Video Encoding

If you have ffmpeg installed, you can record MP4 videos using the mp4 output plugin.

You can optionally use an audio file as input.

Depending on your computer and/or your setup, MP4 encoding can use a lot of CPU time, which will slow down display and also break timers (auto sequence/colormap/image changes for example). To avoid this, use the --soft-timers option.

Encoding can be started and stopped through the web interface:

To automatically begin encoding when Le Biniou is started, use the --start-encoding option.

Encoding an audio track using a playlist

You can batch-encode an audio track using sequences with the --playlist (or -P) option.

This option takes a JSON filename as argument:

{
    "soft timers": true,
    "mode": "cycle",
    "end": "exit",
    "seed": 2847592,
    "tracks": [
        {
            "sequence": "My sequence #1",
            "duration": 20
        },
        {
            "sequence": "1596643366",
            "duration": 30.5
        }
     ]
}

You can set:

• soft timers: optional, use soft timers (recommended when encoding). If not set, defaults to true.
• mode: optional, set the order for playing tracks. Can be cycle, shuffle or random. If the track list’s duration - matches the audio track length, you should use cycle or shuffle. If not set, defaults to cycle.
• end: what to do when playing all sequences are done. If not set, Le Biniou will continue running. If set to exit, - encoding will stop. Note that encoding will automatically stop when the end of the audio track is reached, so this - is not really needed.
• seed: optional, a positive random integer to seed the PRNG, so you can get reproducible videos.
• tracks: mandatory, must be a list of sequence names with their duration.

So, given this example.json playlist:

{
    "tracks": [
        {
            "sequence": "My sequence #1",
            "duration": 20
        },
        {
            "sequence": "1596643366",
            "duration": 30.5
        }
     ]
}

HD encoding (1920×1080, 30fps) can be achieved using:

$ lebiniou --input sndfile --audio /path/to/some.wav --output mp4 --start-encoding --width 1920 --height 1080 --max-fps 30 --playlist example.json

The video will be saved as ~/.lebiniou/mp4/my_track-YYYY-MM-DD_HH-MM-SS.mp4.

Tweak mp4 output quality

The mp4 output plugin uses FFMPEG's default values for video and audio encoding quality, which are not optimal and can lead to compression artifacts in both streams if you aim high quality.

Le Biniou provides 2 environment variables to tweak both to your convenience:

• LEBINIOU_MP4_CRF, which sets the FFMPEG parameter -crf, which is the Constant Rate Factor for x264 encoding. It defaults to the same value as FFMPEG with libx264 encoding, 23. From FFMPEG's wiki:

  The range of the CRF scale is 0–51, where 0 is lossless, 23 is the default, and 51 is worst quality possible. A lower value generally leads to higher quality, and a subjectively sane range is 17–28. Consider 17 or 18 to be visually lossless or nearly so; it should look the same or nearly the same as the input but it isn't technically lossless.

• LEBINIOU_MP4_AUDIO_ENCODING_RATE, which sets the FFMPEG parameter -b:a, which is the audio bitrate for AAC encoding. Its default value is the same as FFMPEG one, 128k.

Recommended bitrate for HQ stereo audio is 224k to 384k. More info at FFMPEG's wiki .

Exemple above with HQ 1080p mp4 output:

$ LEBINIOU_MP4_CRF=17 LEBINIOU_MP4_AUDIO_ENCODING_RATE=384K lebiniou --input sndfile --audio /path/to/some.wav --output mp4 --start-encoding --width 1920 --height 1080 --max-fps 30 --playlist example.json