[any ANONYMOUS forum user]

*.ISMV are fragmented MPEG-4 files with
- VC-1 or H.264 for video
- WMA 10 Pro or AAC-LC for audio

The ISMV file format is covered by the ISO MPEG-4 standard, but WMA Pro is not.
MPEG-4 and AAC-LC would be part of the MPEG-4 standard. VC-1 is an SMPTE standard.

ASF was a great format for bit-pumping - the MIPS-per-Mbps ratio was much better than other formats of its era. However, it simply wasn't well set up to allow a byterange to encapsulate a fragment that could potentially be a single closed GOP. Since server hardware is so much more powerful these days, plus proxy caching so dramaticallly reduces the load on the origin server, going for a somewhat more complex server-side parsing methodology made good sense.

The MPEG-4 fragmented format was able to do everything we needed, so it was simplest to just use that rather than make up something new. Plus it's a good excuse to say "moof" in public.

It's our intent to make the Smooth Streaming file format 100% ISO MPEG-4 compatible.

Since we're using standard file formats we expect many other tools will come out that support authoring the *.ismv files at least.

[Stream Recorder]

I haven't seen any free offline players supporting .ISMV video files.

But you can convert ISMV to MP4 and then play MP4 files with any player including freeware VLC player or freeware SMPlayer:
How to convert ISMV video file to MP4

[woinrigod]

From an article on how to play ISMV file (http://www.faasoft.com/articles/ismv-to-mp4-avi-mov-wmv.html), we learn that:

ISMV file is used by Microsoft IIS web server to deliver one video on different bitrate to Silverlight client over HTTP. This technology is called Smooth Streaming. Actually, ISMV is one kind of MP4 file. The video in it is split into 2-second chunks. Client can request video chunk by chunk.

To publish a video with Smooth Streaming, web master encode the video into several ISMV files with Expression Encoder, each for different bitrate. It will generate one ISM file and one ISMC file to describe information about these ISMV files, one for server and one for client. When Siverlight player plays a video, it request ISMC file at first to know how many bitrate available. Then it request the first chunk of loweast bitrate ISMV file to test network and CPU speed. If speed is enough, it will request following chunks in higher bitrate ISMV file. And it will switch between different bitrate to get highest quality and keep playing smooth at the same time.

Or

Go to http://forums.iis.net/t/1181405.aspx