AVAssetWriter with non-constant frame rate

Question

Created Nov ’17

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I'm trying to export a series of JPG images into a H264 movie (ideally it would be a motion JPEG movie, but unfortunately out AVAssetWriter

does not support this codec). The images originate from a professional surveillance camera with VFR (variable frame rate), hence I compute the CMTime

based on the time they have been captured, which results in a non-constant frame rate.

When I do this, the AVAssetWriter always fails to render the movie:

Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedFailureReason=An unknown error occurred (-16364), NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x604000245a90 {Error Domain=NSOSStatusErrorDomain Code=-16364 "(null)"}}

When I change the CMTime instances to be e.g.

CMMakeTime( frameIndex * 150, 600 )

it works, albeit resulting in a slightly wrong output.

Any idea how I could fix this? Is AVAssetWriter supposed to support that scenario?

Answered by Media Engineer in 278050022

-16364 means invalid timestamp. Asset Writer certainly supports variable frame rate video. Please double check your timestamps for consistency. Perhaps you're going backwards in time?

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Answer 1

Media Engineer OP

Apple

Nov ’17

Accepted Answer

-16364 means invalid timestamp. Asset Writer certainly supports variable frame rate video. Please double check your timestamps for consistency. Perhaps you're going backwards in time?

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Answer 2

DrMickeyLauer OP

Nov ’17

Yay! Another check showed me that my time codes were indeed going backwards (off-by-one error, for the last image I computed 0 instead of the correct base value). The export works great now!

Thanks a lot, bford!

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Answer 3

Moksh_Suthar OP

Apr ’21

hello guys,
I am also facing this problem.
time of asset writer going backward but I don't know how to solve this problem can you help me.

Code Block WARNING: Trouble appending pixel buffer at time: CMTime(value: 80, timescale: 600, flags: __C.CMTimeFlags(rawValue: 1), epoch: 0) Optional(Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedFailureReason=An unknown error occurred (-16364), NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x2828f7ed0 {Error Domain=NSOSStatusErrorDomain Code=-16364 "(null)"}})

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