Consider the following, if you dare:

> ffmpeg -f concat -safe 0 -i <(find . -iname '*.flac' -and -type f -print0 | parallel --null printf '"file %q"' '{=1 my $pwd=qx(pwd); $pwd =~ s/^\s+|\s+$//g; $_=($pwd . "/" . q()) =}{1}' \&\& echo) -b:a 128k -c:a aac -y o.aac

1.
>  find . -iname '*.flac' -and -type f -print0    Finds all files in the current directory and its subdirectories with 
a case-insensitive file extension .flac. It prints the results separated 
by a null character (ASCII 0).

2. >  parallel --null printf '"file %q"' '{=1 my $pwd=qx(pwd); $pwd =~ 
s/^\s+|\s+$//g; $_=($pwd . "/" . q()) =}{1}' \&\& echo   GNU parallel 
reads the null-separated input from the find command and processes them 
in parallel. For each input file, it does the following:

3.
    a. > `{=1 my $pwd=qx(pwd); $pwd =~ s/^\s+|\s+$//g; $_=($pwd . "/" . 
q()) =}`
    Gets the current working directory and removes any leading or
    trailing whitespace. It then concatenates the current directory path
    with the input file name.

    b.
> `printf '"file %q"'    This part formats the output, escaping any special characters in the
    filename, and prefixing it with "file ".

    c.
> \&\& echo    Just adds \n to all lines.

4.
> ffmpeg -f concat -safe 0 -i <(...) -b:a 128k -c:a aac -y o.aac
    Finally, ffmpeg reads the list of escaped file paths (generated @ №2)
    using process substitution <(...). The concat demuxer is used to
    concatenate the input files, -safe0 is specified to allow unsafe file
    paths, and the output is encoded with an AAC codec at 128 kbps
    bitrate, overwriting the output file o.aac if it exists.

Or, ffmpeg *should* do that. It can't:

> [concat @ 0x559da1fd1cc0] Impossible to open '/home/fred/Workspace/gcloud-synthesize-voice/./[af-ZA] Ek hoop dit is nie die geval nie.$\nHoop in die een hand en kak in die ander..flac'
> /proc/self/fd/11: No such file or directory

I should not have to rename my files, ffmpeg is what's broken here. The 
raw output being:

> fred@デブ狸~/Workspace/gcloud-synthesize-voice%  find . -iname '*.flac' -and -type f -print0 | parallel --null printf '"file %q"' '{=1 my $pwd=qx(pwd); $pwd =~ s/^\s+|\s+$//g; $_=($pwd . "/" . q()) =}{1}' \&\& echo
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[af-ZA\]\ Ek\ hoop\ dit\ is\ nie\ die\ geval\ nie.$'\n'Hoop\ in\ die\ een\ hand\ en\ kak\ in\ die\ ander..flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[ar-XA\]\ آمل\ أن\ لا\ يكون\ الأمر\ كذلك.$'\n'املئ\ يدك\ الواحدة\ بالأمل\ والأخرى\ بالسوء..flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[bg-BG\]\ Надявам\ се,\ че\ това\ не\ е\ така.$'\n'Надявай\ се\ в\ едната\ ръка\ и\ срах\ в\ другата..flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[bn-IN\]\ আমি\ আশা\ করি\ এটা\ সত্যি\ না।$'\n'একটা\ হাতে\ আশা\ আর\ অপরে\ বিষম\ চিন্তা।.flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[ca-ES\]\ Espero\ que\ no\ sigui\ el\ cas.$'\n'Esperança\ a\ una\ mà\ i\ merda\ a\ l\'altra..flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[cmn-CN\]\ 我希望不是这样。$'\n'一手抓希望，一手抓屎。.flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[cmn-TW\]\ 我希望不是這樣。$'\n'一手抓希望，一手抓屎。.flac
> file /home/fred/Workspace/gcloud-synthesize-voice/./\[cs-CZ\]\ Doufám,\ že\ to\ není\ pravda.$'\n'Nadej\ se\ v\ jedné\ ruce\ a\ hovno\ v\ druhé..flac


And so on.

This is surely a bug, right? (Unfortunately GNU Parallel's weird NUL 
handling does not help clarify the question, but xargs mangles things 
worse.)

-- 
------------------------------------------------------------------------

Best,
Fred Brennan
[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

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