How can I convert my AAC and MP3 audio files to FLAC?

I am not an expert, but as far as I know, FLAC is lossless compression. This is what you'd want to use when compressing a CD to a format if you don't want to lose any data from the original format. You can move between lossless compressed forms, but there's no use in moving from a lossy form (i.e., MP3, AAC, WMV, etc.) to a lossless form, since you've already lost data from the original. In fact, you're better off never moving from one lossy compression to another lossy compression (i.e., from MP3 to OGG), because you will degrade the quality of your data in the process. (I suppose in theory it would be possible not to, but it certainly isn't practical.)

I'd agree with the above, and not bothing with converting existing files. It will provide no practical benefit (other than ethical?) and if you ever want to play this music on most portables, you'll just have to re-encode it to something like mp3. If you still have the original cd's for any of your collection, you could re-rip them to FLAC. This along with ripping any new music to FLAC means that you can start building a lossless music collection.

Your mentioning of bitrate and "better than CD" quality indicate that you're missing out on a couple fundamental bits of info. 1. Compressed audio formats can be categorized as either "lossy" or "non-lossy". Examples of lossy formats are MP3, Ogg, AAC. These formats actually sacrifice quality in exchange for incredible compression, making the most of limited disk space. Lossy formats have a bitrate associated with them (or a "quality" setting), which allows you to determine what level of trade-off space vs quality is acceptable to you. Non-lossy formats, FLAC for example, do not sacrifice any quality in the transition. They make a perfect digital copy of every bit from the original source. The bitrate is not a measure of quality anymore, it's simply a measure of how much compression the software was able to achieve, without sacrificing any data. These files are generally much larger than lossy formats, and, in my opinion, the quality issue is negligible (FLAC vs 192kbps ogg, for example, sound the same to me). 2. Once information is lost, it cannot be recovered. If your source material is a CD, no software encoding is going to get you "better than CD" quality. You can't achieve a higher level of quality than your source material. Similarly, if your source is a 128kbps MP3, you aren't going to be able to make it sound better by re-encoding it as a 192kbps Ogg file, or a FLAC file. The information that got stripped out by converting to the MP3 is permanently lost. The only way to get better quality is to go back to your CD (or other high quality source material) and re-encode based on that. Like I said, my opinion is FLAC is overrated for most uses, and the good lossy formats are where it's at. I keep my music in 192kbps Ogg and it sounds beautiful to me. There have been some studies showing that as many as 10 transcodings have to take place before you really start sacrificing quality in an Ogg file, so I'm not too stressed about future portability. If hard drives in the 1-2TB range are available cheaply in a few years, I'll probably change my stance on this.

I'll admit...I have no idea of the answer. But I did a yahoo search. http://www.hydrogenaudio.org/forums/index.php?showtopic=29764 and http://www3.sympatico.ca/alexnn/alex/applescripts/iTunes_to_flac.html plus http://scriptbuilders.net/files/itunestoflac0.11.html How I found these: http://search.yahoo.com/search?fr=FP-pull-web-t&ei=UTF-8&p=itunes+and+flac

It's not necessarily true that you need MP3s for portable devices. My player (Cowon iAudio X5L) is great, it does MP3, Ogg, FLAC, and WMA formats.

http://www.dbpoweramp.com/ can convert from aac and mp3 to FLAC or ogg, whichever you would prefer. It will also convert as many files as you can shove in a folder. It is fairly simple to use and the codecs are all available off the front page. You may have to pay for the mp3 codec as it isn't free to them. I'm not sure if you will need that to convert from mp3 though.

Okay, thanks for the info. I was planning to convert my CD audio sources to FLAC. I guess the MP3 can just remain MP3. (All the AAC files came from CD sources.) But, (since they've all ready been compressed) is there anyway to add the same types of metadata found in AAC to MP3?

there is such a thing as OGG FLAC, which is flac in an ogg wrapper. that will support metadata for sure. but googling reveals that almost nothing understands ogg flac right now. there is a metadata data structure defined for flac, but i have no idea if any of the flac-creation tools actually support it. from flac --explain: -T, --tag=FIELD=VALUE Add a Vorbis comment. Make sure to quote the comment if necessary. This option may appearmore than once to add several comments. NOTE: all tags will be added to all encoded files.

http://mp3bookhelper.sourceforge.net/ supports FLAC tags. IIRC, they're the same type of tags as Ogg Vorbis. If you want the highest quality rips from your own CDs, be sure to check out the http://www.ubernet.org/?p=UberStandard. which is a pretty good guide. It assumes you're compressing to EAC but is easily adaptable to FLAC (in short: use User Defined Encoder in EAC, select FLAC.EXE as the encoder, use command line "--best %d %s"). Oh yeah, except EAC is a Windows app. I've heard it runs under Wine. Converting MP3 files to FLAC: although you won't lose any quality, it's a pretty silly move -- your files will be several times larger. Also, it'd then be difficult to tell which FLACs came from lossy sources and which ones didn't. You're probably better off just replacing them altogether with lossless rips. The nice thing about lossless is that it doesn't matter which format they're in; you can always convert to your preferred format without any quality loss (SHN or APE to FLAC, for instance).