使用FFmpeg进行X11屏幕录制时出现Past duration过大等错误的求助

Let's break down what's going wrong and get you a working screen recording command tailored to your 1920x1080 display.

First, Fix the Syntax Error in Your Original Command #

Your initial command has a critical typo: the -s (resolution) parameter uses a space between 1920 and 1080—FFmpeg interprets this as two separate invalid arguments. It should be 1920x1080 without spaces.

Address the "Not Enough Frames to Estimate Rate" Warning #

This happens because FFmpeg needs more data to properly detect the stream's rate. Add these two parameters to give it enough buffer:

• probesize 100M: Increases the amount of data FFmpeg reads to probe the stream
• analyzeduration 100M: Gives FFmpeg more time to analyze the stream before starting encoding

Fix "Past Duration Too Large" Warnings & Slow Recording Speed (0.382x) #

These issues stem from slow encoding performance. By default, FFmpeg might use a slow encoder preset that can't keep up with your 30fps capture. Switch to the ultrafast preset for libx264 (the most efficient H.264 encoder) to boost speed, and set a reasonable CRF (Constant Rate Factor) for balanced quality and file size.

The Final Working Command #

ffmpeg -f x11grab -framerate 30 -probesize 100M -analyzeduration 100M -s 1920x1080 -i :0 -c:v libx264 -preset ultrafast -crf 23 -threads 0 /tmp/capture.mp4

Let's walk through the key parameters:

• -framerate 30: Locks in your desired capture frame rate
• -c:v libx264: Uses the widely supported H.264 video encoder
• -preset ultrafast: Prioritizes encoding speed over file size (you can tweak this to fast or medium later if you want smaller files and don't mind slower recording)
• -crf 23: Balances quality and file size (lower values = better quality, higher = smaller files; 23 is a reliable default)
• -threads 0: Lets FFmpeg use all available CPU cores for faster processing

Optional: Add Audio Capture #

If you want to include system audio, add the ALSA input (use arecord -l to list your audio devices if default doesn't work):

ffmpeg -f x11grab -framerate 30 -probesize 100M -analyzeduration 100M -s 1920x1080 -i :0 -f alsa -ac 2 -i default -c:v libx264 -preset ultrafast -crf 23 -c:a aac -b:a 192k -threads 0 /tmp/capture_with_audio.mp4

内容的提问来源于stack exchange，提问作者showkey