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Was this work done on data stored in lossy formats? The appendix with the talk about format conversion makes it sound like it. Should this not have been the fir
by _Microft 5y ago
Was this work done on data stored in lossy formats? The appendix with the talk about format conversion makes it sound like it. Should this not have been the first thing to be avoided („garbage in, …“)?
- gbh444g 5y agoYeah, it was mostly mp3 and ogg files. If you're suggesting flac would be better, I don't think flac adds much clarity over a decent 320 kbps mp3.
- deleted 5y ago[deleted]
- slver 5y agoOn the other hand it’s not as if bird songs are encoded binary information. They’re complex to our ears, but probably hold up pretty well under common audio compression algorithms.
- _Microft 5y agoWhy would one bother what effects psychoacoustic models might or might not have on your data when you could simply circumvent the problem completely?
- enriquto 5y agoYou are right in the abstract, but these are very high-resolution "lossy" signals. If you look at the spectral response of the bird songs it falls well inside the part where there is no signal loss. Your complain is like bothering about a face recognition system because it used lossily compressed but very high-resolution images. That criticism would be just as nonsensical. A more meaningful criticism would be the use of the wigner transform itself, which seems to produce ringing artifacts in the visualization, not seen on the more common windowed fft.
- slver 5y agoYou assume the author has access to lossless sources, or has the funding and means to produce the recordings themselves. I don't have this impression. You work with what you have.
- andai 5y agohttps://freesound.org/search/?q=blackbird https://freesound.org/search/?q=blackbird (Filter by WAV, FLAC, or AIFF.)
- squeaky-clean 5y agoTry a more obscure bird species, like the one in the original article. https://freesound.org/search/?q=Eastern+Wood+Pewee https://freesound.org/search/?q=Eastern+Wood+Pewee 1 result https://www.xeno-canto.org/explore?query=Eastern%20Wood%20Pewee https://www.xeno-canto.org/explore?query=Eastern%20Wood%20Pe... 228 results Furthermore, your search for blackbird on Freesound gives 639 results based on a text match, while xeno-canto gives 7449 results from 32 species, with metadata tagging it by species, location, date, time of day.
- andai 5y agoThank you, that's a wonderful website!
- deleted 5y ago[deleted]
- Gravityloss 5y agoGetting data from the real world always results in noise and artefacts etc. If you've done any kind of work with data, a large part is preprocessing. MP3 seems like a very minor source of problems compared to the potential others. Road noise, other birds, lorries backing up, people talking, mislabeling etc.
- TonyTrapp 5y agoThe difference however is that formats like MP3 work on the principle of psycho-acoustics, which means they modify the original audio in a way that is meant to be indistinguishable by human hearing, but it could very well cause a difference in the spectrum in places where it matters for the analysis (it can add and remove frequencies).
- willis936 5y agoThe compression is not wholesale adding or removing frequencies, it is selectively lowering the magnitude and SNR. Overall, the RMSE of 320 kbps mp3 against lossless of many common and simple waveforms is very low. Certainly it is acceptable for something like birdsong measurement.
- Gravityloss 5y agoThat's a great point, hadn't considered that. You changed my opinion.
- IndySun 5y ago>Was this work done on data stored in lossy formats? You're right to mention this. Lossless audio is preferred for analyst software. Even good MP3s tend to top out around 16kHz. The quality of the recording will also be dependent on the microphones used and their frequency range. When we have analysed animal sounds it's useful to play the sample slower, pitched down. Having those higher frequencies recorded well, above 16kHz, make a huge difference to the signals information.