- From: Alexander Cerutti via GitHub <sysbot+gh@w3.org>
- Date: Sun, 23 Jul 2023 22:54:31 +0000
- To: public-tt@w3.org
alexandercerutti has just created a new issue for https://github.com/w3c/ttml2: == SMPTE Time Base: NTSC and PAL magic numbers for droppedFrames == Hello there, I was studying ttml2 standard to create a personal implementation (for a subtitle system available on my Github profile). I was reading about `ttp:dropMode` and droppedFrames in relation to [SMPTE standard (I.3)](https://www.w3.org/TR/2018/REC-ttml2-20181108/#time-expression-semantics-smpte) timings. I was able to find the explanation on the standard document and on external sites, but I wasn't able to find what are the magic numbers for NTSC (54) and PAL (27) used in droppedFrames calculation: NTSC: ``` (hours * 54 + minutes – floor(minutes/10)) * 2; ``` PAL: ``` (hours * 27 + floor(minutes/2) – floor(minutes/20)) * 4; ``` Do you know where can I find the reason for which those numbers are used? Thank you! Please view or discuss this issue at https://github.com/w3c/ttml2/issues/1265 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Sunday, 23 July 2023 22:54:32 UTC