Questions about audio bitrate

[rfg]

I have been using Handbrake for awhile now, and I've found it to be a fine tool. I always use Constant Quality settings, and never use either target file size or average bitrate when having Handbrake do transcoding for me. In general I don't care much about output file sizes because the output files are all just going onto a large capacity portable 2.5" drive that I then use sneaker-net to hand carry over to my HTPC in the living room.

The point is that the process of selecting the "right" video encoding settings for Handbrake is for me (mostly) a no-brainer. I just leave CQ set to around 20 and that's it.

I have noted however that, unfortunately, there does not seem to be an analogous "quality" slider in the case of the audio output encoding. I'd just like to ask "Why not?" For me at least, such a thing would be most helpful.

P.S. I have used Handbrake to transcode quite a lot of material. The pre-existing audio bitrates of these various files vary all over the place... from less than 64Kbps all the way up to 384Kbps. In the absence of a nice simple "no brainer" output quality slider for audio (that even an idiot like me could use) I think that the Next Best Thing would be if there was some way to induce Handbrake to automagically select the exact same output bitrate as whatever the current source file has. I mean it seems obvious to me that if the source file only has AC-3 stereo encoded at 64Kbps, then it would certainly be wasteful (if not to say downright pointless) to perform the transcoding (to AAC) with the output bitrate set to, say, 384Kbps, or even to the default 160Kbps. Am I wrong?

I suppose that the kinds of things that I've suggested above fall into the category of "enhancement requests", and that I should probably be posting them in the specific sub-forum dedicated to such requests. I will be more than happy to do that, but first I just wanted to ask here if there is something I am missing (e.g. if there is some other way with the existing handbrake releases to get what I want) an/or if people who know more about audio transcoding that I do... i.e. just about everybody on planet earth... think that what I'm asking for is fundamentally silly or idiotic in some way that is not immediately obvious to me, e.g. due to my deep ignorance regarding audio & video coding and codecs generally.

[GregiBoy]

I'd just use one of the Passthrough options and then you would get the original audio quality. This does depend on your playback device(s) and iOS devices require the first track to be AAC and I generally encode this at 128k as that is all that is necessary for them (except the ATV) and then include the AC3 passthrough.

The audio track takes up little space compared to the video, no matter what the bitrate but as you have noted, there can be a huge variance in the original source depending on how it is authored.