[Libav-user] libvfilter usage: how to write a text in a frame?

[Leandro Santiago]

Hello to all. I've alread compiled libav* with freetype support, and
now I want to write a text over a frame. I've seen there is a filter
for this (drawtext), but I really don't know how to use it. In fact I
don't know how to use libavfilter, because I couldn't find any
tutorials on the Internet.

Reading the libavfilter/avcodec.h file I saw I have to use
avfilter_fill_frame_from_video_buffer_ref(AVFrame*, const
AVFilterBufferRef *), and til now I have the AVFrame, but I don't have
a AVFilterBufferRef object. How can I create it and how use it with
the drawtext filter? Does the filter depend on the frame's
PixelFormat?

Thx to all.