That article is a bit too dismissive. I agree that one cannot hear the difference between 48KHz/16bit and 192KHz/24bit if you just transfer the data directly to the audio output device. As such, there is no good reason for Opus to support higher than 48KHz (especially since this is lossy compression, anyway). However, in general, that's not all you do with audio data. 192KHz is useful for the same reason that 24 bits is useful. Digital operations often need the extra margin for many of the operations being carried out (IIR-type effects, mixing multiple sources, etc.) This is especially true for the so-called "wet" effects that tend to mangle phase vs frequency (vs "dry" effects which tend to only affect amplitude vs frequency). -a On 6/6/14, 11:03 AM, Gregory Maxwell wrote:> On Sat, Feb 22, 2014 at 8:32 AM, Webdrifter <onzemeelbox at gmail.com> wrote: >> Hello, >> I'm an audiphile. >> Will opus ever be developed to work with sampling rates higher than 48kHz? (I hope so) > > http://people.xiph.org/~xiphmont/demo/neil-young.html > _______________________________________________ > opus mailing list > opus at xiph.org > http://lists.xiph.org/mailman/listinfo/opus >-------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 538 bytes Desc: OpenPGP digital signature Url : http://lists.xiph.org/pipermail/opus/attachments/20140607/5a852ca7/attachment.pgp
I raised the same point when I first read that article ... and I had to read it again to understand that its conclusions are explicitly limited to _distribution_ formats, not _intermediate editing_ formats. No doubt, if you start applying nonlinear functions to your audio signals, the output may depend audibly on ultrasonic components ... but that is not the case for Neil Young's hifi playback, or for Opus. If you are planning on doing the kind of audio editing that involves nonlinear transformations, then you should definitely not be using Opus as your intermediate format anyway. Use FLAC. There are also some philosophical questions about whether mixing in ultrasonics is particularly the right behavior anyway. If I time-stretch my audio, do I really want to hear the previously inaudible ultrasonic tone from my compact fluorescent lightbulb ballast? I think the answer is "maybe", which is different from "yes". On Fri, Jun 6, 2014 at 11:35 PM, Andrew Lentvorski <bsder at allcaps.org> wrote:> That article is a bit too dismissive. I agree that one cannot hear the > difference between 48KHz/16bit and 192KHz/24bit if you just transfer the > data directly to the audio output device. As such, there is no good > reason for Opus to support higher than 48KHz (especially since this is > lossy compression, anyway). > > However, in general, that's not all you do with audio data. > > 192KHz is useful for the same reason that 24 bits is useful. Digital > operations often need the extra margin for many of the operations being > carried out (IIR-type effects, mixing multiple sources, etc.) This is > especially true for the so-called "wet" effects that tend to mangle > phase vs frequency (vs "dry" effects which tend to only affect amplitude > vs frequency). > > -a > > > On 6/6/14, 11:03 AM, Gregory Maxwell wrote: > > On Sat, Feb 22, 2014 at 8:32 AM, Webdrifter <onzemeelbox at gmail.com> > wrote: > >> Hello, > >> I'm an audiphile. > >> Will opus ever be developed to work with sampling rates higher than > 48kHz? (I hope so) > > > > http://people.xiph.org/~xiphmont/demo/neil-young.html > > _______________________________________________ > > opus mailing list > > opus at xiph.org > > http://lists.xiph.org/mailman/listinfo/opus > > > > > _______________________________________________ > opus mailing list > opus at xiph.org > http://lists.xiph.org/mailman/listinfo/opus > >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/opus/attachments/20140606/96f6798a/attachment.htm
On 07/06/14 02:35 AM, Andrew Lentvorski wrote:> 192KHz is useful for the same reason that 24 bits is useful. > Digital operations often need the extra margin for many of the > operations being carried out (IIR-type effects, mixing multiple > sources, etc.) This is especially true for the so-called "wet" > effects that tend to mangle phase vs frequency (vs "dry" effects > which tend to only affect amplitude vs frequency).Actually... no! 24-bit can indeed be useful as extra margin and Opus can actually represent even more dynamic range than 24-bit PCM. That's not the case for 192 kHz. There's no "margin" that 192 kHz buys you over 48 kHz. You can do as much linear filtering as you like, the stuff above 20 kHz isn't going to help you. Jean-Marc
On 6/7/14, 1:55 AM, Jean-Marc Valin wrote:> Actually... no! 24-bit can indeed be useful as extra margin and Opus > can actually represent even more dynamic range than 24-bit PCM. That's > not the case for 192 kHz. There's no "margin" that 192 kHz buys you > over 48 kHz. You can do as much linear filtering as you like, the > stuff above 20 kHz isn't going to help you.But lots of effects are not linear--simulating a tube guitar amplifier, for example. Even something as straightforward as resampling a signal to 44.1KHz is going to benefit from starting at 192KHz rather than 48KHz. There may not be more signal information but there will be less noise. -a -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 538 bytes Desc: OpenPGP digital signature Url : http://lists.xiph.org/pipermail/opus/attachments/20140607/e86351cc/attachment.pgp