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Demo material recommendation
I've performed an experiment with surprising results. The object of this
experiment was to evaluate lossy compression codecs. I decided to use an excellent piano recording of a couple of Rachmaninoff preludes as the material. I ripped these pieces to wav files, and converted the wave files to each of 5 different codecs: LAME mp3 at 256kb/s, for a 5:1 compression ratio LAME mp3 at 128kb/s, for 10:1 WMA9 at 64kb/s, for 21:1 WMA9 at 32kb/s, for 42:1 WMA9 VBR10, for 50:1 The VBR10 variable bit rate file was the smallest one that could be converted back to wav and subsequently burned to a CDR. This is what I did, putting all 5 compressed versions and the original wav file on the CDR in random order. I made 6 copies of this disc and passed them around to discriminating friends, with instructions to rate the fidelity of each file, and rank them in order. I didn't tell them what they should be listening for. All these friends have excellent audio systems, in one case costing over $40,000. So far, 2 people have returned their discs with their comments. Neither of them chose the original wav track as the best; neither chose the WMA VBR file as the worst, inspite of its 50 to 1 compression ratio! I'd like to expand this test to music having a wider dynamic and frequency range. I'd like some suggestions from the group of a classical selection running about 3 minutes that might be more revealing of codec differences than piano music. Try to pick something fairly easy to locate, and preferably a piece generally regarded as a great recording. I'll then rerun this test with the new material. Hopefully, the degradation of the highly compressed files will be easier to pick out. Thanks for your input, Norm Strong |
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In article , Chung
wrote: wrote: I've performed an experiment with surprising results. The object of this experiment was to evaluate lossy compression codecs. I decided to use an excellent piano recording of a couple of Rachmaninoff preludes as the material. I ripped these pieces to wav files, and converted the wave files to each of 5 different codecs: LAME mp3 at 256kb/s, for a 5:1 compression ratio LAME mp3 at 128kb/s, for 10:1 WMA9 at 64kb/s, for 21:1 WMA9 at 32kb/s, for 42:1 WMA9 VBR10, for 50:1 The VBR10 variable bit rate file was the smallest one that could be converted back to wav and subsequently burned to a CDR. This is what I did, putting all 5 compressed versions and the original wav file on the CDR in random order. I made 6 copies of this disc and passed them around to discriminating friends, with instructions to rate the fidelity of each file, and rank them in order. I didn't tell them what they should be listening for. All these friends have excellent audio systems, in one case costing over $40,000. So far, 2 people have returned their discs with their comments. Neither of them chose the original wav track as the best; neither chose the WMA VBR file as the worst, inspite of its 50 to 1 compression ratio! I'd like to expand this test to music having a wider dynamic and frequency range. I'd like some suggestions from the group of a classical selection running about 3 minutes that might be more revealing of codec differences than piano music. Try to pick something fairly easy to locate, and preferably a piece generally regarded as a great recording. I'll then rerun this test with the new material. Hopefully, the degradation of the highly compressed files will be easier to pick out. Thanks for your input, Norm Strong I have found certain piano solos to require high bitrates in order to sound good. Here are a couple of tracks you can try out, Certainly these are common enough so that you should find them in your local library: 1. Glenn Gould's Bach Two-Part Inventions and Three-Part Sinfonias. Sony Classical, SMK-52596. Track 1. 2. Glenn Gould's Goldberg Variations (the first recording). Track 1 (Aria). I have the Sony State of Wonder CD set. I find that Gould's clean playing style and miminal use of the sustain pedal somehow make it easier to tell the difference between mp3's and the original. Though I'm generally against using a piano for this literature, GG certainly did use minimal sustain, which is most appropriate. It bugs me to no end to hear baroque harpsichord and clavichord lit played on a Steinway with pedaling. Ugh! Speaking of piano, I did the Ravel G Major with Jeffrey Kahane this weekend. WOW! What a great artist, and such a fun work! |
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