My $input_aspect= $input_width / $input_height # calculate padding (for black bar letterboxing/pillarboxing) If the video is less wide than the target frame size, the below routine will give a negative letterboxing result (which we will correct later on and use the value for pillarboxing): This assumes that the video is actually full screen or less/letterboxed. Then, here comes the magic that calculates the thickness of the black bars. Now, let's define the target video dimensions:
= "Couldn't read from ffmpeg: $!\n" ĭie "Could not fully get input video dimensions: $input_width x $input_height\n" Open(FFMPEG, "ffmpeg -i '$inFile' 2>&1 |") or $error. In this post we will have a look at how we can dynamically letterbox or pillarbox (black bars on the sides of the video, instead of top/bottom) any input video so that we can fit the video source into a fixed dimension target frame without breaking aspect ratio by squeezing the image. When you use ffmpeg to transcode videos from various sources and in various sizes, formats and aspect ratios to a given destination format, you can't rely on ffmpeg alone to produce the expected results. If you're interested in even more command examples, see these posts:Ĭonvert a video to a fixed screen size by cropping and resizingįor posterity: the older shell-scripting + ffmpeg way of letterboxing / pillarboxing The ffmpeg documentation Wiki has great examples:Īlso for all sorts of scaling transforms, the article on Scaling It forces to "keep the original aspect" and adds appropriate padding by supplying values via -1 (which means: use whatever fits) Note how this scales a video of arbitrary size into a canvas of 1280x720 pixels. Here's how you use ffmpeg's built-in capabilities to convert 4:3 video to 16:9:įfmpeg -i input -vf "scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:-1:-1:color=black" output
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