Radium hack, 128kbs, hq
Internal codec in Producer Pro 2.1, 128kbs, hq
Cool Edit 2000, 128kbs, qual9
(Sound Forge 4.5h, 128kbs, "highest quality")
(Sound Forge 4.5h, commp3.dll, version 1.0, build 219
128kbs, "fastest")
Notes by ff123
Fhg 1.0 build 63i, as found in Producer Pro as an internal codec and in the "Radium" hack as an external (ACM) codec (where its version is1.2 build 63i), mangles a completely out-of-phase signal when it uses joint-stereo. I first noticed this on an old version of l3enc when I tried to code a channel identification test track from a CD which includes an out-of-phase male voice. This characteristic existed all the way up to mp3enc 3.0. In version 3.1 of mp3enc, Fraunhofer changed the codec so that this no longer happens (mp3enc is Fraunhofer's reference encoder - it is the only one which is consistently updated).
The following graphs show what happens when I encode a test tone sweep generated by Sound Forge (4.5 to 22kHz) which has had its right channel inverted with respect to the left. The 1.2 build 63i codec, when in joint stereo, starts filtering an out-of-phase signal at 8.6kHz.
This characteristic of the codec does seem to affect certain tracks of music. See my Audio Samples Page for a clip (ma11short.flac) on which this codec fails miserably. The file has been losslessly compressed using the FLAC format.
Interestingly, the internal codec in Producer Pro 2.1 shows some ripple out past 16kHz, implying that the two codecs are slightly different. Another interesting thing about this codec (plot not shown) is that the cutoff for the normal (non-inverted) sweep occurs out at 20kHz. For some reason, the cutoffs for sweeps are not the same as the cutoffs for actual music.
The low-pass cutoffs for the Xing and QDesign encoders are also unusual: near 20kHz for Xing, and not at all for MVP.
Addendum (Nov. 11, 2000): I didn't notice initially that the level for Sound Forge 4.5h's Fastenc is actually attenuated by about 8dB when compared with the levels on all the other graphs. There is a bug in Recent FastEnc implementation.
Click on the thumbnail images to zoom.
| Codec | Frequency Response |
| FhG 1.2 build 63i Radium hack, 128kbs, hq |
|
| FhG 1.0 build 63i Internal codec in Producer Pro 2.1, 128kbs, hq |
|
| FhG MP3ENC 3.1, 128kbs, hq | |
| FhG "Alternate-bad" codec Cool Edit 2000, 128kbs, qual9 |
|
| FhG "Alternate" codec (Sound Forge 4.5h, 128kbs, "highest quality") |
|
| FhG "FastEnc-bad" codec (Sound Forge 4.5h, commp3.dll, version 1.0, build 219 128kbs, "fastest") |
|
| Xing plugin for AudioCatalyst 2.1, 128kbs | |
| QDesign 1.2.51, 128kbs, high quality | |