/*

     File: APLCustomVideoCompositor.m

 Abstract:  Custom video compositor class implementing the AVVideoCompositing protocol. 

  Version: 1.1

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 */

#import "APLCustomVideoCompositor.h"

#import "APLCustomVideoCompositionInstruction.h"

#import "APLDiagonalWipeRenderer.h"

#import "APLCrossDissolveRenderer.h"

#import <CoreVideo/CoreVideo.h>

@interface APLCustomVideoCompositor()

{

    BOOL                                _shouldCancelAllRequests;

    BOOL                                _renderContextDidChange;

    dispatch_queue_t                    _renderingQueue;

    dispatch_queue_t                    _renderContextQueue;

    AVVideoCompositionRenderContext*    _renderContext;

    CVPixelBufferRef                    _previousBuffer;

}

@property (nonatomic, retain) APLOpenGLRenderer *oglRenderer;

@end

@implementation APLCrossDissolveCompositor

- (id)init

{

    self = [super init];

    if (self) {

        self.oglRenderer = [[APLCrossDissolveRenderer alloc] init];

    }

    return self;

}

@end

@implementation APLDiagonalWipeCompositor

- (id)init

{

    self = [super init];

    if (self) {

        self.oglRenderer = [[APLDiagonalWipeRenderer alloc] init];

    }

    return self;

}

@end

@implementation APLCustomVideoCompositor

#pragma mark - AVVideoCompositing protocol

- (id)init

{

    self = [super init];

    if (self)

    {

        _renderingQueue = dispatch_queue_create("com.apple.aplcustomvideocompositor.renderingqueue", DISPATCH_QUEUE_SERIAL); 

        _renderContextQueue = dispatch_queue_create("com.apple.aplcustomvideocompositor.rendercontextqueue", DISPATCH_QUEUE_SERIAL);

        _previousBuffer = nil;

        _renderContextDidChange = NO;

    }

    return self;

}

- (NSDictionary *)sourcePixelBufferAttributes

{

    return @{ (NSString *)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA],

              (NSString *)kCVPixelBufferOpenGLCompatibilityKey : [NSNumber numberWithBool:YES],

              (NSString *)kCVPixelBufferIOSurfacePropertiesKey : @{}};

}

- (NSDictionary *)requiredPixelBufferAttributesForRenderContext

{

    return @{ (NSString *)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA],

              (NSString *)kCVPixelBufferOpenGLCompatibilityKey : [NSNumber numberWithBool:YES],

              (NSString *)kCVPixelBufferIOSurfacePropertiesKey : @{}};

}

- (void)renderContextChanged:(AVVideoCompositionRenderContext *)newRenderContext

{

    dispatch_sync(_renderContextQueue, ^() {

        _renderContext = newRenderContext;

        _renderContextDidChange = YES;

    });

}

- (void)startVideoCompositionRequest:(AVAsynchronousVideoCompositionRequest *)request

{

    @autoreleasepool {

        dispatch_async(_renderingQueue,^() {

            // Check if all pending requests have been cancelled

            if (_shouldCancelAllRequests) {

                [request finishCancelledRequest];

            } else {

                NSError *err = nil;

                // Get the next rendererd pixel buffer

                CVPixelBufferRef resultPixels = [self newRenderedPixelBufferForRequest:request error:&err];

                if (resultPixels) {

                    // The resulting pixelbuffer from OpenGL renderer is passed along to the request

                    [request finishWithComposedVideoFrame:resultPixels];

                    CFRelease(resultPixels);

                } else {

                    [request finishWithError:err];

                }

            }

        });

    }

}

- (void)cancelAllPendingVideoCompositionRequests

{

    // pending requests will call finishCancelledRequest, those already rendering will call finishWithComposedVideoFrame

    _shouldCancelAllRequests = YES;

    // block until all cancelled or finished

    dispatch_barrier_async(_renderingQueue, ^() {

        // start accepting requests again

        _shouldCancelAllRequests = NO;

    });

}

#pragma mark - Utilities

static Float64 factorForTimeInRange(CMTime time, CMTimeRange range) /* 0.0 -> 1.0 */

{

    CMTime elapsed = CMTimeSubtract(time, range.start);

    return CMTimeGetSeconds(elapsed) / CMTimeGetSeconds(range.duration);

}

- (CVPixelBufferRef)newRenderedPixelBufferForRequest:(AVAsynchronousVideoCompositionRequest *)request error:(NSError **)errOut

{

    CVPixelBufferRef dstPixels = nil;

    // tweenFactor indicates how far within that timeRange we are rendering this frame. This is normalized to vary between 0.0 and 1.0.

    // 0.0 indicates the time at first frame in that videoComposition timeRange

    // 1.0 indicates the time at last frame in that videoComposition timeRange

    float tweenFactor = factorForTimeInRange(request.compositionTime, request.videoCompositionInstruction.timeRange);

    APLCustomVideoCompositionInstruction *currentInstruction = request.videoCompositionInstruction;

    // Source pixel buffers are used as inputs while rendering the transition

    CVPixelBufferRef foregroundSourceBuffer = [request sourceFrameByTrackID:currentInstruction.foregroundTrackID];

    CVPixelBufferRef backgroundSourceBuffer = [request sourceFrameByTrackID:currentInstruction.backgroundTrackID];

    // Destination pixel buffer into which we render the output

    dstPixels = [_renderContext newPixelBuffer];

    // Recompute normalized render transform everytime the render context changes

    if (_renderContextDidChange) {

        // The renderTransform returned by the renderContext is in X: [0, w] and Y: [0, h] coordinate system

        _oglRenderer.renderTransform = _renderContext.renderTransform;

        _renderContextDidChange = NO;

    }

    [_oglRenderer renderPixelBuffer:dstPixels usingForegroundSourceBuffer:foregroundSourceBuffer andBackgroundSourceBuffer:backgroundSourceBuffer forTweenFactor:tweenFactor];

    return dstPixels;

}

@end