Dear ELAN developers,
I would like to report a bug in the signal viewer. It displays the waveform correctly for mono-track .wav files, but not for mono-track audio in encoded or compressed formats (e.g., FLAC, ALAC, MP3, AAC).
I have tested this with different media frameworks in the Apple Silicon version, and the behavior is consistent. Converting the same encoded/compressed files to stereo restores the waveform display.
Mono-track encoded or compressed formats are increasingly common, as wearable recorders are often used to capture one track per speaker. These formats are efficient for transfer and storage, especially in larger documentation projects.
I have provided a set of test files here. The audio was originally recorded as mono-track WAV, then encoded to FLAC/ALAC/MP3/AAC, and further converted to stereo for comparison.
I would greatly appreciate it if you could look into this issue.
Many thanks and best wishes,
Weijian
Dear Weijian,
Thank you for the test files.
Apologies for the delayed response. I am off for a couple of days this week and will look into both the queries and get back to you as soon as I return back.
Best,
Divya
Dear Divya,
Thank you! Please enjoy your time off, and let me know if I can provide any additional detail to assist.
Best,
Weijian
Dear Weijian ,
we made a fix to FFmpeg version of audio extraction, and tested with all mono-track test files added in your zip and the waveform extraction works for all of them. The fix will be part of the next ELAN release.
Incase of AVFoundation version of audio extraction, extracting information about the sample properties is not so straightforward, we will have to take a closer look in the native libraries responsible for the extraction. we will try to improve it in the next release .
The feature of direct waveform extraction from video was introduced in ELAN 6.1 and it has been stated when it was released that it may or may not work depending on the on e.g. video file type. You can find the link here under ( March 22, 2021: Release 6.1).
The best and recommended way is to create the *.wav file outside ELAN and add that as linked file as it is more accurate and will perform better.
Best,
Divya
Dear Divya,
Thank you for fixing this!
Do I correctly understand you that, after the ffmpeg fix is implemented, waveform visualization will be compatible with standalone mono-track non-PCM audio files (e.g. aac/mp3/flac), and not just for mono audio tracks in these codecs that are wrapped with video into a container? I thought this was already implied in your message, but still wanted to confirm.
Best wishes,
Weijian
Hi Weijian,
Yes, assuming you’re referring to the mono audio files you provided us for testing.
Also we found a solution to AVFoundation version of audio extraction for the mono-track files.
The fix will be part of the next ELAN release along with FFmpeg fix.
Best,
Divya
