MKV - Could not write header for output - error

[AdamDanischewski]

I am trying to download the following YouTube video:
https://www.youtube.com/watch?v=9ZVMViSx6Ek

$ youtube-dl --version
2015.05.04

It is stored in a mkv container yet it won't convert, here is the result:
youtube-dl "https://www.youtube.com/watch?v=9ZVMViSx6Ek" --merge-output-format mkv
[youtube] 9ZVMViSx6Ek: Downloading webpage
[youtube] 9ZVMViSx6Ek: Extracting video information
[youtube] 9ZVMViSx6Ek: Downloading DASH manifest
[download] Destination: Hiatus Kaiyote - Breathing Underwater-9ZVMViSx6Ek.f248.webm
[download] 100% of 13.91MiB in 00:11
[download] Destination: Hiatus Kaiyote - Breathing Underwater-9ZVMViSx6Ek.f141.m4a
[download] 100% of 10.53MiB in 00:08
[ffmpeg] Merging formats into "Hiatus Kaiyote - Breathing Underwater-9ZVMViSx6Ek.mkv"
WARNING: Your copy of avconv is outdated, update avconv to version 10-0 or newer if you encounter any errors.
ERROR: Could not write header for output file #0 (incorrect codec parameters ?): Operation not permitted

I have the latest stable mkvtoolnix (for mkv conversion, other packages required?):
Installed: 6.7.0-1
Candidate: 6.7.0-1

I have the latest stable libav-tools (package containing avconv):
Installed: 6:9.18-0ubuntu0.14.04.1
Candidate: 6:9.18-0ubuntu0.14.04.1

[dstftw]

libav in ubuntu repos is outdated, you have to update it at least to 10 as stated in warning (latest ffmpeg will work as well). Alternatively, you can use -f best if you are ok with non overall best quality.

[AdamDanischewski]

Thanks that worked!!

(Guess, that was a good warning message! =)

youtube-dl -f best "https://www.youtube.com/watch?v=9ZVMViSx6Ek" --merge-output-format mkv
[youtube] 9ZVMViSx6Ek: Downloading webpage
[youtube] 9ZVMViSx6Ek: Extracting video information
[youtube] 9ZVMViSx6Ek: Downloading DASH manifest
[download] Destination: Hiatus Kaiyote - Breathing Underwater-9ZVMViSx6Ek.mp4
[download] 100% of 30.08MiB in 00:23

$ ls
Hiatus Kaiyote - Breathing Underwater-9ZVMViSx6Ek.mp4