PDA

View Full Version : DTS Playback



Philip Meyer
2005-11-13, 09:50
I have some DTS flac files. I can stream these via my SB2 to a surround sound amp, and it sounds superb.

However, two things I'm not particularly keen about are:

1) I only hear white noise through the analog outputs.
2) I have the Small VU displayed on the Now Playing screen - this doesn't represent the surround sound being played; I guess it represents the white noise that I'm hearing through the analog outputs.

If I am playing random music through my HiFi, and SlimServer choses a surround sound file, it really doesn't sound good (could this damage speakers?). I appreciate that it might not be possible to downmix multi-channel data to stereo, but is it possible to simply turn off the other outputs when a multi-channel source is playing?

At the moment, I am hoping to avoid the Random Mix problem by tagging all of my DTS surround sound files with an additional GENRE="DTS" tag, and then ensuring this is not ticked in the "genres to include in your mix". I'm not sure though whether this will work though - if I have a track with Rock and DTS genres, and Rock is included but DTS is not included, could the track be selected in a random mix?

Phil

smst
2005-11-14, 03:56
on 2005-11-13 16:50 Philip Meyer said the following:
> I have some DTS flac files. I can stream these via my SB2 to a
> surround sound amp, and it sounds superb.
....
> I appreciate that it might not be possible to downmix
> multi-channel data to stereo, but is it possible to simply turn off
> the other outputs when a multi-channel source is playing?

I've been thinking about similar things recently (I have DTS/AC3 files
ripped from DVD; are yours from DVD or from a DTS CD?) and there was
some discussion about the SB2 firmware disabling analog outputs when
they weren't appropriate:

http://forums.slimdevices.com/showthread.php?p=58089

I don't know what the best way to tag the FLAC files is, however. My
feeling is that overriding GENRE is not the most elegant solution -- but
it might turn out to work for many applications.

Perhaps a new tag would be in order. I've currently set a new tag
called SPDIF_ONLY in parts of my collection, with values like "Dolby
Digital" and "DTS"; I don't think that's particularly obvious either.
Maybe better would be something which explicitly forbade analogue
outputs (NO_ANALOGUE?). It might be worth opening a discussion in the
ripping/tagging forum, come to think of it.

A complementary solution might involve the filename: if files were named
whatever.dts.spdif-flac, say, then they wouldn't be obviously FLAC files
(no Windows file association by default) and you'd also get around the
potential problem of dealing with your software player. But maybe
software players will ignore extension in favour of magic numbers; I
don't know.

I'm very interested in suggestions. My own setup uses the digital
output exclusively at the moment, but I'd like to see this issue
addressed so that it's easier for everyone. (I guess I might get a
second box with analogue outputs in future also.)

Cheers,
Steve

--
Steve Tregidgo

Philip Meyer
2005-11-15, 02:24
>I don't know what the best way to tag the FLAC files is, however. My
>feeling is that overriding GENRE is not the most elegant solution -- but
>it might turn out to work for many applications.
>
I don't like it, but I thought it was the only way to prevent them from being selected for a random mix.

>Perhaps a new tag would be in order. I've currently set a new tag
>called SPDIF_ONLY in parts of my collection, with values like "Dolby
>Digital" and "DTS"; I don't think that's particularly obvious either.
>Maybe better would be something which explicitly forbade analogue
>outputs (NO_ANALOGUE?). It might be worth opening a discussion in the
>ripping/tagging forum, come to think of it.
>
I thought it might be possible to detect based on the encoding, rather than add a new tag. Eg. can anything be determined by looking at the bit rate? Otherwise adding a new tag would seem the logical thing to do.

I have created a new folder specifically to hold for multi-stream encoded files, and set a symbolic link in the SlimServer music folder. Therefore I can identify the files that only play through digital out by browsing that folder. However, there's currently no way of configuring each folder such that files are not also added to the music DB, so the files could still be selected through a random mix and not be pleasant when listening via analog output.

I have two SB's - an SB2 in the lounge and an older SBG in the bedroom. If I tried to play a multi-stream flac file and the two devices were synchronised (SBG with a bit limit), what would happen? I'm assuming slimserver would try to transcode to .mp3 - would this work?

Phil

smst
2005-11-15, 08:14
on 2005-11-15 09:24 Philip Meyer said the following:
> I thought it might be possible to detect based on the encoding,
> rather than add a new tag. Eg. can anything be determined by looking
> at the bit rate? Otherwise adding a new tag would seem the logical
> thing to do.

The decoded WAV file would have a magic number at the start of (and
periodically throughout) the data to indicate it's an S/PDIF-ready
stream (in the case of my converted DTS/AC3 files), or a different magic
number if it's a DTS-WAV ripped from a DTS CD.

So it's possible at the player level, I guess. There's a slim
possibility of a false-positive, but it's unlikely in practice.

> I have two SB's - an SB2 in the lounge and an older SBG in the
> bedroom. If I tried to play a multi-stream flac file and the two
> devices were synchronised (SBG with a bit limit), what would happen?
> I'm assuming slimserver would try to transcode to .mp3 - would this
> work?

If your DTS file is transcoded to MP3 it won't decode to DTS at the
other end. DTS won't survive a lossy transcode; it's not PCM audio so
the encoder's assumptions are all wrong.

--
Steve Tregidgo