FFmpeg - 如何缩放视频然后应用水印？

Question

Im trying to scale a video so that it is always 512 wide where the height changes in proportion to the original video. Once scaled, I then want to apply a watermark/overlay to the video, therefore the video will scale but the watermark wont.

I am able to achieve each of these separately using the following filters:

Scale

-vf "scale=512:-1"

Watermark

-vf "movie=watermark.png [watermark]; [in][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2 [out]"

They work successfully on their own.

However when trying to combine the two, Im having a bit of trouble.

Having both as parameters of course does not work as one will override the other.

Ive tried:

-vf "scale=512:-1,movie=watermark.png [watermark]; [in][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2 [out]"

my thinking was that the scale would be applied first then the watermark but all I get is an error

Too many inputs specified for the "movie" filter.

Error opening filters!

Then changing the , to a ; resulted in:

Simple filtergraph 'scale=512:-1; movie=watermark.png [watermark]; [in][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2 [out]' does not have exactly one input and output.

Error opening filters!

I presume I need to do something more with filterchains but Im struggling to figure it out.

Any ideas anyone?

Many thanks in advance.

Answer 1

You can use the -filter_complex option with the scale and overlay filters:

ffmpeg -i input.mp4 -i logo.png -filter_complex "[0:v]scale=512:-1[bg];[bg][1:v]overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2" output

• See scale and overlay filter documentation for more info.
• No need for the movie source filter as in the other examples.
• You can add -c:a copy if you want to stream copy (re-mux) the original audio instead of re-encoding it. This is useful if your input and output container formats are the same.
• The example will place the logo in the center. For other placement options:
  • Upper left with 10 px padding: overlay=10:10
  • Upper right with 10 px padding: overlay=Ww-10:10
  • Lower right with 10 px padding: overlay=Ww-10:Hh-10
  • Lower left with 10 px padding: overlay=Hh-10:10

Answer 2

Thank you to both @DiJuMx and @LordNeckbeard, you both got me closer to my solution. Ive not tried the filter_complex option yet but it certainly looks simpler.

The solution I found to work is:

-vf "movie=watermark.png [watermark]; [in]scale=512:trunc(ow/a/2)*2 [scale]; [scale][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2 [out]"

Note that Ive replaced the -1 in the scale as that had the potential to cause an uneven number of pixels in the height of the video when scaling which would then cause encoding errors.

Answer 3

From what I understand, this might work:

-vf "movie=watermark.png [watermark]; [in] scale=512:-1,[watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2 [out]"

You apply the scale filter to the input "[in]".

Unfortunately I don't have much experience with the filters on ffmpeg so I can't help further. Sorry