Delays in Audio Sync Playback with FFmpeg: A Solution for MKV Files with HEVC Video, AAC Audio, and MJPEG Subtitles

Introduction

When dealing with multimedia files, especially those containing multiple streams like MKV files with HEVC video, AAC audio, and MJPEG subtitles, audio sync issues may arise. In this article, we will discuss the cause of audio desync and explore a solution using ffmpeg.

Understanding Audio Sync Issues

Audio desync occurs when the audio and video streams in a media file are not perfectly synchronized. This issue can be noticeable when watching movies or listening to audio files. In the context of MKV files, audio desync can be caused by various factors, such as incorrect timestamps, codec issues, or container format problems.

The Role of ffmpeg in Solving Audio Sync Issues

FFmpeg is a versatile multimedia framework capable of handling various audio and video codecs and containers. It can be used to solve audio sync issues in MKV files by adjusting the timestamps of the audio stream to match those of the video stream.

Using ITSOFFSET to Adjust Audio Timestamps

ITSOFFSET is a filter available in ffmpeg that can be used to adjust the timestamps of an audio stream. By applying this filter to the audio stream, we can synchronize it with the video stream in the MKV file.

Applying ITSOFFSET Filter with ffmpeg

To apply the ITSOFFSET filter to an MKV file using ffmpeg, follow these steps:

1. Install ffmpeg on your system, if it is not already installed.
2. Open a terminal or command prompt and navigate to the directory containing the MKV file.
3. Run the following command:

 ffmpeg -i input.mkv -c:v copy -c:a aac -af "itsoffset=0.02" output.mkv
 
 

Replace input.mkv with the name of your input MKV file and output.mkv with the desired output file name. The itsoffset value in the command represents the number of seconds you want to adjust the audio stream. Adjust this value according to your specific needs.

In conclusion, audio desync issues can be frustrating when dealing with multimedia files, especially those containing multiple streams like MKV files. By using ffmpeg and the ITSOFFSET filter, you can easily adjust the timestamps of the audio stream to synchronize it with the video stream and resolve audio desync issues.