Nerd alert!

After popping the DVD-V disc of Deadwing SE into my computer, I noticed that the DTS 5.1 version of the album played back more quietly than the PCM stereo version. I had already noticed that the CD version of the album was mastered with some pretty aggressive limiting, although unlike some other CDs, I don’t notice any distortion or crackling as a result, just a lack of headroom. To me, this translates into how much the music is allowed to breathe. But to be honest, the quieter passages of the album are given a decent amount of headroom in the stereo mix.

So, like any other audio nerd, I wanted to see if I could rip the DTS track, mix it down to stereo, and apply just enough tweaking to get a version of the album on CD that had more dynamic range than the official stereo mix.

I’d never even considered listening to DTS audio outside of DVD playback, but I knew that DVD Decrypter supported raw stream ripping. I used it to rip the full DTS streams off the DVD-V disc as .dts files, which Foobar 2000 can play with the foo_dts plugin. Since I didn’t have any experience mixing down 5.1 to stereo, I found two other FB2K plugins that did: ATSurround and Channel Mixer. I ended up using Channel Mixer to do the mixdown since it supported a “stereoimage width” parameter and level controls for center, rear, and subwoofer mixdown. I used the 1.25 setting on the stereoimage width, 0.9 for center and rear mixdown, and 1.0 for subwoofer mixdown. I also applied a little low-end EQ (-5dB@55Hz, -2dB@77Hz, -1dB@110Hz) to tame the bass. Playing back the DTS with these settings produced a stereo mix that sounded pretty decent and peaked at about -4.5dB. I took that into Sound Forge and used the Wave Hammer plugin to limit at 6dB and maximize. This trimmed the peaks while still leaving plenty of headroom.

deadwing-wavs

Waveforms of the initial crash of the title track of Porcupine Tree’s “Deadwing”. From top to bottom: my rejiggered DTS downmix, the official stereo mix from CD, and the official stereo mix from the LPCM track of the DVD-A (which is 48kHz, 24-bit, but has similar amplitude).

Example:
Deadwing “Official Mix” (23 sec)
OGG
(463k)
MP3
(562k)
Deadwing “Alex’s DTS Downmix” (23 sec)
OGG
(477k)
MP3
(526k)

Listening to my downmixed version compared to the official stereo mix, the difference in volume is quite apparent. Also, I can hear phase problems with the drums in certain areas, and, of course, the panning of many of the musical elements is different. The dynamic range of my version is greater, but because of the discrepancies I can’t say I prefer it to the official stereo mix. I’d like an official stereo mix that had more headroom, but I guess that war has already been lost. Louder is better, right?