videoffmpeg

How can I generate a video file directly from an FFmpeg filter with no actual input file?

FFmpeg has a number of video generating filters, listed in the documentation as "video sources":

Those are great for using with other filters like overlay, but is there any way that I can generate a movie consisting of just one of those video sources without any input video?

Something like:

ffmpeg -vf color=red" red_movie.mp4

Except that that errors out with At least one input file must be specified.

Solution

  • It looks like the options have changed slightly in recent versions.

    To use the filter input sources, you have to:

    1. Set the input format to the libavfilter virtual device using: -f lavfi
    2. Set the filter input source using the -i flag (not -vf)
    3. Provide arguments as complete key-value pairs, like: color=color=red

    This works for ffplay, too, to test your filtergraph: ffplay -f lavfi -i color

    Examples

    In these examples I've added -t 30 to specify that I only want 30 seconds of output.

    Color (Red)

    ffmpeg -f lavfi -i color=color=red -t 30 red.mp4
                     ^     ^    ^
                     |     |    |
                   filter key value

    The key can be shortened to its abbreviated form: -i color=c=red

    SMPTE Color Bars Pattern

    ffmpeg -f lavfi -i smptebars -t 30 smpte.mp4

    Test Source Pattern

    ffmpeg -f lavfi -i testsrc -t 30 -pix_fmt yuv420p testsrc.mp4

    In order for this to playback reliably, you might need to set the pixel format with: -pix_fmt yuv420p

    By default, ffmpeg will use yuv444p (x264, High 4:4:4 Predictive), which some players aren't yet able to decode.

    For instance, the video it creates is crashing VLC 2.0.7 and is just 30 seconds of black in QuickTime Player 10.2 (Mac OS X 10.8.4).

    More info on test source here.

    RGB Test Source

    ffmpeg -f lavfi -i rgbtestsrc -pix_fmt yuv420p -t 30 rgbtestsrc.mp4

    As with the last example, this might not work for you unless you set the pixel format to yuv420p as shown.

    For posterity, here's the version I'm using:

    ffmpeg version 1.2.1
libavutil      52. 18.100 / 52. 18.100
libavcodec     54. 92.100 / 54. 92.100
libavformat    54. 63.104 / 54. 63.104
libavdevice    54.  3.103 / 54.  3.103
libavfilter     3. 42.103 /  3. 42.103
libswscale      2.  2.100 /  2.  2.100
libswresample   0. 17.102 /  0. 17.102
libpostproc    52.  2.100 / 52.  2.100