[FFmpeg-soc] [PATCH] updated! vf_overlay alpha patch and watermarking using PNG with alpha

[Stefano Sabatini]

On date Tuesday 2009-12-01 00:50:50 +0100, Vitor Sessak encoded:
> Artur Bodera wrote:
>> For those that have given up on ffmpeg and +libavfilter -vhook debacle.
>>
>> Here's a "just add water" solution to all your trouble: transparent PNG's
>> and watermarks in recent ffmpeg compilations.
>>
>> I'm attaching a working patch that will enable alpha-transparency in overlay
>> filter. This, on the other hand, will let you use overlay filter to
>> superimpose a video clip or transparent png watermark on another video. This
>> has been tested with recent revisions of svn://
>> svn.ffmpeg.org/soc/libavfilter rev. 5387 and ffmpeg rev. 19868 (16 Sep
>> 2009). Compiled and running under both x86 and x86_64 on linux.
>>
>>
>> Example 1 - insert transparent PNG watermark in bottom left corner of the
>> video:
>> -vfilters "movie=0:png:logo.png [wm];[in][wm] overlay=10:mainH-overlayH-10:1
>> [out]"
>>
>> Notice the last parameter to overlay ":1" - this enables alpha blending.
>>
>>
>> Example 2 - insert 2 different transparent PNG watermarks (second watermark
>> on bottom right corner):
>> -vfilters "movie=0:png:logo.png [wm];movie=0:png:logo2.png [awm];[in][wm]
>> overlay=10:mainH-overlayH-10:1 [int];[int][awm]
>> overlay=mainW-overlayW-10:mainH-overlayH-10:1 [out]"
>>
>> You could chain and add more overlays this way but the efficiency of such
>> approach is yet to be tested.
>>
>>
>> This should save you a lot of time and you can continue to use your favorite
>> transcoder for web video publishing!
>
> While I normally oppose making non-committed code more complex, I think  
> this feature is so often requested that it is worth the extra work in  
> the future. Stefano, Michael, any strong opinion about this?

I'm fine with committing the patch to soc if tested, even better would
be to try to push the filter to the main repo. Does someone want to
volunteer for this?

Regards.