Mainline Hardware Encoding

Mainline Hardware Encoding of video can be achieved through the V4L2 user-space API, for which currently only GStreamer implements the required code.

SoC Support

The following table shows the current supported codecs for encoding for each SoC. Support for decoding is separate.

Encoding With GStreamer

With GStreamer, in general, any V4L2 control can be set using the extra-controls=foo,name=value syntax after the encode pipeline stage identifier, where foo is any name you wish which GStreamer will promptly ignore, name is the name of the V4L2 control as shown by v4l2-ctl --list-ctrls (make sure to pick the right device with -d), and value is whatever value you want to set it to.

JPEG Encoding

This example converts an input MP4 file to an output MJPEG-inside-MKV file at JPEG quality 95, without any audio.

gst-launch-1.0 filesrc location=input.mp4 ! qtdemux name=demux demux.video_0 ! decodebin ! videoconvert ! v4l2jpegenc extra-controls=s,compression_quality=95 ! matroskamux ! filesink location=output.mkv

VP8 Encoding

This example converts an input MP4 file to an output VP8-inside-MKV file with a quantiser between 12 and 28, without any audio. The quantiser value goes from 0 (best quality, biggest filesize) to 63 (worst quality, smallest filesize).

gst-launch-1.0 filesrc location=input.mp4 ! qtdemux name=demux demux.video_0 ! decodebin ! videoconvert ! v4l2slvp8enc min-quality=12 max-quality=28 ! queue ! matroskamux ! filesink location=output.mkv

Alternatively, you can encode in variable bitrate mode with a target bitrate given in bits per second. Do note that Hantro doesn’t seem to do target bitrates below 2 mbit/s. In this example, the file is transcoded at a target bitrate of 3 megabits per second.

gst-launch-1.0 filesrc location=input.mp4 ! qtdemux name=demux demux.video_0 ! decodebin ! videoconvert ! v4l2slvp8enc bitrate=3000000 ! queue ! matroskamux ! filesink location=output.mkv