Separate Audio from Video

Question

float sliderValue = 0.5;
NSURL *audio_url = [[NSBundle mainBundle] pathForResource:@“video_fileName” ofType:@"mp4"]];
AVURLAsset* audio_Asset = [[AVURLAsset alloc]initWithURL:audio_url options:nil];
AVMutableAudioMixInputParameters *audioInputParams = [AVMutableAudioMixInputParameters audioMixInputParameters];

NSString* formattedNumber = [NSString stringWithFormat:@"%.01f", sliderValue];
NSLog(@"formattedNumber %@",formattedNumber);
NSLog(@"formattedNumber %.01f",[formattedNumber floatValue]);

[audioInputParams setVolume:[formattedNumber floatValue] atTime:kCMTimeZero];
[audioInputParams setTrackID:[[[audio_Asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]  trackID]];
AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
audioMix.inputParameters = [NSArray arrayWithObject:audioInputParams];



AVAssetExportSession *exportSession=[AVAssetExportSession exportSessionWithAsset:audio_Asset presetName:AVAssetExportPresetAppleM4A];
exportSession.audioMix = audioMix;

exportSession.outputURL=[NSURL fileURLWithPath:audioPath];
exportSession.outputFileType=AVFileTypeAppleM4A;

[exportSession exportAsynchronouslyWithCompletionHandler:^{
    if (exportSession.status==AVAssetExportSessionStatusFailed) {
        NSLog(@"failed");
    }
    else {
        NSLog(@"AudioLocation : %@",audioPath);
    }
}];

Issue: get asset blank, so app crashes.

[[audio_Asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] [__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array';

thelaws · Answer 1 · 2015-10-14T19:19:46.867

0

The crash has described the issue, you are trying to access an array beyond it's bounds. change:

[audioInputParams setTrackID:[[[audio_Asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]  trackID]];

to:

NSArray * tracks = [audio_Asset tracksWithMediaType:AVMediaTypeAudio];
if([tracks count]) {
    [audioInputParams setTrackID:[[tracks firstObject]  trackID]];
}

Your main issue may be that loading an AVURLAsset might not immediately load all the tracks. You can wrap your method (after getting audio_Asset) in the load method to have better guarantee:

NSString *tracksKey = @"tracks";

[audio_Asset loadValuesAsynchronouslyForKeys:@[tracksKey] completionHandler:  ^{ 
// rest of the code here

edited Oct 14 '15 at 19:19

answered Oct 14 '15 at 18:29

thelaws

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I want to separate audio from video and set audio level as per sliderValue. But Its is working in iOS 7.0 but issue rise in iOS 8. So it is not proper solution. Can you try it ? – Gaurav Oct 14 '15 at 18:31
Does this help: https://stackoverflow.com/questions/19326728/playing-video-from-within-app You have to load the tracks before you can use them – thelaws Oct 14 '15 at 19:16

Separate Audio from Video

1 Answers1