Bestvideo with best audio (opus format) doesn't work for mp4 merge

[hdpcshow]

Please follow the guide below

• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like this: [x])
• Use the Preview tab to see what your issue will actually look like

---

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2018.12.03. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2018.12.03

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones
• Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

---

When i do youtube-dl --format bestvideo+bestaudio --merge-output-format mp4 it doesn't work on videos where only the opus format has the best audio, because opus can't merge with mp4.

My question is, can you guys make it work. For example that it converts the opus format to something else and then merge.

[dstftw]

--recode-video.

[raqueeb]

C:\Downloads\youtube-dl.exe -f bestvideo+bestaudio --recode-video mp4 --ffmpeg-location C:\Downloads\ffmpeg\bin\ffmpeg.exe -o e:%(title)s.%(ext)s https://www.youtube.com/watch.......

but the audio gets degraded.