Having looked at similar posts before it seems like there is a bug with using hardware-accelerated video encoding for Live-DVR. Without proper documentation we are all having to figure out what is a good setting between 0-99 in general without HW encoding turned on. When it is turned on it looks like it is doubling the bitrate.
For example when I have HW turned on and the setting at 75 I see this in the logs:
hevc_vaapi -b:0 17091k -maxrate:0 17091k -bufsize:0 34182k
Keeping in mind when transcoding is turned off the MPEG-2 bitrate for this channel is around 7-9mbps.
To see what other settings are producing I tried at a quality of 35:
hevc_vaapi -b:0 12242k -maxrate:0 12242k -bufsize:0 24484k
Then I tried at a quality of 10:
hevc_vaapi -b:0 9212k -maxrate:0 9212k -bufsize:0 18424k
So check marking the box for Use hardware-accelerated video encoding I would need to set the quality to 10 or lower to get the same bitrate as a regular recording of MPEG-2. This needs to be addressed if you are going to offer this as an option to people.
On top of this issue is there a way we could have HEVC as a regular software transcoding option for Live-DVR instead of only H264?