/*

     File: AVTimecodeReader.m

 Abstract:  Reader class which sets up AVAssetReader and AVAssetReaderTrackOutput to read in timecode tracks and output timecode values. 

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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