Recording flv into mp4, but not recoding mkv

[keybounce]

I want to be able to record flv files into mp4.

So far, I have used this script:

#!/bin/bash
# Usage: youtube-480 url
youtube-dl -f "bestvideo[height<=480][ext=mp4]+bestaudio/[height <=? 480]" --write-sub --recode-video mp4 "$@"

But I discovered recently that if it is fetching a .mkv file (I think it was from vimeo), then it spends forever in ffmpeg trying to convert it.

I'd like to say "Convert a .flv file to .mp4".
I have no problem working with a .mkv instead.

How would I do that?

[dstftw]

mkv is most likely from youtube, and you are getting it due to bestvideo happens to be mp4 and bestaudio - webm. Those can't be merged into mp4 therefore merged into mkv. You may want to force bestaudio to m4a to avoid webm at all: -f bestvideo[height<=480][ext=mp4]+bestaudio[ext=m4a]/[height<=?480].

[keybounce]

That will work, thank you.

I thought webm was a browser-based video playback alternative to flash? Did I mis-understand what it is?

[nwgat]

i noticed youtube can be a little nuts these days, some videos are vp9, vp8 or h264 and they might have opus, vorbis, mp3 or aac (m4a/mp4a) audio so the best container to save youtube is to use mkv, webm is only vp8/vp9 and vorbis/opus, mp4 is only h264 and aac (m4a/mp4a)

the best codecs on youtube these days are

1. VP9
2. AVC aka H.264
3. VP8

1 Vorbis (audio)
2. Opus (audio)

so if the source is only in webm (vp9 and opus audio) it wont mux into mp4
you can force youtube-dl to download another profile that works for mp4 container, perhaps youtube just reencoded the audio from opus to aac