avtimecodereadwrite/AVTimecodeReader.m
/* |
File: AVTimecodeReader.m |
Abstract: Reader class which sets up AVAssetReader and AVAssetReaderTrackOutput to read in timecode tracks and output timecode values. |
Version: 1.2 |
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*/ |
#import "AVTimecodeReader.h" |
#import "AVTimecodeUtilities.h" |
#import <CoreMedia/CoreMedia.h> |
#import <CoreVideo/CVBase.h> |
@interface AVTimecodeReader () |
{ |
AVAssetReader *assetReader; |
AVAssetReaderOutput *timecodeOutput; |
}; |
@property AVAsset *sourceAsset; |
@property NSMutableArray *timecodeSamples; |
@end |
@implementation AVTimecodeReader |
- (id)initWithSourceAsset:(AVAsset *)sourceAsset |
{ |
self = [super init]; |
if (self) |
{ |
self.sourceAsset = sourceAsset; |
self.timecodeSamples = [NSMutableArray array]; |
} |
return self; |
} |
- (NSArray *)readTimecodeSamples |
{ |
AVAsset *localAsset = self.sourceAsset; |
// The use of dispatch_semaphore here is to block the command line tool from exiting before task completion. |
// This should however not be used in an app based on AppKit. Instead of blocking until loading completes, you must allow your main runloop to run while loading continues; to accomplish that, remove the use of the dispatch_semaphore and use the completion block to perform any tasks you need to perform upon completion. |
dispatch_semaphore_t dispatchSemaphore = dispatch_semaphore_create(0); |
[localAsset loadValuesAsynchronouslyForKeys:[NSArray arrayWithObjects:@"tracks", @"duration", nil] completionHandler:^{ |
BOOL success = YES; |
NSError *localError = nil; |
success = ([localAsset statusOfValueForKey:@"tracks" error:&localError] == AVKeyValueStatusLoaded); |
if (success) |
success = ([localAsset statusOfValueForKey:@"duration" error:&localError] == AVKeyValueStatusLoaded); |
// Set up the AVAssetReader reading samples or flag an error |
if (success) |
success = [self setUpReaderReturningError:&localError]; |
if (success) |
success = [self startReadingAndOutputReturningError:&localError]; |
if (!success) |
[self readingDidFinishSuccessfully:success withError:localError]; |
dispatch_semaphore_signal(dispatchSemaphore); |
}]; |
dispatch_semaphore_wait(dispatchSemaphore, DISPATCH_TIME_FOREVER); |
return self.timecodeSamples; |
} |
- (BOOL)setUpReaderReturningError:(NSError **)outError |
{ |
BOOL success = YES; |
NSError *localError = nil; |
AVAsset *localAsset = self.sourceAsset; |
// Create asset reader |
assetReader = [[AVAssetReader alloc] initWithAsset:localAsset error:&localError]; |
success = (assetReader != nil); |
// Create asset reader output for the first timecode track of the asset |
if (success) { |
AVAssetTrack *timecodeTrack = nil; |
// Grab first timecode track, if the asset has them |
NSArray *timecodeTracks = [localAsset tracksWithMediaType:AVMediaTypeTimecode]; |
if ([timecodeTracks count] > 0) |
timecodeTrack = [timecodeTracks objectAtIndex:0]; |
if (timecodeTrack) { |
timecodeOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:timecodeTrack outputSettings:nil]; |
[assetReader addOutput:timecodeOutput]; |
} else { |
NSLog(@"%@ has no timecode tracks", localAsset); |
} |
} |
if (!success && outError) |
*outError = localError; |
return success; |
} |
- (BOOL)startReadingAndOutputReturningError:(NSError **)outError |
{ |
BOOL success = YES; |
NSError *localError = nil; |
// Instruct the asset reader to get ready to do work |
success = [assetReader startReading]; |
if (!success) { |
localError = [assetReader error]; |
} else { |
CMSampleBufferRef currentSampleBuffer = NULL; |
while ((currentSampleBuffer = [timecodeOutput copyNextSampleBuffer])) { |
[self outputTimecodeDescriptionForSampleBuffer:currentSampleBuffer]; |
} |
if (currentSampleBuffer) { |
CFRelease(currentSampleBuffer); |
} |
} |
if (!success && outError) |
*outError = localError; |
return success; |
} |
- (void)readingDidFinishSuccessfully:(BOOL)success withError:(NSError *)error |
{ |
if (!success) { |
[assetReader cancelReading]; |
} |
} |
- (void)outputTimecodeDescriptionForSampleBuffer:(CMSampleBufferRef)sampleBuffer |
{ |
CMBlockBufferRef blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer); |
CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer); |
if (blockBuffer && formatDescription) { |
size_t length = 0; |
size_t totalLength = 0; |
char *rawData = NULL; |
OSStatus status = CMBlockBufferGetDataPointer(blockBuffer, 0, &length, &totalLength, &rawData); |
if (status != kCMBlockBufferNoErr) { |
NSLog(@"Could not get data from block buffer"); |
} |
else { |
CMMediaType type = CMFormatDescriptionGetMediaSubType(formatDescription); |
uint32_t frameQuanta = CMTimeCodeFormatDescriptionGetFrameQuanta(formatDescription); |
uint32_t tcFlag = CMTimeCodeFormatDescriptionGetTimeCodeFlags(formatDescription); |
if (type == kCMTimeCodeFormatType_TimeCode32) { |
int32_t *frameNumberRead = (int32_t *)rawData; |
// frameNumberRead is stored big-endian. Convert it to native before passing in to the utility function. |
CVSMPTETime timecode = timecodeForFrameNumberUsingFrameQuanta(EndianS32_BtoN(*frameNumberRead), frameQuanta, tcFlag); |
[self.timecodeSamples addObject:[NSValue value:&timecode withObjCType:@encode(CVSMPTETime)]]; |
} else if (type == kCMTimeCodeFormatType_TimeCode64) { |
int64_t *frameNumberRead = (int64_t *)rawData; |
// frameNumberRead is stored big-endian. Convert it to native before passing in to the utility function. |
CVSMPTETime timecode = timecodeForFrameNumberUsingFrameQuanta(EndianS64_BtoN(*frameNumberRead), frameQuanta, tcFlag); |
[self.timecodeSamples addObject:[NSValue value:&timecode withObjCType:@encode(CVSMPTETime)]]; |
} |
} |
} |
} |
@end |
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