rating audio tracks quality

[spoRv]

Let's talk about audio tracks found on common released media, so leave out AAC, MP3, FLAC and others; MPEG multichannel, even if it could be found on DVD, it is really uncommon (I think maybe I have one title with this codec).

So, given the fact the audio mix is the same, as the number of channels and bits used, I think this could be the chart of most common multichannel audio tracks, from best to worst quality:

1. PCM/DTS-HD MA/Dolby TrueHD (all lossless)
   
2. DTS 1509/1536kbps (full rate)
   
3. Dolby Digital 640kbps
   
4. Dolby Digital 448kbps
   
5. Dolby Digital 384kbps
   
6. DTS 755/768kbps (half rate)
   
7. Dolby Digital 320kbps
   

(DTS found on laserdisc should be equiparable to the full rate found on DVD/BD, apart the sampling frequency)
don't know where to place Dolby Digital Plus.

Do you agree?

[zoidberg]

As I understand it Dolby Digital plus is classed as an HD audio format with a core of 640kbps, so it (should) be superior to ac3 640kbps.

[captainsolo]

The key is checking source and track quality in audio editing software. This is something I hope to do when I finally build a PC, but it really has gotten to the point, as with digital music releases, that one has to import the audio and check the dynamic range and levels overall between sources. Many LDs I've collected for their soundtracks were unfortunately sourced from lower generation print materials so that their PCM audio can be hissy, scratchy, full of noise or degraded in comparison to the cleaner DD 2.0 DVD audio. But then again, at times the later track can be reduced in dynamic range and over-cleaned leaving the old noisy track preferable.

I guess what I'm trying to say is that the technical numbers are not always the most reliable sign of quality.

[zoidberg]

I think spoRv is thinking in terms of 'best case' ie the same master encoded via the different codecs.

[spoRv]

I think spoRv is thinking in terms of 'best case' ie the same master encoded via the different codecs.

Exactly; I started the thread thinking about a choice I should make: better a 448kbps AC3 (albeit PAL, that needs to be converted to 23.976fps), o a 755kbps DTS (with its high frequency rolloff)?

As by many DTS Full bitrate (1509/1536kbps) sounds as good as 640kbps AC3, mathematically a DTS Half bitrate should sound as good as a 320kbps AC3, hence a 448kbps must sound much better... in theory, of course!

[captainsolo]

Ah.....good idea then.

Wait, half bitrate DTS has a rolloff?

[jerryshadoe]

I agree that to truly rate an audio track, you need to look at the spectral analysis of it and "contrast-and-compare" it to whatever secondary source you have.

[ilovewaterslides]

I don't understand how a half-bitrate DTS soundtrack can be worse than a AC3 384 kbps one.  
Same number of channels, similar type of compression but twice the bitrate. How can it be worse?
When I get a DTS track on a DVD I'm usually happy with it as it is less compressed than the regular AC3 tracks.

[spoRv]

Because they use different compression algorhythms... it's like MPEG-2 and H.264... how can the latter be better at less than half bitrate than the former? Same answer for AC-3 and DTS.

Also, do not forget the high frequency rolloff of the DTS half rate.

Said that, I love DTS, but, if I should pack more tracks in a single file, and space is a concern, I'd go with a smaller AC-3 version of comparable quality.

[ilovewaterslides]

Fair enough. People used to say that with AAC over AC3 which in my opinion is pretty stupid. I still prefer AC3.
Your point about DTS seems to be spot-on anyway. I heard about it before but I wasn't sure. Will have to compare all of my DVDs for that matter