Saturday, October 1, 2011

Fixing UPnP/DLNA sharing on 2nd drive under Windows 7


Though I may be a few years late to the party, I finally have a capable Home Theater PC (HTPC) and HDTV setup in my living room. For simplicity for the entire family, it's running Windows 7's Media Center.

My favorite feature of a HTPC-solution is the digital video recorder (DVR) functionality - including the options to pause and replay live TV. My family previously had a hard-drive enabled DVD player / DVR with this functionality built-in - but without an ATSC digital tuner, its use is now limited to analog cable. I since had a newer Philips DVD player / DVR with similar features - including an ATSC digital tuner - but it was only standard-definition (SD), not high-definition (HD), and recorded content had issues with volume levels as well as not supporting closed captioning and other broadcast features.

Disappointingly, these types of devices are appearing to be pushed out of the market in favor of versions that require monthly fees. Other than a new subscription to Netflix and our DVDs, most of what we watch is free broadcast television - without paying monthly fees for cable or satellite television service. I'm excited to have a HTPC-based DVR that is also fee-free. Much of the broadcast television we watch is also in HD, for free - something most paid-for TV services are still behind in for not offering without yet additional fees!

Besides having a direct HDMI connection between the PC and the TV, both devices support UPnP/DLNA. I'll prefer the HDMI connection as the primary link between the HTPC and its connected TV - mostly as it doesn't require to have an extra encode/decode step to stream the video over Ethernet. The DLNA method is also missing a few features that are natively available from the HTPC - including some simpler features such as closed captioning. However, the DLNA feature is certainly nice to have as a convenience for quickly streaming videos, pictures, or music from any other computer connected to the network - without needing to first add a wired connection, or otherwise transfer the media to a USB flash drive or another connected device.

UPnP/DLNA issue

I ran into some difficulties, however, when trying to stream content from my primary laptop - also running Windows 7 x64, Professional. My laptop simply would not show itself as a media server device. It wasn't a problem with the TV, as other clients on the network could also see all the other servers - just not my laptop. I eventually found that I could create new user accounts in Windows, and then my laptop became visible as a server - but only for the new user accounts, and not my primary user account. Unfortunately, this was something a bit more complicated than adjusting the "Media streaming options" in the Control Panel for my user account.

UPnP uses Simple Service Discovery Protocol (SSDP) for discovery. Not finding anything significant within the Windows Event Log, and not finding any other tools within Windows that could help troubleshoot the issue, I used Wireshark to try to determine what was causing the issue. I found several SSDP HTTP NOTIFY packets, with a URL of something like http://[fe80::5ddf:5cb8:a7e1:bbcb]:2869/upnphost/udhisapi.dll?content=uuid:eb1c9c01-e5c3-4eea-bea2-d9f0a6fb2bcf. Following the URL, XML was returned that described the media servers for all other media servers and users on the network - including from my own laptop, but not for my primary user account. This confirmed that the issue was with my server, and not the network or clients.

I eventually ran across several posts of other users having very similar symptoms, including:

Unfortunately, they were all unanswered (both replied to - especially with many non-solutions to the first). However, they all had something in common with my laptop setup: The user profile directory was moved off of the system drive. This should be a common setup - using disk partitions to separate the user data from the program data. Another common scenario for this today is to have the OS on a high-performance SSD, and a larger HDD for the user data. However, as Windows doesn't easily provide for configuring this setup, it isn't surprising that this isn't a more visible issue.

My Solution

In both threads, the users seemed to infer that the problem must have been in the file copy / move of the user profile directory between drives. Fortunately, at least in my case, this had nothing to do with the content of the files - but with the security permissions / Access Control Lists (ACLs).

