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Topic: Cutoff frequencies of lossy codecs (Read 839 times) previous topic - next topic
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Cutoff frequencies of lossy codecs

Hello. Firstly, I want to say that I was wanted to open this topic in the "Lossy audio compression" category but I could not do that because opening a topic in there without selecting a sub category is not possible and this topic is not about a specific audio codec.

I started to see that most lossy encoders are starting to give higher and higher cutoff frequencies for a given bitrate (for example, FhG vs Lame). This may sound attractive, but a higher cutoff frequency means more black space in the frequency area and this sounds horrible to me. (An ABX is not needed per TOS because this is not about quality, this is about "sound color".) For example, a FhG MP3Enc lowest quality encoded 16kbps 11025Hz mono MP3 is pretty good for me, but a FhG Fastencc and especially Lame encoded 16kbps 11025Hz mono MP3 is not very good because of the higher cutoffs. The same thing applies for (for example) FhG MP3Enc encoded 64kbps 44100Hz mono and Lame encoded 64kbps 44100Hz mono. (I can't give an ABX because all of these files are totally untransparent to me. Of course, this does not mean they are all bad.) Of course, very low cutoff points are not good too, but I think the modern encoders are giving too higher cutoff points than the sweet spot. For example, I think 24kbps is the lowest bitrate that makes sense with 11025Hz cutoffless MP3's. Why those modern encoders are giving higher and higher cutoff points every day?



Re: Cutoff frequencies of lossy codecs

Reply #3
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This may sound attractive, but a higher cutoff frequency means more black space in the frequency area and this sounds horrible to me. (An ABX is not needed per TOS because this is not about quality, this is about "sound color".) For example, a FhG MP3Enc lowest quality encoded 16kbps 11025Hz mono MP3 is pretty good for me,
I don't mean to sound rude, but you have a strange idea of what constitutes 'sound color' and an even more strange sense of what constitutes 'good sound'! It must be clear by now that you are in a minority of one. Ultra low bitrate/samplerate does NOT generate anything that sounds good by any metric, certainly not in mp3.

Re: Cutoff frequencies of lossy codecs

Reply #4
I don't know much about low bitrate encoding.    I suspect the LAME developers don't care much about it.    From what I can tell, they are more interested in getting transparent, or near-transparent compression, possibly at the lowest bitrate that's possible.   

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Why those modern encoders are giving higher and higher cutoff points every day?
Maybe because a lot of people judge quality by looking at the spectrum rather by listening?  Of course that's not what we do here.

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I started to see that most lossy encoders are starting to give higher and higher cutoff frequencies for a given bitrate (for example, FhG vs Lame). This may sound attractive, but a higher cutoff frequency means more black space in the frequency area and this sounds
With lossy compression some data must be thrown-away.   There are trade-offs.   If you force it to keep the highest frequencies something else will be thrown away, and what gets thrown-away may be more important than the high frequencies.    Once you are hearing compression artifacts different people may prefer different tradeoffs.    At higher quality settings, I assume the default LAME settings are optimized for most listeners and most program material    OGG or AAC may be able to do better, but I'm pretty sure LAME has been pushed as far as it can go.

Also at higher quality settings, it you hear an artifact it's usually not the loss of high frequencies you hear.   It's usually something else.    The highest audio frequencies (near 20kHz) are weak in normal program material so even if you can hear to 20kHz with loud test-tones in a hearing test, they are usually masked (drowned out) by not-as-high frequencies.     Eliminating "drowned out" sounds is the main way lossy compression gets-away with throwing-away data. 

You are limited to half the sample rate (Nyquist) so at a sample rate of 11,025 the audio can't go above 5512Hz (even with lossless compression or no compression.)

Re: Cutoff frequencies of lossy codecs

Reply #5
Higher cutoff point also looks worse on the spectrum in most cases for me.

Re: Cutoff frequencies of lossy codecs

Reply #6
Higher cutoff point also looks worse on the spectrum in most cases for me.

I'm still confused by what you're describing, but you should listen with your ears, not eyes.

Re: Cutoff frequencies of lossy codecs

Reply #7
@saratoga Looks like you didn't see the word "also". This means I already normally listen with my ears.

Re: Cutoff frequencies of lossy codecs

Reply #8
@DVDdoug I think OGG is doing worse. I prefer 22050Hz 32kbps FhG encoded MP3 over 22050Hz 32kbps Aotuv encoded OGG Vorbis, because it has richer spectrum as it has a narrower frequency range.

Re: Cutoff frequencies of lossy codecs

Reply #9
People generally says humans can hear up to 20kHz but I think nobody can hear above 18kHz and no adult can hear above 16kHz.

Re: Cutoff frequencies of lossy codecs

Reply #10
People generally says humans can hear up to 20kHz but I think nobody can hear above 18kHz and no adult can hear above 16kHz.
IIRC, some people have heard both 24 and 27 in trials, but at sound pressure levels you don't want to be exposed to for more than split seconds. That research was on how far up one should measure noise to protect against it, not on what you need to preserve.