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Comment by tincholio | Hacker News Reader

Opus at over 40 or 60Kbps for voice sounds like overkill, nevermind 500kbps. What's the rationale for using such high bitrates?

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I configured the max possible bitrate in the spec. I wanted to find out what is being used in the end. And how it sounds. Most people are calling without a microphone. Please use a headset.

You should look up some subjective quality test results for Opus (voice). The MOS curve flattens at about 40kbps, IIRC.

OpusFAQ: "Opus scales from about 6 to 512 kb/s" - https://wiki.xiph.org/OpusFAQ#In_what_ways_is_Opus_optimized...?

Edit: quote from section 1.14 (direct link does not work bc of the question mark in their section ID)

Probably marketing and the HiFi industry has demonstrated that such people are a nice niche income stream. Some say a fool and their money, I say each to their own and their choice.

But I'm sure there are always edge-case valid uses for such audio quality. Maybe talk to bats and dolphins in the future is now one step closer than before is another way of looking at this.

Opus doesn't support any sample rates higher than 48khz, so no bat encoding. Some other audio codecs do, but it doesn't really make a lot of sense and I doubt they've been properly tuned for it.

Oh indeed you are spot on - https://wiki.xiph.org/OpusFAQ#Does_Opus_support_higher_sampl...

But that 500kbs sound just feels warmer to me (on my laptop).

I think the 500 limit is a max bitrate setting, independent of any specific codec. If you deliver audio+video you will need to consider exactly how much of the bandwidth you use for audio. But when doing audio only, simply using the highest possible bitrate seems to be a reasonable choice. In most cases the network will set limited.

Samplerate is an independent dimension of bitrate - although not really because lower bitrates can store fewer samples.

It's equivalent to the resolution of an image.

Sample rate is limit on the frequencies in the original signal that you can represent in your digitization without aliasing.

Sample rate != bit rate. 48khz samples at 16bits each is 768kbps mono. 1.5Mbps stereo. But that's before compression.

The point was that Opus can't store bat sounds because they're ultrasonic and it isn't. Dolphins may be possible though I think whales might be filtered out due to being subsonic.

Opus at sample rate of 48khz, still only encodes frequencies up to 20khz of listening range (think of opus as having 40khz sampling rate).

This is same as audio CDs, which although are in 44khz sampling rate, have a red book recommendation to always filter out anything over 20khz.

Thing is, most people can't hear well over 16khz. Some can hear 18khz. 20khz is peak possibility. To encode 20khz wave we need 40khz sampling rate. Everything else is marketing.

"640k [bitrate] ought to be enough for everyone"...

For mono audio, even 32k Opus is nearly CD quality, and 64k is indistinguishable from uncompressed audio in non-audiophile contexts.

500k is simply ludicrous.

Would not be ridiculous for serious online musical collaboration where you might want to send many channels at once. Perhaps there is some benefit to multiplexing inside Opus, instead of having separate channels? (Probably a similar argument as the one in favor of monorepos).

In this context, latency is far more important than actual audio quality. Human ears are notoriously bad at judging the "quality" of sound, but extremely good at detecting latency between visuals and audio. This is why lip sync is such a problem in home cinema systems.

Well, considering that I can hear a difference between lossless and ~80k Opus (stereo) with a decent headphone amp and 16 EUR Sony in-ear's, I can't share your sentiment. Granted, this is fairly pathological synth sound (the intro/first 30s of Night Club's "Magnetic"), but I would hardly call that listening equipment audiophile.

80k stereo is (approximately) 40k mono. We seem to have the same sentiment.

No, I'm saying that this is very much distinguishable without exotic hardware, on music not deliberately created to expose compression artifacts. And at a bit rate higher than what you claimed to be transparent on non-audiophile setups. And calling <20$ headphones (that includes an in-line microphone) on a Thinkpad's built-in headphone amplifier "audiophile" seems inappropriate. I do hear a difference (on FLAC) between those cheap headphones and some ultra-low-distortion 2-way half-open headphones, with the latter being notably more clear.

You said 64k stereo aren't distinguishable from FLAC with normal, consumer-grade listening equipment. I said I hear a difference between 80k stereo and FLAC using a laptop built-in headphone amp and the cheapest headphones that didn't look like a consumable.

They said 64k mono is indistinguishable, not 64k stereo.

You're talking about stereo and I'm talking about mono, as I tried to explain in the previous comment.

the idea that 64k opus is indistinguishable from uncompressed is so ridiculous... the caveat being "if you have shitty equipment" is not any sort of argument at all. if you have shitty equipment, nothing ever matters. is that an argument for anything at all?

people love dunking on hifi-- it's such a meme at this point.

edit: ah yes, i forgot about the "i disagree" button to the left of my name... feel free to use it, i guess. clearly, as a hifi stan, i doth protest too much... (and am just an idiot)

every other commenter agrees that this is a bad take, but i guess because i highlighted that this sort of comment is typical to this discourse i am somehow breaking social mores

At this sort of bitrate I am wondering if AAC-LD ( Low Delay ) could be used on Apple platform.

And speaking of that I am wondering if patent has expired on that just like AAC-LC.

Why? Opus is superior to AAC-LD, not patent encumbered and, as far as I know, supported by Safari for WebRTC.

I am just increasingly fond of "patent free" codec. Like AAC-LC and Good old MP3.

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