How to count the frame drop when playing a video?

[zlinuxboy]

Hi, community.

I want to evaluate an arm64 cpu's decoder and render performance by counting the framedrop when playing different kind of encoding video, such as h264, h265, av1, vp9.
I have been tried the following lua script but failed.

local log_file_path = "./mpv.log"  -- Update this path

local function log_stats()
    local time_pos = mp.get_property_number("time-pos", 0)
    local decoder_frame_drop_count = mp.get_property_number("decoder-frame-drop-count", 0)
    local renderer_frame_drop_count = mp.get_property_number("frame-drop-count", 0)
    local log_entry = string.format("Time: %.2fs, Decoder Drops: %d, Renderer Drops: %d\n",
                                    time_pos, decoder_frame_drop_count, renderer_frame_drop_count)
    local log_file = io.open(log_file_path, "a")
    if log_file then
        log_file:write(log_entry)
        log_file:close()
    else
        print("Error: Unable to open log file.")
    end
end

mp.add_hook("on_unload", 50, log_duration("on_unload"))

-- mp.register_event("end-file", log_duration("end-file"))
-- mp.register_event("playback-restart", log_duration("playback-restart"))
-- mp.register_event("shutdown", log_duration("shutdown"))

there are always zero value no matter end-file, shutdown, on_unload event.
acturally, I could saw frame drop value is non-zero by mpv osd info

so how to fix it?