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Author Topic: DSM-510 videos: flawless with XP, awful with Win7.  (Read 3425 times)

nas

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DSM-510 videos: flawless with XP, awful with Win7.
« on: October 15, 2010, 06:40:26 AM »

Hello,

after relating the problems with the quality of my video files after upgrading my PC from XP to Win7 I received this response from a kind Microsoft engineer:

Quote
Guys, as I have mentioned earlier, for all the PULL scenarios it is up to the device to pick up the right format. The DLNA Media Server implemented in Win XP and Win Vista was limited in terms of media transcoding capabilities. Especially for video, Windows served only the native formats. (Other nonMS servers do the same thing).

In Win7 though, we added transcoding capabilities. That means, that for each video file, Win offers a set of alternative formats for devices to choose from. These are exposed as separate URIs which the device can grab and pull content from. Each one of them is included in the so called XML RES elements (to follow the DLNA\UPnP terminology), published by the server over the network. Besides the URI itself, the RES element contains a set of DLNA and UPnP defined metadata that are associated with that URI: duration, bitrate, DLNA Profile Name, mime type, resolution, etc.

When a device browses the media server for a media item, it grabs all these RES elements. What it should do, is to analyze each element one by one (based on the associated metadata) and pick exactly the one that it thinks is the best for its capabilities (matches the preferred resolution, mime type, DLNA Profile Name, bitrate, etc.). There will always be a native RES element (that is just the raw file as it is on disk) and several other transcoded RES elements for various formats and resolutions.

However, since Win7 is probably the only server exposing these capabilities so far, devices (including older devices like DLink DSM-510) may not be comfortable with this choosing algorithm (defined in the DLNA specs though). So some of them may do crazy choices, like always choosing the first RES element, or the last one, or preferring WMV or MPEG over everything else.  In some cases they may have a good reason for this (e.g. AVI files are kind of strange, since they can come in so many flavors and without proper classification (there is no DLNA PN to tell you whether is a DivX or XVid or something else). A device may just choose not to render AVI if there is some other RES there that it knows for sure that it can support. That is simply because they do not want to risk a crash or a failure)

So, to summarize. The device and ONLY the device has the option to choose. There is no downgrade in Win7 from Vista or XP in terms of how Windows serves the native content. What is different is number of alternative  transcoding elements, that may confuse some devices. Apparently there is no logical reason for the device to behave differently though, but as I mentioned in the AVI example, you may never know. Normally, if they choose native URI in WMP 11, they should continue choosing the same thing in Win7.

What I would suggest, is to contact the manufacturer of the device and ask them. In the mean time, I will get this problem to our Windows Logo Team and try to enforce some rules, while also engaging these device manufacturers. Unfortunately, if they do not decide to fix the issue and update the firmware, there is no short term solution.

I hope this answer to your questions.

Thanks a lot

Question: is there any hope for us, poor DSM-510 owners?  ???

Thanks.
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ECF

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Re: DSM-510 videos: flawless with XP, awful with Win7.
« Reply #1 on: October 27, 2010, 03:18:12 PM »

I would recommend using something like TVersity or the D-Link media server application.
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