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fix: wrong timecode calculation on NTSC framerates

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minjaesong
2025-11-16 02:49:03 +09:00
parent 5c87325366
commit aa7e20695d
4 changed files with 74 additions and 27 deletions
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12
video_encoder/encoder_tav.c
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@@ -8108,13 +8108,14 @@ static void write_timecode_packet(FILE *output, int frame_num, int fps, int is_n
fwrite(&packet_type, 1, 1, output);
// Calculate timecode in nanoseconds
// For NTSC (29.97 fps): time = frame_num * 1001000000 / 30000
// For NTSC framerates (X000/1001): time = frame_num * 1001 * 1000000000 / (fps * 1000)
// For other framerates: time = frame_num * 1000000000 / fps
uint64_t timecode_ns;
if (is_ntsc_framerate) {
// NTSC uses 30000/1001 fps (29.97...)
// To avoid floating point: time_ns = frame_num * 1001000000 / 30000
timecode_ns = ((uint64_t)frame_num * 1001000000ULL) / 30000ULL;
// NTSC framerates use denominator 1001 (e.g., 24000/1001, 30000/1001, 60000/1001)
// To avoid floating point: time_ns = frame_num * 1001 * 1e9 / (fps * 1000)
// This works for 24fps NTSC (23.976), 30fps NTSC (29.97), 60fps NTSC (59.94), etc.
timecode_ns = ((uint64_t)frame_num * 1001ULL * 1000000000ULL) / ((uint64_t)fps * 1000ULL);
} else {
// Standard framerate
timecode_ns = ((uint64_t)frame_num * 1000000000ULL) / (uint64_t)fps;
@@ -10779,7 +10780,8 @@ int main(int argc, char *argv[]) {
// Update ENDT in extended header (calculate end time for last frame)
uint64_t endt_ns;
if (enc->is_ntsc_framerate) {
endt_ns = ((uint64_t)(frame_count - 1) * 1001000000ULL) / 30000ULL;
// NTSC framerates use denominator 1001 (e.g., 24000/1001, 30000/1001, 60000/1001)
endt_ns = ((uint64_t)(frame_count - 1) * 1001ULL * 1000000000ULL) / ((uint64_t)enc->output_fps * 1000ULL);
} else {
endt_ns = ((uint64_t)(frame_count - 1) * 1000000000ULL) / (uint64_t)enc->output_fps;
}