これが私にとってどのように機能したかです。あなたが解決した方法では、アプリを将来的にスケーリングすることはできません。物事を正しく行う方法を最初から学んだ方が、時間と労力を犠牲にしてでも学ぶことができます。
私のアプリでは、アセットライターを作成した後...
_writer = [[AVAssetWriter alloc] initWithURL:_outURL fileType:AVFileTypeQuickTimeMovie error:outError];
...動画アセット トラックを作成します...
NSArray *videoTracks = [_asset tracksWithMediaType:AVMediaTypeVideo];
if ([videoTracks count] > 0)
assetVideoTrack = [videoTracks objectAtIndex:0];
...そして、アセット リーダーは、そこから出力オブジェクトを追跡します。
_readerVideoOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:assetVideoTrack outputSettings:decompressionVideoSettings];
[_reader addOutput:_readerVideoOutput];
次に、ビデオ トラックのフォーマット記述プロパティを配列に読み込み、各プロパティにアクセスするときに各要素を CMFormatDescriptionRef オブジェクトとしてキャストします。
CMFormatDescriptionRef formatDescription = NULL;
NSArray *formatDescriptions = [assetVideoTrack formatDescriptions];
if ([formatDescriptions count] > 0)
formatDescription = (__bridge CMFormatDescriptionRef)[formatDescriptions objectAtIndex:0];
次に、クリーン アパーチャ設定とピクセル アスペクト比設定の両方を読み込んで、最後にどちらかを選択します。
if (formatDescription)
{
NSDictionary *cleanAperture = nil;
NSDictionary *pixelAspectRatio = nil;
CFDictionaryRef cleanApertureFromCMFormatDescription = CMFormatDescriptionGetExtension(formatDescription, kCMFormatDescriptionExtension_CleanAperture);
if (cleanApertureFromCMFormatDescription)
{
cleanAperture = @{
AVVideoCleanApertureWidthKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureWidth),
AVVideoCleanApertureHeightKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureHeight),
AVVideoCleanApertureHorizontalOffsetKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureHorizontalOffset),
AVVideoCleanApertureVerticalOffsetKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureVerticalOffset)
};
}
CFDictionaryRef pixelAspectRatioFromCMFormatDescription = CMFormatDescriptionGetExtension(formatDescription, kCMFormatDescriptionExtension_PixelAspectRatio);
if (pixelAspectRatioFromCMFormatDescription)
{
pixelAspectRatio = @{
AVVideoPixelAspectRatioHorizontalSpacingKey : (id)CFDictionaryGetValue(pixelAspectRatioFromCMFormatDescription, kCMFormatDescriptionKey_PixelAspectRatioHorizontalSpacing),
AVVideoPixelAspectRatioVerticalSpacingKey : (id)CFDictionaryGetValue(pixelAspectRatioFromCMFormatDescription, kCMFormatDescriptionKey_PixelAspectRatioVerticalSpacing)
};
}
// Add whichever settings we could grab from the format description to the compression settings dictionary.
if (cleanAperture || pixelAspectRatio)
{
NSMutableDictionary *mutableCompressionSettings = [NSMutableDictionary dictionary];
if (cleanAperture)
[mutableCompressionSettings setObject:cleanAperture forKey:AVVideoCleanApertureKey];
if (pixelAspectRatio)
[mutableCompressionSettings setObject:pixelAspectRatio forKey:AVVideoPixelAspectRatioKey];
compressionSettings = mutableCompressionSettings;
}
}
ここで混乱しました。一部のビデオ トラックには 1 つがあり、もう 1 つがなく、その逆もあります。したがって、両方をロードしてから、完全に戻ったプロパティのセットを選択し、そうでないセットを破棄します。
ファイルの読み取りと iPhone への書き込みに必要なすべてのメソッドを入れ子にする方法は実際には 1 つしかないことに注意してください。さまざまなバリエーションがあります。あなたがこれまでにできる最も健全で賢明なことは、正しい方法でそれを行っていることを確認することです.
