ffmpeg commands

July 22nd, 2010

This post contains a number of useful commands for ffmpeg, a tool for converting video file formats. This post shows how to convert AVI to MPEG, MPEG to FLV, how to extract sound from a video, and how to get still frames from a video. Video information You can have ffmpeg read a video file […]

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This post contains a number of useful commands for ffmpeg, a tool for converting video file formats. This post shows how to convert AVI to MPEG, MPEG to FLV, how to extract sound from a video, and how to get still frames from a video.

Video information

You can have ffmpeg read a video file and show information about it like so:

This will tell you the video length, bitrate, and video and audio stream formats, e.g.

Getting a still from a video

In order to get a single frame from a video and save it as a JPEG so that you can use it as a preview, do:

This will record 1 frame (vframes=1) at a framerate of 1 (r=1), at position 1:15 , ignoring audio (-an). You can record multiple stills this way: set the number of frames (vframes) to the number of stills you want, and specify a framerate. If you set r=10, stills will be recorded every 10 seconds. You will need to specify a naming system for the output files:

You can specify the frame size (resolution) for your stills:

Or fiddle with the aspect ratio:

Extracting sound from a video file

If you want to extract the sound from a video file and save it off as an mp3, do:

Here, we use -vn to disable video. We set the audio sampling rate to ar=44.1 kHz, number of channels to ac=2, and the bitrate to ab=192 bps. The result is saved to mp3 (we force mp3 format using the -f flag).

Convert video formats

Nothing could be easier in ffmpeg (ignoring bags of flags to finetune the output). Converting AVI to MPEG is done like this:

And the other way around:

Or AVI to FLV:

The flag you’ll probably need is:

This will change the movie resolution to 320×240, which will be handy when you plan to show your video online.

Full documentation for ffmpeg is here.

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