Comment by ndiddy
7 hours ago
The biggest advantage for having a good AAC encoder isn't efficiency, it's that for nearly the past 2 decades the de facto standard for live streamed video has been RTMP with H.264 video and AAC audio. There is basically no support for any other codecs. If you want to send a video stream to Youtube or Twitch, you will be sending H.264 and AAC. If you want an idea of how ubiquitous this is, I just checked in OBS and it will not even let you select different video and audio codecs in streaming mode, it just (correctly) assumes that anybody who's streaming will be streaming H.264 and AAC.
YouTube actually supports H.265 and VP9 ingest, depending on the streaming protocol. I can actually stream 4K@60 H.265 from my Mac Studio with < 5% CPU usage due to the hardware encoder support in OBS.
https://developers.google.com/youtube/v3/live/guides/ingesti...
Also the fact that hardware-accelerated AAC and even full AAC offload is ubiquitous in modern-ish hardware. I think my rice cooker can play AAC audio
No one really offloads AAC, apart from Apple. Opus can be decoded on very cheap microcontrollers entirely in software using the reference library.
On a microcontroller doing nothing else sure. But on a phone, a tablet, a laptop, you absolutely want hardware decode to preserve your battery life.
The RTMP protocol comes from Adobe Flash which only supported a limited set of codecs, the only still useful ones being H264 and AAC. Nobody published the needed protocol extension "enhanced RTMP" until 2022 and it still isn't supported widely. RTMP is not a generic container for any codec, like Mastroska - RTMP is tightly coupled to the codec.
Plus, at 96+ kbps (assuming an Apple-quality AAC-LC encoder) Opus loses its quality advantage. So at higher bitrates, the benefit of choosing Opus is that encoders/decoders are royalty-free.
Am I reading that chart wrong? I see Opus ahead across every bitrate.
The evaluation tools used are helpful for encoder development, but at best they're imperfect proxies for human perception, and their predictions are often inconsistent with the human experience. I assume that statements like "apparently the best AAC encoder" aren't meant to be taken too seriously, since everybody who does this stuff knows that ABX/MUSHRA tests with real humans is what tells the tale.
On Opus vs. AAC specifically, there's a long history of studies like https://www.researchgate.net/publication/301428302_Perceived... to help answer that question. (There are interesting charts at the top of page 1175.)
Sample accurate editing is with AAC is a pain though. Especially if you also have video, because frame rates are usually incompatible.
If you want flexibility without fully transcoding both audio and video, Opus is your friend
Opus is your friend as long as the software you’re using supports it—besides, Apple’s AAC-LC can beat out Opus in low bitrates scenarios.
Whether you like it or not, AAC is still the standard.
I think often of how all it would have taken was a bomb for the 10 or so people that years ago at some browser vendor consortium out of pure self centeredness went „nah lets fragment“. We could have saved many many collective years, electricity and eyeballs simply watching the most basic content.
At one point in I think 2012 three of us who normally all live in different countries were riding in the same car in Australia. We advised the driver to be extra careful (she was dating one of us, so incentives were aligned).
But it is nice to hear that you have been thinking of us, too.