Skip to main content
Topic: How does applying lowpass affect overall audio quality? (Read 4112 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

How does applying lowpass affect overall audio quality?

Hello, new member here. Hope this isn't the wrong place for this topic. I tried searching for a similar topic but couldn't find one - probably because of having no idea what to look for.

I have a few questions about applying a 17.5KHz lowpass in qaac q91 or lame V 2. I've tested my hearing and determined that I can't hear any difference through double blind testing. In fact I can't hear any pure tone above 17400Hz. So,

1. Apart from the smaller filesize, how does it affect the overall audio quality of the output for the above mentioned encoders?
2. Is it worth reencoding my whole library from loseless source, given a few hundred megabytes can be saved? Are there other benefits or drawbacks?

These questions rose from testing the FhG encoder with a similar lowpass, which changes the filesize in a totally opposite manner. The filesize increases a little, though there is no audible difference in the output. But I guess (just a guess, correct me if it's wrong) it's not wasting bits, rather using them well to encode in higher quality. Why, then, qaac or lame doesn't do the same? Or is it totally irrelevant?

If this topic has been discussed before, please just point to it. Any help will be greatly appreciated. And, English is not my native language, so pardon my mistakes, please.

How does applying lowpass affect overall audio quality?

Reply #1
Hello, new member here. Hope this isn't the wrong place for this topic. I tried searching for a similar topic but couldn't find one - probably because of having no idea what to look for.

I have a few questions about applying a 17.5KHz lowpass in qaac q91 or lame V 2. I've tested my hearing and determined that I can't hear any difference through double blind testing. In fact I can't hear any pure tone above 17400Hz. So,

1. Apart from the smaller filesize, how does it affect the overall audio quality of the output for the above mentioned encoders?
2. Is it worth reencoding my whole library from loseless source, given a few hundred megabytes can be saved? Are there other benefits or drawbacks?

These questions rose from testing the FhG encoder with a similar lowpass, which changes the filesize in a totally opposite manner. The filesize increases a little, though there is no audible difference in the output. But I guess (just a guess, correct me if it's wrong) it's not wasting bits, rather using them well to encode in higher quality. Why, then, qaac or lame doesn't do the same? Or is it totally irrelevant?

If this topic has been discussed before, please just point to it. Any help will be greatly appreciated. And, English is not my native language, so pardon my mistakes, please.

1. There is a small chance that the bits that were encoding the highest frequencies, when applied to the rest of the frequency range instead, will improve the audible quality, but you will probably not hear it in q91 or V2, which are essentially transparent already.
2. Storage space is cheap, but only you can decide between the space saved and the time and effort required to reencode.
Different encoders make choices differently, so it is not surprising that there would be differences.

How does applying lowpass affect overall audio quality?

Reply #2
Reencoding isn't worth while.
lame3995o -Q1.7
opus --bitrate 140

How does applying lowpass affect overall audio quality?

Reply #3
Thanks for the clarifications. For now I'll stick with my old encoded files but use lowpass on new encodes. 

 
SimplePortal 1.0.0 RC1 © 2008-2019