Talk:ShowFrameNumber

Revision as of 18:20, 3 January 2016

ShowSMPTE: integral or drop-frame framerates only

On reading text-overlay.cpp ShowSMPTE::ShowSMPTE, it looks like the framerate must be an integer (±0.001) or be in drop-frame range (eg, 23.975 - 23.977); framerates like 24.25 will be rounded to int(24.25+0.5)==24.0 and the time calculation will be off. This can't be right!

## (source 24fps)
ShowTime(y=50) ## top center
ShowSMPTE ## time is correct

AssumeFPS(24000, 1001)
ShowTime(y=50)
ShowSMPTE ## time is correct

AssumeFPS(24.25) ## any number not an integer ±0.001 or listed in drop-frame table
ShowTime(y=50)
ShowSMPTE ## time is wrong

Raffriff42 04:08, 29 December 2015 (CET)

Inserted a warning re: non-integral frame rates with ShowSMPTE -- Raffriff42 06:28, 1 January 2016 (CET)

If I understand it correctly, the timecodes will always be off for non-integral frame rates. That is, unless you treat them all as drop frames, and count how much frames should be dropped every minute (note: this will not be the SMPTE standard anymore). Perhaps better would have been to throw an error for non-integral framerates and not being one of those standard drop-frame ranges. Admin 17:52, 3 January 2016 (CET)

Edit2: Did you actually run that script (with source fps = 24.25)? AviSynth throws an error in my case. Relevant code:

rate = int(_rate + 0.5);

...

else if (abs(_rate - rate) > 0.001) {

env->ThrowError("ShowSMPTE: rate argument must be 23.976, 29.97 or an integer");

ShowSMPTE: fps argument

I don't quite get the fps argument; is it to force a different framerate for timecode display purposes? For example, to show 24fps film frames on a 30fps video clip?
Raffriff42 04:17, 29 December 2015 (CET)

On testing, it seems the frame rate is overridden, throwing off the real time reading. Would not be useful in the above scenario.

Inserted an "unclear" tag, like this: roses are blue^(unclear) -- Raffriff42 06:28, 1 January 2016 (CET)

Good question. I will ask Ian. Admin 18:20, 3 January 2016 (CET)