I was using a script to batch re-encode audio to AAC using the libvo-aac encoder.

FOR %f IN (*.mkv) DO call ffmpeg.exe -i "%f" -c:v copy -c:a libvo_aacenc -b:a 256k "%f"

However since I am on windows building ffmpeg with fdk-aac is a bit of a pain and qaac is regarded as the superior encoder I would like to pipe ffmpeg to use qaac instead.

I am not too knowledgeable about ffmpeg but I did find a comment here: How to use ffmpeg to downmix 5.1 DTS HD MA or Dolby TrueHD to stereo AAC with Dolby Pro Logic II? (last comment)

after trying that command I receive this error:

ERROR: CoreAudioToolbox.dll: The specified module could not be found.

However I do indeed have quicktime and Apple Application Support installed as well as the flac and libsnd libaries in the ffmpeg folder.

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I'm using the Zeranoe Windows x64 Static build

EDIT: I got it working with the 32bit qaac and flac libraries but It still won't work with the 64 bit versions.

2 Answers 2


Solved this issue by installing the 64-bit version of Itunes (actually I just extracted AppleApplicationSupport64.msi from the installer.) Since there was no 64-bit installer for this included in quicktime I was rather confused.


I noticed that you were inputting an MKV?

I use qaac and ffmpeg in a Windows batch file to convert audio in the MKV to aac then Mux it back into the MKV container.

@ echo off

for %%a in (*.mkv) do ("ffmpeg" -i "%%~na.mkv" -f wav - | qaac -a 160 - -o "%%~na.m4a" --threading)
for %%a in (*.mkv) do (ffmpeg -i "%%~na.mkv" -i "%%~na.m4a" -c:v copy -c:a copy -map 0:0 -map 1:0 "%%~na_.mkv")

I know this is a little messy but it works for me. I use an average bitrate of 160 and threading (I also encode the video stream but here it is only copied). Also both ffmpeg and qaac are in my environment variables so I don't have to put the whole path.exe on the command line.

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