Hello,

I am trying to convert my upgraded iTunes 256kbps VBR m4a files to an "optimal" mp3 format to play on my car CD/MP3 player. While I am electing mp3 to let me store more music on a single CD, I wish to retain as much of the m4a file's audio quality as reasonably possible... I realize I am going from one "lossy" format to another, but is there a "best practice" in doing so? I tried the mp3 encoder in iTunes, but found it buggy, so I am using the free MediaCoder Audio Edition.

I set the MediaCoder AE to mp3 (LAME codec) and enabled VBR (value 0/highest). Although, for example, MCAE reports the "transcoded" MPEG container's bitrate is 288kbps, the mp3 audio file shows as "128Kbps VBR"...

My questions are:

1) Is it not possible to retain the original 256Kbps VBR bit rate during the encoding into mp3?

2) Am I going about this the wrong way and/or is there a better approach?

I am new to this so any positive suggestions are greatly appreciated.

Thanks.

You could use ABR rather than VBR if you prefer to keep the bit rate approximately the same, though it wouldn't be recommended from a perspective of maintaining the highest level of quality possible. Your decision to use V0 is, in my opinion, a good one.

With any VBR encoder, you should expect certain tracks to have bit rates lower or higher than what is commonly touted as the "average". Depending on the files you're encoding, the average bit rate of LAME V0 may be significantly lower, approximately the same or significantly higher than the 245kbps "average" of V0. Always remember that VBR attempts to achieve consistent quality, not a consistent average bit rate.


Not really, no. If the goal is to transcode from AAC to MP3 while retaining a high level of quality, then I definitely feel like you're executing effectively on that goal. Some may argue that you may possibly be somewhat better off using a constant bit rate of 320kbps for your transcodes, but I wouldn't necessarily argue that.

assuming your car player cannot play m4a files? then i would just 'invest' into a pack of CDRW media and do some audio CDs from your lossy files... (lossy -> lossless).

Thanks, Ron.

I just tried "insane" 320Kbps CBR and it increased a 10MB m4a file to a 12 MB mp3... I can live with that if it turns out to be the closest to a "lossless" conversion of a "lossy" format...

I will keep tinkering. I appreciate you confirming that I am at least on the right path...

On a side note, I did hear some popping artifacts on the first (trial) mp3 I burned... would you assume that is from the 40x (max) burn speed my burner used by default, or bad mp3 ripping off a CD?

Thanks.

Well, there are two stages in which pops could be introduced during this process. The first is from the conversion from AAC to MP3, which would be incredibly unlikely if not entirely impossible. The second would be during the CD writing itself, and it's possible your media can't cope with being burned at 40X, but I think that's also fairly unlikely. If the discs are rated for that, they should generally be able to write at that speed.

First verify that the MP3s are okay by auditioning them as-is on your PC, then, if all seems okay, write a disc at the same speed but going through the extra step of verifying the burn (how you go about this depends on your burning app). If that goes successfully and you're still having issues with clicks/pops, there's something else at play here (as for what that could be I really don't have a clue).

Obviously if the original M4As have pops/clicks to begin with, you're unfortunately stuck with them unless you have the capability to re-rip the original CDs (if that applies here).

Just to add to hat Ron said, I would also make sure that your source disc is free from any scratches. I recently burned a CD-RW disc containing mp3 files. One of the files had pops and dropouts. It turns out that the file was burned right onto a scratch in the disc. My car's CD deck could not read the entire mp3 file so that produced those audible flaws. I hear this much more on damaged audio CDs, this was my first time experiencing this issue with a mp3 data CD.