Hi,

I will soon be able to play lc aac files from an usb stick in my car. The gear: Nothing special here, a simple 150 EUR car radio, 2 front speakers and 2 oval 14cm back speakers. The goal: putting as much stuff onto the usb device as possible, at adequate quality, i.e. no obvious degration in sound or artifacts.

I was thinking about converting stuff to -lc -br 100000 which will allow me to put 45 hrs. of stuff onto a 2GB stick.

Music will be from orchestral classical (I'll apply a limiter/expander on those) over idm to rammstein.

I reckon 100 kbps lc aac could be as artifact safe as ~140 mp3 lame/vbr...

What are your car encoding experiences, what do you think?

I reckon it should be very close to lame 130k. Best to try a few tracks in the car and see.

In a usually noisy environment like the car's one it's safe to say that you'll generally have a hard time noticing any artifacts even at low bitrates, because you're likely not to concentrate on the sound of your music as much as in the privacy of one's home. I'm speaking about comparable experiences of mine in conjunction with an Ogg Vorbis-capable car stereo here, which was always fed with -q1 (~80 kbit/s) files. I had made some tests with a few different tracks and bitrates (48, 64, 80, 96 kbit/s) prior to choosing the final one.

Surprise, in the car I wasn't able to clearly identify the 64 kbit/s material, though I gotta add that the installed speakers were rather cheap ones; yours might be a bit better. Adding the facts that usually I wouldn't just sit in the car, concentrating on the sound of my music, and hearing the motor noise as well, I decided this quality level to be sufficient. But since I had already encoded a 80 kbit/s collection for my flash-based portable player before, I sticked to it instead of creating a new 64 kbit/s one. The limited space savings weren't worth the additional amount of work in my opinion.

These experiences are transferable to Nero LC-AAC, as my personal ABX tests have shown so far. Under normal circumstances I can't distinguish LC-AAC and Vorbis from each other at bitrates in the 64 - 96 kbit/s range. Hence I'd suggest you to try some ~80 kbit/s encodings (-q 0.31) as well, though I wonder for what reason you're planning to go for a bitrate setting instead of a VBR one. The quality might audibly suffer from this.

Thanks for letting me know about your experiences.

-br <bits per second> -> Well, this is a vbr setting at last!? Or is it rather conservative in bitrate distribution?

It specifies an average bitrate, i.e. variations are present, but they're not aimed to quality as much as a pure VBR mode. I'd suggest going for one of the -q settings instead.

-lc -q 0.15: ~64 kbit/s
-q 0.31: ~80 kbit/s
-q 0.34: ~96 kbit/s

The actual bitrates might vary very much, depending on the contents you encode. Quality modes aim for a certain quality, not a specific bitrate. Don't let yourself confuse by your first encoding tests with the orchestral music you mentioned above. Due to classical compositions often consisting of many quiet parts, they're commonly encoded using comparably low bitrates. But throughout many different genres the bitrates I listed here should be about correct. At least in my case, while encoding around 2600 tracks, the -q 0.34 setting led to an average bitrate of 97 kbit/s.

Edit: Typo