Knowledge Base

Problem

Videos recorded in MediaRecorder play back with audio in Windows Media Player but have no audio when opened in QuickTime Player or Datavyu on Mac.

Details

MediaRecorder may encode audio at a sample rate (e.g., 48 kHz) that is not natively supported by QuickTime Player or Datavyu. These applications expect audio at 44.1 kHz. The issue is in the recorded file's audio track and cannot be adjusted within MediaRecorder itself. Affects cross-platform workflows where videos are recorded on Windows and analysed on Mac using QuickTime-based tools.

Solution

1. Confirm the issue: open the recorded file in Windows Media Player (audio present) and QuickTime or Datavyu (audio absent).
2. Install ffmpeg on the machine where re-encoding will be performed (https://ffmpeg.org/).
3. Re-encode the audio track of the affected file(s) to 44.1 kHz using the following command:
ffmpeg -i input.mp4 -c:v copy -ar 44100 -c:a aac output.mp4
Replace 'input.mp4' with the actual filename; 'output.mp4' will be the corrected file.
4. Verify the output file plays with audio in QuickTime Player and Datavyu.
5. For batch processing, repeat the command for each affected file or write a simple script to loop over the files.