“customVideoCompositorClass”的 HelloWorld 但出现黑色视频

Question

我尝试编写一个 IOS 应用程序来了解

customVideoCompositorClass

的工作原理。 然而，在我的代码之后，我得到了一个带有正确声音的黑色视频。

sourcePixelBuffer

始终为零。我哪里错过了？

我的视频源：MPEG-4 AAC、H.264

我的代码：

#import <AVFoundation/AVFoundation.h>
#import "AAPLViewController.h"

@implementation CustomVideoCompositor

- (nullable id<AVVideoCompositionInstruction>)requiredSourceTrackIDsForFrame:(CMTime)frameTime {
    return nil;
}

- (NSArray<AVVideoCompositionInstruction *> *)requiredPixelBufferAttributesForRenderContext {
    return nil;
}

- (void)startVideoCompositionRequest:(AVAsynchronousVideoCompositionRequest *)request {
    // Extract source pixel buffer
    NSArray *a = request.sourceTrackIDs;
    CVPixelBufferRef sourcePixelBuffer = [request sourceFrameByTrackID: (int)a[0]];

    [request finishWithComposedVideoFrame:sourcePixelBuffer];
}

- (NSDictionary *)sourcePixelBufferAttributes {
    return @{
        (id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA)
    };
}

- (void)renderContextChanged:(AVVideoCompositionRenderContext *)newRenderContext {
}

@end

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSURL *url = [[NSBundle mainBundle] URLForResource:@"1" withExtension:@"mov"];
    AVAsset *asset = [AVAsset assetWithURL:url];
    
    AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoCompositionWithPropertiesOfAsset:asset];
    videoComposition.customVideoCompositorClass = [CustomVideoCompositor class];
    
    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:asset];
    playerItem.videoComposition = videoComposition;

    AVPlayer *player = [AVPlayer playerWithPlayerItem:playerItem];
    AVPlayerViewController *controller = [[AVPlayerViewController alloc] init];
    self.playerViewController = controller;
    
    CGSize videoSize = [[[asset tracksWithMediaType:AVMediaTypeVideo] firstObject] naturalSize];

    [self addChildViewController:controller];
    [self.view addSubview:controller.view];

    controller.view.frame = CGRectMake(-70, 270, videoSize.width * SCALE, videoSize.height * SCALE);
    controller.view.transform = CGAffineTransformMakeRotation(M_PI_2);
    controller.player = player;
    controller.showsPlaybackControls = YES;
    [player pause];
    [player play];
}

Answer 1

事实证明我需要转换

TrackID

而不是直接将其转换为

int

- (void)startVideoCompositionRequest:(AVAsynchronousVideoCompositionRequest *)request {
    // Extract source pixel buffer
    NSArray *sourceTrackIDs = request.sourceTrackIDs;
    if (sourceTrackIDs.count == 0) {
        NSLog(@"No source track IDs found in the request");
        return;
    }

    CMPersistentTrackID trackID = [sourceTrackIDs[0] intValue]; // Assuming only one track ID is provided
    
    CVPixelBufferRef sourcePixelBuffer = [request sourceFrameByTrackID: trackID];
    
    if (!sourcePixelBuffer) {
        NSLog(@"Failed to extract source pixel buffer for track ID: %d", trackID);
        return;
    }
    
    [request finishWithComposedVideoFrame:sourcePixelBuffer];