Prefer output format mp4 if possible

[kik4444]

Is there any syntax that I'm missing for --merge-output-format that allows you to set it to prefer mp4 over mkv? Currently I'm downloading with this format -f bestvideo[fps=60]+bestaudio/bestvideo+bestaudio/best, and sometimes, depending on the video, the result can be merged into an mp4, but sometimes it can't, so I set --merge-output-format to mkv. However, is it possible to set it to prefer mp4 if possible and fall back to mkv if not?

[ealgase]

It always prefers mp4 by default. If that doesn't work, it merges to mkv instead.

(bionic)ealgase@localhost:~/Downloads/youtube-dl$ youtube-dl -f bestvideo+140 kJQP7kiw5Fk
[youtube] kJQP7kiw5Fk: Downloading webpage
[youtube] kJQP7kiw5Fk: Downloading video info webpage
[download] Destination: Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f137.mp4
[download] 100% of 122.13MiB in 00:15
[download] Destination: Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f140.m4a
[download] 100% of 4.27MiB in 00:00
[ffmpeg] Merging formats into "Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.mp4"
Deleting original file Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f137.mp4 (pass -k to keep)
Deleting original file Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f140.m4a (pass -k to keep)

(bionic)ealgase@localhost:~/Downloads/youtube-dl$ youtube-dl -f bestvideo+bestaudio kJQP7kiw5Fk
[youtube] kJQP7kiw5Fk: Downloading webpage
[youtube] kJQP7kiw5Fk: Downloading video info webpage
WARNING: Requested formats are incompatible for merge and will be merged into mkv.
[download] Destination: Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f137.mp4
[download] 100% of 122.13MiB in 00:15
[download] Destination: Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f251.webm
[download] 100% of 4.40MiB in 00:00
[ffmpeg] Merging formats into "Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.mkv"
Deleting original file Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f137.mp4 (pass -k to keep)
Deleting original file Luis Fonsi - Despacito ft. Daddy Yankee-kJQP7kiw5Fk.f251.webm (pass -k to keep)

[remitamine]

if you want to always get an mp4 file, then use a format selector with compatible formats.
https://github.com/ytdl-org/youtube-dl#format-selection-examples

[kik4444]

But if I don't specify anything, it'll merge everything into a webm. And if I specify mp4 when that's not possible, I get ERROR: Stream #1:0 -> #0:1 (copy)

[kik4444]

if you want to always get an mp4 file, then use a format selector with compatible formats.
https://github.com/ytdl-org/youtube-dl#format-selection-examples

I'm not talking about the quality from -format, I'm talking about merging it into a mp4 with --merge-output-format. I don't always want mp4, I want the best quality, and I'd prefer it to be merged into an mp4 if possible, and if not, then an mkv.

[kik4444]

For example, when using -format you can use the / character to prefer some other format if your first choice isn't available, so I thought that using something like --merge-output-format mp4/mkv would work with the same logic, but it doesn't. Is there something I'm missing?

[remitamine]

and @ealgase already answered this, don't touch the --merge-output-format option then, this option is used to force a particular container, youtube-dl by default will choose an appropriate container for the selected formats.

[kik4444]

and @ealgase already answered this, don't touch the --merge-output-format option then, this option is used to force a particular container, youtube-dl by default will choose an appropriate container for the selected formats.

Exactly, my question is whether it's possible to force it to use the mp4 container whenever possible (for example when the video format is mp4) with the ability to fall back to mkv (if the format is webm for example)

[ealgase]

@kik4444 webm is literally just mkv with a different file extension.

[remitamine]

I said don't use --merge-output-format and you will get what you want.