Eliminating Extra Lines when Displaying Text File using FFplay and FFmpeg

In this article, we will discuss how to eliminate extra lines when displaying a text file using FFplay or FFmpeg. Displaying text files with FFplay or FFmpeg can sometimes result in additional, unwanted lines. We will explain the causes and solutions for this issue.

Understanding FFplay and FFmpeg

FFplay and FFmpeg are powerful, open-source media processing tools, part of the FFmpeg project. While FFmpeg is primarily used for transcoding, muxing, demuxing, and filtering multimedia data, FFplay is a simple media player that can be used for testing, debugging, and basic media playback.

Extra Lines Issue in Text Display

When displaying a text file (using the -vf "drawtext" filter) with FFplay or FFmpeg, you might face an issue where extra lines appear between the actual text lines. This problem is caused by the automatic line wrapping and the spacing options in the FFmpeg drawtext filter.

Causes of Extra Lines

The extra lines are usually caused by one or more of the following reasons:

• Automatic line wrapping due to character limits per line:
-vf "drawtext=fontfile=/path/to/font.ttf: \ text='Original Text': fontcolor=white: \ fontsize=24: box=1: boxcolor=black: \ boxborderw=5: x=10: y=10: \ width=w-20: height=h-20: \ overflow_wrap=line: \ line_spacing=0"
• Using default margins and line spacing settings:
-vf "drawtext=fontfile=/path/to/font.ttf: \ text='Original Text': fontcolor=white: \ fontsize=24: box=1: boxcolor=black: \ boxborderw=5: x=10: y=10: \ width=w-20: height=h-20: \ marginb=10: marginl=10"

Solving the Extra Lines Issue

To solve this issue and eliminate the extra lines, you need to adjust the line wrapping and spacing options in the FFmpeg drawtext filter.

• Restrict the line wrapping to only break at specific characters:
-vf "drawtext=fontfile=/path/to/font.ttf: \ text='Original Text': fontcolor=white: \ fontsize=24: box=1: boxcolor=black: \ boxborderw=5: x=10: y=10: \ width=w-20: height=h-20: \ overflow_wrap=char: \ line_spacing=0"
• Manually set line spacing to 0:
-vf "drawtext=fontfile=/path/to/font.ttf: \ text='Original Text': fontcolor=white: \ fontsize=24: box=1: boxcolor=black: \ boxborderw=5: x=10: y=10: \ width=w-20: height=h-20: \ line_spacing=0"

We have discussed the issue of extra lines displaying while showing text files with FFplay or FFmpeg and provided explanations and solutions to overcome this problem. By customizing line wrapping and spacing options in the FFmpeg drawtext filter, it is possible to display text files without extra lines.

References

• FFmpeg Official Website
• FFmpeg Drawtext Filter Documentation