Why doesn’t automatic remux to MP4 work with Custom Output (FFmpeg)?

[drodi]

Hey guys,

I have an issue with OBS’s automatic remux feature, and I’m not sure if it’s a bug or just a limitation of the software. Let me explain what’s happening:

As far as i know, there are two ways to remux MKV recordings to MP4 in OBS:

1. Manual Remux: After recording, I go to File > Remux Recordings, choose the MKV file, and manually convert it to MP4.
2. Automatic Remux: By enabling the Automatically remux to MP4 after recording option in Settings > Advanced, OBS should remux MKV files to MP4 automatically as soon as the recording ends.

Here’s the issue:

• If I use the Standard recording type in Settings > Output > Recording, the automatic remux works perfectly, my MKV file gets converted to MP4 right after the recording finishes.
• But if I use the Custom Output (FFmpeg) recording type and choose the Matroska (MKV) container, the automatic remux feature doesn’t work at all. The MKV file is saved, but it isn’t remuxed to MP4 automatically, even though I’ve enabled the remux option in the advanced settings.

Does anyone know why this happens? Is it a limitation/bug with the Custom Output (FFmpeg) mode?

Thank you guys for your help.

 

[Suslik V]

MP4 has limited set of supported codecs and sample formats unlike MKV. So, it is simplification.
Something similar to:

UI: Disable auto-remux for AV1+PCM, use MOV for PCM by derrod · Pull Request #8770 · obsproject/obs-studio

Description With additional audio/video codec options auto-remux will not work in all cases. For example using a PCM audio codec is not yet supported in MP4, and while we can use MOV in most cases,...

github.com