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 obviously, but 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 😂), I used to use fre:ac because it included good encoders like FDK.
Anyway normally 224kbps is plenty with AAC, for stereo. Around 200 with opus or AAC I don’t hear the difference with flac (music).
For movies you have to consider the number of audio channels, if you have a surround sound setup. Migh be safer to go a bit higher for 7.1 or more channels, but I have no direct experience.
As I don’t want to reduce the quality of an already lossy codec, I’m instead comparing identical audio tracks of the same release that differ only in their codecs and bitrates. For instance, would a stereo 224kbps AC3 audio track be equivalent to a 128kbps AAC audio track, or is one of the two better than the other?
From a quick look on wikipedia, looks like AC3 does not support VBR. That is enough to make AAC twice as good at least, especially since movies have a lot of silence in them, so your ratio of 1:2 equivalence seems right to me
Sorry I edited my other reply heavily because I noticed later that you were interested in some exact bitrate numbers… I don’t know enough about AC3 to know an equivalent number, all I can say is those numbers I’ve written for opus and AAC are in my experience enough to enjoy any movie.