それがどのように見えるかに興味がある場合は、ここにあります：
#import "ExportVideo.h"
@implementation ExportVideo
@synthesize url = _url;
@synthesize renderer = _renderer;
- (id)initWithURL:(NSURL *)url usingRenderer:(GLKitView *)renderer {
NSLog(@"ExportVideo");
if (!(self = [super init])) {
return nil;
}
self.url = url;
self.renderer = renderer;
NSString *serializationQueueDescription = [NSString stringWithFormat:@"%@ serialization queue", self];
_mainSerializationQueue = dispatch_queue_create([serializationQueueDescription UTF8String], NULL);
NSString *rwAudioSerializationQueueDescription = [NSString stringWithFormat:@"%@ rw audio serialization queue", self];
_rwAudioSerializationQueue = dispatch_queue_create([rwAudioSerializationQueueDescription UTF8String], NULL);
NSString *rwVideoSerializationQueueDescription = [NSString stringWithFormat:@"%@ rw video serialization queue", self];
_rwVideoSerializationQueue = dispatch_queue_create([rwVideoSerializationQueueDescription UTF8String], NULL);
return self;
}
- (void)startProcessing {
NSDictionary *inputOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
_asset = [[AVURLAsset alloc] initWithURL:self.url options:inputOptions];
NSLog(@"URL: %@", self.url);
_cancelled = NO;
[_asset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObject:@"tracks"] completionHandler: ^{
dispatch_async(_mainSerializationQueue, ^{
if (_cancelled)
return;
BOOL success = YES;
NSError *localError = nil;
success = ([_asset statusOfValueForKey:@"tracks" error:&localError] == AVKeyValueStatusLoaded);
if (success)
{
NSFileManager *fm = [NSFileManager defaultManager];
NSString *localOutputPath = [self.url path];
if ([fm fileExistsAtPath:localOutputPath])
success = [fm removeItemAtPath:localOutputPath error:&localError];
}
if (success)
success = [self setupAssetReaderAndAssetWriter:&localError];
if (success)
success = [self startAssetReaderAndWriter:&localError];
if (!success)
[self readingAndWritingDidFinishSuccessfully:success withError:localError];
});
}];
}
- (BOOL)setupAssetReaderAndAssetWriter:(NSError **)outError
{
// Create and initialize the asset reader.
_reader = [[AVAssetReader alloc] initWithAsset:_asset error:outError];
BOOL success = (_reader != nil);
if (success)
{
// If the asset reader was successfully initialized, do the same for the asset writer.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
_outputURL = paths[0];
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:_outputURL withIntermediateDirectories:YES attributes:nil error:nil];
_outputURL = [_outputURL stringByAppendingPathComponent:@"output.mov"];
[manager removeItemAtPath:_outputURL error:nil];
_outURL = [NSURL fileURLWithPath:_outputURL];
_writer = [[AVAssetWriter alloc] initWithURL:_outURL fileType:AVFileTypeQuickTimeMovie error:outError];
success = (_writer != nil);
}
if (success)
{
// If the reader and writer were successfully initialized, grab the audio and video asset tracks that will be used.
AVAssetTrack *assetAudioTrack = nil, *assetVideoTrack = nil;
NSArray *audioTracks = [_asset tracksWithMediaType:AVMediaTypeAudio];
if ([audioTracks count] > 0)
assetAudioTrack = [audioTracks objectAtIndex:0];
NSArray *videoTracks = [_asset tracksWithMediaType:AVMediaTypeVideo];
if ([videoTracks count] > 0)
assetVideoTrack = [videoTracks objectAtIndex:0];
if (assetAudioTrack)
{
// If there is an audio track to read, set the decompression settings to Linear PCM and create the asset reader output.
NSDictionary *decompressionAudioSettings = @{ AVFormatIDKey : [NSNumber numberWithUnsignedInt:kAudioFormatLinearPCM] };
_readerAudioOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:assetAudioTrack outputSettings:decompressionAudioSettings];
[_reader addOutput:_readerAudioOutput];
// Then, set the compression settings to 128kbps AAC and create the asset writer input.
AudioChannelLayout stereoChannelLayout = {
.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo,
.mChannelBitmap = 0,
.mNumberChannelDescriptions = 0
};
NSData *channelLayoutAsData = [NSData dataWithBytes:&stereoChannelLayout length:offsetof(AudioChannelLayout, mChannelDescriptions)];
NSDictionary *compressionAudioSettings = @{
AVFormatIDKey : [NSNumber numberWithUnsignedInt:kAudioFormatMPEG4AAC],
AVEncoderBitRateKey : [NSNumber numberWithInteger:128000],
AVSampleRateKey : [NSNumber numberWithInteger:44100],
AVChannelLayoutKey : channelLayoutAsData,
AVNumberOfChannelsKey : [NSNumber numberWithUnsignedInteger:2]
};
_writerAudioInput = [AVAssetWriterInput assetWriterInputWithMediaType:[assetAudioTrack mediaType] outputSettings:compressionAudioSettings];
[_writer addInput:_writerAudioInput];
}
if (assetVideoTrack)
{
// If there is a video track to read, set the decompression settings for YUV and create the asset reader output.
NSDictionary *decompressionVideoSettings = @{
(id)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange],
(id)kCVPixelBufferIOSurfacePropertiesKey : [NSDictionary dictionary]
};
_readerVideoOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:assetVideoTrack outputSettings:decompressionVideoSettings];
[_reader addOutput:_readerVideoOutput];
CMFormatDescriptionRef formatDescription = NULL;
// Grab the video format descriptions from the video track and grab the first one if it exists.
