Nest SDM integration - how to adjust ffmpeg parameters?

The nest SDM integration has been working well for the most part. However, when I try to view the stream from HomeKit video integration it appears to have a very slow frame rate. I suspect it’s due to a conservative default parameter. Doing ps | grep ffmpeg during a streaming of nest video feed I can see some of the parameters used in ffmpeg.

> ps | grep ffmpeg
83862 root      0:00 ffmpeg -i rtsps://stream-us1-bravo.dropcam.com:443/sdm_live_stream/[redacted] -hide_banner -nostats -map 0:v:0 -an -c:v copy -tune zerolatency -pix_fmt yuv420p -r 30 -b:v 299k -bufsize 1196k -maxrate 299k -payload_type 99 -ssrc 10019161 -f rtp -srtp_out_suite AES_CM_128_HMAC_SHA1_80 -srtp_out_params [redacted_token]@srtp://xxx:59087?rtcpport=59087&localrtpport=59087&pkt_size=1316

I could not find in any documentation guide as how to adjust these default parameters. I would greatly appreciate any tip on how to adjust this. Thank you.

Update looks like these parameters are from here

not sure where {v_max_bitrate} is defined though.