Ubuntu下FFmpeg命令中-r参数的用法及官方说明咨询

Hey there! Let's break down exactly what the -r parameter does in your FFmpeg command, plus its official specifications:

先看你的命令里的-r 60 #

In your command:

ffmpeg -i input_video -vf scale=w=320:h=-1 -y -vcodec libx264 -preset ultrafast -r 60 output_video

The -r 60 here acts as an output option (since it's placed before the output file name). It forces the output video to have a frame rate of 60 frames per second (fps).

If your input video has a different frame rate, FFmpeg will automatically adjust: it'll duplicate frames if the output fps is higher than the input, or drop frames if it's lower.

-r参数的两种核心用法 #

1. Output option (most common for your use case) #

When placed before the output file, -r fps sets the exact frame rate of the output video. You can use numerical values (like 60), fractions (e.g., 30000/1001 for NTSC 29.97fps), or even abbreviations where supported.

2. Input option #

If you place -r fps before the -i input_video part, it changes how FFmpeg interprets the input's timing:

• It ignores any existing timestamps stored in the input file
• Instead, it generates new timestamps assuming the input has a constant frame rate of fps

This is different from the -framerate option, which is typically used for input sources that don't have built-in frame rate info (like image sequences).

官方文档原文引用 #

-r[:stream_specifier] fps (input/output,per-stream) 设置帧率（Hz值、分数或缩写形式）。作为输入选项时，忽略文件中存储的任何时间戳，转而假设恒定帧率fps生成时间戳，这与部分输入场景中使用的-framerate选项不同……

内容的提问来源于stack exchange，提问作者machinery