AVPlayer currentTime is Negative Value

Introduction

In this article, we’ll delve into the world of AVPlayer and explore a common issue that developers often face when using it to play audio files. Specifically, we’ll examine why AVPlayer’s currentTime property sometimes displays a negative value at start time.

Background

AVPlayer is a powerful tool for playing media in iOS and macOS applications. It provides an easy-to-use API for handling video playback, including seeking, buffering, and more. However, like any complex technology, AVPlayer has its quirks and nuances that can be tricky to master.

In this article, we’ll take a closer look at the currentTime property and why it might display a negative value at start time.

Seeking with Tolerance

When using AVPlayer to play audio files, you may need to seek to specific points in the media. However, seeking is not always an exact science. To account for minor discrepancies in playback timing, AVPlayer introduces a concept called “tolerance.”

Tolerance allows you to specify a buffer zone around your desired seek point. When you call seek(to:), AVPlayer will try to find the closest match within this tolerance range.

Types of Seek Methods

AVPlayer provides two main types of seek methods:

1. seek(to:): This method seeks to a specific point in the media without any tolerance.
2. seek(to:toleranceBefore:toleranceAfter:): This method allows you to specify a tolerance range around your desired seek point.

When using seek(to:), AVPlayer will round your desired time to the nearest available timestamp, which can result in a negative value if the media starts at zero.

Why Is currentTime Negative?

Now that we’ve covered seeking and tolerance, let’s get back to the original issue. When you start playing an audio file using AVPlayer, its currentTime property might display a negative value.

This behavior occurs because of how AVPlayer handles seeking. When you call seek(to:), AVPlayer will try to find the closest match within the specified tolerance range. If the media starts at zero and your desired seek point is also zero, AVPlayer will round it down to the nearest available timestamp, resulting in a negative value.

Here’s an example of how this might happen:

// Assume we have an audio file that starts playing at time 0.
avPlayer.seek(to: CMTime.zero)

In this case, avPlayer.currentTime might display -0.001 or something similar.

To fix this issue, you need to use a seek method with tolerance. Here’s the corrected code:

// Assume we have an audio file that starts playing at time 0.
avPlayer.seek(to: CMTime.zero, toleranceBefore: kCMTimeZero, toleranceAfter: kCMTimeZero)

Using seek(to:) without specifying a tolerance can lead to issues like this. By using the second seek method with tolerance, you ensure that AVPlayer seeks accurately to your desired point.

Best Practices

To avoid issues like this in the future, follow these best practices when working with AVPlayer:

1. Use seek(to:toleranceBefore:toleranceAfter:): When seeking to a specific point, use this method to specify a tolerance range.
2. Handle negative values carefully: If you receive a negative value for currentTime, it might be due to the media starting at zero or an incorrect seek time.
3. Test thoroughly: Always test your app with different audio files and scenarios to ensure that AVPlayer is working correctly.

Conclusion

AVPlayer’s currentTime property can sometimes display a negative value at start time, but this behavior can be easily fixed by using the correct seek method with tolerance. By following best practices and understanding how seeking works in AVPlayer, you can write more robust code for playing audio files in your iOS or macOS applications.

Example Code

Here’s an example of how to use seek(to:toleranceBefore:toleranceAfter:) in Swift:

import AVFoundation

class Player {
    let avPlayer = AVPlayer()

    func playAudio() {
        // Load the audio file
        guard let url = Bundle.main.url(forResource: "your_file", withExtension: "mp3") else { return }

        // Create a URL request for playing the audio file
        let request = AVURLAsset(url: url).loadedValue

        // Set the request as the player's current asset
        avPlayer.replaceCurrentItem(with: request)

        // Seek to 100 seconds with tolerance 0
        let CMTime = CMTimeMake(100, 1)
        avPlayer.seek(to: CMTime, toleranceBefore: kCMTimeZero, toleranceAfter: kCMTimeZero)
    }
}

By using seek(to:toleranceBefore:toleranceAfter:), you ensure that your app seeks accurately to the desired point in the media.

Last modified on 2024-09-27