I agree with this change - I use VSE regularily and 9/10 of my strips need to be in alpha over mode.

The only other functionality aspect that might make this better would to actually remember the setting of the last strip added. So it could default to 'cross' and then if the strip is changed to 'alpha over' it the next strip added would default to 'alpha over'.

Just my two cents, but why the extra variable (default_VSE_strip_blend_mode), when you could have just replaced SEQ_TYPE_CROSS with SEQ_TYPE_ALPHAOVER ?

If it's for readability, then I'd suggest a name more consistent with the rest of the sequencer API, e.g.: sequencer_strip_default_blend_mode.

I used a variable to be self-documenting. I am not married to the name, and if this patch gets accepted for commit it should be slightly easier for the committer to change the name of the variable than it would be to figure out which instances of SEQ_TYPE_CROSS are blend_mode initializations and needed to be changed.

@Antonis Ryakiotakis (psy-fi), could you check with artists on this?

Try make an image with alpha and overlay it on an opaque backdrop, cross gives quite strange behavior (at least different to gimp/photoshop)

I see a small difference with some test images but I can't be entirely sure too...do you have any test files we can share?

For the record I don't mind changing this to alpha over.

also i think that when an user adds an effect strip it should use the same blend mode as the original strip