Failure to append frames to video file using AVAssetWriterVideoInput. Fails with undocumented error -12738 at the end

Question

I am using an AVAssetWriterVideoInput to append buffers to a file. I have this code:

 if ( _assetWriter.status == AVAssetWriterStatusWriting ) {
    // If the asset writer status is writing, append sample buffer to its corresponding asset writer input
    if (mediaType == AVMediaTypeVideo) {
      if (_assetWriterVideoInput.readyForMoreMediaData) {
        if (![_assetWriterVideoInput appendSampleBuffer:sampleBuffer]) {
          NSLog(@"error: %@", [_assetWriter.error localizedFailureReason]);
          NSLog(@"error: %@", [_assetWriter.error localizedRecoveryOptions]);
          NSLog(@"error: %@", [_assetWriter.error localizedDescription]);
          NSLog(@"error: %@", [_assetWriter.error domain]);
          NSLog(@"error: %@", [_assetWriter.error userInfo]);
        } else
          NSLog(@"frame saved");
      }
    }

this line

    if (![_assetWriterVideoInput appendSampleBuffer:sampleBuffer]) {

fails with unknown error and code -12738 that, obviously is not found on any documentation, as expected with all apple docs.

Also, I doubt this is an unknown error for the simple reason that there are a lot of codes for unknown errors inside AVFoundation and if the system is picking code -12738 it obviously knows more than saying it is unknown.

Looking at the file being saved, it stays 0 megabytes, because no buffer/frame is saved.

This AVAssetWriterVideoInput was created like this:

  CMVideoDimensions dimensions = CMVideoFormatDescriptionGetDimensions(currentFormatDescription);
  NSUInteger numPixels = dimensions.width * dimensions.height;
  NSUInteger bitsPerSecond;

  // Assume that lower-than-SD resolutions are intended for streaming, and use a lower bitrate
    NSUInteger bitsPerPixel = 11.4; // This bitrate matches the quality produced by AVCaptureSessionPresetHigh.

  bitsPerSecond = numPixels * bitsPerPixel;

  NSDictionary *videoCompressionSettings = @{AVVideoCodecKey                  : AVVideoCodecH264,
                                             AVVideoWidthKey                  : @(dimensions.width),
                                             AVVideoHeightKey                 : @(dimensions.height),
                                             AVVideoCompressionPropertiesKey  : @{ AVVideoAverageBitRateKey      : @(bitsPerSecond),
                                                                                   AVVideoMaxKeyFrameIntervalKey : @(30)}  };

  if ([_assetWriter canApplyOutputSettings:videoCompressionSettings forMediaType:AVMediaTypeVideo])
  {
    // Intialize asset writer video input with the above created settings dictionary
    _assetWriterVideoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoCompressionSettings];
    _assetWriterVideoInput.expectsMediaDataInRealTime = YES;

and the buffer, when it is appended has the following characteristics:

CMSampleBuffer 0x1009e12a0 retainCount: 1 allocator: 0x1b762cbb8
    invalid = NO
    dataReady = YES
    makeDataReadyCallback = 0x0
    makeDataReadyRefcon = 0x0
    formatDescription = <CMVideoFormatDescription 0x170443210 [0x1b762cbb8]> {
    mediaType:'vide' 
    mediaSubType:'BGRA' 
    mediaSpecific: {
        codecType: 'BGRA'       dimensions: 1920 x 1080 
    } 
    extensions: {<CFBasicHash 0x17087c2c0 [0x1b762cbb8]>{type = immutable dict, count = 2,
entries =>
    0 : <CFString 0x1b1c6d460 [0x1b762cbb8]>{contents = "Version"} = <CFNumber 0xb000000000000022 [0x1b762cbb8]>{value = +2, type = kCFNumberSInt32Type}
    2 : <CFString 0x1b1c6d3e0 [0x1b762cbb8]>{contents = "CVBytesPerRow"} = <CFNumber 0xb00000000001e002 [0x1b762cbb8]>{value = +7680, type = kCFNumberSInt32Type}
}
}
}
    sbufToTrackReadiness = 0x0
    numSamples = 1
    sampleTimingArray[1] = {
        {PTS = {290309939228910/1000000000 = 290309.939}, DTS = {INVALID}, duration = {INVALID}},
    }
    imageBuffer = 0x170321180

I have a sample code here if you want to check the problem. That code is prepared to shoot video in 4K. Change the line AVCaptureSessionPreset3840x2160 to AVCaptureSessionPresetHighinsideProcessadorVideo.m` if your device cannot do that. The sample code crops a rectangle from the video stream and applies a comic effect to it. Thanks

Is this a problem similar to your other question http://stackoverflow.com/a/41207678/22147? — Rhythmic Fistman, Dec 18 '16 at 11:05
sorry for the delay answering this: no. Tried that. Problem persists. — Duck, Jan 17 '17 at 18:18
Since the regular documentation does not give a clue about this error code, I suspect that the error comes from another routines (not the appendSampleBuffer). Have you looked at other possible causes for problems? Is it possible that you are running out of memory? Are you writing to an existing folder? Do you have access to this folder? You are appending, does it already have data? etc.. — Vincent, Jan 23 '17 at 19:11
Ah in that case see http://stackoverflow.com/questions/3846331/avcapture-appendsamplebuffer — Vincent, Jan 23 '17 at 21:47
@Vincent - thanks for the answer. I have also tried that without success. Thanks. Please try the code included on the link on the question and see what you think. Thanks. — Duck, Jan 23 '17 at 22:35

score 1 · Accepted Answer · answered Jan 26 '17 at 20:05

I tried your sample but couldn't reproduce the error -12783. However I got another error -12780. I used iPhone 6s so not sure if it is due to that.

In any case, I could fix the error -12780. You are facing this issue due to old timestamp. I added some logs in your app for debugging purpose. See below

2017-01-26 15:00:35.809590 NotWriting[16829:3116125] starting at 401051199680537 2017-01-26 15:00:35.809986 NotWriting[16829:3116125] appending video buffer with timestamp 401051199680537 2017-01-26 15:00:35.810008 NotWriting[16829:3116125] presentationTimeStamp is less than last frame timestamp, So probably will fail 2017-01-26 15:00:35.815605 NotWriting[16829:3116125] error: An unknown error occurred (-12780)

When you are writing a buffer, you have to make sure the presentation timestamp is greater than the last frame you wrote otherwise the writing will fail. You can add a check with the following logic:

CMTime  presentationTimeStamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
      if(CMTIME_COMPARE_INLINE(presentationTimeStamp, <=, lastpresentationTimeStamp))
      {
          NSLog(@"presentationTimeStamp is less than last frame timestamp, So rejecting frame");
          return;
      }
      lastpresentationTimeStamp = presentationTimeStamp;

Failure to append frames to video file using AVAssetWriterVideoInput. Fails with undocumented error -12738 at the end

1 Answers1