I recently started using AAC instead of LAME MP3 to export multiple tracks. Compared to the LAME export options, I find the single slider to be somewhat puzzling. Using numbers from 10 to 500 as a figure of merit doesn’t give me any point of reference to say, iTunes or even some kind of average bitrate. I realize that AAC uses variable bitrates, but certainly the configuration UI could give me something to hang my hat on.
Even if the current slider UI were to be retained, it might be beneficial to display some kind of subjective indication of the kind of quality being produced (such as “telephone”, “AM”, “FM”, “CD”, “studio”, or maybe “medium”, “standard”, “extreme”, “insane”), that would update as the user moves the slider through the ranges.
Barring that, a prominent table in the documentation that describes what the numeric setting yields, quality-wise or size-wise would be appreciated.
I suspect they did that because the actual description of what’s happening isn’t easy. The 10,000 foot view (3048M) is AAC can get the same quality at one jump less bit rate than MP3. 192 AAC is roughly equivalent to 256 MP3, but it’s not a linear transition. It gets messy down where they start to fall apart. I can’t believe that AAC-32 is equivalent to MP3-64. It would be nice…
As the coding schemes get more complex, they depend more and more on the type of content – and take longer.
The Wikipedia article is pretty clear if you scan down past all the technical jargon.
In the land of video, it got ridiculous. Everybody fell in love with h.264 and left us with the coding task. Let’s see. It’s Midnight on the west coast and with high-quality two-pass, we’ll have your short video by… about… 2PM.