Bob Latham said:
In article ,
Richard Robinson wrote:

Hello. I'm baffled and looking for help.

I've been trying to play audio over my home wifi :- the backend is a
raspbery pi sending audio out via USB into a DAC, the frontend is a
laptop running Debian 8, sending to a pulseaudio "SMC9514 hub digital
stereo (IEC958) on pi@raspberypi" sink (I find pulseaudio deeply obscure
and offputting, but I haven't found much else that offers the
possibility of doing this at all). This connects, to the extent of
getting a noise out of the speakers, but the sound is useless - broken
up, stuttering, as much silence than sound - it gives the impression
that the data's just not being sent fast enough.

Wifi-wise, the pi is the bottleneck, with 'iwconfig wlan0' giving "Bit
Rate=54 Mb/s" (the rest of the system could go faster). But
handwavingly, this is ~5megabytes/sec, CD-quality sound is
~10megabytes/min, so I'd have expected that to be plenty.

(I've tried wav and a highly-compressed mp3, doesn't seem to make much
difference, I'm guessing it's decompressed before sending ? But it
wouldn't help anyway, having a DAC and cheap storage I don't want to use
a lossy format).

So what am I missing ? Is there some deep reason why this won't work, am
I doing something stupid, what's going on ?

As regards the rip format for music, unless you have extremely good
reasons for not doing so (I'm confident you haven't), use flac. Rip to

Thanks ... and, yes. New stuff comes in as flac. But ...

flac and get your tags sorted from the start rather have to come back
later and sort hundreds of albums.

.... I have a lot of 'historical' mp3s with no proper tagging, from the days
when storage was more of an issue. That's one reason why I'd prefer the
laptop hard disk to be my main storage, rather than put a hard disk behind
the raspbery pi - the laptop software/screen gives a nicer interface than
remotedestopping into the pi (I also have CDs to re-rip, which would be
easier that way). I could do the latter, if all else fails, but I want to
explore the alternative first, it'd just be a bit more convenient if I can
get it to work.

I'm not familiar with the kit you are using but FWIW here is my opinion.

My best guess is that you are trying to push music from a laptop to a
music renderer via wi-fi.

Yes.

I know many people push music via USB from a laptop directly into a dac

Yes. I've been doing that for a while, it works fine through a USB cable.
It's just that a cable stretched across the floor is not a good idea, sooner
or later I _will_ trip over it. I lost a nice pair of headphones that way
once; so wifi would be a better idea.

but I've never seen or heard of it being done with wi-fi in the link too.

I'm suprised; it seemed like the obvious next step, to me. Maybe I'm just
weird (shrug).

Personally, I've never liked the idea of 'push' music systems, it seems to
me that making sure the buffer in the renderer is neither overflowing or
empty is a bit tricky and far worse if you use wi-fi.

I advise using a pull system. The renderer pulls music from the server as
it requires it to keep the buffer just right. There are plenty of these
systems around.

Ah. That's a thing I hadn't taken seriously - I was guessing that given the
throughput numbers above, buffering wouldn't be an issue. Being proud of my
ability to be wrong, I will check out the idea of 'pull'.

To be clear, by a 'pull' system you mean that the music player software
lives on the machine that's wired into the amp (the pi, in my case) and it
sucks the music files down from a remote hard disk somewhere else on the
local network (the laptop, in my case) ?

Using flac I can stream hi-rez 192Khz/24bit music over wireless N all day
without an error but this does depend on how clear your local area is,
have you looked to see how many other wi-fi systems in your area are on
the same channel.

Ah, again. No, I hadn't, but will. I'm new to wifi in general, I've always
only done desktops/ethernet until I started playing with this stuff.

With pull systems, some pull from an SMB share on a PC or NAS eg. Sonos
and Bluesound and other systems pull from a UPnP server. Originally I
preferred the simplicity of the SMB connection but later I've seen the
advantage of UPnP, in particular there is only one central index no matter
how many clients/renderers. MinimServer is easy to setup - not a problem.

For your raspberry pi code Google OpenHome UPnP.

Thank you. This gives me some Things To Try Next.



I know others will not agree but that's life, not everyone will vote
"Leave" today either. :-)

Me, for example :-)




--
Richard Robinson
"The whole plan hinged upon the natural curiosity of potatoes" - S. Lem

My email address is at http://www.qualmograph.org.uk/contact.html