How should AVI files be detected in avifile?

James Hawkins truiken at
Fri Jan 8 14:47:45 CST 2010

On Fri, Jan 8, 2010 at 12:40 PM, Julius Schwartzenberg
<julius.schwartzenberg at> wrote:
> Hi,
> Maybe you know, I hope to submit several fixes and tests for avifile soon.
> Vitaliy Margolen pointed out I should be create proper temporary files in
> the system's tmp directory so I implemented this. This actually showed a new
> bug in Wine's avifile:
> Wine's avifile does not handle normal avi files with an filename extension
> different than avi (f.e. tmp), while Windows XP's avifile has no problems
> with those at all.
> The problem is in this part of the code:
> I discussed it with Roderick a bit on IRC and he said the whole registry
> check is flawed and there should be detection for AVI files based on the
> content of the file. I then did some tests and replaced line 247 (return
> AVIERR_UNSUPPORTED;) with "clsidHandler = CLSID_AVIFile;" which always
> forces the correct handler for AVI files. With that change I get the exact
> same behaviour as on Windows:
> Proper AVI files always work, irregardless of their filename extension.
> Files in which I replaced "AVI LIST" (the magic with which AVI files can be
> detected) with "AV2 LIST" in a hex editor fail on both Windows and Wine. On
> both they immediately fail with the error that my file is not an AVI file.
> So this means that there already is proper detection in Wine based on the
> content of the file! There is just one extra obstacle in front now.
> I'm not very familiar (yet) with COM, CLASS IDs and how files are generally
> handled in Wine. Also I don't really know much about VFW, I especially
> cannot imagine what other files than AVI files would need to be read using
> avifile (but from the code I except this is possible). So my question is:
> What do you think would be an appropriate way to solve this? Should I just
> remove the obstacle or add my change? Or do something completely different?
> Also if anyone can shed more light on the current idea behind the code, this
> would be welcome!
> Thanks a lot in advance,
> Julius

Write and submit tests that show the correct behavior, then submit a
patch that makes Wine match that behavior.  In general, questions like
"What's the right fix?" can be answered by thorough, well-thought out

James Hawkins

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