this post was submitted on 13 Mar 2024
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AAC vs AC3 bitrates (lemmy.dbzer0.com)
submitted 8 months ago by Zedstrian@lemmy.dbzer0.com to c/piracy@lemmy.dbzer0.com
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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?

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[–] pipes@sh.itjust.works 15 points 8 months ago* (last edited 8 months ago) (1 children)

Hi Zedstrain If compressing, why not opus? AAC is almost as good but you have to make sure you're using a good encoder, and its licensing is not as open.

Anyway I found this table, next to "Music Storage", it shows the suggested bitrate values depending on the number of audio channels, from 96 to 450. Should applicable to movies, and to AAC (maybe adding 10% bitrate?).

For movies I'd use these values personally:

2 channels: kbps 128 (150 AAC)

6 (5.1): 196 (224 AAC)

8 (7.1): 256 (300 AAC)

[–] Zedstrian@lemmy.dbzer0.com 6 points 8 months ago (2 children)

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?

[–] pipes@sh.itjust.works 5 points 8 months ago

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

[–] pipes@sh.itjust.works 3 points 8 months ago

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.