Added example of SDAVAssetExportSessionDelegate

SDAVAssetExportSession.m

@@ -129,15 +129,26 @@ - (void)exportAsynchronouslyWithCompletionHandler:(void (^)())handler
         {
             [self.writer addInput:self.videoInput];
         }
-        NSDictionary *pixelBufferAttributes = @
+        if ([self.delegate respondsToSelector:@selector(exportSession:renderFrame:withPresentationTime:toBuffer:)])
         {
-            (id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA),
-            (id)kCVPixelBufferWidthKey: @(self.videoOutput.videoComposition.renderSize.width),
-            (id)kCVPixelBufferHeightKey: @(self.videoOutput.videoComposition.renderSize.height),
-            @"IOSurfaceOpenGLESTextureCompatibility": @YES,
-            @"IOSurfaceOpenGLESFBOCompatibility": @YES,
-        };
-        self.videoPixelBufferAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:self.videoInput sourcePixelBufferAttributes:pixelBufferAttributes];
+            // If a pixel format was specified in videoInputSettings, use the same pixel format for the render buffers
+            // In practice, kCVPixelFormatType_32BGRA always seems to be the fastest (even when transcoding between YpCbCr formats, such as H.264)
+            // This is despite the fact that the YpCbCr pixel buffers are less than half the size (12 bits/pixel vs. 32 bits/pixel)
+            id pixelFormat = self.videoInputSettings[(id)kCVPixelBufferPixelFormatTypeKey];
+            if (!pixelFormat)
+            {
+                pixelFormat = @(kCVPixelFormatType_32BGRA);
+            }
+            NSDictionary *pixelBufferAttributes = @
+            {
+                (id)kCVPixelBufferPixelFormatTypeKey: pixelFormat,
+                (id)kCVPixelBufferWidthKey: @(self.videoOutput.videoComposition.renderSize.width),
+                (id)kCVPixelBufferHeightKey: @(self.videoOutput.videoComposition.renderSize.height),
+                @"IOSurfaceOpenGLESTextureCompatibility": @YES,
+                @"IOSurfaceOpenGLESFBOCompatibility": @YES,
+            };
+            self.videoPixelBufferAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:self.videoInput sourcePixelBufferAttributes:pixelBufferAttributes];
+        }
     }
 
     //

SDAVAssetExportSessionDelegateExample.h

@@ -0,0 +1,17 @@
+//
+//  SDAVAssetExportSessionDelegateExample.h
+//
+// This file is part of the SDAVAssetExportSession package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+//
+
+#import <Foundation/Foundation.h>
+#import "SDAVAssetExportSession.h"
+
+@interface SDAVAssetExportSessionDelegateExample : NSObject <SDAVAssetExportSessionDelegate>
+
+- (void)exportSession:(SDAVAssetExportSession *)exportSession renderFrame:(CVPixelBufferRef)pixelBuffer withPresentationTime:(CMTime)presentationTime toBuffer:(CVPixelBufferRef)renderBuffer;
+
+@end

SDAVAssetExportSessionDelegateExample.m

@@ -0,0 +1,74 @@
+//
+//  SDAVAssetExportSessionDelegateExample.m
+//
+// This file is part of the SDAVAssetExportSession package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+//
+
+#import "SDAVAssetExportSessionDelegateExample.h"
+
+/**
+ * An example implementation of `SDAVAssetExportSessionDelegate` that just copies the input 'pixelBuffer' to the output 'renderBuffer' unmodified.
+ * You can control the pixel format that the 'AVAssetReaderTrackOutput' produces by setting 'exportSession.videoInputSettings':
+ *
+ *     exportSession.videoInputSettings = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA) };
+ *
+ * The default format of kCVPixelFormatType_32BGRA is generally the fastest for transcoding, even when the input video is a YpCbCr format, such as H.264
+ */
+
+@implementation SDAVAssetExportSessionDelegateExample
+
+- (void)exportSession:(SDAVAssetExportSession *)exportSession renderFrame:(CVPixelBufferRef)pixelBuffer withPresentationTime:(CMTime)presentationTime toBuffer:(CVPixelBufferRef)renderBuffer
+{
+    // Print the presentation times of the frames
+    // CMTimeShow(presentationTime);
+
+    // Print details -- just for the first frame
+    if (presentationTime.value == 0)
+    {
+        OSType sourceFormat = CVPixelBufferGetPixelFormatType(pixelBuffer);
+        OSType destFormat = CVPixelBufferGetPixelFormatType(renderBuffer);
+        size_t dataSize = CVPixelBufferGetDataSize(pixelBuffer);
+
+        NSLog(@"source format: %@, dest format: %@, planar: %d, size: %zu", NSFileTypeForHFSTypeCode(sourceFormat), NSFileTypeForHFSTypeCode(destFormat), CVPixelBufferIsPlanar(pixelBuffer), dataSize);
+    }
+
+    // Copy the source pixel buffer to the output pixel buffer.
+    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
+    CVPixelBufferLockBaseAddress(renderBuffer, 0);
+
+    if (CVPixelBufferIsPlanar(pixelBuffer))
+    {
+        // Planar formats, such as kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange and kCVPixelFormatType_420YpCbCr8BiPlanarFullRange.
+        size_t planeCount = CVPixelBufferGetPlaneCount(pixelBuffer);
+
+        for (size_t i = 0; i < planeCount; i++)
+        {
+            int height = (int)CVPixelBufferGetHeightOfPlane(pixelBuffer, i);
+            size_t bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, i);
+
+            void *pixelBufferBaseAddress = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, i);
+            void *renderBufferBaseAddress = CVPixelBufferGetBaseAddressOfPlane(renderBuffer, i);
+
+            memcpy(renderBufferBaseAddress, pixelBufferBaseAddress, height * bytesPerRow);
+        }
+    }
+    else
+    {
+        // Packed formats, such as kCVPixelFormatType_32BGRA, kCVPixelFormatType_32ARGB, and kCVPixelFormatType_422YpCbCr8.
+        int height = (int)CVPixelBufferGetHeight(pixelBuffer);
+        size_t bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer);
+
+        void *pixelBufferBaseAddress = CVPixelBufferGetBaseAddress(pixelBuffer);
+        void *renderBufferBaseAddress = CVPixelBufferGetBaseAddress(renderBuffer);
+
+        memcpy(renderBufferBaseAddress, pixelBufferBaseAddress, height * bytesPerRow);
+    }
+
+    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
+    CVPixelBufferUnlockBaseAddress(renderBuffer, 0);
+}
+
+@end