avutil/timecode: allow drop frame timecodes for multiples of 30000/1001 fps

Signed-off-by: Marton Balint <cus@passwd.hu>

libavutil/timecode.c

@@ -33,16 +33,13 @@
 
 int av_timecode_adjust_ntsc_framenum2(int framenum, int fps)
 {
-    /* only works for NTSC 29.97 and 59.94 */
+    /* only works for multiples of NTSC 29.97 */
     int drop_frames = 0;
     int d, m, frames_per_10mins;
 
-    if (fps == 30) {
-        drop_frames = 2;
-        frames_per_10mins = 17982;
-    } else if (fps == 60) {
-        drop_frames = 4;
-        frames_per_10mins = 35964;
+    if (fps && fps % 30 == 0) {
+        drop_frames = fps / 30 * 2;
+        frames_per_10mins = fps / 30 * 17982;
     } else
         return framenum;
 
@@ -196,8 +193,8 @@ static int check_timecode(void *log_ctx, AVTimecode *tc)
         av_log(log_ctx, AV_LOG_ERROR, "Valid timecode frame rate must be specified. Minimum value is 1\n");
         return AVERROR(EINVAL);
     }
-    if ((tc->flags & AV_TIMECODE_FLAG_DROPFRAME) && tc->fps != 30 && tc->fps != 60) {
-        av_log(log_ctx, AV_LOG_ERROR, "Drop frame is only allowed with 30000/1001 or 60000/1001 FPS\n");
+    if ((tc->flags & AV_TIMECODE_FLAG_DROPFRAME) && tc->fps % 30 != 0) {
+        av_log(log_ctx, AV_LOG_ERROR, "Drop frame is only allowed with multiples of 30000/1001 FPS\n");
         return AVERROR(EINVAL);
     }
     if (check_fps(tc->fps) < 0) {
@@ -252,7 +249,7 @@ int av_timecode_init_from_string(AVTimecode *tc, AVRational rate, const char *st
     tc->start = (hh*3600 + mm*60 + ss) * tc->fps + ff;
     if (tc->flags & AV_TIMECODE_FLAG_DROPFRAME) { /* adjust frame number */
         int tmins = 60*hh + mm;
-        tc->start -= (tc->fps == 30 ? 2 : 4) * (tmins - tmins/10);
+        tc->start -= (tc->fps / 30 * 2) * (tmins - tmins/10);
     }
     return 0;
 }

libavutil/timecode.h

@@ -49,9 +49,9 @@ typedef struct {
  * Adjust frame number for NTSC drop frame time code.
  *
  * @param framenum frame number to adjust
- * @param fps      frame per second, 30 or 60
+ * @param fps      frame per second, multiples of 30
  * @return         adjusted frame number
- * @warning        adjustment is only valid in NTSC 29.97 and 59.94
+ * @warning        adjustment is only valid for multiples of NTSC 29.97
  */
 int av_timecode_adjust_ntsc_framenum2(int framenum, int fps);