Ever since I made a switch to the iPhone, I've been looking for a solution that would allow me to play the video content that I viewed the most on my device. The iPhone only natively supports MP4 videos encoded to a specific resolution. If I wanted to view any other common third party format, for example, AVI, DIVX or MKV, I would have to convert videos to iPhone MP4 - a time consuming process that often results in errors and audio sync issues.
Up until a few months ago, there were no real solutions to watching an unconverted MKV on your iOS device. The recently released VLC for iOS (now withdrawn from iTunes due to licensing issues) could open a large number of video formats, but was like a slideshow when playing higher bitrate MKV videos. Thankfully, AVPlayer, available for iPhone/iPod Touch and in an HD version for iPad, has much better performance when it comes to playback of MKVs and high bitrate videos as of version 1.3.
The performance of MKVs is much smoother on AVPlayer than on VLC:
Formats that can be played by AVPlayer on iOS:
XVID/DIVX (including AC3) AVI,WMV,RMVB,ASF,H264,MKV… most of all movie file formats.
SMI, SRT Subtitles.
Rotation Lock / Aspect ratio:auto/16:9/4:3/1:1/Full screen
Folder Management:Pass code/Move/Rename/Create
For AVPlayer, file transfers come in two flavours: USB and WiFi. The USB transfer (aka File Sharing) works the same way it does through many other apps in iTunes as introduced in iTunes 9.1. Simply navigate to the iPhone -> Apps -> AVPlayer, and then drag and drop files onto the device.
The WiFi transfer very simple to use and does not require installing any additional software on one's desktop. When you open the AVPlayer app and select WiFi transfer, it opens a window with the local IP address opened at port 8080. Just navigate to the address shown and you'll be presented with a basic menu where you can navigate through folders and upload files. The process itself is secure because as soon as you navigate away from the WiFi transfer option on the iPhone, the web access is shut off. This also means that if you want to push large amounts of data through WiFi, then you won't be able to do anything else with the phone until the upload is complete.
The WiFi transfer is also one of the few ways to bypass USB transfer's artificial limit of 2gb of data per application on the iPhone and iPod Touch. However, no such restriction is placed on the iPad version, which can comfortably handle filling the app full to the brim with videos through USB transfer.
AVPlayer has very robust folder management. It's very easy to move around large numbers of videos into folders, subfolders, etc. When tapping the configuration spanner in the top right, checkboxes are made available next to video files and also an option to 'select all'. From this stage you can move these files to any folder or subfolder, and rename or delete. There is also an option to set a PIN for a specific folder.
The gestures in this app are very useful and customisable. For example, I have my AVPlayer setup so that a triple touch fast forwards 30 seconds, and a double touch rewinds 10 seconds. This is handy for skipping through videos (like intro sequences) without fiddling with the small seeking bar.
I'm not sure about how useful this feature, but the way that it is implemented by default is unintuitive and leaves a lot to be desired. Default controls put speed control as single touch gestures (which means that you will accidentally tap to speed up or slow down playback all the time). Also speeding up makes the playback of the video much more inconsistent (presumably because it has to process many more frames at a time).
This feature allows you to grayscale an image or improve the colour. Surprisingly not necessarily a junk feature (especially if you enjoy viewing 'camcorder' videos), as you can change the colour of a badly optimised video into something more viewable. Also it is surprising that this feature doesn't seem to impact the playback of video a great deal.
AVPlayer is definitely the best solution for playing videos on your iOS device, and probably the only one that can do MKVs and non-MP4 high definition videos to any degree of competence. I suspect that future iterations of the software (or faster processors being released by Apple) will eventually allow for higher bitrate non-MP4 videos to be playable as well.