我有一个功能，可以在 iphone/ipad 上将视频重新编码为可管理的比特率。这是:*更新的工作代码，现在有音频! :) *
-(void)resizeVideo:(NSString*)pathy{
NSString *newName = [pathy stringByAppendingString:@".down.mov"];
NSURL *fullPath = [NSURL fileURLWithPath:newName];
NSURL *path = [NSURL fileURLWithPath:pathy];
NSLog(@"Write Started");
NSError *error = nil;
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:fullPath fileType:AVFileTypeQuickTimeMovie error:&error];
NSParameterAssert(videoWriter);
AVAsset *avAsset = [[[AVURLAsset alloc] initWithURL:path options:nil] autorelease];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:1280], AVVideoWidthKey,
[NSNumber numberWithInt:720], AVVideoHeightKey,
nil];
AVAssetWriterInput* videoWriterInput = [[AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings] retain];
NSParameterAssert(videoWriterInput);
NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
videoWriterInput.expectsMediaDataInRealTime = YES;
[videoWriter addInput:videoWriterInput];
NSError *aerror = nil;
AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:avAsset error:&aerror];
AVAssetTrack *videoTrack = [[avAsset tracksWithMediaType:AVMediaTypeVideo]objectAtIndex:0];
videoWriterInput.transform = videoTrack.preferredTransform;
NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput *asset_reader_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:videoOptions];
[reader addOutput:asset_reader_output];
//audio setup
AVAssetWriterInput* audioWriterInput = [[AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeAudio
outputSettings:nil] retain];
AVAssetReader *audioReader = [[AVAssetReader assetReaderWithAsset:avAsset error:&error] retain];
AVAssetTrack* audioTrack = [[avAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVAssetReaderOutput *readerOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:audioTrack outputSettings:nil];
[audioReader addOutput:readerOutput];
NSParameterAssert(audioWriterInput);
NSParameterAssert([videoWriter canAddInput:audioWriterInput]);
audioWriterInput.expectsMediaDataInRealTime = NO;
[videoWriter addInput:audioWriterInput];
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
[reader startReading];
dispatch_queue_t _processingQueue = dispatch_queue_create("assetAudioWriterQueue", NULL);
[videoWriterInput requestMediaDataWhenReadyOnQueue:_processingQueue usingBlock:
^{
[self retain];
while ([videoWriterInput isReadyForMoreMediaData]) {
CMSampleBufferRef sampleBuffer;
if ([reader status] == AVAssetReaderStatusReading &&
(sampleBuffer = [asset_reader_output copyNextSampleBuffer])) {
BOOL result = [videoWriterInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
if (!result) {
[reader cancelReading];
break;
}
} else {
[videoWriterInput markAsFinished];
switch ([reader status]) {
case AVAssetReaderStatusReading:
// the reader has more for other tracks, even if this one is done
break;
case AVAssetReaderStatusCompleted:
// your method for when the conversion is done
// should call finishWriting on the writer
//hook up audio track
[audioReader startReading];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
dispatch_queue_t mediaInputQueue = dispatch_queue_create("mediaInputQueue", NULL);
[audioWriterInput requestMediaDataWhenReadyOnQueue:mediaInputQueue usingBlock:^
{
NSLog(@"Request");
NSLog(@"Asset Writer ready :%d",audioWriterInput.readyForMoreMediaData);
while (audioWriterInput.readyForMoreMediaData) {
CMSampleBufferRef nextBuffer;
if ([audioReader status] == AVAssetReaderStatusReading &&
(nextBuffer = [readerOutput copyNextSampleBuffer])) {
NSLog(@"Ready");
if (nextBuffer) {
NSLog(@"NextBuffer");
[audioWriterInput appendSampleBuffer:nextBuffer];
}
}else{
[audioWriterInput markAsFinished];
switch ([audioReader status]) {
case AVAssetReaderStatusCompleted:
[videoWriter finishWriting];
[self hookUpVideo:newName];
break;
}
}
}
}
];
break;
case AVAssetReaderStatusFailed:
[videoWriter cancelWriting];
break;
}
break;
}
}
}
];
NSLog(@"Write Ended");
}
不幸的是，如果我传递的视频超过 2 秒，应用程序就会疯狂地消耗内存并崩溃!代码看起来相当简单，但我似乎无法让它工作!
我应该在写完后在某处释放缓冲区吗？如果有任何意见，我将不胜感激。
最佳答案
-copyNextSampleBuffer 返回一个带 +1 保留的 CMSampleBufferRef(复制方法就是这样做的)。这意味着您必须释放该对象。由于您没有这样做，您将在每次通过 while() 循环时泄漏一个副本。
此外，您在不管理自动释放池的情况下紧密地运行该循环。如果在您调用的任何例程中有对象被自动释放，它们将不会被释放，直到您上面的自动释放池耗尽。由于您的 while() 循环持续时间基于输入，因此它是添加手动自动释放池的理想选择。
另一件需要考虑的事情:因为您是与 while() 循环同步运行的，您将阻塞线程并可能在您的继续条件上不必要地旋转数次。 AVAssetWriterInput 提供了一种替代机制，可以在资源可用时使用 libdispatch 异步处理数据:-requestMediaDataWhenReadyOnQueue:usingBlock:
关于iphone - 使用 AVAssetWriter 进行视频编码 - CRASHES，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8191840/