[FFmpeg-devel] Need help on bug#3302 - Cannot draw opaque text on transparent frame

Michael Niedermayer michaelni at gmx.at
Sun Jun 22 21:18:02 CEST 2014

On Sun, Jun 22, 2014 at 04:44:03PM +0200, Michael Niedermayer wrote:
> On Sat, Jun 21, 2014 at 10:52:24PM +0300, Andrey Utkin wrote:
> > Dear core developers related to this functionality (lavfi/drawutils).
> > I'd like to have this issue https://trac.ffmpeg.org/ticket/3302 fixed
> > in next couple of days, for particular application. Exactly, what i
> > need to do is fading in/out text overlays. Of course this issue has
> > alternative ways to solve, e.g. make drawtext filter actually to
> > implement fading by by-frame evaluation of text alpha value. Currently
> > i suppose to work on the latter as it seems easier, but still i am
> > interested in the solution for original issue. I am ready to work on
> > the code, but i am disoriented in existing routines and need guidance.
> i would suggest that first the blend code is changed to work only
> on matching sample formats. That is resample the text to yuv(a) 123
> when the image onto which it is drawen is yuv(a)123
> this would make the code about a factor of 5 faster by not repeatly
> resampling the data, i would guess.
> it will also make the blend code much simpler to understand
> next there is not just one way to blend a rgba/yuva bitmap onto
> another, there are multiple ways
> a enum should be added to select which is to be used.
> Iam happy to help find / list the equations for that
> this code could then also be used by vf_overlay

also see vf_blend, ive forgotten about it almost

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20140622/3a7cc511/attachment.asc>

More information about the ffmpeg-devel mailing list