I have a mp4 video file and I want to remove all frames, that do not have a certain color.
I know about the colorhold filter, which turns everything grey except the specified color. But then I would need to remove every grey frame and I could not find a way to do that.
I just want some confirmation, because I have the sneaking suspicion that I wont be able to do what I want to do, given that I already ran into some errors about ffmpeg not being able to overwrite the input file. I still have some hope that what I want to do is some kind of exception, but I doubt it.
I already used ffmpeg to extract a specific frame into its own image file, I've set the thumbnail of a video with an existing image file, but I can't seem to figure out how to set a specific frame from the video as the thumbnail. I want to do this without having to extract the frame into a separate file and I don't want to create an output file, I want to edit the video directly and change the thumbnail using a frame from the video itself. Is that possible?
You're probably better off asking it in IRC zeronode #ffmpeg-devel.
I'd look at "-ss 33.5" or a more precise filter "-vf 'select=gte(n,1000)'" both will give same or very similar result at 30 fps video.
You can pipe the image out to your own process via pipe if you like of course without saving it : "ffmpeg ... -f jpeg -|..."
It is described here how ot burn a srt file into a video.
However, I want to put a semi-transparent background to the subtitles so that the texts can be read more easily. How can I do that?
ASS subtitles can have a semi-transparent background for the text.
With aegisub
The easiest way to do this is with aegisub.
Open your subtitles file with aegisub.
Click Subtitle → Styles manager.
Under Current Script choose Default, then press the Edit button.
Experiment with the Outline and Shadow values. Check Opaque box.
Under Colors click the color under Outline or Shadows. A window will appear. Adjust the value of the Alpha box to change transparency.
Save the subtitles as an .ass file.
Now you can use the AAS file to make hardsubs or softsubs with ffmpeg.
Without aegisub
If you want hardsubs you can use the subtitles filter to add the transparent background with the force_style option.
ffmpeg -i input -filter_complex "subtitles=subs.ass:force_style='OutlineColour=&H80000000,BorderStyle=3,Outline=1,Shadow=0,MarginV=20'" output
This will work with any text based subtitles supported by FFmpeg because the filter will automatically convert them to ASS.
See SubStation Alpha (ASS) style fields for formatting options.
Issue with multiple lines
If your subtitles contains multiple lines, due to auto-wrapping of long lines or an intentional line break, the backgrounds will overlap and potentially look ugly as shown below:
You can avoid this by:
Changing the Outline and Shadow sizes to 0.
The alpha settings of the shadow will control the transparency of the background box. Click on the shadow color to adjust the Alpha of the shadow color to your desired transparency level.
Edit the ASS file in a text editor. In the Style line change the value corresponding with BorderStyle to 4. This will fill the bounding box background of each subtitle event. Example Style line:
Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H80000000,&H80000000,-1,0,0,0,100,100,0,0,4,0,0,2,10,10,10,1
Example:
Note that BorderStyle=4 is a non-standard value, so it may not work properly in all players.
Thanks to sup and wm4 for the BorderStyle suggestion.
Using drawbox
The drawbox filter can be used to create a background box.
This may be useful if you want the box to span the width.
ffmpeg -i input -filter_complex "drawbox=w=iw:h=24:y=ih-28:t=max:color=black#0.4,subtitles=subs.ass" output
Downside is that you have to account for line breaks or word wrapping for long subtitles. Simply making the box taller to compensate will suffice, but will look ugly because the subtitles baseline remains static: the single line subtitles will have more padding on the top than the bottom.
Create a png with a transparent box and a alpha channel in your favoured size. You can use e.g. gimp or photoshop.
Then use this command:
ffmpeg -i video.mp4 -i logo.png -filter_complex "[0:v][1:v]overlay=10:10" \
-codec:a copy out.mp4
where 10:10 is the distance from the upper left corner.
After that you can insert your subtitles.
ffmpeg -i input.mp4 -filter_complex "subtitles=input.srt:force_style='BackColour=&H80000000,BorderStyle=4,Fontsize=11'" output.mp4
BackColour=&H80000000 means having a %50 opaque black background.
Its a hex representation of color, AABBGGRR.
You can use this Aegisub script. This script automatically generate transparent background for every line of subtitle.
With the current version of libass (0.15) and the current version of ffmpeg (N-100402-g0320dab265, compiled from source, probably the same as version 4.2), you can use this bash script
INFILE="movie.mp4"
SUBS="subtitles.srt"
OUTFILE="result.mp4"
ffmpeg -i "${INFILE}" -vf subtitles=${SUBS}:force_style='Borderstyle=4,Fontsize=16,BackColour=&H80000000'" "${OUTFILE}"
to burn subtitles.srt into movie.mp4 and save it as result.mp4.
The subtitles will appear correctly boxed in a 50% transparent rectangle,
even when there are 2 lines in a subtitle.
I need to add text in between a video. I have seen drawtext and seems it wont give effects to the text to be displayed.
My intention is to show a text within a box with some background to that box which should fly from left to right in between a video at a particular time. Is it possible with FFMPEG? I have tried different options with drawtext and nothing seems to be working. Any ideas on how to make it?
or is it possible to achieve by combining imagemagick and FFMPEG command?
How to make a zoom-in effect using ffmpeg. I need to create a video with a single image with Zoom-in as effect using FFMPEG. The Zoom-in should be bit slow. I have searched in the document and could find a sample. Can I get a command line sample?