README

This is a simple video recording app for iOS that mimics vine’s touch to record feature.
For a list of known bugs, see below.

##RUNNING THE PROJECT This project uses cocoa pods, so make sure to build from the workspace file, not the xcodeproj.

####3rd party libraries used:
GPUImage to filter recorded videos in post-processing.
FRDLivelyButton to animate navigation buttons between views.

##ARCHITECTURE

###VCAppDelegate The app delegate creates the navigation controller and sets up its view controller hierarchy.

###VCNavigationController This UINavigationController subclass enables customization of the navigation buttons to work with FRDLivelyButton. In viewDidLoad, two buttons (leftButton & rightButton) are initialized and added to the view. The child view controllers then use the leftButton and rightButton properties of VCNavigationController to dynamically set the button styles. The one drawback to this method is that it limits the button appearance to the built-in button styles of the library.

###VCGalleryViewController The gallery view controller relies on user defaults to fetch the number of videos the user has saved. The generateThumbnailForRowAtIndexPath and generateLabelForRowAtIndexPath methods are used to generate the appropriate background image and timestamp label for each cell.

###VCSaveAndShareViewController This ViewController gets initialized with a video url from the didSelectRowAtIndexPath delegate method in VCGalleryViewController. It uses an AVPlayer wrapped in a UIView from my VCClipViewer subclass to play and loop the video. From this screen, users can save the video to their photo library, attach it in an email, or send it in a text message.

###VCRecordViewController This ViewController handles recording videos and is heavily based on Apple’s RosyWriter. When the view appears, setUpCaptureSession creates a new capture session and adds video and audio inputs/outputs. The method also adds a preview layer to the view. When a user touches and holds down anywhere on the screen, the app starts recording a new video clip to a file. On touch up, the url is stored in an array, which gets passed to VCPostProcessingViewController when the user is ready to edit the video. When recording, a NSTimer is used to keep track of how much time has elapsed and limits the cumulative duration of all the recorded clips to 5 seconds long. At every tick from the timer, updateTime calls startAnimation to animate the timeline indicator at the top of the screen.

###VCPostProcessingViewController The post processing ViewController handles filtering and saving videos. When initialized, all the recorded clip urls are stored in an array. On viewWillAppear, an AVComposition is created to string together the clips into a single video, which is then exported to local storage. That file is then used as an input to create filtered versions.

A UIPageViewController is used to handle swiping between different filters. When a user swipes to a new filter, preloadNextFilterwithPrevIndex determines the next filter in the stack and starts processing it to a new file. If processing finishes before the user swipes to the next filter, that next filter is played from the pageViewController:didFinishAnimating: delegate method. However, if the user swipes to the next filter before it is finished being processed, observeValueForKeyPath:ofObject: handles playing the filtered version when the assetWriter is done processing. To make this work, a VCMovieWriterProgressObject is used to add key-value observers in viewDidAppear for each filter type. As a result, we can monitor the state of the assetWriter when the pageViewController animates. If you are wondering why it matters to keep track of the state of the assetWriter (specifically whether it is in the process of writing or if it is finished writing), it is because in order to play a video, it needs to be completely done processing; we will get an error if we try to play an asset that is still being processed so we need to make sure the video asset isn't still being changed when we go to play it.

Each new filter is saved to a unique file so we only need to process the original video one time per filter. These files are saved so long as the user stays on the processing screen. In the worst case scenario - if the user swipes through all 15 filters, VidClips will have 16 variations of the movie file (including the non-filtered version) stored in memory. When the user cancels or saves the video, these files are cleared in viewWillDissapear.

##BUGS

1. Filter Freezing — This bug occurs in VCPostProcessingViewController when the GPUImageWriter freezes and doesn’t finish processing a filtered video. This bug can be identified when the console logs a bunch of lines in the format - "Current frame time : 7.265985 ms" - that are not followed by “GPUImageMovieWriter Finished Writing”. A couple of factors can contribute to this bug including swiping the PageViewController too fast and recording longer videos. I’ve spent a couple hours trying to figure out how to prevent this and as far as I can tell, it’s a bug within the GPUImage framework. However, it's entirely possible that there is a threading issue on my end. The app breaks when this bug occurs because it relies on the completion handler of the assetWriter (called movieWriter in the file) to change the asset writing status. So, if the assetWriter never finishes writing, the completion block is never executed, resulting in filters never getting played. Canceling the video and re-recording should fix this. To minimize the likelihood of running into this bug, record shorter videos and don’t try changing the filters too quickly.

2. Blank or Black Thumbnails — Occasionally, the generateThumbnailForRowAtIndexPath method will generate blank or entirely black thumbnail frames. I have some ideas on how to ensure that this doesn’t happen but I haven't had time to implement them yet. If you save a video and don't see it in the gallery, try tapping the area where it should be to see if a blank thumbnail was created.

These are the major bugs I found myself running into when testing. If you come across one of them, try restarting the app or deleting it from your phone and re-compiling it. Also, please note that I've only tested on a 5s so if you are using an earlier model iPhone, you may run into additional bugs I haven’t seen yet.

##License The MIT License (MIT)

Copyright (c) 2014 Eric Appel

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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