Obvious iTunes/AAC conversion question

[RonM]

But I don't know the answer.

I'm not sure of the bitrate of the current (plus) versions of files from iTunes, and am not sure that would tell me the answer anyway.

I generally use dBpoweramp to rip CDs and convert files. I use it to convert my iTunes AAC files (although my primary app, Squeezecenter/Squeezebox, now supports AAC directly). I will continue converting because other apps I use don't do AAC.

The question is, what is the optimal target bit rate to use, one that preferably captures whatever data is in the original file? Obviously, a lossless format would do but at the cost of very much larger filesize.

I'm mostly converting to WMA, but sometimes to MP3. It's a random thing. . .

Suggestions?

Ron

[LtData]

Re: Obvious iTunes/AAC conversion question

Various tests show that normally around 192kbps-224kbps, especially if VBR is used, most people can't tell a difference between the CD and the rip, though this varies from person to person and also depends on equiptment.

[RonM]

Re: Obvious iTunes/AAC conversion question

That's for ripping; I was wondering about converting.

The objective is to capture as much of the original data as possible; when ripping I always rip to two files -- lossless (for use on my main system and as backup) and lossy (for use on my portable devices). Dbp is perfect for this, since it can be set up to do it.

I'd prefer not to lose more data from an already lossless original, hence my question.

As I understand it, the compression algorithms identify adjacent sample points that are the same, or that are sufficiently similar given the quality target, and recodes them as the same but without individually describing each point. The lower the quality setting, the broader the definition of "sufficiently similar".

If this is essentially correct, then converting from one lossy format to another may not result in significant additional data loss. If the two formats have similar quality settings (bit-rate settings), the conversion algorithm may not identify many opportunities for further compression, since those opportunities have already been identified and implemented.

I'd say that the best choice for a conversion setting (AAC to MP3, for instance) would be to choose an MP3 quality setting just above that used to create the AAC file in the first place.

My knowledge here is pretty shaky, and I'm assuming parallels with image compression. So I might well be wrong.

Ron

[RonM]

Re: Obvious iTunes/AAC conversion question

I'd prefer not to lose more data from an already lossless original, hence my question.

I meant to write ". . . from an already LOSSY original. . ."

R.

[RonM]

Re: Obvious iTunes/AAC conversion question

Still no response.

If I'm converting iTunes AAC files (as downloaded from iTunes, in the plus format) to WMA, say, am I ok using quality setting 95? 98? or will both of those lose some detail, even if not particularly audible, and I should just bite the bullet and use lossless? Yes, I know, AAC is already lossy, but I'm trying to keep from losing anything MORE when converting.

What about converting to MP3?

R.

[Spoon]

Re: Obvious iTunes/AAC conversion question

Any conversion to lossy removes some detail, the higher the bitrate the less is lost. Lossless is the way to go.

[ed_315]

A WAV to AAC (Nero) Failure...

Hello everyone
I'm not a good english writer, as you can see...

I have a "problem" I've got dbPoweramp Reference 13
When I try to convert a .wav file to .aac one, using the AAC Encoder, the ouput files are: one file containing the ".tmp" extension (with the right size), and the other one is a ".aac" (of 0 kb)...both unrecognizable for the dbPoweramp
All the neccesary files (mp4creator.exe, NeroAACEncoder, Encoder.txt, Toaac.bat and the Nero.bmp) are stored properly (in dbPoweramp>>Encoders>>AAC)
What's wrong?
I'm using other software instead...:(

[Spoon]

Re: A WAV to AAC (Nero) Failure...

Have you tried to create m4a files instead? (that contain AAC)? My guess is the AAC encoder is failing on the last step to extract from an m4a file the aac file.