倒在這個問題：

CFDictionaryRef empty; // empty value for attr value. 
CFMutableDictionaryRef attrs; 
empty = CFDictionaryCreate(kCFAllocatorDefault, // our empty IOSurface properties dictionary 
          NULL, 
          NULL, 
          0, 
          &kCFTypeDictionaryKeyCallBacks, 
          &kCFTypeDictionaryValueCallBacks); 
attrs = CFDictionaryCreateMutable(kCFAllocatorDefault, 
            1, 
            &kCFTypeDictionaryKeyCallBacks, 
            &kCFTypeDictionaryValueCallBacks); 

CFDictionarySetValue(attrs, 
        kCVPixelBufferIOSurfacePropertiesKey, 
        empty);

然後你只需要通過本字典作爲參數傳遞給CVPixelBufferCreate

我發現這個解決方案在這裏：http://allmybrain.com/2011/12/08/rendering-to-a-texture-with-ios-5-texture-cache-api/

來源

2013-03-29 22:35:32 Laz

作物CMSampleBufferRef

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