Command line tool to extract audio from all video files in current directory, in parallel.
- ffmpeg 4.4.2
- GNU parallel 20210822
- Output filename has all spaces in the input filename replaced with underscroll for ease of use in Linux.
- Supports Parallel Processing using GNU Parallel.
- Supports AAC (Advanced Audio Coding Standard) and all codecs supported by FFmpeg.
A. Copy this script into the folder you need to perform conversion, and then run
chmod +x convert_file.sh(one time only)./convert_file.sh arg1 arg2
B. Alternatively, you can add the script to your path such as (~/.local/bin in Ubuntu) and run it from anywhere.
- To convert all files in the folder with mp4 extension to aac use:
./convert_file.sh mp4 aac
Performance improvement numbers for a sample size of 9 different MP4 videos to be converted to AAC sound files on a 4 core processor
| Time type | Serial | Parallel | Speedup (Serial time / Parallel time) |
|---|---|---|---|
| real | 0m20.106s | 0m8.476s | 2.372 |
| user | 0m30.313s | 0m20.698s | 1.46 |
| sys | 0m1.141 | 0m2.711s | 0.42 |
Maximum theoretical speedup = Number of processors
Deviation from ideal = (4 - 2.4) / 4 = 40%
This means the practical speedup came to approximately 60% of the maximum speedup.
This deviation is due to running it on a feature rich, Graphical Interface Operating System, consistent with the average usecase. This deviation can also be due to the fact that not all videos take the same time to convert. If all videos took the same time to convert, one might get a better speedup. The aim here is to get realistic numbers that a user can expect, not to paint a rosy picture.
In conclusion, the speedup of approximately 2.4 achieved makes a very good case for the use of GNU Parallel. Parallel implementation takes less than half the time that a serial implementation would take.