Complex format selection

[dundua]

I am trying to download a YouTube video in both mp4/m4a and webm formats in the best quality, but the following command only downloads the mp4/m4a files. Is there something wrong when processing the format selection or is there something wrong with my syntax?

debian@debian:~/Downloads/_test$ youtube-dl -f bestvideo[ext=mp4]+bestaudio[ext=m4a],bestvideo[ext=webm]+bestaudio[ext=webm] -v https://www.youtube.com/watch?v=7vuKF0BpyDA
[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'-f', u'bestvideo[ext=mp4]+bestaudio[ext=m4a],bestvideo[ext=webm]+bestaudio[ext=webm]', u'-v', u'https://www.youtube.com/watch?v=7vuKF0BpyDA']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2015.09.28
[debug] Python version 2.7.3 - Linux-3.2.0-4-686-pae-i686-with-debian-stretch-sid
[debug] exe versions: none
[debug] Proxy map: {}
[youtube] 7vuKF0BpyDA: Downloading webpage
[youtube] 7vuKF0BpyDA: Downloading video info webpage
[youtube] 7vuKF0BpyDA: Extracting video information
[youtube] 7vuKF0BpyDA: Downloading DASH manifest
[youtube] 7vuKF0BpyDA: Downloading DASH manifest
[info] 7vuKF0BpyDA: downloading video in 2 formats
WARNING: You have requested multiple formats but ffmpeg or avconv are not installed. The formats won't be merged.
[debug] Invoking downloader on 'https://r18---sn-hp57kn7r.googlevideo.com/videoplayback?id=eefb8a174069c830&itag=137&source=youtube&requiressl=yes&mn=sn-hp57kn7r&ms=au&mm=31&pl=47&mv=m&nh=IgpwcjAzLm1pYTA0KgkxMjcuMC4wLjE&ratebypass=yes&mime=video/mp4&gir=yes&clen=92838871&lmt=1407648237662567&dur=257.675&mt=1443565047&signature=9C1FEA9754F9549F870237390112FEB2F81FBC96.25C6DA6B611CC76ACCC89546FEF114CC6D88B045&sver=3&upn=EfkzZatif5g&key=dg_yt0&fexp=9406989,9408710,9409069,9415365,9415485,9416023,9416126,9417707,9418153,9418448,9420348,9421013&ip=2602:306:bdc6:98e0:e0a3:581e:1e92:b31d&ipbits=0&expire=1443586680&sparams=ip,ipbits,expire,id,itag,source,requiressl,mn,ms,mm,pl,mv,nh,ratebypass,mime,gir,clen,lmt,dur'
[download] Destination: YouTube Birthday Karaoke Night-7vuKF0BpyDA.f137.mp4
[download]   0.3% of 88.54MiB at 276.10KiB/s ETA 05:27

[dstftw]

Works fine. Post the full output of youtube-dl when run with --verbose option.

[dundua]

Sorry, I was using an older version on my Windows machine which did not support it. The updated version on my Linux machine works fine.