Even after moving my user profile to a new drive / partition, folders such as "My Videos" have an added "Read" permission granted to "WMPNetworkSvc" (which is obviously the account for the "Windows Media Player network service"). This permission does not exist on (nor does it need to exist on) parent folders. However, there is a quirk in Windows where at least limited access needs to be granted to the root of the hosting drive, otherwise accounts can't access any data within the drive - regardless of what child ACLs may be present. This was not an issue on the C:\ drive, as by default, the "Read" permission is granted to "Users", and additionally has other special permissions granted to "Authenticated Users" - both which should apply to the "WMPNetworkSvc" account. Such permissions, however, did not exist on my data drive - which only had permissions defined for my personal account, the "Administrators" group, and the "SYSTEM" group.

The fix is rather simple - give the "WMPNetworkSvc" limited access to the root of the alternate drive hosting the user profile. By limited, I'm not kidding - and keeping access to the absolute minimum only follows best security practices. (You'll need to use the "Advanced" button to open the "Advanced Security Settings" dialog for this):

  1. From the drive properties, "Security" tab, click "Advanced".
  2. From the "Advanced Security Settings" dialog, on the bottom of the "Permissions" tab, click "Change Permissions...".
  3. On the 2nd dialog that pops-up, click "Add...".
  4. Type in "NT Service\WMPNetworkSvc" (without the quotes), click "Check Names" to make sure it is recognized, then click "OK".
    • The "NT Service" prefix is necessary to resolve the Windows service account. There is no other known way to be able to select it through the UI options.
  5. In the "Permission Entry" dialog that pops-up:
    1. Under "Apply to", select "This folder only".
    2. Under "Permissions:", check only the "Allow" checkbox for "Traverse folder / execute file".
    3. Click "OK".
  6. Click "OK" to close all 3 remaining dialogs.
  7. Restart the "Windows Media Player Network Sharing Service" (WMPNetworkSvc) Windows service.

All of the above UI steps can also be easily replaced with the following commands. Simply replace "D:\" with the drive letter that the Windows Media Player network service needs access to:

icacls D:\ /grant "NT Service\WMPNetworkSvc":(X)
net stop WMPNetworkSvc
net start WMPNetworkSvc

This is certainly not meant to nor will this help fix the many different types of issues that exist with network media sharing. However, hopefully this will benefit those who have organized their systems on to separate drives or partitions, and are experiencing the same issue.


Anonymous said...

AAAARGH! This looked like such a promising fix but it hasn't made any difference !!
I still can't get my DLNA TV to recognise my photos on my laptop's second hard drive. Even when I go to each photo in turn and enable WMP permission and enable it for each folder above that photo it doesn't work!!
Only 1 photo on the whole drive is visible on the TV and that's the one of penguins that comes in Win 7's SAmple Photos folder - for some reason this has the necessary permissions. WHAT'S GOING WRONG ?????

Thanks for your help...

Unknown said...

It seemed to sort itself out when I deleted all my pictures then created new folders to put them back into, (having set the WMP permission for the drive obviously).
So now I can see most of my photos...
Thanks for this life-saving post!

Anonymous said...

LIFE SAVER! I was starting to doubt my sanity... worst of all, Windows didn't even try to mention access error in eventlog when this failed... as if Permission Denied for WMP Network service would be too much for Security events. Shame on MS, and best of thanks to you!

Anonymous said...

Thanks so much, worked like a charm!! Windows Media Player was not showing my drives other than C: and this fixed it.

Chris Treber said...

Thank. You. So. Much.

I have a BIG external drive with my media on, and - nothing would show up on the network.

I'd like to buy you a beer. Paypal?



Unknown said...

Got my stuff to work. Thanks a ton man.
Just 3 command .....Awesome.
Thanks for posting these on your link

Fran├žois Collard said...

Thanks a lot: should be a life-saving post for me too (Win 7 PC invisible to DLNA for TV and audio device, user profile on D: partition, whilst other XP PCs and even the same PC when it is on Linux; I have been pulling off my hair for weeks). But, though I think I did the whole thing with command line then checked through the UI, I cannot get it to work. Maybe another issue, or a misconfiguration on Windows Media Player (this soft is such a terrible mess, and Media Center is even worse – I never tried to use them before I needed DLNA!)