How to convert local video into CMSampleBuffer for unit tests

Media Technologies Audio
jordi OP
Created Jun ’20
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Hi,

I'm working on an app that uses the live camera output to perform text recognition.

In order to improve the performance , I want to write some unit tests to check how well the text recognition works over time. I want to load a video from my app bundle, and use that as the 'camera output' so that I can write tests around what should and what should not get recognized.

I'm trying to find out how to generate a CMSampleBuffer from a video so I can feed that into my Vision request. Any ideas? Thanks!
Answered by Media Engineer in 617315022
Another option, if you don't need the frames in real-time, is to use AVAssetReader.
Replies  5
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Engineer OP
Apple
Jun ’20
Take a look at Action & Vision sample code. The CameraViewController class supports two modes: live camera capture and reading form the video file.
The idea is to use AVPlayerItemVideoOutput together with CADisplayLink - this will closely simulate the live camera capture scenario.
The actual conversion of CVPixelBuffer to CMSampleBuffer happens inside CADisplayLink callback.
See handleDisplayLink(_ displayLink: CADisplayLink) function.


2
Media Engineer OP
Apple
Jun ’20
Accepted Answer
Another option, if you don't need the frames in real-time, is to use AVAssetReader.
1
jordi OP
Jul ’20
Thanks to both of you for the suggestions! Got a first version up and running!
0
jordi OP
Jul ’20
Oops, I wanted to choose the other answer as 'the answer'. Can't undo it now, sorry!
0
alex-any OP
Jul ’20
Could you, please, share how you finally mocked buffers in tests? Have you used handleDisplayLink or AVAssetReader?
0
How to convert local video into CMSampleBuffer for unit tests
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