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I am using my Nokia C2-01 which does not accept mp3s. I am thinking how to convert my mp3s to aac because it should maintain the sound quality well. Another option is to convert mp3 to m4a but I think it is not so good because m4a is mostly a container. There is a lot of discussion about the reverse: convert from aac/m4a to mp3 but not relevant here. I did not find anything relevant in apt-get for aac.

[Michael] I can do for one file ffmpeg -i test.mp3 test.aac but for many files the following does not work where the command is wrying to overwrite some .mp3 files for some reason.

ffmpeg -i *.mp3 *.aac

Output for a single file with ffmpeg

Command ffmpeg -i test.mp3 test.aac takes a lot of time (50 seconds for 9 MB file) and takes a lot of space (9 < 27 MB), with its output in the following. The increment of the space is significant. I think a less space taking format could be better.

ffmpeg version 3.2.2-1~bpo8+1 Copyright (c) 2000-2016 the FFmpeg developers built with gcc 4.9.2 (Debian 4.9.2-10) configuration: --prefix=/usr --extra-version='1~bpo8+1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --disable-libebur128 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libiec61883 --enable-libopencv --enable-frei0r --enable-libx264 --enable-chromaprint --enable-shared libavutil 55. 34.100 / 55. 34.100 libavcodec 57. 64.101 / 57. 64.101 libavformat 57. 56.100 / 57. 56.100 libavdevice 57. 1.100 / 57. 1.100 libavfilter 6. 65.100 / 6. 65.100 libavresample 3. 1. 0 / 3. 1. 0 libswscale 4. 2.100 / 4. 2.100 libswresample 2. 3.100 / 2. 3.100 libpostproc 54. 1.100 / 54. 1.100 [mp3 @ 0x5619e57e29a0] Estimating duration from bitrate, this may be inaccurate Input #0, mp3, from 'test.mp3': Duration: 00:49:26.67, start: 0.000000, bitrate: 24 kb/s Stream #0:0: Audio: mp2, 22050 Hz, mono, s16p, 24 kb/s Output #0, adts, to 'test.aac': Metadata: encoder : Lavf57.56.100 Stream #0:0: Audio: aac (LC), 22050 Hz, mono, fltp, 69 kb/s Metadata: encoder : Lavc57.64.101 aac Stream mapping: Stream #0:0 -> #0:0 (mp2 (native) -> aac (native)) Press [q] to stop, [?] for help size= 25740kB time=00:49:26.67 bitrate= 71.1kbits/s speed=53.5x video:0kB audio:25303kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.725856% [aac @ 0x5619e57f44c0] Qavg: 375.695
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  • @drewbenn How to overcome such a challenge? - - Can you keep the space same from mp3 to acc? Please, see the body for bigger space taken by aac than mp3. Commented Apr 5, 2017 at 17:58
  • @don_crissti Is the following approach good from here unix.stackexchange.com/a/229046/16920? - - I am thinknig how to make the structure of parallel for the loop attempt. Actually, I am more interested in how to make this with Zsh and parallel. Commented Apr 6, 2017 at 18:16
  • @don_crissti Yes, they are in the same directory. Commented Apr 6, 2017 at 18:38
  • it's been included in derobert's answer. Commented Apr 6, 2017 at 19:42

3 Answers 3

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You need to use a loop in the shell to loop over all the MP3 files, as ffmpeg typically only wants one output file per run. In bash, it'd look like:

for f in *.mp3; do ffmpeg -i "$f" "${f%.mp3}.aac" done

Note that for sound quality reasons, you probably want to give ffmpeg some options. The ffmpeg AAC Encoding Guide has details, but as a quick example that middle line might become:

ffmpeg -i "$f" -c:a libfdk_aac -vbr 3 "${f%.mp3}.aac"

(PS: It's somewhat surprising your phone doesn't support MP3, support is very common and its listed on the spec sheet for your phone).

don_chrissti offers an alternative using GNU Parallel (which should be quicker on multi-core processors, as it will run multiple encodes simultaneously): 

parallel ffmpeg -i {} -c:a libfdk_aac -vbr 3 {.}.aac ::: *.mp3

Please note there is a moreutils version of parallel as well, which has completely different syntax (and won't work in the above).

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  • Yes, I was surprised too. The support is incomplete, not standard mp3. The resolution is not to use mp3 format, but acc or m4a. - - Can you estimate how much the space changes with your latter command in comparison to mp3? Commented Apr 6, 2017 at 18:13
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    @LéoLéopoldHertz준영 no idea about the space requirements. AAC should be a smaller than MP3 for the same quality, but that's when encoding from non-compressed (or lossless). Transcoding may be different. Personally I use FLAC, Opus, and Ogg Vorbis... Commented Apr 6, 2017 at 18:16
  • It would be great to get some firsh-hand experience about the issues. I really like FLAC too. Commented Apr 6, 2017 at 18:17
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I can do for one file ffmpeg -i test.mp3 test.aac but for many files the following does not work where the command is wrying to overwrite some .mp3 files for some reason. ffmpeg -i *.mp3 *.aac

The asterisk is just going to expand to all MP3 files in your directory, so the first in the list will just try to overwrite the second. You need to write a loop. Assuming your shell is bash:

for mp3file in *.mp3; do ffmpeg -i "$mp3file" "`basename "$mp3file" .mp3`.aac" done
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I really recommend ffmpeg a command line format converter.

If you need a GUI I recommend Qwinff, Qwinff can also convert multiple files easily.

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  • How can you do the case with many files with ffmpeg? - - Testing it now. Commented Apr 5, 2017 at 17:53
  • Qwinff is not in apt-get and also in very early stage of development. Commented Apr 5, 2017 at 17:59
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    @Léo Léopold Hertz 준영 Qwinff is working great on my machine, do try it. Also use "apt" instead of "apt-get". Commented Apr 6, 2017 at 6:23
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    @Léo Léopold Hertz 준영 maketecheasier.com/apt-vs-apt-get-ubuntu Commented Apr 9, 2017 at 9:11

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