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Topic: Near Lossless Bitrate for Opus 1.1 for different channel configuration (Read 5495 times) previous topic - next topic
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Near Lossless Bitrate for Opus 1.1 for different channel configuration

I wanted to configure opus encoder in such a way that the decoded files  are near lossless.

What bitrate i need to set for stereo , 5.1 and 7.1 channels in VBR mode such that i get near lossless compression?
Also any idea how much latency is added when i do set in " OPUS_APPLICATION_AUDIO " application mode as compared to "OPUS_APPLICATION_RESTRICTED_LOWDELAY"?

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #1
I don't get it. You want to have maximum quality in lossy encoding? Use maximum bitrate.
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Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #2
Use bit rate's at 320 - 512kbps.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #3
What does "near lossless" mean? Being lossless is a binary attribute, it's either lossless or it's not. If it's not lossless it's lossy, and the only useful metric (for music) to assess its quality is transparency. The agreed open way here to determine your transparency threshold is conducting a blind test.

That said, to keep the probability of artifacts to a minimum you might want to choose the highest settings an encoder offers, though that might not offer a tangible benefit, and is probably not at all necessary to achieve transparency for most if not all listeners. The purpose of lossy audio is to vastly reduce file size while maintaining transparency. If you need something in its best quality use a lossless audio format.
It's only audiophile if it's inconvenient.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #4
What does "near lossless" mean? Being lossless is a binary attribute, it's either lossless or it's not. If it's not lossless it's lossy, and the only useful metric (for music) to assess its quality is transparency. The agreed open way here to determine your transparency threshold is conducting a blind test.

Well, if I understand it right, "crazyingeneer" actually _meant_ transparency but used a little bit fuzzy term. But the question remains: what are the (generally accepted) bitrates for Opus being transparent at different channel settings.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #5
Also any idea how much latency is added when i do set in " OPUS_APPLICATION_AUDIO " application mode as compared to "OPUS_APPLICATION_RESTRICTED_LOWDELAY"?
The difference in latency is 3.5 ms. For "audio", the latency is the frame size plus 6 ms, whereas for restricted-lowdelay, the latency is the frame size plus 2.5 ms.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #6
Thanks for the replies.

What i meant by near-lossless is as much as possible improve quality of encoded audio.

Yes for stereo 512 kbps did the trick. But for 5.1 / 7.1 opus encoder uses LPF on LFE channel.

I used 255 mapping_family, but started getting other weird issues.

How do i get rid of LPF in LFE channel in opus encoder as encode LFE as normal audio channel?

Thanks,

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #7
First thing that strikes me is that if you don't want a low pass on the LFE channel for 5.1, then what you really want is 6.0.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #8
Yes. 6.0. But somehow its not working, its giving me corrupted audio in surround channels.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #9
One small observation
What i meant by near-lossless is as much as possible improve quality of encoded audio.

Yes for stereo 512 kbps did the trick.
512 kbps for stereo is a total waste of bitrate.
96-128 kbps is transparent for speakers. 128-256 kbps is transparent  for headphones.
Everything higher than that is useless for such codecs as AAC and Opus.  These codecs already reach 500+ kbps for some frames when VBR 256 kbps is used.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #10
Yes. 6.0. But somehow its not working, its giving me corrupted audio in surround channels.
Actually, Opus does not currently have a mapping for 6.0. The easiest way around that would be to simply encode it as 6.1 with silence for the LFE.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #11
edit: nvm, did not take into account 6-channel source's effect on bitrate.

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #12
"edit: nvm, did not take into account 6-channel source's effect on bitrate."

- I did not get this point. What do you mean by edit nvm? opus source code?

 

Re: Near Lossless Bitrate for Opus 1.1 for different channel configuration

Reply #13
"edit: nvm" = "Post edited: nevermind"

 
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