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Topic: Can higher bitrates sometimes sound worse than lower ones (Read 1307 times) previous topic - next topic
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Can higher bitrates sometimes sound worse than lower ones

because of poor optimisation?

For example, let's say an encoder is optimised to give the best quality between 128 kbps and 256 kbps. Could using 320 kbps with this encoder sound worse than 256 kbps due to that?

Do any encoders have this problem, especially FDK and opus-tools?

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #1 –
No.

...As long as you define "better" as sounding more like the uncompressed original and the CODEC isn't badly designed.

The bitrate is (partially) related to how much information is thrown-away to make a smaller file and with a higher bitrate less data is thrown-away.

But you may prefer the lower less-accurate bitrate.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #2 –
Of course it "could", if the development didn't catch an issue. I wonder, for example: what about those encoders capable of creating free-format MP3; are they really well-tuned for it? Surely we can acknowledge if it had low priority ever since it got pretty clear that free-format would never be a big thing.
 

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #4 –
Why would they when in VBR they can reach up to 1mbit+ for AAC/Vorbis/Musepack, While Opus it 510kbps. Only LAME MP3 seems to fail even If the actual VBR bit rate Is 580kbps because It short block detection Is not very good. Yet with Helix 5.2.4 you have the -SBT switch that set to 100, It will give 50 ~ 95% short if It detects transients at the cost of the bit rate being 220 ~ 315kbps.


OptimFrog PC | Vorbis at Q6(Phone)

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #5 –
Quote from: fred-hy on
because of poor optimisation?

For example, let's say an encoder is optimised to give the best quality between 128 kbps and 256 kbps. Could using 320 kbps with this encoder sound worse than 256 kbps due to that?

Do any encoders have this problem, especially FDK and opus-tools?

Normally no the higher bitrate has less error , But it may be possible in this way :

There is an artifact audiable with lower bitrate, You encode with higher bitrate but artifact is still there and:
The error gets shifted in way that makes the higher bitrate sound different (more objectionable) even though the objective quality is overall higher.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #6 –
Here's an example of an opus file that, at least to me, sounded worse (less like the original) at high bitrates: https://hydrogenaudio.org/index.php/topic,122093.0.html

I also think it's normal that some codecs get tested more thoroughly at lower bitrates, because that's their more typical use case.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #7 –
The sample Brand linked is interesting, though the claim that higher the bitrate the worse it sounds isn't entirely correct.
At certain bitrates Opus refrains from trying to encode the noise between ~12 kHz and ~15 kHz, but once bitrate increases above those thresholds it stupidly encodes parts of that frequency range. For example 128 kbps is worse than 150 kbps, and while 256 kbps sounds worse than 150 kbps, 320 kbps is once again better than 150 kbps.
It's not doing a worse job because bitrate increases, it just doesn't seem to understand what it's encoding and sprinkles the extra bits randomly leading to awful artifacting.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #8 –
Quote from: Case on
The sample Brand linked is interesting, though the claim that higher the bitrate the worse it sounds isn't entirely correct.
At certain bitrates Opus refrains from trying to encode the noise between ~12 kHz and ~15 kHz, but once bitrate increases above those thresholds it stupidly encodes parts of that frequency range. For example 128 kbps is worse than 150 kbps, and while 256 kbps sounds worse than 150 kbps, 320 kbps is once again better than 150 kbps.
It's not doing a worse job because bitrate increases, it just doesn't seem to understand what it's encoding and sprinkles the extra bits randomly leading to awful artifacting.

Do you have a source for this?

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #9 –
Quote from: fred-hy on
Quote from: Case on
The sample Brand linked is interesting, though the claim that higher the bitrate the worse it sounds isn't entirely correct.
At certain bitrates Opus refrains from trying to encode the noise between ~12 kHz and ~15 kHz, but once bitrate increases above those thresholds it stupidly encodes parts of that frequency range. For example 128 kbps is worse than 150 kbps, and while 256 kbps sounds worse than 150 kbps, 320 kbps is once again better than 150 kbps.
It's not doing a worse job because bitrate increases, it just doesn't seem to understand what it's encoding and sprinkles the extra bits randomly leading to awful artifacting.

Do you have a source for this?
Don't understand the question. He's done his homework!

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #10 –
@fred-hy : as john33 said, I just tested it myself.
Generally speaking lossy codecs should always improve quality the more bits you give them. When you increase the bitrate they can more accurately store what they want. Also as you increase the bitrate they can store larger frequency range.

This Opus behavior looks like a serious bug or their modeling of human hearing is badly mistaken. I can't think of any good excuse for the behavior this sample demonstrates.

I'm well aware you don't hear with your eyes but I'll post some spectrograms either way, as in this instance they do demonstrate things quite well.
Original audio:
X

At 48 kbps Opus sounds very watery and thin, and frequency analysis shows that most frequencies have changed by quite a bit:
X

At 64 kbps things have improved, but now there are a couple of weird frequency spikes that make chirping sounds:
X

As bitrate increases those spikes disappear and the lower frequency noise gets fuller spectrum. This is 96 kbps (I don't hear difference in the noise):
X

As nominal bitrate rises to 128 kbps Opus has again introduced a lot of chirping:
X

As bitrate increases the chirping lessens, this at 150 kbps:
X

And by 160 kbps they are all gone:
X

And when bitrate is pushed further up somewhere around 220 kbps Opus once again thinks that introducing the chirping artifacts is a good idea:
X

This time when bitrate is increased the chirping gets worse. At 260 kbps:
X

Until you give Opus enough bits so that it can fill the entire spectrum it wanted to fill without the chirping artifacts. This is at 400 kbps, but 320 kbps spectrum is identical:
X

Here the subjective quality increases as the bitrate rises until encoder bug ruins everything, but as bitrate increases again the glitch will get circumvented eventually. I think it's just bad luck that around 256 kbps seems to have the worst chirping, I think some other sample could produce similar results at different bitrates.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #11 –
Just out of curiosity, you've reported this to the developer back then, right, @Case‍ ? 
The older the 'lossier' - meaning: my hearing & my music collection.
After all, I listen to the music, not the media it's on.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #12 –
Day before yesterday was the first time I saw and tested the sample.

Re: Can higher bitrates sometimes sound worse than lower ones

Reply #13 –
Oh, I got the impression you'd spotted it at an earlier date.
The older the 'lossier' - meaning: my hearing & my music collection.
After all, I listen to the music, not the media it's on.