NSArray *formatDescriptions = [assetVideoTrack formatDescriptions];
if ([formatDescriptions count] > 0)
formatDescription = (__bridge CMFormatDescriptionRef)[formatDescriptions objectAtIndex:0];
CGSize trackDimensions = {
.width = 0.0,
.height = 0.0,
};
// If the video track had a format description, grab the track dimensions from there. Otherwise, grab them direcly from the track itself.
if (formatDescription)
trackDimensions = CMVideoFormatDescriptionGetPresentationDimensions(formatDescription, false, false);
else
trackDimensions = [assetVideoTrack naturalSize];
NSDictionary *compressionSettings = nil;
// If the video track had a format description, attempt to grab the clean aperture settings and pixel aspect ratio used by the video.
if (formatDescription)
{
NSDictionary *cleanAperture = nil;
NSDictionary *pixelAspectRatio = nil;
CFDictionaryRef cleanApertureFromCMFormatDescription = CMFormatDescriptionGetExtension(formatDescription, kCMFormatDescriptionExtension_CleanAperture);
if (cleanApertureFromCMFormatDescription)
{
cleanAperture = @{
AVVideoCleanApertureWidthKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureWidth),
AVVideoCleanApertureHeightKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureHeight),
AVVideoCleanApertureHorizontalOffsetKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureHorizontalOffset),
AVVideoCleanApertureVerticalOffsetKey : (id)CFDictionaryGetValue(cleanApertureFromCMFormatDescription, kCMFormatDescriptionKey_CleanApertureVerticalOffset)
};
}
CFDictionaryRef pixelAspectRatioFromCMFormatDescription = CMFormatDescriptionGetExtension(formatDescription, kCMFormatDescriptionExtension_PixelAspectRatio);
if (pixelAspectRatioFromCMFormatDescription)
{
pixelAspectRatio = @{
AVVideoPixelAspectRatioHorizontalSpacingKey : (id)CFDictionaryGetValue(pixelAspectRatioFromCMFormatDescription, kCMFormatDescriptionKey_PixelAspectRatioHorizontalSpacing),
AVVideoPixelAspectRatioVerticalSpacingKey : (id)CFDictionaryGetValue(pixelAspectRatioFromCMFormatDescription, kCMFormatDescriptionKey_PixelAspectRatioVerticalSpacing)
};
}
// Add whichever settings we could grab from the format description to the compression settings dictionary.
if (cleanAperture || pixelAspectRatio)
{
NSMutableDictionary *mutableCompressionSettings = [NSMutableDictionary dictionary];
if (cleanAperture)
[mutableCompressionSettings setObject:cleanAperture forKey:AVVideoCleanApertureKey];
if (pixelAspectRatio)
[mutableCompressionSettings setObject:pixelAspectRatio forKey:AVVideoPixelAspectRatioKey];
compressionSettings = mutableCompressionSettings;
}
}
// Create the video settings dictionary for H.264.
NSMutableDictionary *videoSettings = (NSMutableDictionary *) @{
AVVideoCodecKey : AVVideoCodecH264,
AVVideoWidthKey : [NSNumber numberWithDouble:trackDimensions.width],
AVVideoHeightKey : [NSNumber numberWithDouble:trackDimensions.height]
};
// Put the compression settings into the video settings dictionary if we were able to grab them.
if (compressionSettings)
[videoSettings setObject:compressionSettings forKey:AVVideoCompressionPropertiesKey];
// Create the asset writer input and add it to the asset writer.
_writerVideoInput = [AVAssetWriterInput assetWriterInputWithMediaType:[assetVideoTrack mediaType] outputSettings:videoSettings];
[_writer addInput:_writerVideoInput];
}
}
return success;
}
- (BOOL)startAssetReaderAndWriter:(NSError **)outError
{
BOOL success = YES;
// Attempt to start the asset reader.
success = [_reader startReading];
if (!success) {
*outError = [_reader error];
NSLog(@"Reader error");
}
if (success)
{
// If the reader started successfully, attempt to start the asset writer.
success = [_writer startWriting];
if (!success) {
*outError = [_writer error];
NSLog(@"Writer error");
}
}
if (success)
{
// If the asset reader and writer both started successfully, create the dispatch group where the reencoding will take place and start a sample-writing session.
_dispatchGroup = dispatch_group_create();
[_writer startSessionAtSourceTime:kCMTimeZero];
_audioFinished = NO;
_videoFinished = NO;
if (_writerAudioInput)
{
// If there is audio to reencode, enter the dispatch group before beginning the work.
dispatch_group_enter(_dispatchGroup);
// Specify the block to execute when the asset writer is ready for audio media data, and specify the queue to call it on.
