-
-<p>
-<strong>When enabled</strong> the external timecode source is assumed to use 29.970000 fps instead of 30000/1001. SMPTE 12M-1999 specifies 29.97df as 30000/1001. The <acronym title="specification">spec</acronym> further mentions that drop-frame timecode has an accumulated error of -86ms over a 24-hour period. Drop-frame timecode would compensate exactly for a NTSC color frame rate of 30 * 0.9990 (ie 29.970000). That is not the actual rate. However, some vendors use that rate - despite it being against the specs - because the variant of using exactly 29.97 fps yields zero timecode drift.
+<p class="warning">
+ 29.97 drop-frame timecode is another corner case. While the SMPTE 12M-1999
+ specifies 29.97df as 30000/1001 frames per second, not all hardware devices
+ follow that standard. The checkbox
+ <kbd class="option">Lock to 29.9700 fps instead of 30000/1001</kbd> allows
+ to use a compatibility mode for those devices.<br />
+ When enabled, the external timecode source is assumed to use 29.970000 fps
+ instead of 30000/1001. SMPTE 12M-1999 specifies 29.97df as 30000/1001. The
+ <abbr title="specification">spec</abbr> further mentions that drop-frame
+ timecode has an accumulated error of -86 ms over a 24-hour period.
+ Drop-frame timecode would compensate exactly for a NTSC color frame rate
+ of 30 * 0.9990 (ie 29.970000). That is <em>not</em> the actual rate. However,
+ some vendors use that rate — despite it being against the specs
+ — because the variant of using exactly 29.97 fps yields zero timecode
+ drift.