Change wmv's FourCC ?

[Music Fan]

Hi,
I would like to know if there is a tool to change wmv's FourCC, from wmv2 to wmv3 for example.
Thanks ;)

[Music Fan]

I found a trick to do that.
Save the wmv file in avi with Virtual Dub in direct stream copy mode, change the FourCC with AVI FourCC Changer and put it again in a wmv container with VLC.
Then save it with Windows Media File Editor to remove the "unneeded bytes" seen with GSpot in the file created by VLC.
The FourCC is well changed by AVI FourCC Changer, we can verify it with GSpot and Mediainfo.

My aim was to play it on my standalone players (which play wmv1 and wmv3 but not wmv2) without re-encoding, but it didn't work.
But changing the FourCC of a Mpeg-4 Visual FMP4 file (from FMP4 to DIVX) made it readable by my Sony player, that's why i believed it could maybe work with wmv.

[clsid]

FMP4 and DIVX are both FourCCs for the exact same format, namely MPEG-4 ASP. That is why it worked.

[Music Fan]

MPEG-4 ASP is not a codec, it's a family of codecs.
WMV codecs are from the same family but my players play wmv1 (wmv7) and wmv3 (wmv9) but not wmv2 (wmv8), weird isn't it ?
So, being from the same codec's family is not enough.
But i'm not very astonished, wmv come from Microsoft ...

[clsid]

Wrong. The MPEG-4 videos are all compatible. WMV2 and WMV3 are different formats.

[Music Fan]

WMV2 and WMV3 are different formats.
Are you sure of that or it's a supposition because I say my players can't play wmv2 ?
Wmv is also a kind of mpeg-4 ;
http://en.wikipedia.org/wiki/Wmv#Windows_Media_Video

How do you explain that my players can play wmv1 and not wmv2, while wmv1 is older than wmv2 ?
Do you know the exact differences between wmv1, 2 and 3 ?
Wmv2 seem to have something specific.
If these 3 codecs are not classified in a particular category, does it mean that they are unique and not to be compared with other codecs, even when their FourCC are very similar ?

The MPEG-4 videos are all compatible.
I guess you mean ASP, because mpeg-4 include AVC and dvd players can't play AVC.
Are you sure that standalone players compatible with Divx can play all MPEG-4 ASP codecs ?
Don't forget that some players can't play Qpel or GMC, so the compatibility depends on certain conditions.

This article is confusing ;
http://en.wikipedia.org/wiki/MPEG-4_Part_2
MPEG-4 Part 2 is H.263 compatible in the sense that a basic H.263 bitstream is correctly decoded by an MPEG-4 Video decoder.
What do they call mpeg-4 video decoder ?
I'm not sure that a standalone player can player all h263 streams, because FLV is also a kind of h263 ;
http://en.wikipedia.org/wiki/FLV#Format_details

The more I read, the less I understand, it's hard to know what a player can play, especially with a Blu-ray player as my Sony which plays some Mpeg-4 ASP, AVC, wmv1, wmv3, ... but not wmv2.

In my opinion, we can't make generalities and we have to test each codec to know what is a player able to do.
Unless wmv2 is an exception.

[clsid]

If you in the ffmpeg code you will see that all MPEG-4/H.263 variants are handled pretty much he same way.

The MS variants differ from the standard and also differ based on the version:
http://git.libav.org/?p=libav.git;a=blob;f=libavcodec/msmpeg4.c;hb=HEAD

[Music Fan]

Thanks for this link but I don't understand anything, I'm not programmer.:o
You didn't say what's the difference between what you call mpeg-4 and the 3 kind of wmv (and especially wmv2), which are also based on Mpeg-4.

[Midzuki]

You'd better complain at the manufacturer of your SAPs :) A WMV1 decoder should not be able / required to decompress WMV2, and WMV3 is actually a watered-down version of VC-1.

[Music Fan]

Weird reasoning, it doesn't explain why two players of two different manufacturers (Sony and Pioneer) decode wmv1 and wmv3 but not wmv2.
And I don't "complain", I try to understand a situation.

[Midzuki]

But you should complain at them :) They didn't warn you that you were buying crippled firmware.

[Reimar]

Weird reasoning, it doesn't explain why two players of two different manufacturers (Sony and Pioneer) decode wmv1 and wmv3 but not wmv2.
And I don't "complain", I try to understand a situation.

Simple: WMV1 is really simple so it's no effort to support it (probably is done in software on some kind of CPU) and probably everyone has an implementation around from ages ago.
WMV3 is mostly the same as VC-1 which is required for Bluray and thus "universally" supported. I have a suspicion that actually some special WMV3 features (IIRC mostly old features from beta versions that did not make it into VC-1) might actually _not_ be supported by those players.
With none of these advantages WMV2 is stuck with the fact that WMV is basically irrelevant, and irrelevant stuff is at most supported when it's no effort like for WMV1 and WMV3.

[Midzuki]

As a matter of fact, the licensing fees for WMV-capable firmware are obscenely-low :devil: :D Consciously or not, the manufacturers's intention is to skrew the end-users, even if that means saving US$ 0.49 per every 500,000 units produced. :mad:

[Music Fan]

That's probably the good explanation because wmv2 doesn't have to be decoded with very difficulty.