80 kbps personal listening test (summer 2005)
Reply #63 – 2005-07-12 17:16:46
Back to the upcoming MP3 96 kbps Pool. I have encoded the second group of 35 various samples, and bitrate was significantly higher than the average one obtained with the classical group.iTunes classical = 100 kbps iTunes various = 104 kbps => with iTunes, the bitrate for the second group is within the +/- 10% tolerence I've fixed. VBR is possible I'd say Audition q30 classical = 96 kbps Audition q30 various = 112 kbps => with Audition, the bitrate for the second group is 20% higher than the target bitrate. Even if I admit that the average bitrate for these 35 short samples doesn't entirely correspond the the average bitrate of full albums, it's clearly too high. As a consequence, I've lowered the setting to VBR q20. Lowpass is automatically adjusted, but doesn't significantly drop (from 14780 to 14440 Hz). Bitrate:Audition q20 classical = 89 kbps Audition q20 various = 102 kbps => bitrate is now within the acceptable range for both group. However, bitrate for classical now reaches the critical limit of 87 kbps (96kbps -10%) and is not fully comparable with the bitrate obtained with iTunes (100 kbps). Then I've tried VBR q25. It's a manual preset, and there's no defaulted lowpass value for manual VBR setting. I've therefore choose 14600 Hz. Bitrate:Audition q25 classical = 92 kbps Audition q25 various = 107 kbps => excessive deviation with the second group (+11...12%) At this stage, I have four possibilities:1/ Using Q20: bitrate is OK for group2, bitrate is OK for group1 but too low when compared to iTunes at 100 kbps.2/ Using Q25: bitrate is OK for classical, but is too high for group23/ Trying Q22..23 in order to obtain an unlikely better compromise => in all cases, the selected setting can't be the optimal one for none of both musical category.4/ Using two different settings for the two different groups. To me, this possibility makes sense. As someone planning to encode classical only, I won't choose anything else than VBR Q30 which match the desired bitrate. If someone plan to encode something different, he won't probably happy with Q30 (~110 kbps) and will certainly go for Q20, and even maybe a slightly lower setting. The dual bitrate problem will also occur with other listening tests. All VBR encoders can't output the same bitrate with different kind of samples. It can be experienced with faac, Nero AAC, Lame MP3, Fhg MP3, MPC, WMA9 and WMA9Pro. In all case, I will have to make compromises which probably not correspond to the users' choices. Using two different settings (each one corresponding to the rational choice of someone listening to either "various music" [yes, the concept sucks] or "classical music"]. I could also play a dangerous game: testing iTunes and Audition VBR encodings at an excessive bitrate, cross my finger and hope to see LAME win. The scenario is possible I'd say. iTunes has clearly no chance to pass the pool even with a winning bitrate; but I'm less confident with a contender such as Audition. I feel that solution 2 (Q25 for both group) and solution 4 (Q20 for various, Q30 for classical) are the two more pertinent. What would be the best in your opinion?
Wavpack Hybrid: one encoder, one encoding for all scenarios WavPack -c4.5hx6 (44100Hz & 48000Hz) ≈ 390 kbps + correction file WavPack -c4hx6 (96000Hz) ≈ 768 kbps + correction file WavPack -h (SACD & DSD) ≈ 2400 kbps at 2.8224 MHz