xHE-AAC: Transparency Rate?

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xHE-AAC: Transparency Rate?

2021-04-11 02:10:34

Since xHE-AAC is supported in the m4a container, which makes it compatible with the stock iOS music player; I'm thinking of switching my 256kbps AAC collection with xHE-AAC. I'm hoping to get similar quality in the 90-128kbps range, however I'm not familiar with the format considering how new it is. So like the title says, is there a known transparency bitrate for xHE-AAC? Judging by the press-releases on the Fraunhofer website, the codec seems to be more geared towards TV and movie audio at low bitrates. However, the page for the Exhale encoder states that it preforms well at medium-to-high bitrates. So which is it? Am I going about this all wrong? Should I just use HE-AAC? If only iOS supported Opus I would be using that.

Re: xHE-AAC: Transparency Rate?

Reply #1 – 2021-04-11 16:12:56

I can't hear music in HE-AAC and still use AAC-LC at 256kbps when I can't help it. Honestly at high bitrate there is no difference between encoders. Please note that Exhale cannot be considered an xHE-AAC encoder, for the use of the registered trademark it is necessary to obtain a certification from the owner of the same. Furthermore, iTunes does not allow you to add songs compressed with these encoders to the library.

Re: xHE-AAC: Transparency Rate?

Reply #2 – 2021-04-11 16:13:35

Quote from: celona on 2021-04-11 16:12:56

I can't hear music in HE-AAC and still use AAC-LC at 256kbps or lossless. Honestly at very high bitrate there is no difference between encoders. Please note that Exhale cannot be considered an xHE-AAC encoder, for the use of the registered trademark it is necessary to obtain a certification from the owner of the same. Furthermore, iTunes does not allow you to add songs compressed with these encoders to the library.

Re: xHE-AAC: Transparency Rate?

Reply #3 – 2021-04-12 12:30:21

Quote from: celona on 2021-04-11 16:12:56

iTunes does not allow you to add songs compressed with these encoders to the library.

As the latest MacOS doesn’t use iTunes to send music to iOS devices (it’s done directly from Finder), could anyone with a Mac let us know if it’s possible to sync xHE-AAC MP4 files.

Re: xHE-AAC: Transparency Rate?

Reply #4 – 2021-04-12 12:32:37

Quote from: ManekiNeko on 2021-04-12 12:30:21

As the latest MacOS doesn’t use iTunes to send music to iOS devices (it’s done directly from Finder), could anyone with a Mac let us know if it’s possible to sync xHE-AAC MP4 files.

It is the same with Music version 1.1.3.3, you can try by downloading the files that I have uploaded in another thread.

https://hydrogenaud.io/index.php?topic=118888.msg996097#msg996097

Re: xHE-AAC: Transparency Rate?

Reply #5 – 2021-04-12 18:57:32

Quote from: br441 on 2021-04-11 02:10:34

Since xHE-AAC is supported in the m4a container, which makes it compatible with the stock iOS music player; I'm thinking of switching my 256kbps AAC collection with xHE-AAC. I'm hoping to get similar quality in the 90-128kbps range, however I'm not familiar with the format considering how new it is. So like the title says, is there a known transparency bitrate for xHE-AAC? Judging by the press-releases on the Fraunhofer website, the codec seems to be more geared towards TV and movie audio at low bitrates. However, the page for the Exhale encoder states that it preforms well at medium-to-high bitrates. So which is it? Am I going about this all wrong? Should I just use HE-AAC? If only iOS supported Opus I would be using that.

For exhale's definition of "medium-to-high bitrates" please see https://hydrogenaud.io/index.php?topic=118888.msg980837#msg980837.
You find a listening test here indicating that, above ~128 kbps stereo, xHE-AAC gives you little to no audible advantage over AAC-LC:

You could, however, give exhale CVBR mode 9 (~192 kbps stereo) a try against your 256-kbps AAC-LC encodings. But the question remains whether that 25% bitrate saving would be worth re-encoding your entire collection.

Chris

Re: xHE-AAC: Transparency Rate?

Reply #6 – 2021-04-13 07:56:43

Quote from: C.R.Helmrich on 2021-04-12 18:57:32

indicating that, above ~128 kbps stereo, xHE-AAC gives you little to no audible advantage over AAC-LC

Viewed the other way: Why not exhale for AAC? Assuming xHE compatibility is not an issue,
is there any reason not to stick to exhale and ditch all other AAC encoders?

