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Cannot play DTS-CD in pass-through mode with M-Audio Transit USB

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Fonzo:
I'm currently using the latest trial-version of MC12 and the software is just brilliant and on this extensive forum I already solved a lot of small playback issues and codec settings. There is however a problem I cannot solve:

I connected a M-Audio Transit USB to my Sony DTS-receiver through optical SPDIF TOSlink. I use ffdshow from the latest CCCP codec-pack. When playing DTS-content from DVD in MC12 -such as Donald Fagen's Kamakiriad- the signal is passed-though correctly, using the "Dolby Digital/DTS pass-through 16-bit / 48000Hz" option in the M-Audio control panel and the ASIO playback setting in MC12 itself. The sound quality is absolutely stunning. :)

However, when playing .dts/.wav files, DTS-CD-images (on my hard disk as .cue with.wav files) or loaded in a virtual drive (.ngc and .img), the signal can only be played when selecting the "2-In/2-Out, 24-bit, 8000 – 48000 Hz" option in the M-Audio control panel. The output to the speakers is 5.1 and the receiver indicates DTS 3/2.1 output, BUT I noticed a quality difference between these two M-Audio control panel options mentioned above when playing DTS-DVD. Output though "pass-through" just sounds better. I already tried ASIO4ALL as alternative driver in MC12, but nogo. I also found some related topics on this forum: http://yabb.jriver.com/interact/index.php?topic=39539.0 and http://yabb.jriver.com/interact/index.php?topic=39200.0. I setup ffdshow correctly (I guess) using glynor's Wiki DTSWAV article: DTS (and AC3) are set to SPDIF, DSP inside MC12 is disabled. But there is no way I can use "pass-through" when playing .dts/.wav files or DTS-CD images. I assume the bitstream is handled by the M-Audio itself and send through SPDIF to my receiver, rather than passed-through and handled by the receiver itself which only works when playing DTS-DVDs. The latter sounds much better.

Any suggestions?

Alex B:
DTS audio CDs have the DTS signal coded inside standard 44.1 kHz/16-bit Red Book CD audio format. You should not let the output go through DirectShow filters that may alter or process the signal.

MC12 is capable of bit perfect 44.1 kHz/16-bit PCM playback (from wav or losslessly compressed files or from standard CD-audio). Inside MC you must disable everything that is related with DSP including the internal volume and replay gain adjustments.

An ASIO driver is needed for bypassing the Windows kernel mixer. Also the soundcard & its drivers must be capable of bit perfect 44.1 kHz pass through (but this should fine with the Transit).

Fonzo:
Thanks for your quick reply.

I already assumed I have to somehow bypass the DirectShow filters. Everything in DSP is already unchecked. 'System Volume' is selected in Player ==> Volume. I forgot to mention, when playing .dts and .wav files in combination with the M-Audio control-panel option "Dolby Digital/DTS pass-through 16-bit/48000Hz", MC12 pops up with the following dialog:

(1) "The ASIO device 'M-audio USB ASIO Interface' does not support the sample rate of 44100Hz".

Followed by:

(2) "Playback could not be started on the output 'ASIO using the format '32 bits Per Sample, 2 Channels'.
This output may not be supported by your hardware. You can use DSP Studio to change the output to a compatible format. Also, make sure that you system has a valid sound playback device and that it is properly configured in playback options."

And now it's getting rather interesting: when selecting the "ASIO4ALL v2" drivers instead of the "M-Audio ASIO Interface" in Outout Mode Settings, the two error messages above are gone. The .dts file is playing and I can see the Spectrum Analyzer bargraph. But alas, there is no sound an no DTS indication on my receiver.

I fiddled around with the Channel Offset settings and changed it from 1 to 6, but this only results in a dialog box which indicates 'ASIO Start Return Value: -1 (should be 0) and 'Plugin Open Return Value: -1 (should be 0)' folowed by the same second dialog box mentioned above (2).

Any clue?

Alex B:

--- Quote from: Fonzo on May 09, 2007, 11:56:18 am ---Thanks for your quick reply.

I already assumed I have to somehow bypass the DirectShow filters. Everything in DSP is already unchecked. 'System Volume' is selected in Player ==> Volume. I forgot to mention, when playing .dts and .wav files in combination with the M-Audio control-panel option "Dolby Digital/DTS pass-through 16-bit/48000Hz", MC12 pops up with the following dialog:

(1) "The ASIO device 'M-audio USB ASIO Interface' does not support the sample rate of 44100Hz".

Followed by:

(2) "Playback could not be started on the output 'ASIO using the format '32 bits Per Sample, 2 Channels'.
This output may not be supported by your hardware. You can use DSP Studio to change the output to a compatible format. Also, make sure that you system has a valid sound playback device and that it is properly configured in playback options."

And now it's getting rather interesting: when selecting the "ASIO4ALL v2" drivers instead of the "M-Audio ASIO Interface" in Outout Mode Settings, the two error messages above are gone. The .dts file is playing and I can see the Spectrum Analyzer bargraph. But alas, there is no sound an no DTS indication on my receiver.

I fiddled around with the Channel Offset settings and changed it from 1 to 6, but this only results in a dialog box which indicates 'ASIO Start Return Value: -1 (should be 0) and 'Plugin Open Return Value: -1 (should be 0)' folowed by the same second dialog box mentioned above (2).

Any clue?
--- End quote ---

Let's make one thing clear first. Are your files ripped from 5.1 DTS Music Discs ?
(- similar to these: http://www.5point1.com/Products-5_1_DTS_Music_Disc_2.html)

If yes, then you should not use anything that you would not use for bit perfect PCM 2-channel stereo playback through SPDIF. The used software and drivers should not be "aware" of the special nature of this audio signal. If you can play 44.1 kHz PCM stereo bit perfectly through SPDIF then you can play 44.1 kHz DTS .wav files or mounted disc images too. The only difference is that your external DTS receiver detects the signal and decodes it. If the files are ripped from DTS CDs you should not use the .dts extension.

If the files are 48000 kHz and not in a wav container (possibly extracted from DVD video) then you may need to find suitable DirectShow filters and settings for bit perfect pass through. This may not be easy.

A couple of years ago I wrapped some extracted 48 kHz DD audio tracks succesfully in the Matroska container file format for pass through playback, but I have not tried DTS. This thread has some info about that: http://yabb.jriver.com/interact/index.php?topic=26055.0.

Fonzo:
Note sure, these files are all below 800MB and the bitrate is 1.411 (or 44.1 kHz) in MC12. So, I guess they're from 5.1 DTS Music Discs. I have .wav with .cue file and a mounted DVD-RIP image (from Beethoven, can't help it) of which MC12 says they're both 44,1kHz, but refuses it to play in the M-Audio's DTS/DD pass-thru mode. Full DVD is played through the NVIDA decoder (or whatever suitable coded such as AC3filter) and SPDIF in pass-thru mode. I also have some some .dts single-track files, which only play if I rename the extension to .wav, otherwise MC12 says the M-Audio USB ASIO Interface does not support 6 output channels. Same problem when I switch to the ASIO4ALL driver.

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