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如何在iPhone上使用CVPixelBufferPool与AVAssetWriterInputPixelBufferAdaptor配合使用？（涉及IT技术）

iphoneobjective-cavfoundationavassetwriter
17

我已成功使用以下代码从图像创建视频

-(void)writeImageAsMovie:(NSArray *)array toPath:(NSString*)path size:(CGSize)size duration:(int)duration 
{
    NSError *error = nil;
    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                                  [NSURL fileURLWithPath:path] fileType:AVFileTypeQuickTimeMovie
                                                              error:&error];
    NSParameterAssert(videoWriter);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt:size.height], AVVideoHeightKey,
                                   nil];
    AVAssetWriterInput* writerInput = [[AVAssetWriterInput
                                        assetWriterInputWithMediaType:AVMediaTypeVideo
                                        outputSettings:videoSettings] retain];

    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                     assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                     sourcePixelBufferAttributes:nil];
    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);
    [videoWriter addInput:writerInput];


    //Start a session:
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];

    CVPixelBufferRef buffer = NULL;
    buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:0] CGImage]];
    [adaptor appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];

    //Write samples:
    for (int i = 0;i<[array count]; i++)
    {
        if([writerInput isReadyForMoreMediaData])
        {
            NSLog(@"inside for loop %d",i);
            CMTime frameTime = CMTimeMake(1, 20);

            CMTime lastTime=CMTimeMake(i, 20); //i is from 0 to 24 of the loop above

            CMTime presentTime=CMTimeAdd(lastTime, frameTime);

            buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:i] CGImage]];

            [adaptor appendPixelBuffer:buffer withPresentationTime:presentTime];

        }
        else
        {
            NSLog(@"error");
            i--;
        }
    }
    NSLog(@"outside for loop");

    //Finish the session:
    [writerInput markAsFinished];
    [videoWriter finishWriting];
}

我在这里使用了CVPixelBufferRef，但我希望能够使用CVPixelBufferPoolRef和AVAssetWriterInputPixelBufferAdaptor一起使用。

有没有人能够提供一个示例代码，让我可以进行调试并使用呢？

4个回答
15

因为您传递了空的'sourcePixelBufferAttributes'，所以像素缓冲池将不会被创建：

AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput sourcePixelBufferAttributes:nil];

可以传递一些属性，例如：

NSDictionary *bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];

然后你可以使用池来创建像素缓冲区，例如：

CVPixelBufferPoolCreatePixelBuffer (NULL, adaptor.pixelBufferPool, &pixelBuffer);
谢谢回复，但我已经以你所说的相同方式解决了这个问题。 - Atulkumar V. Jain
3
使用缓冲池和适配器，性能是否明显提高（或可测量）？ - kevlar
1
@kevlar 从个人经验来说，使用池会有天壤之别。只需要一行代码就可以修复内存泄漏:D - jakenberg
6

@Atulkumar V. Jain：太好了！祝你好运^^ @Brian：你说得对，谢谢，我已经纠正了它，现在它可以工作了，这是可行的代码（如果其他人需要它 :-)）

CVPixelBufferRef buffer = NULL;
buffer = [self pixelBufferFromCGImage:[[imagesArray objectAtIndex:0] CGImage]];
CVPixelBufferPoolCreatePixelBuffer (NULL, adaptor_.pixelBufferPool, &buffer);

[adaptor_ appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];

__block UInt64 convertedByteCount = 0;
dispatch_queue_t mediaInputQueue =  dispatch_queue_create("mediaInputQueue", NULL);
static int i = 1;
int frameNumber = [imagesArray count];

[writerInput requestMediaDataWhenReadyOnQueue:mediaInputQueue usingBlock:^{
    while (1){
        if (i == frameNumber) {
            break;
        }
        if ([writerInput isReadyForMoreMediaData]) {

            CVPixelBufferRef sampleBuffer = [self pixelBufferFromCGImage:[[imagesArray objectAtIndex:i] CGImage]];
            NSLog(@"inside for loop %d",i);
            CMTime frameTime = CMTimeMake(1, 20);

           CMTime lastTime=CMTimeMake(i, 20); //i is from 0 to 19 of the loop above

           CMTime presentTime=CMTimeAdd(lastTime, frameTime);       

        if (sampleBuffer) {
                [adaptor_ appendPixelBuffer:sampleBuffer withPresentationTime:presentTime];
                i++;
                CFRelease(sampleBuffer);
            } else {
                break;
            }
        }
    }
    NSLog (@"done");
    [writerInput markAsFinished];
    [videoWriter finishWriting];     

    CVPixelBufferPoolRelease(adaptor_.pixelBufferPool);
    [videoWriter release];
    [writerInput release];      
    [imagesArray removeAllObjects];


}];
4

不要使用“for”循环，改用以下代码：

dispatch_queue_t mediaInputQueue =  dispatch_queue_create("mediaInputQueue", NULL);
[writerInput requestMediaDataWhenReadyOnQueue:mediaInputQueue usingBlock:^{

