-- An MPEG-2 elementary stream shows the frame a search names.  testScripts/esFrames.m2v is twelve
-- flat gray frames, frame k at luma 32 + 16k, coded as I, P, and B frames (IBBPBBIBBPBI), made by
--
--     python3 -c "import sys; [sys.stdout.buffer.write(bytes([32 + 16 * k]) * 19200 + bytes([128]) * 9600) for k in range(12)]" |
--         ffmpeg -f rawvideo -pix_fmt yuv420p -s 160x120 -r 25 -i - -c:v mpeg2video -g 6 -bf 2 -q:v 1 -f mpeg2video esFrames.m2v
--
-- Such a stream times its I and P frames by decode time alone, and the decoder hands each one over a
-- frame later than that:  a search to frame k showed frame k - 1, a search to the first frame of a
-- segment never seen showed nothing, and with B frames some searches landed far off.  Whatever disc
-- it was given, the scene runs itself again with the clip for a disc, searches to every frame out of
-- order, and reads the picture back with vldpGetYUVPixel.  Each check prints "ESFRAMES ok" or
-- "ESFRAMES FAIL".
dofile("Singe/Framework.singe")

local CLIP     = "testScripts/esFrames.m2v"
local FRAMES   = 12
local BASE     = 32           -- Luma of frame 0
local STEP     = 16           -- Luma added for each frame after it
local SETTLE   = 8            -- Frames a search is given to show
local ORDER    = { 5, 0, 11, 1, 7, 2, 10, 3, 9, 4, 8, 6, 0 }
local frames   = 0
local turn     = 0
local due      = 2
local failures = 0


local function check(name, ok, detail)
	if ok then
		debugPrint("ESFRAMES ok " .. name)
	else
		failures = failures + 1
		debugPrint("ESFRAMES FAIL " .. name .. (detail and ("  (" .. detail .. ")") or ""))
	end
end


function onOverlayUpdate()
	local luma = 0
	local seen = 0

	frames = frames + 1
	overlayClear()
	if discGetFrameCount() ~= FRAMES then
		-- Not the clip yet:  again, with the clip for a disc.
		if frames == 1 then
			scriptExecute({ SCRIPT = "testScripts/scene105.singe", VIDEO = CLIP })
		end
		return OVERLAY_UPDATED
	end
	if frames < due then
		return OVERLAY_UPDATED
	end
	if turn > 0 then
		luma = vldpGetYUVPixel(overlayGetWidth() / 2, overlayGetHeight() / 2)
		seen = math.floor((luma - BASE) / STEP + 0.5)
		check("search to " .. ORDER[turn], (seen == ORDER[turn]) and (discGetFrame() == ORDER[turn]), "picture " .. seen .. ", disc " .. discGetFrame())
	end
	turn = turn + 1
	if turn > #ORDER then
		singeScreenshot("last")
		debugPrint(string.format("ESFRAMES RESULT failures=%d", failures))
		singeQuit()
	else
		discSearch(ORDER[turn])
		due = frames + SETTLE
	end
	return OVERLAY_UPDATED
end