Hello all!

I am new to this forum, but I hope I am posting in the right section.

Currently, I am working on a project where I need to upsample quite a bit of varied source material from 44.1KHz to 48KHz.

I need to convert an existing SACD-DTS project into a DVD-VIDEO/DTS project, and DVD only accepts 48KHz DTS while the SACD original contains 44.1KHz DTS. Sadly I do not have access to the original source.

As this is intended as a reference disc for high-end audio demonstrations I have to be very careful to keep degradation to an absolute minimum.

The only software I currently have at my disposal is iZotope RX and I am hoping that it can do the job well, as I am hoping to avoid the need to purchase additional software... not getting paid for this project

I am certainly not an expert on these things, which is why I feel the need to ask for advice, so to the point:

As I said I need to upsample 6 mono sources (L C R LFE SL SR) from 44.1KHz to 48KHz using iZotope RX.

Does anyone have any pointers as to how iZotope should be configured to produce a result that is as faithful to the source as possible? It would be interesting to hear the motivation as well, perhaps there are even several schools on how to do this properly
Given my ignorace regarding SRC algorithms, it would also be interesting to hear your thoughts on whether it is possible that the SRC may affect the phase of the audio at any part of the spectrum.

Regards,
Dave

What is SACD-DTS? SACD that was recorded, then converted to DTS CD? And you want to decode it, resample and re-encode to DTS again?


Linear phase SRC - no. Minimum phase SRC - yes, but generally only at high frequencies.

The source files I've been given are marked SACD-DTS, but honestly I cannot say how they've been produced and sadly, yes, I only have the DTS encoded version to work with (raw .dts files). Even though the DTS source is of exceptional quality, naturally I would have used the originals if I could, but they were apparently lost when the studio went out of business last year.

Decode, resample and re-encode... yes... I know... tell me about it ^^ Thing is I don't have much choice at this point, so yes, I am aware that I can never obtain reference quality (i realize that my previous post may have suggested that this is what I am trying to do) on the resulting dvd given the circumstances, but I really just want to do an as good a job as I possibly can, which is the main reason I am asking the pro's for suggestions

Probably an hybrid SACD with DTS on the CD track?

If you want to keep the original DTS stream, either:
-You can rename to .wav and burn on a CD.
-Try to make a non-compliant DVD.
-If you need video and/or a basic video menu, rename your .dts to .wav and use the Video-CD format. Video CD sound is CDA tracks. (You can play Video CD sound on a standard CD player. In fact, you can hack a standard CD player to pay VCD with a video decoding board. The SPDIF output will send DTS correctly. But, I'm not sure VCD-DTS exists, so a DVD player with on-board DTS decoding might not detect the stream.)


Otherwise, if DVD is absolutely required, here's a decompress-recompress solution:
http://forums.afterdawn.com/thread_view.cfm/722371

I'm not an expert... all of the following might be wrong...

As I understand it, upsampling is not usually a problem. I'd trust iZotope. With downsampling, you need to filter before resampling (low-pass anti-alaising filter). But with upsampling, you don't have to worry about any above-Nyquist frequencies in the original file, so filtering is not needed. I think the filtering is a bigger problem (more mathematically complex, requires more compromise, might introduce phase shift, etc.) than the actual resampling/interpolation part of the algorithm.

I suspect the DTS recoding will be the "weak link" in the process, and it might introduce some phase shifts... I dunno... If you can allocate the disc space, I'd use a higher bitrate than the original.

DragonMaster, thank you for your suggestions - however I absolutely do require DVD I have already built the menus and rendered three hours of video that visualizes the music, tracklists, current track/position/length that are to go on the disc. I am interested in your non-compliant DVD suggestion though, will see if I can even do this and if so see if it will play back on the target device. Interesting, software suggestions?

The article you posted was one of the first I found when trying to find answers to my questions, and I actually did use Tranzcode to decompress and split the DTS tracks into discrete channels, but used iZotope (default settings) for SRC. I am a bit worried about the quality of Tranzcode, but I ended up using the "real" DTS Pro Encoder instead of Surcode, because the Surcode DTS generated some extremely unpleasant clicks in the surround-right channel when played back on hardware DTS receivers (software decoders worked fine though, weird). Still waiting for a response from Surcode support. No way they're keeping my moniez if their software doesn't work properly.

DVDdoug, ah yes I do trust iZotope I was mainly inquiring about recommended settings. What I've been using so far is default settings, perhaps that's good enough... Yes, I have no doubt you're right about the DTS encoding being worse than any damage iZotope should be able to do. Perhaps I've misjudged this link, you think it is so bad the settings may not even matter much? My insight into what happens during DTS encoding is severely limited.

You need to filter for both up-sampling and down-sampling. The difference is that with up-sampling, you filter *after* the resampling. Say you want to up-sample from 8 to 16 kHz. Doing so creates a mirror image (aliasing) of the 0-4 kHz spectrum in the 4-8 kHz range. You need to filter that out otherwise the output will sound really bad. When considering rate conversions like 44.1<->48, the up-sampling and down-sampling do pretty much the same time (you use the same code), with just slightly different ratios and filter coefs.