What is DVR-MS?

What is DVR-MS format?

DVR-MS (Microsoft Digital Video Recording) is a proprietary video and audio file container format, developed by Microsoft.

DVR-MS codec and container:
Audio and video are wrapped in an ASF container with the extension DVR-MS. Video is encoded using the MPEG-2 standard and audio using MPEG-1 Layer II or Dolby Digital AC-3 (ATSC A/52). The format extends these standards by including metadata about the content and digital rights management. The extension was originally used by Zach Johnson who at the time was a developer for the television recording engine for Microsoft Windows XP Media Center Edition.

The digital video recorder feature of Microsoft Windows XP Media Center Edition and the Windows Vista version of Windows Media Center create files in this format. If a recorded broadcast is marked as copy protected, the resultant DVR-MS file can only be played back on the recording device. Unprotected DVR-MS files (files not marked in this way) can be played back on any device running:

* At least Windows XP with Service Pack 1 and Microsoft hotfix 810243 which adds DVR-MS support to DirectShow
* Windows XP with Service Pack 2 and later Windows operating systems
* Windows Mobile 6
* For older Windows operating systems, any third-party media player which supports the DVR-MS format through DirectShow on Windows or by other means on Windows or other platforms

Although it is not possible to edit unprotected DVR-MS files through other software programs such as Protected DVR-MS Converter, the files can be edited using it.

MediaPortal also uses this format and comes with the plugin My Burner with which it's possible to (automatically) convert the DVR-MS files to regular MPEG-2. Also, Orb uses the DVR-MS file format for recording and streaming audio and video via its web-based DVR.

Some universal transcoders may be able to convert DVR-MS to other formats, such as DVR-MS Converter. DVR-MS can also be converted to another format using ffmpeg with DirectShow settings and a compatible MPEG-2 decoder like NVIDIA's PureVideo Decoder. Changing only the container format (extracting the original MPEG-2 data without any visual loss) is possible via VLC media player's transcoding wizard.

The DVR-MS format files are an ASF file containing multiple MPEG-2, and data streams. Files in this format are generated from the Stream Buffer Engine (SBE.dll), a DirectShow component created by Matthijs Gates for Microsoft Windows XP and Microsoft Windows Vista.

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Why Media Center Records to DVR-MS?

Every time I see a post about what Microsoft should do to make Media Center better it never fails that one of the first replies to “record to something other than DVR-MS.” No matter how many times people request this, it will not happen. DVR-MS is a necessary format for Media Center for various reasons; the main ones from a user perspective are metadata, content protection, and hardware resources.

* Metadata – Metadata is very important to Media Center, as with any PVR. Standard MPEG-2 isn’t going to be able to hold the same amount of metadata (none, actually). You might be saying “I don’t need to stinkin’ metadata,” and you would be wrong. Show title, recording date, duration, etc are all part of what DVR-MS brings. Remember, DVR-MS is really just MPEG-2 within an ASF wrapper, so you can strip the MPEG-2 out easily. Having the metadata within the file is helpful when converting the format to other formats like WMV, and also when copying the file to other PC’s. The metadata stays attached in both of these scenarios.

* Content Protection – You can complain all you want about Microsoft supporting DRM, but it’s not going to change anything. Supporting CGMS-A in Media Center since the first version can be seen as the first step to CableCARD support. It can be seen as the first step to DIRECTV/Dish support. Notice how no other PC PVR has these, and then notice the file formats they record in. PVR’s that record to vanilla MPEG-2 will be forced to change to a format like DVR-MS to get support for anything new. Yes, there are problems with CGMS-A, big ones in fact (post on that coming later).

* Resources – This one never fails too, “I want to record to XviD!” I say “Why?” It’s important to remember to recording directly to MPEG-4 means that your CPU is going to be encoding the video on-the-fly. That means lower video quality, and it ups the system requirements for the PC. Media Center supports two NTSC (or two CableCARD Tuners) plus two ATSC Tuners. If you were to record to XviD you are going to be lucky to have support for two tuners. Even with dual-core and quad-core processors, it is still going to tax the system to much. When hardware manufactures start including hardware MPEG-4 encoders on their cards, this will change. However, very few are doing this right now and I don’t expect it ever to be supported in Media Center. I think we will see the first MPEG-4 capture come with the DIRECTV solution.