[FFmpeg-user] concat demuxer filter_complex (fade)

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, April 16, 2020 3:48 AM, Ted Park <kumowoon1025 at gmail.com> wrote:

> Hi,
>
> > I learned, that it's possible to define multiple inputs and reference then
> > later in the filter_complex to the different inputs like this:
> > ffmpeg -i vid1.mkv -i vid2.mkv -i vid3.mkv -filter_complex
> > "[0:v]fade=t=in:st=0:d=1[v0]; [1:v]fade=t=in:st=0:d=1[v1];
> > [2:v]fade=t=in:st=0:d=1[v2];
> > [v0][0:a][v1][1:a][v2][2:a]concat=n=3:v=1:a=1[v][a]" -map "[a]" -map "[v]"
> > out.mkv
> > But is this possible with using the concat demuxer (providing the files by
> > writing them into a file) too? And if yes how?
> > (Goal is to specify the videos through a file, using the concat demuxer, but
> > apply the fade filter to each of the video files before concatenating them.
> > Is it possible to make this in one step?)
>
> > Can you please elaborate what you mean by fragile and complicated?
>
> I mean, you've got to see how that is complicated if nothing else.
>
> Anyway, I remembered that using the ffconcat file, you can define streams within the virtual single input from the concat demuxer, but I've only ever seen it used to specify specific elementary streams within vob files, not sure if it can be used with other demuxers. Maybe someone else does?

Actually I don't see why it should be complicated. Maybe we're writing about different things. You're still writing about the concat demuxer but I already came to the conclusion that its easier to use the concat filter if you want to insert transitions, since otherwise you'd have to preprocess the images into videos and already add the transition at this point. With the concat filter, you can use one filterchain to add the transitions and concatenate the images in one step (no additional video files in the preprocessing process)

With kind regards