ffm positions: What Are They and How to Choose the Right One?

Okay, so today I wanted to mess around with ffmpeg and figure out how to get super precise control over where my videos and images end up on the screen. You know, like when you see those fancy video layouts with multiple clips playing at once? That’s what I was aiming for.

Getting Started

First things first, I needed to refresh my memory on the basics of ffmpeg. I’ve used it before for simple stuff like converting video formats, but this was going to be a bit more involved. So, I spent some time digging through the documentation and old projects.

The “Overlay” Filter

The key to all this is the “overlay” filter in ffmpeg. This is what lets you put one video (or image) on top of another. It’s pretty straightforward: you tell it where to position the overlay using x and y coordinates.

My initial test was pretty basic. I had two video files, let’s call them “*4” and “*4”. I wanted “*4” to appear in the top-left corner of “*4”.

Here’s the command I started with:

ffmpeg -i *4 -i *4 -filter_complex "overlay=x=0:y=0" *4

This worked! My “*4” was smack-dab in the top-left corner, just like I wanted.

Playing with Coordinates

Of course, the top-left corner is rarely where you want things. So, I started experimenting with different x and y values. Remember, (0,0) is the top-left. Increasing ‘x’ moves the overlay to the right, and increasing ‘y’ moves it down.

• Moving to the center: I figured out that to center the overlay, I needed to know the width and height of both videos. Let’s say “*4” is 1280×720 and “*4” is 320×180. To center it, I used:

  
  ffmpeg -i *4 -i *4 -filter_complex "overlay=x=(main_w-overlay_w)/2:y=(main_h-overlay_h)/2" *4
  

  See that `main_w`, `main_h`, `overlay_w`, and `overlay_h`? ffmpeg has those built-in, so it does the math for you!

• Bottom-right corner: This was just a matter of using `main_w-overlay_w` for x and `main_h-overlay_h` for y.

Multiple Overlays

Things got really interesting when I wanted to add more than one overlay. This is where the `filter_complex` part gets, well, more complex.

I added a third video, “*4”. Now, I wanted “*4” in the top-left and “*4” in the bottom-right.

ffmpeg -i *4 -i *4 -i *4 -filter_complex "[0:v][1:v]overlay=x=0:y=0[v1];[v1][2:v]overlay=x=main_w-overlay_w:y=main_h-overlay_h" *4

Let’s break that down a bit:

• `[0:v][1:v]overlay=x=0:y=0[v1]` This part takes the first input (*4, which is `0:v`) and the second input (*4, which is `1:v`), overlays them, and calls the result `[v1]`.

• `[v1][2:v]overlay=x=main_w-overlay_w:y=main_h-overlay_h` This takes the result from the previous step (`[v1]`) and the third input (*4, `2:v`) and overlays them. Since we didn’t give it a name at the end, this becomes the final output.

It took some trial and error, but I eventually got it working exactly how I pictured it!

Conclusion of Today

I’m pretty happy with what I learned today. I can now position videos and images exactly where I want them using ffmpeg. There’s still a lot more to explore, like animating the overlays and using more advanced filter options, but this is a solid foundation. It’s not super polished, but it’s a start. I’m just jotting down my progress as I go, so I can remember what the heck I did!