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Old 25th March 2024, 16:53   #961  |  Link
benwaggoner
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Originally Posted by Selur View Post
'AAC True VBR mode' https://github.com/nu774/qaac/wiki/Command-Line-Options
https://wiki.hydrogenaud.io/index.ph..._AAC#afconvert
There have been some discussions over at HydrogenAudio about whether vbr or tvbr are better.
Ah. So "vbr" there is a CVBR (Constrained VBR) ala setting --crf with a --vbv-maxrate and --vbv-bufsize. That's going to be preferable for streaming and combined video/audio delivery, as peak bitrates worst case can be defined. We need that for video as profile/level define a maximum bitrate for compatibility which we want to stay under.

TVBR would be an uncapped VBR, ala just using --crf or --qp without any profile/level VBV limitations. Potentially slightly better sound quality, and preferable for file-based playback.

Since there's only so high a bitrate can go with a codec, in practice there's not likely to be that much a difference unless the constrained bitrate is quite constrained.
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Old 25th March 2024, 17:06   #962  |  Link
kurkosdr
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Originally Posted by benwaggoner View Post
100 Kbps can matter if targeting mobile devices, and xHE-AAC decode is effectively universal on mobile: Android, iOS, and Fire OS have all supported xHE-AAC decode for a couple of replacement cycles now.

And with new codecs like VVC, we can push video bitrates down enough that audio becomes an increasingly large part of the total payload.
As long as xHE-AAC stays away from video broadcast (DVB and ATSC), I am happy. Streamers can always encode an HE-AAC fallback for older devices and serve accordingly (I don't like the idea of throwing away good smartphones in the name of "replacement cycles"/planned obsolescence, I still use my Nexus 5 and 5X as secondary phones). Although on streaming you won't save 100kbps but 30kbps (in our example above) because you are not streaming all 3 languages (audio streams) simultaneously like you do on broadcast. So, I highly doubt the usefulness of it, but as long as they provide a fallback (as they do usually), it's not an issue.

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Old 25th March 2024, 17:57   #963  |  Link
MoSal
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Originally Posted by kurkosdr View Post
As long as xHE-AAC stays away from video broadcast (DVB and ATSC), I am happy. Streamers can always encode an HE-AAC fallback for older devices and serve accordingly (I don't like the idea of throwing away good smartphones in the name of "replacement cycles"/planned obsolescence, I still use my Nexus 5 and 5X as secondary phones). Although on streaming you won't save 100kbps but 30kbps (in our example above) because you are not streaming all 3 languages (audio streams) simultaneously like you do on broadcast. So, I highly doubt the usefulness of it, but as long as they provide a fallback (as they do usually), it's not an issue.
This whole discussion was weird, since it managed to ignore the two facts that:

1- Opus exists.
2- Audio codecs don't need hardware (accelerated) support. Platform-level support is not an absolute requirement either. Apps can add software decoding for any audio codec without a noticeable downside like too much battery drainage (assuming no unusual complexity requirements).

There is a reason why xHE-AAC is not that exciting.

---

There is a third fact that HE-AAC is shit for anyone who has any respect for their ears. But let's not get into that.
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Old 26th March 2024, 00:56   #964  |  Link
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[QUOTE=kurkosdr;1999619]As long as xHE-AAC stays away from video broadcast (DVB and ATSC), I am happy. Streamers can always encode an HE-AAC fallback for older devices and serve accordingly (I don't like the idea of throwing away good smartphones in the name of "replacement cycles"/planned obsolescence, I still use my Nexus 5 and 5X as secondary phones).[QUOTE]
xHE-AAC is supported on really old phones. As long as it can upgrade to Android 9 or iOS 13, the decoder is there. That's all the way back to the iPhone 6s for Apple. Android updates are up to the whim of the OEM, of course, but five years is enough to get a pretty complete ecosystem refresh for mobile. Certainly most streaming apps don't support OS versions earlier than those.

But yeah, for broadcast broadcast, introducing new codecs is fraught and generally part of a massive shift. ATSC 1.0 to 3.0, for example (which still exists more in theory than practice). DVB seems to be able to get an update in more than once every few decades .

Quote:
Although on streaming you won't save 100kbps but 30kbps (in our example above) because you are not streaming all 3 languages (audio streams) simultaneously like you do on broadcast. So, I highly doubt the usefulness of it, but as long as they provide a fallback (as they do usually), it's not an issue.
There are several big benefits of xHE-AAC for streaming
  1. Seamless switching between all bitrates. That wasn't supported between LC and HEv1 or HEv1 and HEv2.
  2. Single codec scalable from perceptually lossless music down to very low bitrate speech
  3. Better speech quality in general at lower bitrates
  4. Better compression efficiency than any legacy AAC variant at any given bitrate or perceptual quality threshold.
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