![]() ![]() Exploring these sounds helps to define a boundary case for MP3 salvaging.Īs a preliminary foray into codec ghost composition, I am creating a series of pieces based on the songs used in the original MP3 listening tests. And yet these files do leave a residue behind when encoded to MP3. If anything can be encoded well by this format, it should be these files. ![]() To that end, these songs represent a kind of best-case scenario for an MP3 encoding. these songs carved out the space of sounds that could be successfully encoded as MP3's. ![]() Tom's Diner by Suzanne Vega, Fast Car by Tracy Chapman, a Haydn Trumpet concerto. In a sense, each of these songs acts as a resonant filter for every file encoded in the MP3 format. Tom's Diner - Verse 1 - 128kbps MP3 "Ghost" ExampleĪs previously stated, the MP3 codec was refined using listening tests designed by european audio engineers and featuring the music they chose. Tom's Diner - Verse 1 - "Ghost" extracted via masking Exampleĭifferent ways of handling phase estimation also lead to slightly different results.Įxamples 10 & 11. Different extraction techniques are possible, each leading to slightly different output.Įxample 9. However, corresponding time-frequency bins which differ significantly between the two files betray spots where information has been altered or deleted. Where the two files are the same or similar, the information in the original audio has been largely preserved in the MP3. Tom's Diner - Verse 1 - 128kbps MP3 "Ghost" Example I then analyze, compare, and take the difference between both files.Įxample 8. Tom's Diner - Verse 1 - 128kbps MP3 Example Tom's Diner - Verse 1 - UncompressedĮxample 7. In the music I've made (moDernist, etc.) using this process, I've used 320kbps MP3's.Įxample 6. I chose 128kbps for these examples because that was the "high-quality" bit rate used in the original MP3 development listening tests. Using the Bregman, pyo, and pydub libraries, along with the LAME MP3 encoder, I begin with an uncompressed WAV file and save it as an MP3 file, 128kbps in this example, which does quite well. Sine Tone Chords - UncompressedĮxample 4. Still, some material has been left behind which, upon examination, is quite interesting.Įxample 3. In comparison, low-frequency sine tones sound quite good as an MP3 encoded at 320kbps MP3. White, Pink, and Brown Noise - Lowest Possible Bit Rate MP3 (8kbps) White, Pink, and Brown Noise - UncompressedĮxample 2. This lossy compression codec has thus come to dominate unanticipated listening spaces.ĭespite its highly touted performance in listening tests, the MP3 compression codec does generate audible artifacts and remove perceptible sonic information, especially when implemented at low bit rates.įor example, white, pink, and brown noise, when compressed to the lowest possible MP3 bit rate, sounds very different from the original random signal.Įxample 1. Many listeners today listen exclusively to MP3 files, even in settings where the gains from a higher fidelity format would be clearly perceptible. ![]() Regardless, the MP3 is not always the most appropriate format for a given task, and a critical evaluation of the technology and its limitations is warranted. How a standard which subtly reduces the audible quality of soundfiles has remained in place, despite massively increased bandwidths and storage capacity is impressive, and highlights the foresight (and fortune) of the format's creators. The MP3 standard, designed in the early 1990's by the Moving Pictures Experts Group, has become an interesting object of critique in contemporary technology studies (Sterne, 2006). What are these lost sounds? Are they sounds which human ears can not hear in their original context due to universal perceptual limitations or are they simply encoding detritus? It is commonly accepted that MP3's create audible artifacts such as pre-echo, but what does the music which this codec deletes sound like? In the work presented here, techniques are considered and developed to recover these lost sounds, the ghosts in the MP3, and reformulate these sounds as art. These tests determined which sounds were perceptually important and which could be erased or altered, ostensibly without being noticed. Listening tests, primarily designed by and for western-european men, and using the music they liked, were used to refine the encoder. First published in 1993, this codec implements a lossy compression algorithm based on a perceptual model of human hearing. The MPEG-1 or MPEG-2 Layer III standard, more commonly referred to as MP3, has become a nearly ubiquitous digital audio file format. The Ghost in the MP3 The Ghost in the MP3įor updates follow on: soundcloud or facebookĭownload uncompressed audio: /album/the-ghost-in-the-mp3 ![]()
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