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About this siteFor six years, the Internet Nexus served as my technology blog, but I've since started blogging at the SuperSite Blog instead. If you're looking for the blog, please head there. --Paul Thursday, April 29, 2004iTunes 4.5 and WMA transcoding iTunes 4.5 just completed transcoding the WMA portion of my music library, or about 700 songs. It took the application 5 hours to do this, on a Pentium 4 2.8 GHz system with 768 MB of RAM. That seems a bit excessive, but hey, you only have to do it once.
A number of people wrote in, taking exception to my "sounds like crap" comments about transcoding. As I suspected, however, none of these people had actually spent time transcoding. So let's look at how this works. Each audio codec, be it WMA, MP3, AAC, or whatever, uses its own compression scheme. That is, when you encode a song in one of these formats, the encoder analyzes the song, picks out the parts it can drop, and then morphs the song into a compressed file that is smaller than the original. If it does a good job, it drops the parts you wouldn't usually hear, though true audiophile often point out that any compressed file is unacceptable. To most people, however, compressed files can sound great if they're encoded right. And, generally speaking, higher quality encoding schemes, like WMA and AAC, can create higher quality compressed files at lower bitrates than lower-quality encoding schemes, like MP3. That is, in my experience, a 128 Kbps WMA or AAC file sounds identical to a 160 Kbps MP3 file, and the resulting WMA/AAC files are smaller. When you transcode, you convert one compressed file into a different compressed format. Because each format has its own compression scheme, however, you're now converting a lossy compressed file (with certain bits missing) into another lossy compressed file (with other bits missing). Best case, the results are OK, but you can generally hear the difference with over-the-air speakers, and can always hear the difference with headphones. Worst case, they sound like crap. Any time you move from one format to another, you're just going to lose quality. It's a fact. My personal experience with transcoding is actually pretty vast. I've now ripped my entire CD collection to disk at least three times, once in WMA format to the PC, once in MP3 format to the Mac (with iTunes), and once to MP3 format to the PC. I used to use a Microsoft audio conversion tool to move files from 160 Kbps MP3 format to 64 Kbps WMA to best utilize the odd 40 MB disk limit of a Iomega portable audio device (this seems quaint in the days of 40 - 60 GB portable devices, eh?). More recently, I converted my 250+ iTunes Music Store-purchased Protected AAC songs to CD, then re-ripped them back to the PC in 128 Kbps MP3 format so I could have clean, unprotected versions of the songs that would work in any media player and portable audio device (I've switched from the iPod to a Dell DJ). In all the transcoding I've done, the results were similar regardless of the formats. The resulting songs are generally tinny sounding, with muddy bass. But again, it's better than nothing. Well, now I've transcoded almost 700 songs from WMA to AAC using Apple's new converter in iTunes 4.5. I'm happy to report that the results are decent within the confines of the limitations of transcoding. Yes, there are obvious issues with tinniness, but these are more obvious with headphones, and less so from the PC speakers. I haven't listened to every song, of course, but I do have a selection of three songs I've set aside specifically for testing purposes, and I've been analyzing how they sound compared to online store-purchased WMA and AAC originals. They exhibit the same issues I've described again, but... you know, they're not horrible. Unless you're an audiohphile, I guess. The end result, of course, is that I'm still surprisingly positive about iTunes 4.5. Good stuff. [ Posted at 4:07 PM | Permalink ]
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