Olivia Kukar, Ariyan Kalami, Brian Nguyen, Rishi Chandra
AbstractAudio file compression standards are relatively consistent across different platforms, regardless of what a given audio file actually contains. We are analyzing differences in sound between audio files of different levels of compression and comparing the noticeability of these differences across different types of audio, namely different genres of music. We hope to identify certain types of audio that can be compressed at different levels than others in order to propose more efficient compression schemes for those subgenres.
Compressing audio files is essential to efficiently streaming and storing music. Audio codecs are the languages used to compress audio files. The encoding process takes analog signal inputs and converts them into a digital form. Then, the codec decodes it back into analog signals for your device to play the music. The codec can either be classified as lossy or lossless. Lossy compression slightly changes the audio after the decoding process and lossless compression maintains the audio quality after decoding.
2. Methods and Materials
Audio files were collected from a variety of music genres. The goal of the project is to determine which genre of music sounded the most similar to the original audio. Using Logic Pro X, the sampling rate of a specific audio file was modified to various frequencies. The variables used ranged from 64000 kHz to 11025 kHz. The next step required human reviewers to process the compressed audio files and compare them to the original. A value was assigned to the individual file containing the reviewer’s opinion of how satisfied they are with the compressed audio file. The value assigned to the file was a rating from 1 to 10. The data collected was logged into a spreadsheet on Google Sheets. There were a total of 100 audio files that were rated by three individual reviewers. Then, the three scores for each compressed file were averaged to determine the aggregate score.
We found that some genres, such as classical music, are much easier to compress in terms of lossless compression. The difference between different compressed versions of such songs were very minimal, and even nonexistent at times. This is the case with genres such as classical because there aren’t as many instruments or vast ranges between sounds at different frequencies. In this sense, our study did work. In the future, we could try testing and research on even more types of genres to see if any respond the same way that classical did.
Thank you to professor Tsachy Weissman and to all of the Stanford staff who made this research experience possible through sharing their time, efforts and equipment.
Stephens, C. (2018, September 10). After MP3: The Past, Present, and Future of Audio Codecs. Retrieved from https://www.premiumbeat.com/blog/past-present-future-audio-codecs/
Lee, J. (2019, February 26). The 10 Most Common Audio Formats: Which One Should You Use? Retrieved from https://www.makeuseof.com/tag/audio-file-format-right-needs/
Encoding audio and video – Revision 1 – GCSE Computer Science – BBC Bitesize. (n.d.). Retrieved from https://www.bbc.com/bitesize/guides/z7vc7ty/revision/1
Lee, J. (2016, July 25). 5 Tips for Optimizing Audio File Sizes. Retrieved from https://www.makeuseof.com/tag/5-tips-optimizing-audio-file-sizes/
48K Vs. 44.1 Khz 16 Vs. 24 Bit depth. (2018, April 05). Retrieved from https://community.spotify.com/t5/Desktop-Windows/48K-Vs-44-1-Khz-16-Vs-24-Bit-depth/td-p/866401
Pendlebury, T. (2015, July 05). Apple Music vs. Spotify: Is there a difference in sound quality? Retrieve from https://www.cnet.com/news/apple-music-vs-spotify-is-there-a-difference-in-sound-quality/