[_writerAudioInput requestMediaDataWhenReadyOnQueue:_rwAudioSerializationQueue usingBlock:^{
// Because the block is called asynchronously, check to see whether its task is complete.
if (_audioFinished)
return;
BOOL completedOrFailed = NO;
// If the task isn't complete yet, make sure that the input is actually ready for more media data.
while ([_writerAudioInput isReadyForMoreMediaData] && !completedOrFailed)
{
// Get the next audio sample buffer, and append it to the output file.
CMSampleBufferRef sampleBuffer = [_readerAudioOutput copyNextSampleBuffer];
if (sampleBuffer != NULL)
{
BOOL success = [_writerAudioInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
sampleBuffer = NULL;
completedOrFailed = !success;
}
else
{
completedOrFailed = YES;
}
}
if (completedOrFailed)
{
// Mark the input as finished, but only if we haven't already done so, and then leave the dispatch group (since the audio work has finished).
BOOL oldFinished = _audioFinished;
_audioFinished = YES;
if (oldFinished == NO)
{
[_writerAudioInput markAsFinished];
}
dispatch_group_leave(_dispatchGroup);
}
}];
}
if (_writerVideoInput)
{
// If we had video to reencode, enter the dispatch group before beginning the work.
dispatch_group_enter(_dispatchGroup);
// Specify the block to execute when the asset writer is ready for video media data, and specify the queue to call it on.
[_writerVideoInput requestMediaDataWhenReadyOnQueue:_rwVideoSerializationQueue usingBlock:^{
// Because the block is called asynchronously, check to see whether its task is complete.
if (_videoFinished)
return;
BOOL completedOrFailed = NO;
// If the task isn't complete yet, make sure that the input is actually ready for more media data.
while ([_writerVideoInput isReadyForMoreMediaData] && !completedOrFailed)
{
// Get the next video sample buffer, and append it to the output file.
CMSampleBufferRef sampleBuffer = [_readerVideoOutput copyNextSampleBuffer];
/* PROCESS FRAME HERE */
//CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
//_currentBuffer = pixelBuffer;
//[self performSelectorOnMainThread:@selector(processFrame) withObject:nil waitUntilDone:YES];
/* ------------------ */
if (sampleBuffer != NULL)
{
BOOL success = [_writerVideoInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
sampleBuffer = NULL;
completedOrFailed = !success;
}
else
{
completedOrFailed = YES;
}
}
if (completedOrFailed)
{
// Mark the input as finished, but only if we haven't already done so, and then leave the dispatch group (since the video work has finished).
BOOL oldFinished = _videoFinished;
_videoFinished = YES;
if (oldFinished == NO)
{
[_writerVideoInput markAsFinished];
}
dispatch_group_leave(_dispatchGroup);
}
}];
}
// Set up the notification that the dispatch group will send when the audio and video work have both finished.
dispatch_group_notify(_dispatchGroup, _mainSerializationQueue, ^{
BOOL finalSuccess = YES;
NSError *finalError = nil;
// Check to see if the work has finished due to cancellation.
if (_cancelled)
{
// If so, cancel the reader and writer.
[_reader cancelReading];
[_writer cancelWriting];
}
else
{
// If cancellation didn't occur, first make sure that the asset reader didn't fail.
if ([_reader status] == AVAssetReaderStatusFailed)
{
finalSuccess = NO;
finalError = [_reader error];
NSLog(@"_reader finalError: %@", finalError);
}
// If the asset reader didn't fail, attempt to stop the asset writer and check for any errors.
[_writer finishWritingWithCompletionHandler:^{
UISaveVideoAtPathToSavedPhotosAlbum(_outputURL, nil, nil, nil);
[self readingAndWritingDidFinishSuccessfully:finalSuccess withError:[_writer error]];
}];
}
// Call the method to handle completion, and pass in the appropriate parameters to indicate whether reencoding was successful.
});
}
// Return success here to indicate whether the asset reader and writer were started successfully.
return success;
}
- (void)readingAndWritingDidFinishSuccessfully:(BOOL)success withError:(NSError *)error
{
if (!success)
{
// If the reencoding process failed, we need to cancel the asset reader and writer.
[_reader cancelReading];
[_writer cancelWriting];
dispatch_async(dispatch_get_main_queue(), ^{
// Handle any UI tasks here related to failure.
});
}
else
{
// Reencoding was successful, reset booleans.
_cancelled = NO;
_videoFinished = NO;
_audioFinished = NO;
dispatch_async(dispatch_get_main_queue(), ^{
// Handle any UI tasks here related to success.
});
}
NSLog(@"readingAndWritingDidFinishSuccessfully success = %@ : Error = %@", (success == 0) ? @"NO" : @"YES", error);
}
@end