S/PDIF Output delay problem

I recently tried the optical spdif output of my laptop, and found that it takes a small ammount of time (about 0.5s) before it actualy outputs the signal. This means that the first sec of so of any sound is simply cut off, for example, when i pling the windows volume control, the sound is too short to ever appear. Its not an issue with the device thats recieveing the signal, its simply that the soundcard sees fit to simply stop the optical out as soon as thers no sound to output.

I have been searching around for a fix on this for ages with no luck, its seems to be a problem that a good ammount of people are having. If its of any use il post the exact details of sound card and driver versions etc on request.

Any help would be much appreciated, its an extreemly frustrating problem

Just to clarify, as soon as the recieveing device locks on to the signal it works brilliantly, thers absolutely no audiable delay between it and the analogue output. The problem as far as i can tell is that the sound card sees fit to "unlock" the spdif stream (stop clocking it), which means that next time some sound id output, it takes a moment for the recieveing device to "lock" back on the the stream again, anyway... onto the exact details:

$ Soundcard
This is a laptop were dealing with here so the soundcard is integrated (onto the southbridge), as follows:

South Bridge: VT8237
Codec type: VT1618
Driver Version: 6.14.1.4130 (latest available from system mtfr)
The S/PDIF out is optical (mini toslink)

$ Recieveing Device
Im using a Technics SJ-MD150 minidisk deck to recieve the signal, via a standard 5M optical cable. I have ruled out the possibility of this being faulty in any way. Its able to recieve streams from other devices (CD players, consoles, etc) via optical in without problems. Im using its "Monitor" function to take in the signal, and and ouptut it to my amp via its standard analogue out (What im basicaly tryin to do here is use my minidisk deck's DAC instead of the one in my laptop)

I have done lots of experimentation, and it seems to be a case of "tricking" the soundcard to keep the spdif output active.. So, for example if i play a video in WMP, and mute the sound, this keeps the spdif output active (even though no sounds coming out) and playing any other sounds, like music thru itunes, the windows volume control plinger all work fine. I have also found that simply running quicktime, and keeping that open for some reason keeps the spdif output active and everything works fine.

The mindisk deck displays a message that tells you if it has locked onto the spdif signal, or not, and when i play a sound (from silence before) i see it briefly flicker to "unlocked" and back to /working corectly/ as it re-locks on to the stream. Its this delay thats causing the problem. I just need to find a proper way to keep the spdif output active.

Thanks for taking the time to reply

I imagine that would be insanely difficult... Id have to make my own device that would accept the spdif signal, synthesize a clock from it, so that when the laptop stops output it could keep clocking.. and then when the spdif on the laptop becomes active it will likely be out of synch with the clock running in the theoretical device!

Thers one other point tho which i didint make clear. The delay isnt cuased by the computer. The spdif signal becomes active instantly as a sound starts, no delay at all. Its just that the minidisk deck needs a half sec or so to lock onto a new signal (since the spdif has been inactive until a sound starts) If i could keep the spdif output active, the minidisk deck would never unlock from the signal (appart from, obviously when it was first turned on), and thus there would never be any delays. Im sure this is the kinda thing that could be done by a new driver.. but thers simply not a newer version available! and unfortunately i wouldnt have the first idea about how to modify the driver to achieve that functionality

Hmm. i did some experimentation. I connected my CD players optical out to the minidisk deck, and found it will synch almost instantaneously as i plug it it in. Like the guy in the link above, i can hold the connector and simply point it in out out and the sound comes on or off *almost* instantaneously. So, maybe there is something going on with the soundcard delaying output. Although its odd because the spdif becomes active (i see the minidisk deck start to lock on the instant i play a sound) iy just takes longer to synch from the comp than from other sources. Verry odd! I wonder if maybe its outputting a nonstandard stream... According to the fairly uninformative soundcard options its outputing standard PCM... so it should be fine.. but somethings clearly amiss!. I wish there were more options to experiment with, but thers none available. I even had a peek in the ol' registry, but thers no usufull looking keys there.

I definitely agree tho, it should'nt take more than a few frames to synch, and ecven if it took tens of frames that would stilll only correspond to a minute fraction of a second of audio when were dealing with 16bit 44.1KHz.. its almost like its requiring hundreds of frames, or for some reasons having a hard time synching.

You know,

I've looked all over for an answer to this...

I'm currently reviewing some code that may allow for S/PDIF keepalive (similar to outputting a silent WAV or similar on a channel).

There may be a way to loop and crossfade a very short and silent WAV clip or similar with a small background sound player...

That's about all I can think of for now.

here is a little trick I use with iTunes to help with the delay.

I enable the Crossfader option and set it to 1 sec. The first song you play will still have a delay but once its over it will cross into the next song. This is ideal if you are playing a playlist but not if you are just browsing songs in your library.

in iTunes the crossfader is under Edit > Preferences > Playback then check the box and select the length of time you wish the crossfade to begin.

*Note: If you enable this on your system and have your ipod syncing auto with iTunes then you may inadvertently enable it on your ipod as well.


chris

Hi all, I would like to ask if anyone had encountered the solution for this, maybe we can develop a windows service that permanently outputs some frecuency to the spdif interface (in shared mode) so it keeps the channel opened and doesn't interfere with other sounds...