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AutoSub is a CLI application to generate subtitle files (.srt, .vtt, and .txt transcript) for any video file using either Mozilla DeepSpeech or Coqui STT. I use their open-source models to run inference on audio segments and pyAudioAnalysis to split the initial audio on silent segments, producing multiple smaller files (makes inference easy).

⭐ Featured in DeepSpeech Examples by Mozilla


  • Clone the repo
    $ git clone
    $ cd AutoSub
  • [OPTIONAL] Create a virtual environment to install the required packages. By default, AutoSub will be installed globally. All further steps should be performed while in the AutoSub/ directory
    $ python3 -m pip install --user virtualenv
    $ virtualenv -p python3 sub
    $ source sub/bin/activate
  • Use the corresponding requirements file depending on whether you have a GPU or not. If you want to install for a GPU, replace requirements.txt with requirements-gpu.txt. Make sure you have the appropriate CUDA version
    $ pip install .
  • Install FFMPEG. If you're on Ubuntu, this should work fine
    $ sudo apt-get install ffmpeg
    $ ffmpeg -version               # I'm running 4.1.4
  • By default, if no model files are found in the root directory, the script will download v0.9.3 models for DeepSpeech or TFLITE model and Huge Vocab for Coqui. Use to download DeepSpeech model and scorer files with the version number as argument. For Coqui, download from here
    $ ./ 0.9.3
  • For .tflite models with DeepSpeech, follow this


  • If you don't have the model files, get them
    $ ./ 0.9.3
  • For a CPU build
    $ docker build -t autosub .
    $ docker run --volume=`pwd`/input:/input --name autosub autosub --file /input/video.mp4
    $ docker cp autosub:/output/ .
  • For a GPU build that is reusable (saving time on instantiating the program)
    $ docker build --build-arg BASEIMAGE=nvidia/cuda:10.1-cudnn7-runtime-ubuntu18.04 --build-arg DEPSLIST=requirements-gpu.txt -t autosub-base . && \
    docker run --gpus all --name autosub-base autosub-base --dry-run || \
    docker commit --change 'CMD []' autosub-base autosub-instance
  • Finally
    $ docker run --volume=`pwd`/input:/input --name autosub autosub-instance --file ~/video.mp4
    $ docker cp autosub:/output/ .

How-to example

  • The model files should be in the repo root directory and will be loaded/downloaded automatically. Incase you have multiple versions, use the --model and --scorer args while executing
  • By default, Coqui is used for inference. You can change this by using the --engine argument with value "ds" for DeepSpeech
  • For languages other than English, you'll need to manually download the model and scorer files. Check here for DeepSpeech and here for Coqui.
  • After following the installation instructions, you can run autosub/ as given below. The --file argument is the video file for which subtitles are to be generated
    $ python3 autosub/ --file ~/movie.mp4
  • After the script finishes, the SRT file is saved in output/
  • The optional --split-duration argument allows customization of the maximum number of seconds any given subtitle is displayed for. The default is 5 seconds
    $ python3 autosub/ --file ~/movie.mp4 --split-duration 8
  • By default, AutoSub outputs SRT, VTT and TXT files. To only produce the file formats you want, use the --format argument
    $ python3 autosub/ --file ~/movie.mp4 --format srt txt
  • Open the video file and add this SRT file as a subtitle. You can just drag and drop in VLC.

How it works

Mozilla DeepSpeech is an open-source speech-to-text engine with support for fine-tuning using custom datasets, external language models, exporting memory-mapped models and a lot more. You should definitely check it out for STT tasks. So, when you run the script, I use FFMPEG to extract the audio from the video and save it in audio/. By default DeepSpeech is configured to accept 16kHz audio samples for inference, hence while extracting I make FFMPEG use 16kHz sampling rate.

Then, I use pyAudioAnalysis for silence removal - which basically takes the large audio file initially extracted, and splits it wherever silent regions are encountered, resulting in smaller audio segments which are much easier to process. I haven't used the whole library, instead I've integrated parts of it in autosub/ and autosub/ All these audio files are stored in audio/. Then for each audio segment, I perform DeepSpeech inference on it, and write the inferred text in a SRT file. After all files are processed, the final SRT file is stored in output/.

When I tested the script on my laptop, it took about 40 minutes to generate the SRT file for a 70 minutes video file. My config is an i5 dual-core @ 2.5 Ghz and 8GB RAM. Ideally, the whole process shouldn't take more than 60% of the duration of original video file.


In the age of OTT platforms, there are still some who prefer to download movies/videos from YouTube/Facebook or even torrents rather than stream. I am one of them and on one such occasion, I couldn't find the subtitle file for a particular movie I had downloaded. Then the idea for AutoSub struck me and since I had worked with DeepSpeech previously, I decided to use it.


I would love to follow up on any suggestions/issues you find :)