如何在ffmpeg中为字幕设置背景? [英] How to set background to subtitle in ffmpeg?

问题描述

.

1. 使用 aegisub 打开您的字幕文件.
2. 点击Subtitle → 样式管理器.
3. 在Current Script 下选择Default，然后按下Edit 按钮.
4. 使用 Outline 和 Shadow 值进行实验.选中不透明框.
5. 在Colors 下，点击Outline 或Shadows 下的颜色.将出现一个窗口.调整 Alpha 框的值以更改透明度.
6. 将字幕另存为 .ass 文件.

现在您可以使用 AAS 文件通过 ffmpeg 制作

您可以通过以下方式避免这种情况:

1. 将 Outline 和 Shadow 大小更改为 0.
2. 阴影的 alpha 设置将控制背景框的透明度.单击阴影颜色以将阴影颜色的 Alpha 调整为所需的透明度级别.

3. 在文本编辑器中编辑 ASS 文件.在 Style 行中，将 BorderStyle 对应的值更改为 4.这将填充每个字幕事件的边界框背景.示例 Style 行:

   Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H80000000,&H80000000,-1,0,0,0,100,100,0,0,4,0,0,2,10,10,10,1

示例:

请注意，BorderStyle=4 是一个非标准值，因此它可能无法在所有播放器中正常工作.

_感谢

ffmpeg -i input -filter_complex "drawbox=w=iw:h=24:y=ih-28:t=max:color=black@0.4,subtitles=subs.ass" 输出

缺点是你必须考虑到长字幕的换行或换行.简单地使框更高以进行补偿就足够了，但会看起来很难看，因为字幕基线保持静态:单行字幕的顶部填充比底部多.

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?

解决方案

ASS subtitles can have a semi-transparent background for the text.

With aegisub

The easiest way to do this is with aegisub.

1. Open your subtitles file with aegisub.
2. Click Subtitle → Styles manager.
3. Under Current Script choose Default, then press the Edit button.
4. Experiment with the Outline and Shadow values. Check Opaque box.
5. Under Colors click the color under Outline or Shadows. A window will appear. Adjust the value of the Alpha box to change transparency.
6. 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:

1. Changing the Outline and Shadow sizes to 0.
2. 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.

3. 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.

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