AAC vs AC3 bitrates
In the past I’ve chosen I’ve often kept AC3 audio tracks thinking that their substantially higher bitrates made them better than the AAC tracks I compared them to. As I’ve since learned that AAC can be comparable to AC3 at a substantially lower bitrate, to have a means of comparing the two codecs, what would the AAC-equivalent bitrates be for 224kbps and 640kbps AC3?
Hi Zedstrain, I’m guessing we’re talking about movies’ audio tracks. Passthrough is always best if we can stomach the storage space, especially if the video is taking a lot more space anyway.
If compressing, why not opus? Should be at least slighly better than AAC, it’s constantly improving and thanks to its licensing the encoders you’ll find included in any up-to-date software like Handbrake should work really well.
With AAC (which does sound great and is very close to opus) you’re gonna see bigger differences depending on the encoder. I only used it for music and podcasts (when I got into modding classic iPods 😂), but to avoid installing encoder libraries in the system and using ffmpeg which I’m too dumb for, I used fre:ac because it included good encoders like FDK.
Anyway normally 224kbps is plenty with AAC, I would never go higher for music for example. For movies there’s the multiple channels thing to consider, might be safe to go a bit higher for 7.1 or more channels, but I have no direct experience.
Definitely needs some more testing as those numbers in the table look low to me. Archiving vs listening is a key point and storage is relatively cheap.
Listening on cheap Bluetooth headphones then you can get away with a low bitrate. If you are using better gear and/or music that has a lot of dynamic range and comes from strings (piano/classical/etc) then I would recommend 320 but your mileage may vary.
Listen, compare and decide. I have a library of about 110k tracks (musicbrainz-Picard is amazing) and I wish I had:
As others mentioned having a good encoder is an issue for AAC. And some skills in using it, tuning, etc.
Nearly all quality releasers now use AC3/EAC3 or FLAC. Tigole is the last one who uses AAC to my knowledge and the rest of the QXR group rolls their eyes at it.
You’re not going to get a meaningful reduction in bitrate and file size with AAC over EAC3/AC3 without loss of quality. We’re talking maybe you can shave 2-300kbps off an AAC version versus an AC3 5.1 track. And it’s tricky. So much so no one other than that one person I mentioned bothers. At least no one accepted in the higher echelons as competent in creating acceptably transparent encodes.
If a source has EAC3 (itself capable of up to halving the bitrate required vs AC3) or AC3 I’d recommend keeping it as they tend to already be efficient. They’re also universally compatible as codecs. Re-encode those big 1500kbps DTS tracks and those even bigger monster lossless Dolby and DTS tracks but I’d leave efficient codecs like AC3 alone.
Zedstrian
pipes
BlueTardis