Audio Track Shows Up As Video Track

Hi there, I’m trying to merge a video file and an audio file with mkvtoolnix, but the audio file seems to just be showing up as a video file.

Here’s the two files I’m trying to merge:

As you can see here, they both are showing up as video:

And here’s the entirety of the media info for the audio file:

Complete name                            : audio.ac3
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
File size                                : 600 MiB
Duration                                 : 2 h 10 min
Overall bit rate mode                    : Constant
Overall bit rate                         : 644 kb/s

Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Duration                                 : 2 h 10 min
Bit rate mode                            : Constant
Bit rate                                 : 640 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 600 MiB (100%)
Service kind                             : Complete Main
Time code of first frame                 : 00:00:00:00 (23.976 fps), embedded in stream

I encoded the audio with Dolby Encoding Engine, and think I did it right.

When I open the audio file with mpv, the audio seems to work fine. When I do merge the two files, they just show up as two video tracks rather than an audio and a video track.

Could I get some help figuring out what’s going wrong?


This usually happens when the obvious type (AC-3) cannot be detected for some reason. In such cases the more unlikely types will be probed later. Unfortunately AVC/H.264 & HEVC/H.265 have such weakly typed bitstream formats that it’s very likely other content can be mis-detected as them, which seems to happen here. But again, the AC-3 detection is done first & fails, which is likely a bug in mkvmerge.

If you want me to take a closer look, please file an issue over on Gitlab & upload a sample AC-3 file to my file server.