使用AVAssetWriter的视频编码 - CRASHES [英] Video Encoding using AVAssetWriter - CRASHES
问题描述
我有一个功能，应该在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！ :) *
I have a function that is supposed to re-encode a video to a manageable bitrate on iphone/ipad. Here it is: *UPDATED WORKING CODE, NOW WITH AUDIO! :) *
-(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，如果我传入的视频时长超过2秒，应用程序像疯狂和崩溃一样吸收记忆！代码看起来相当简单，但我似乎无法让它工作！
我应该在写完之后在某处释放缓冲区吗？对于有任何输入的人，我会非常感激。
Unfortunately, if I pass in a video any longer than 2 seconds, the app sucks up memory like crazy and crashes! The code seems fairly simple, but I cannot seem to get it to work!
Am I supposed to release the buffer in there somewhere after it is written? I would be most greatful to anyone that has any input.
推荐答案
-copyNextSampleBuffer返回一个带有+1 retain的CMSampleBufferRef（复制方法）去做）。这意味着您必须释放该对象。因为你没有这样做，所以你会在每次通过while（）循环时泄漏副本。
-copyNextSampleBuffer is returning a CMSampleBufferRef with +1 retain (copy methods do that). This means you must release the object. Since you're not doing so, you're going to leak a copy every pass through your while() loop.
另外，你正在紧紧地运行那个循环管理自动释放池。如果在您正在调用的任何例程中有自动释放的对象，则在您上方的自动释放池耗尽之前，它们不会被释放。由于你的while（）循环持续时间是基于输入的，所以它是添加手动自动释放池的一个很好的候选者。
Additionally, you're running that loop tightly without managing an autorelease pool. If there are objects being autoreleased in any of the routines you're calling, they will not be released until the autorelease pool above you drains. Since your while() loop duration is based on input, it's a good candidate for adding a manual autorelease pool.
还有一件事要考虑：因为你正在运行这个与while（）循环同步，你将阻塞线程并可能在你的继续条件下多次不必要地旋转。 AVAssetWriterInput提供了另一种机制，可以在资源可用时使用libdispatch异步处理数据：-requestMediaDataWhenReadyOnQueue：usingBlock：
One other thing to consider: because you're running this synchronously with a while() loop, you'll block the thread and possibly spin unnecessarily over your continue condition several times. AVAssetWriterInput provides an alternative mechanism to use libdispatch to process data asynchronously as resources become available: -requestMediaDataWhenReadyOnQueue:usingBlock:
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