[Cin] Is the Waveform properly calibrated ?

Andrew Randrianasulu randrianasulu at gmail.com
Fri Nov 20 00:47:19 CET 2020

В сообщении от Friday 20 November 2020 01:51:29 Pierre autourduglobe via Cin написал(а):
> When I analyze a sequence of SMPT ntsc SD color bars generated by my DV 
> camera. The Waveform correctly indicates that the black bands are at 7.5 
> IRE but places the white band at around 92 IRE instead of 100 IRE and 
> the colored bands around 70 IRE instead of 75 IRE...
> This in a project in DV ntsc YUV 720x480 format with the preferences 
> "YUV colors space" to BT601 and "YUV color range" to JPEG.
> If you choose instead the preference "YUV color range" in MPEG, the 
> white band is correctly at 100 IRE and the colored bands are 75 IRE, 
> but... the black bands are now wrongly at 0 IRE...

Unfortunately I don't even know off-head what IRE mean in this context ... :(

But yes, there is possibility some settings not applied uniformely  
(because whole jpeg/mpeg thing was  implemented relatively lately in Cin's life)

You might try other Cin forks and see if they behave correctly...

I on mu side have some sad reincarnation of now-closed bug about inconsistent frame in compositor.
I was trying to make screenshot of exact (timecoded) frame , and ...I never figured out seqyence of actions 
(play, seek, framestep) to get my exact frame. It often works OK initially, but after just few seeks 
around it become off-by-one (usually one frame behind), and sometimes it return back to consisten state 
(I look at bottom of main window for hh:mm:ss.frames reading ... and I added this patch to assetpopup.C:

diff --git a/cinelerra-5.1/cinelerra/assetpopup.C b/cinelerra-5.1/cinelerra/assetpopup.C
index b414455c..915f3b63 100644
--- a/cinelerra-5.1/cinelerra/assetpopup.C
+++ b/cinelerra-5.1/cinelerra/assetpopup.C
@@ -959,6 +959,7 @@ int SnapshotMenuItem::handle_event()

                double position = edl->local_session->get_selectionstart(1);
                int64_t source_position = (int64_t)(position * edl->get_frame_rate());
+               printf("source_position from snapshot: %i \n", source_position);
                ret = !render_engine.vrender ? 1 :
                        render_engine.vrender->process_buffer(frame, source_position, 0);
                if( !ret )

it prints frame number each time I try to use snapshot function ....

I see Cin uses LocalSession::get_selectionstart(int highlight_only) in localsession.C and then 
/searching for keyword 'position'/ mwindow->edl->align_to_frame . Not sure, may be those two 
actually round things slightly differently? But I tried to use align_to_frame in this screenshot function 
and  it was consistently in step with original method ...in the wrong cases too!

I haven't tried render one frame yet, but I had problem seeing (and rendering!) 
very first timecode "...21" on this dvcam video I tried to use to check interlaced 
encoding .. :/ I tried to set in/out points by seeking to very beginning and framestepping, 
and by mouse selection ... I sometimes see first frame flashing if I do play 
backward - but render still starts from "...22"!

> So no possibility to have a good reading.
> This is true whether I use the X11-OpenGL video driver or just X11.
> I got the same results (problems) using the color bar from the Grass 
> Valley site:
> http://www.gvgdevelopers.com/K2DevGuide/Clips2/NTSC_SD_DV25_colorbar.avi
> http://www.gvgdevelopers.com/K2DevGuide/Clips2/NTSC_SD_DV50_colorbar.avi
> http://www.gvgdevelopers.com/K2DevGuide/Clips2/NTSC_SD_DVCAM_colorbar.avi
> Is the Waveform properly calibrated ?
> Pierre

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