CODEWITHSUNDEEP
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barndog
barndog

Reputation: 7173

Most performant method of processing video and writing to file - ios AVFoundation

I want to read in a video asset on disk and a bunch of processing on it, things like using a CICropFilter on each individual frame and cutting out a mask, splitting up one video into several smaller videos, and removing frames from the original track to "compress" it down and make it more gif-like.

I've come up with a few possible avenues:

  1. AVAssetWriter and AVAssetReader

In this scenario, I would read in the CMSampleBuffers from file, perform my desired manipulations, then write back to a new file using AVAssetWriter.

  1. AVMutableComposition

Here, given a list of CMTimes I can easily cut out frames and rewrite the video or even create multiple compositions for each new video I want to create, then export all of them using AVAssetExportSession.

The metrics I'm concerned about: performance and power. That is to say I'm interested in the method that offers the greatest efficiency in performing my edits while also giving me the flexibility to do what I want. I'd imagine the kind of video editing I'm describing can be done with both approaches but really I want the most performant/with the best capabilities.

Upvotes: 3

Views: 1349

Answers (1)

Tim Bull
Tim Bull

Reputation: 2495

In my experience AVAssetExportSession is slightly more performant than using AVAssetReader and AVAssetWriter for a straight forward format A -> format B type conversion, however that said, it's probably not by enough to be too concerned about.

According to Apple's own documentation https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html#//apple_ref/doc/uid/TP40010188:

You use an export session to reencode an existing asset into a format defined by one of a small number of commonly-used presets. If you need more control over the transformation, in iOS 4.1 and later you can use an asset reader and asset writer object in tandem to convert an asset from one representation to another. Using these objects you can, for example, choose which of the tracks you want to be represented in the output file, specify your own output format, or modify the asset during the conversion process.

Given the nature of your question, it seems like you don't have much experience with the AVFoundation framework yet. My advice is to start with AVAssetExportSession and then when you hit a road block, move deeper down the stack into AVAssetReader and AVAssetWriter.

Eventually, depending on how far you take this, you may even want to write your own Custom Compositor.

Upvotes: 2

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