Does any one know of an application that can convert audio to text? I'm running ubuntu 12.04 LTS.


4 Answers 4


The software you can use is Vosk-api, a modern speech recognition toolkit based on neural networks. It supports 7+ languages and works on variety of platforms including RPi and mobile.

First you convert the file to the required format and then you recognize it:

ffmpeg -i file.mp3 -ar 16000 -ac 1 file.wav

Then install vosk-api with pip:

pip3 install vosk

Then use these steps:

git clone https://github.com/alphacep/vosk-api
cd vosk-api/python/example
wget https://alphacephei.com/kaldi/models/vosk-model-small-en-us-0.3.zip
unzip vosk-model-small-en-us-0.3.zip
mv vosk-model-small-en-us-0.3 model
python3 ./test_simple.py test.wav > result.json

The result will be stored in json format.

The same directory also contains an srt subtitle output example, which is easier to evaluate and can be directly useful to some users:

python3 -m pip install srt
python3 ./test_srt.py test.wav

The example given in the repository says in perfect American English accent and perfect sound quality three sentences which I transcribe as:

one zero zero zero one
nine oh two one oh
zero one eight zero three

The "nine oh two one oh" is said very fast, but still clear. The "z" of the before last "zero" sounds a bit like an "s".

The SRT generated above reads:

00:00:00,870 --> 00:00:02,610
what zero zero zero one

00:00:03,930 --> 00:00:04,950
no no to uno

00:00:06,240 --> 00:00:08,010
cyril one eight zero three

so we can see that several mistakes were made, presumably in part because we have the understanding that all words are numbers to help us.

Next I also tried with the vosk-model-en-us-aspire-0.2 which was a 1.4GB download compared to 36MB of vosk-model-small-en-us-0.3 and is listed at https://alphacephei.com/vosk/models:

mv model model.vosk-model-small-en-us-0.3
wget https://alphacephei.com/vosk/models/vosk-model-en-us-aspire-0.2.zip
unzip vosk-model-en-us-aspire-0.2.zip
mv vosk-model-en-us-aspire-0.2 model

and the result was:

00:00:00,840 --> 00:00:02,610
one zero zero zero one

00:00:04,026 --> 00:00:04,980
i know what you window

00:00:06,270 --> 00:00:07,980
serial one eight zero three

which got one more word correct.

Tested on vosk-api 7af3e9a334fbb9557f2a41b97ba77b9745e120b3.

  • also, as an addition to this answer, there's a cool demo of both speech recognition and voice command tools here: youtube.com/…
    – Daithí
    Jan 8, 2015 at 10:22
  • How do you add an acoustic model to the system?
    – jarno
    Feb 8, 2015 at 13:38
  • You just download it and unpack, there is no such thing as "add to the system" Feb 8, 2015 at 13:56
  • @NikolayShmyrev Where should I unpack it so that pocketsphinx_continuous finds it?
    – jarno
    Feb 8, 2015 at 14:14
  • 4
    Well, I installed packages pocketsphinx-utils, pocketsphinx-hmm-en-hub4wsj and pocketsphinx-lm-en-hub4 in universe repository of Ubuntu 14.04. Then pocketsphinx_continuous -infile file.wav -hmm en_US/hub4wsj_sc_8k -lm en_US/hub4.5000.DMP 2> pocketsphinx.log worked. Maybe they are not optimal packages, but they were best matches I could find in the repositories.
    – jarno
    Feb 8, 2015 at 15:05

I know this is old, but to expand on Nikolay's answer and hopefully save someone some time in the future, in order to get an up-to-date version of pocketsphinx working you need to compile it from the github or sourceforge repository (not sure which is kept more up to date). Note the -j8 means run 8 separate jobs in parallel if possible; if you have more CPU cores you can increase the number.

git clone https://github.com/cmusphinx/sphinxbase.git
cd sphinxbase
make -j8
make -j8 check
sudo make install
cd ..
git clone https://github.com/cmusphinx/pocketsphinx.git
cd pocketsphinx
make -j8
make -j8 check
sudo make install
cd ..

Then, from: https://sourceforge.net/projects/cmusphinx/files/Acoustic%20and%20Language%20Models/US%20English/ download the newest versions of cmusphinx-en-us-....tar.gz and en-70k-....lm.gz

tar -xzf cmusphinx-en-us-....tar.gz
gunzip en-70k-....lm.gz

Then you can finally proceed with the steps from Nikolay's answer:

ffmpeg -i book.mp3 -ar 16000 -ac 1 book.wav
pocketsphinx_continuous -infile book.wav \
    -hmm cmusphinx-en-us-8khz-5.2 -lm en-70k-0.2.lm \
    2>pocketsphinx.log >book.txt

Sphinx works alright. I wouldn't rely on it to make a readable version of the text, but it's good enough that you can search it if you're looking for a particular quote. That works especially well if you use a search algorithm like Xapian (http://www.lesbonscomptes.com/recoll/) which accepts wildcards and doesn't require exact search expressions.

Hope this helps.

  • 4
    every thing works like a charm but in my case i had to run following command to fix pocketsphinx_continuous: error while loading shared libraries: libpocketsphinx.so.3: cannot open shared object file: No such file or directory -------> export LD_LIBRARY_PATH=/usr/local/lib -------> export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig Sep 19, 2017 at 11:30
  • This is also recommended at cmusphinx.github.io/wiki/tutorialpocketsphinx/…
    – andrybak
    Sep 19, 2019 at 21:58

I you are looking to convert speech to text you could try opening up your Ubuntu Software Center and search for Julius


"Julius" is a high-performance, two-pass large vocabulary continuous speech recognition (LVCSR) decoder software for speech-related researchers and developers.

Or another option that isn't in the Software Center is Simon

... is an open-source speech recognition program and replaces the mouse and keyboard.

Reference Links




  • 2
    Could you add to this answer an example of how to run Julius? It is phenomenally unclear from the documentation. Mar 7, 2020 at 0:17

You can use Mozilla DeepSpeech is an opensource speech-to-text tool. But you will need to train the application or download Mozilla's pre-trained model. For my project, the accuracy was still not sufficient, as audio files were not good quality, and used Transcribear instead, a web based editor with speech-to-text capabilities, but you will need to be connected online to upload recordings to the Transcribear server.

  • I am considering transcribing about 70 hours by one speaker (accented, clear non-native en). Can DeepSpeech be trained using the existing mp3 files.
    – LenB
    Apr 26, 2020 at 19:18

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