gnu parallel with ffmpeg does not process first file

Question

I have some files

Joapira___BERLINA_DEL_HIERRO.mp4
Joapira___EL_BAILE_DEL_VIVO.mp4
Joapira___EL_CONDE_CABRA.mp4
Joapira___FLAIRE.mp4
Joapira___MAZULKA_DEL_HIERRO.mp4
Joapira___MEDA_A_MANOLITO_DIAZ_ARTESANO_TALLISTA.mp4

that I want to convert to some other formats with ffmpeg and GNU parallel. For example to convert them to flac I do

parallel --bar ffmpeg -i "{}" -map_metadata 0 "{/.}.flac" ::: *

or to convert them to mp3 I do

parallel --bar ffmpeg -i "{}" -vn -ar 44100 -ab 128k -map_metadata 0 "{/.}.mp3" ::: $@

but the process continues forever and the first file is always missing. Why?

Info

I am on Fedora 22 using

GNU parallel 20160222

and

ffmpeg version N-80953-gd4c8e93-static http://johnvansickle.com/ffmpeg/

Update

Fascinating, I tried it with ffmpeg version 2.6.8 (comes with Fedora) and it works!! And even with the most recent static build from git it does not. :-(

Update 2

When I run ps auxwww and search for ffmpeg I see all the jobs with the state Rl, except for the command of the file that is missing, which has the state T.

GNU parallel has the state S+, but sometimes during the processing of the working files changes to R+.

The man page of ps says the following about the states:

D    uninterruptible sleep (usually IO)
R    running or runnable (on run queue)
S    interruptible sleep (waiting for an event to complete)
T    stopped by job control signal
t    stopped by debugger during the tracing
W    paging (not valid since the 2.6.xx kernel)
X    dead (should never be seen)
Z    defunct ("zombie") process, terminated but not reaped by its parent

<    high-priority (not nice to other users)
N    low-priority (nice to other users)
L    has pages locked into memory (for real-time and custom IO)
s    is a session leader
l    is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+    is in the foreground process group

Maybe this helps to understand the problem.

Answer 1

Solution is —as suggested by @OleTange in a comment— to update to a newer version of parallel, i.e. GNU parallel 20161122. EVerything works again.

And it is better to protect the commands from shell interaction with single quotes, i.e.:

parallel --bar 'ffmpeg -i {} -map_metadata 0 {/.}.flac' ::: *

and

parallel --bar 'ffmpeg -i {} -vn -ar 44100 -ab 128k -map_metadata 0 {/.}.mp3' ::: $@