bit perfect SPDIF recording... Options

[psme]

hi,

I know the topic has been asked before but I couldn't find a clear answer...

My setup:
PC A as spdif source, onboard spdif coaxial output, Win7 64bit, foobar2000 with wasapi plugin, 44.1khz 16bit wav dts file downloaded from http://www.kellyindustries.com/sounds.html#dts output to a Pioneer receiver, receiver correctly see the spdif as DTS

PC B as spdif recorder, sound card is M-Audio Audiophile 192, Win7 32bit, sound card driver downloaded from m-audio website, in the driver panel, it sees the external spdif source correctly in 44.1khz, external spdif clock is selected and locked

I tried a few audio recording softwares, such as REAPER, wavosaur, Cool Edit pro etc, the resulting recorded wav file when playback on the PC A, the Pioneer receiver does NOT go to DTS and only output white noise.

According to the post in this thread, a user tested M-Audio Audiophile 192 works in bit perfect SPDIF recording, but detail system and software is not mentioned...
http://www.gearslutz.com/board/so-much-gea...ecording-2.html

Please give me some hint! Thanks in advance.

[probedb]

Do you need to put a specific WAV header in for DTS audio? I'm guessing the software you mentioned understands the input but is putting a 16-bit 44.1Khz stereo header? I could be talking rubbish of course

[AndyH-ha]

S/PDIF is simply a way to transfer digital data from one place to another. The receiving end must understand what the data is and process it accordingly. As example, take a simple single channel 44.1kHz sample rate audio file transferred over S/PDIF. If you set up the receiving program to believe the data is at a higher or lower sample rate, that is what it will write. The resulting playback with be too fast or too slow, even though the data is exactly the same.

I don't know about the capabilities of the programs you used at the receiving end but some may not be capable of creating a DST format file. Any that are would need to be told specifically what the input is and what they are to do with it. You can't simply say it is a 44.1kHz stereo file and then expect a DTS decoder to understand the finished product.

Also, unless you have no other way of communicating between the two computers, S/PDIF would not be the means of choice. Copying the file onto a flash drive or USB hard drive, or sending it over ethernet, is easier, faster, and more reasonable.

[Juha]

AndyH-ha is correct when saying recording software you already mentioned isn't capable for DTS recording.
Why?
Because of those all records mono/stereo wav files --> to get DTS stream recorded you need to extract each DTS channel to separate audio tracks.

I suppose there's software for "recording" (copying) from DTS sources through digital path but, I don't know one for sure (there's software from Hermann Seib called VSTHost which allows to set #channels to be recorded but, as I have never tried if it works with multichannel input streams through S/PDIF ...).

(Creative has some audio interfaces where you can set the recording through S/PDIF to be bit-matched. Maybe they have software included for to capture the data as well.)


As suggested, copying is the easy way to go.

Juha

This post has been edited by Juha: Nov 5 2011, 06:45

[Alex B]

Actually, the data stream in a DTS wave file is stored exactly like a standard 2 channel PCM audio stream. It is quite possible to verify the recording system's bit-perfectness by recording a DTS wave file that is played as a stereo wave file (i.e. without running it through a DTS decoder) and transmitted through S/PDIF. If the bits do not change, the recording can be saved to a new 2 ch wave file that performs exactly like the source DTS wave file.

I have tested a setup that can record through S/PDIF without changing the content anyhow. I have explained it here: http://www.hydrogenaudio.org/forums/index....st&p=626748

I am guessing that the OP didn't use the M-Audio ASIO driver (to bypass the Window mixer) and/or a recording program & settings that do not dither or otherwise alter the content.

For some uses, like transferring the contents of digital audio tapes to a hard drive, bit perfect S/PDIF recording might actually be useful. As said, for copying DTS files there are easier and faster methods.

This post has been edited by Alex B: Nov 5 2011, 17:35

[psme]

Thanks for the feedback. I got it working!

1st setup:
- source: PCa onboard spdif output, win7 64bit, foobar2000 wasapi
- recorder: PCb M-Audio 192 spdif input, win7 32bit

2rd setup:
- source: PCb onboard spdif output, win7 32bit, foobar2000 wasapi
- recorder: PCb M-Audio 192 spdif input, win7 32bit (well, they are the same PC!)

tested audio recording software:
- wavosaur, does NOT work, recorded wav has random bit flip
- audacity, does NOT work, recorded wav has random bit flip
- cool edit pro, does NOT work, recorded wav has random bit flip
- REAPER, WORKS in ASIO or wasapi mode, recorded wav is bit perfect compared to the original file

For some reason, with the 1st setup using 2 PC, only 16bit output/recording gave bit perfect result using REAPER. That took me a while to sort out. Since 24bit output/recording works fine in the 2rd setup, I guess the onboard spdif on the PCa simply does not support 24bit output...

Also, using the current M-Audio website win7 sp1 32bit driver, the driver control panel can not detect any spdif input signal at >96khz using external clock. When the spdif input source is >96khz using external clock, the driver panel always shows 96khz. I need to select internal clock and manually select the correct sampling rate in the driver panel. And the recorded wav up to 192khz 24bit is perfect using REAPER. So I guess it's all good.

Test files used are CD DTS from http://www.kellyindustries.com/sounds.html#dts and Weiss bit transparency check wav file at http://www.weiss.ch/downloads/dac202fw/dac202-trnz-wav.zip