(Go to end for the conclusion) For those interested in compressed audio (mp3, ogg, flac etc) I thought I would share some of my recent experiences so others might be able to save some time in determining which format to use. Certainly the format choice will often depend on the device and system you plan to play them on. For the purposes of my testing I wanted a format that I could tolerate on my high-end home theater and audio system. And since we are dealing with a subjective and individual "perception" of "sound quality" my conclusions may not necessarily match those made by others. And finally, if you listen to music on cheap headphones and a portable mp3/music player, the distinction between the various formats and bit rates will be very negligible.
This recent interest in testing/comparing encoding methods came about from the past week of testing/installing various HTPC systems (Home Theater PC). I have been playing with MythTV, Freevo, myHTPC and SnapStream and will eventually do a review of these as well. From what I have seen so far, MythTV is the way to go if you run Linux, but be prepared for lots of tweaking and time to configure. If you need a mostly out-of-the-box solution for Windows, check out myHTPC but recording doesn't seem to work that well yet. SnapStream is also not bad but is really tied to proprietary 3rd party tools for program guide (but you can use XMLTV) and Internet Explorer. So back to audio encoders. About a year ago I decided to rip/encode all my cd's to mp3. This was before I knew much about the formats and just went gung-ho with mp3 all at 128kbs trying to save space and without any quality testing. First mistake. I soon found that many cd's and specific sounds (like Metallica's drums) and most bass just sounded lousy. I blamed it on bit rate and so re-did the whole collection of around 7000 titles. Second mistake. Well I still don't spend much time listening to mp3's on my main system, which is where I am often seated with a laptop, working. The reason is simply sound quality. Although many types of music sound tolerable (instrumental with predominantly high frequencies and few complex, overlapping frequencies), most music with wide frequency ranges, deep and complex low frequencies, just sound terrible. Although the sound is more tolerable when I am listening at my main workstation (Creative Labs SB Live-MP3-5.1, Advent AV-570's, 35wpc, Acoustic Research S108PS, 8" 120wpc Sub), many complex passages still sound lousy. So, I decided today that I would try out some different encoding methods, bit rates and compression schemes. Although I have not finished I did find some interesting and satisfying results. Test Piece: Tragically Hip, Fully Completely, Courage for Hugh Maclennan Note: Variables passed through GRIP 1) Ripped as .wav (45mb) (no compression, cd-quality) 2) Encoded as .flac (32.2mb) (-0 compression-min) flac -V -0 3) Encoded as .flac (30.6mb) (-5 compression-default) flac -V -5 -o %m %w 4) Encoded as .flac (30.5mb) (-8 compression-max) flac -V -8 -o %m %w 5) Encoded as .ogg (7.9mb) (q8 quality) oggenc -o %m -a %a -l %d -t %n -N %t -G %G -d %y -q 8 6) Encoded as .ogg (6.0mb) (q6 quality) oggenc -o %m -a %a -l %d -t %n -N %t -G %G -d %y -q 6 7) Encoded as .ogg (3.9mb) (q4 quality) oggenc -o %m -a %a -l %d -t %n -N %t -G %G -d %y -q 4 8) Encoded as .mp3 (10.2mb) (320kbps) lame -h -b %b %w %m 8) Encoded as .mp3 (6.1mb) (192kbps) lame -h -b %b %w %m 10) Encoded as .mp3 (5.1mb) (160kbps) lame -h -b %b %w %m Tools: Redhat 9 (2.4.20-18.9) grip 3.0.4 lame 3.93 flac 1.1.0 oggenc 1.0 Testing Equipment: Yamaha DSP-A1 (just used as a pre-amp) Adcom GFA-555 (200wpc power amp) Rega Planet CD-Transport (I used the Rega's Burr-Brown D/A converter) Klipsch KLF-30 Main Speakers Sound Dynamics THS-15 150wpc 15" Sub Audio Quest Viper 1 meter RCA Interconnects Audio Quest Crystal Hyperlitz bi-wired Speaker Cables Panamax 1500 Power Conditioner Compaq Presario Laptop running RH9 Testing Environment: Seated between the main speakers which were 10' apart, I was 10' from each speaker, toed in slightly to the center. Laptop on my lap I would start the original cd in the Rega and play the ripped/encoded file through XMMS and do A/B comparisons at the same sound levels. I will eventually re-do all the testing and set sound levels with a sound meter. MP3: Although the 320kbps bit rate made for almost tolerable sound, all 3 of the mp3's sounded dull, compressed and the bass just plain sucked big time and was often very audibly distorted. Unless I have done something wrong with the encoding parameters, or there exists a better encoder than lame, my mp3 days are gone. A/B switching between any mp3 and the original source was NOTICEABLY different (worse) from the original cd. Ogg: WOW!! Even the smallest 3.9mb ogg file sounded NOTICEABLY better than the 320kbps, 10.2 mb mp3 file. Playing the 7.9 (q8 quality) was "almost" indistinguishable from the original cd. I could only notice the slightest, and I mean slightest distortion at high levels with the bass. I was VERY impressed with the sound quality of ogg and hope to see the same results when I do more testing with other material. Flac: This is a lossless encoding scheme and so file sizes are significantly larger. The differences between the three compression levels was almost inaudible, and compared to the original cd, almost indistinguishable. However, once again it appears that it is the lower frequencies that show up the differences, although minimally. The bass on some passages of the test piece, when compared A/B to the cd source, was lacking in some resolution. Some "details" of the bass appeared to be gone, or muffled. But once again these were very, very subtle differences only noticeable after repeated listening sessions played over and over and various levels. Also, running 30 feet of standard rca cable from my laptop to the pre-amp may also be affecting the sound quality of these tests. Conclusions: MP3 is crap!! for anything but small, portable and less-than-audiophile-quality listening. If you need to save space and retain audio quality truly comparable to the original cd, then ogg is the way to go. And using the quality level of q8, you would be hard pressed to notice a difference, even at high levels. If it is near-perfect audiophile quality your looking for, and plan to play your music on a decent system, and have the disk space to spare, then flac is the best choice, even at the highest (-8) compression level. I plan to do more testing with other source material and hope that the results turn out the same. At the very least this relatively informal day of testing has shown me that all the time I spent ripping my music to mp3, was wasted time. Until I have the 250 gb's of space for all flac, I will probably go with ogg-q8 for now. <hr> <b><font color=blue size=4>Open Enterprise Solutions</font> <font color=red>Linux & Open Source Solutions for Business</font></b> Johnny Stork, B.A. Calgary, AB <a href="http://www.openenterprise.ca";> www.openenterprise.ca</a>
