[HOW-TO] force h264 encoding to include b frames?

[maholli]

Using picamera2, I am manually sending an h264 stream in ~200 byte chunks and reconstructing / displaying the stream.

I have things nominally working, but since there is inherently packet loss as part of my application, it would work a lot better if the encoded h264 could include B-Frames.

@davidplowman is it possible to specify b frames to the v4l2 encoder? Maybe by setting something similar to V4L2_CID_MPEG_VIDEOENC_NUM_BFRAMES?

For demo purposes, below is the video and encoder configs I've been using to baseline:

video_config = picam2.create_video_configuration(
    raw=None,
    lores=None,
    main={"size": (320,240), 'format': 'YUV420'},
    buffer_count=8,
    encode="main",
    )
picam2.configure(video_config)
encoder = H264Encoder(bitrate=62000,framerate=25.0,iperiod=5,enable_sps_framerate=True,repeat=True)

And to observe the frame types, I've been using ffprobe -show_frames -i test.h264 | grep "pict_type" on a picamera2 output file.

Any insight would be much appreciated! Thanks :)