[FFmpeg-devel] movie Filter reload Option

[TalkVideo at TalkVideo.net]

On Wed, May 08, 2019 at 07:26:16PM -0400, TalkVideo at TalkVideo.net wrote:
> Please see this (very Short) thread for background. It is
> incorporated here.
> 
> http://ffmpeg.org/pipermail/ffmpeg-devel/2019-May/243721.html
> 
> The drawtext Filter has a reload Option, and when I use overlay
> with a PNG Image, like so:
> -f image2 -loop 1 -i overlay.png 
> 
> I can manipulate the overlay by changing out the PNG File while
> the ffmpeg command is running.  (It works with RTMP sending to YouTube).
> 
> I can make it "disappear" by copying a 1-pixel alpha PNG Image into 
> the "overlay.png" file. 
> 
> I can manipulate the displayed drawtext in real-time by changing the contents of the 
> "textfile" the drawtext filter uses when the "reload" option is set.
> 
> So far, so good.
> 
> What about doing the same with a video. That means that the movie filter
> would reload (or at least check) the file specified as input to that filter, with each run
> of the loop if a reload option was set, perhaps. ffmpeg appears to read that file once, at inception.
> 
> Is there currently a way to accomplish this or would one have to add that to he code?
> 
> Thanks.
> 


Answering my own question, it looks like in src_movie.c in movie_common_init()
there is a call to avformat_open_input() to get the file for the first time.

Something like that could be re-done in rewind_file(), to check and reload the 
file anew, if necessary, insted of just rewinding the existing copy in memory.