Honest non-neutral non-independent opinion, please ;-)

Re: xHE-AAC: Transparency Rate?

Reply #7 – 2021-04-13 11:17:46

Try it, so you find out the problems. They depend on what you use and are destined to gradually disappear, eg. FFMPEG now converts xHE-AAC to AAC because the decoding library is not always included; if you try to upload a video to YouTube you may never end, other programs require the installation of a decoder, because Windows still does not have one, on the mobile front zero problems from Android 9 and later. These are problems that do not depend on the encoder, but they exist.

Re: xHE-AAC: Transparency Rate?

Reply #8 – 2021-04-14 19:16:37

Quote from: Porcus on 2021-04-13 07:56:43

Viewed the other way: Why not exhale for AAC? Assuming xHE compatibility is not an issue,
is there any reason not to stick to exhale and ditch all other AAC encoders?

Honest non-neutral non-independent opinion, please ;-)

AAC-LC plays everywhere and is much faster at encoding than exhale.

Re: xHE-AAC: Transparency Rate?

Reply #9 – 2021-04-14 23:39:42

Exhale is meant to target 96kbps or lower, not 128kbps. If you're going to target 128kbps, you may as well use a regular LC AAC encoder.

Re: xHE-AAC: Transparency Rate?

Reply #10 – 2021-05-31 00:26:11

Quote from: br441 on 2021-04-11 02:10:34

So like the title says, is there a known transparency bitrate for xHE-AAC?

Exhale is good enough at 72kb/s-96kb/s for me, on most generic pop songs. I could go down to 40kbps if I'm not listening through my main IEMs.

If you only plan to have these songs on your iOS main storage, go for it. Even going to 96 from 192 is a 50% reduction and totally worth it if most of your songs don't need a high bitrate. It really adds up with the more songs you have. I don't really know a lot about iOS support (e.g., importing the songs to your library and such) so you should definitely give it a try yourself first.

Quote from: synclagz on 2021-04-14 19:16:37

AAC-LC plays everywhere and is much faster at encoding than exhale.

xHE-AAC will be supported in Windows soon and iOS/Android's newer versions already support it well. So if I want to save space on my phone with no SD slot then compatibility with some TV from 2009 doesn't really matter to me, and the encoding speed also doesn't matter especially when using multiple exhale instances in parallel on a modern processor.

Large companies are preferring to encode videos with AV1 using the slow encoder for the storage/bandwidth savings rather than trying a faster codec and I would do the same if space was limited on my phone.

BTW, the Fraunhofer encoder for xHE-AAC goes up to 320kbps and IMO produces the closest waveform (to the original) compared to AAC-LC, LAME or even Opus, so I would trust it even for archival and as an editing intermediate format, sort of like ProRes for audio.

Re: xHE-AAC: Transparency Rate?

Reply #11 – 2021-05-31 09:23:13

On my side, my tagged classical music library was very recently encoded to xHE-AAC with Exhale at ~96 kbps.

Before that and following this test I made, my library was built upon LC-AAC 144 kbps, LC-AAC 128 kbps and also Opus 100 kbps for experimental purposes.

As a result I never heard anything annoying with LC-AAC 144 kbps; LC-AAC 128 was close to transparency on a huge majority of tracks and all irritating issues I had were always with Opus 100 kbps encodings (in other words each time I heard something wrong and checked the file format it was an Opus encoding — and it happened countless times).

At the moment Exhale -3 (average bitrate: 98 kbps on ~1000 hours of music) gives a pretty high quality on many tracks but I still hear from time to time some audible distortions I didn't heard with LC-AAC 128 kbps. I would say, for my hearing and for my music (and from my very little experience too) that USAC brings a real but small gain compared to a fully mature AAC encoder at this bitrate level. I'm sure Exhale outperforms AAC at 96 kbps; I'm quite sure it's not as good as AAC ~128 kbps. So Exhale 96 kbps is somewhere between 96…128 kbps AAC range.

And again, most encodings are absolutely fine and can even compete with any high bitrate encodings (depending on how critical your listening abilities and settings are).

NB : I'll soon publish a test that compares Exhale vs FhG USAC vs OPUS at 96 kbps

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