video -- text

Side note: to turn off annoying inactivity blanking, say when using a non-VLC player...

$ xset s -dpms

And then to restore it (if desired)....

$ xset s dpms

Some ppl find they have to add "$ xset s" entries "noblank" and/or "off", that is to use all three. In vanilla Arch for example, all three are required

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This post is a trail of crumbs for incorporating graphic, moving text into video -- a long term, continually evolving project. There are also some screenwriting notes at the bottom, since scripts are sometimes scrolled or portions used for graphics, etc.This top portion reviews subtitles, and a previous post (1/2021), wherein I addressed the basics of static titles or labels. The subtitle information includes both user-selected, and forced subtitles. So there's a lot to cover this post: subtitles, basic labeling, graphic text.

subtitles

Subtitles can be added to videos in an optional or forced capacity. Here's a page.

There are many subtitle formats, however we want our player to be able to use them. I see these most often and they have somewhat different applications.

1. SRT from the SubRip days. This is the most common but appears to only have bold, italic and underline.
2. ASS the most expressive, according to the last post in this thread. Fonts colors, etc. I've never used it.

extract subtitles

Get the subtitle (.SRT) file from the video and look it over, update it, re-imbed it, etc

$ ffmpeg -i foo.mp4 somename.srt

To extract them from YouTube videos, where a person might have seen a foreign film can require more reading. Typically they're just in English and will come in a VTT file, received with the following:

$ youtube-dl --all-subs --skip-download [URL]

from prior post*

*CPU intensive render, verify unobstructed system cooling.

For one or more lines of text, we can use the "drawtext" ffmpeg filter. Suppose we want to display the date and time of a video, in Cantarell font, for six seconds, in the upper left hand corner. If we have a single line of text, we can use ffmpeg's simple filtergraph (noted by "vf"). 50 pt font should be sufficient size in 1920x1080 video.

$ ffmpeg -i video.mp4 -vf "[in]drawtext=fontfile=/usr/share/fonts/cantarell/Cantarell-Regular.otf:fontsize=50:fontcolor=white:x=100:y=100:enable='between(t,2,8)':text='Monday\, January 17, 2021 -- 2\:16 PM PST'[out]" videotest.mp4

Notice that a backslash must be added to escape special characters: Colons, semicolons, commas, left and right parens, and of course apostrophe's and quotation marks. For this simple filter, we can also omit the [in] and [out] labels. Here is a screenshot of how it looks during play.

Next, supposing we want to organize the text into two lines. We'll need one filter for each line. Since we're still only using one input file to get one output file, we can still use "vf", the simple filtergraph. 10pixels seems enough to separate the lines, so I'm placing the second line down at y=210.

$ ffmpeg -i video.mp4 -vf "drawtext=fontfile=/usr/share/fonts/cantarell/Cantarell-Regular.otf:fontsize=50:fontcolor=white:x=100:y=150:enable='between(t,2,8)':text='Monday\, January 18\, 2021'","drawtext=fontfile=/usr/share/fonts/cantarell/Cantarell-Regular.otf:fontsize=50:fontcolor=white:x=100:y=210:enable='between(t,2,8)':text='2\:16 PM PST'" videotest2.mp4

We can continue to add additional lines of text in a similar manner. For more complex effects using 2 or more inputs, this 2016 video is the best I've seen.

Ffmpeg advanced techniques pt 2 (19:29) 0612 TV w/NERDfirst, 2016. This discusses multiple input labeling for multiple filters.

PNG incorporation

If I wanted to do several lines of information, an easier solution than making additional drawtexts, is to create a template the same size as the video, in this case 1980x1080. Using, say GiMP, we could create picture with an alpha template with several ines that we might use repeatedly, and save in Drive. There is then an ffmpeg command to superimpose a PNG over the MP4.

additional options (scripts, text files, captions, proprietary)

We of course have other options for skinning the cat: adding calls to text files, creating a bash script, or writing python code to call and do these things.

The simplest use of a text files are calls from the filter in place of writing the text out each filter.

viddyoze: online video graphics option. They reender it on the site, but it's not a transparent overlay, but a 720p MP4.

viddyoze review (14:30) Jenn Jager, 2020. Unsponsored review. Explains most of the 250 templates. Renders to quicktime (if alpha), or MP4 is not.~12 minute renders

screenwriting

We of course need a LaTeX format, but then...

Answer these 6 Questions  (14:56) Film Courage, 2021. About, want, get it, do about it, does/doesn't work, end.
PBX - on-site or cloud  (35:26) Lois Rossman, 2016. Cited mostly for source 17:45 breaks down schematically.
PBX - true overhead costs  (11:49) Rich Technology Center, 2020. Average vid, but tells hard facts. Asteriks server ($180) discussed.