    CVPixelBufferRef buffer = NULL;
    buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:0] CGImage]];
    CVPixelBufferPoolCreatePixelBuffer (NULL, adaptor.pixelBufferPool, &buffer);

    [adaptor appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];
    int i = 1;
     while (writerInput.readyForMoreMediaData) {
         NSLog(@"inside for loop %d",i);
         CMTime frameTime = CMTimeMake(1, 20);

         CMTime lastTime=CMTimeMake(i, 20); //i is from 0 to 19 of the loop above

         CMTime presentTime=CMTimeAdd(lastTime, frameTime);

         if (i >= [array count]) {
             buffer = NULL;
         }else {
              buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:i] CGImage]];
         }          
         //CVBufferRetain(buffer);

         if (buffer) {
             // append buffer
             [adaptor appendPixelBuffer:buffer withPresentationTime:presentTime];
             i++;
         } else {
             // done!

             //Finish the session:
             [writerInput markAsFinished];
             [videoWriter finishWriting];                

             CVPixelBufferPoolRelease(adaptor.pixelBufferPool);
             [videoWriter release];
             [writerInput release];
             NSLog (@"Done");
             [imageArray removeAllObjects];              
             break;
         }
     }
}];
谢谢你的帮助，但我已经解决了这个问题并且也完成了这个项目。 - Atulkumar V. Jain
1
这个程序中还存在一个错误，即在迭代数组之前，写入器可能会变为“未准备好”。如果将计数器移出块，并清理循环条目的任何索引键，则应该没问题。 - Brian King
4

我搞定了！

这是示例代码链接：git@github.com:RudyAramayo/AVAssetWriterInputPixelBufferAdaptorSample.git

下面是你需要的代码：

- (void) testCompressionSession
{
    CGSize size = CGSizeMake(480, 320);

    NSString *betaCompressionDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Movie.m4v"];

    NSError *error = nil;

    unlink([betaCompressionDirectory UTF8String]);

    //----initialize compression engine
    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:betaCompressionDirectory]
                                                           fileType:AVFileTypeQuickTimeMovie
                                                              error:&error];
    NSParameterAssert(videoWriter);
    if(error)
        NSLog(@"error = %@", [error localizedDescription]);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey,
                                       [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                       [NSNumber numberWithInt:size.height], AVVideoHeightKey, nil];
    AVAssetWriterInput *writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];

    NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                                               [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];

    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                                                                                         sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];
    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);

    if ([videoWriter canAddInput:writerInput])
        NSLog(@"I can add this input");
    else
        NSLog(@"i can't add this input");

    [videoWriter addInput:writerInput];
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];

    //---
    // insert demo debugging code to write the same image repeated as a movie

    CGImageRef theImage = [[UIImage imageNamed:@"Lotus.png"] CGImage];

    dispatch_queue_t dispatchQueue = dispatch_queue_create("mediaInputQueue", NULL);
    int __block frame = 0;

    [writerInput requestMediaDataWhenReadyOnQueue:dispatchQueue usingBlock:^{
        while ([writerInput isReadyForMoreMediaData])
        {
            if(++frame >= 120)
            {
                [writerInput markAsFinished];
                [videoWriter finishWriting];
                [videoWriter release];
                break;
            }

            CVPixelBufferRef buffer = (CVPixelBufferRef)[self pixelBufferFromCGImage:theImage size:size];
            if (buffer)
            {
                if(![adaptor appendPixelBuffer:buffer withPresentationTime:CMTimeMake(frame, 20)])
                    NSLog(@"FAIL");
                else
                    NSLog(@"Success:%d", frame);
                CFRelease(buffer);
            }
        }
    }];

    NSLog(@"outside for loop");

}

- (CVPixelBufferRef )pixelBufferFromCGImage:(CGImageRef)image size:(CGSize)size
{
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, 
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil];
    CVPixelBufferRef pxbuffer = NULL;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width, size.height, kCVPixelFormatType_32ARGB, (CFDictionaryRef) options, &pxbuffer);
    // CVReturn status = CVPixelBufferPoolCreatePixelBuffer(NULL, adaptor.pixelBufferPool, &pxbuffer);

    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL); 

    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
    NSParameterAssert(pxdata != NULL);

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pxdata, size.width, size.height, 8, 4*size.width, rgbColorSpace, kCGImageAlphaPremultipliedFirst);
    NSParameterAssert(context);

    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image);

    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}
你是不是想取消注释 pixelBufferFromCGImage 函数内的 CVPixelBufferPoolCreatePixelBuffer 行？或者你决定不使用 CVPixelBufferPoolCreatePixelBuffer 了吗？ - taber
当我写下这段代码时，我感到非常迷茫，因为它是许多不同代码集的编译，我试图重新设计...请不要介意一些注释掉的东西，因为我还在学习和测试...我将不断改进示例并提交更多的AVFoundation代码。 - Orbitus007
1
不要使用这段代码 - 它是错误的。要使用池，您只需要调用CVPixelBufferPoolCreatePixelBuffer。 - AlexeyVMP
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