SMPTE 12M timecode can only count frames up to 39, because the tens-of-frames
value is stored in 2 bit. In order to resolve this 50/60 fps SMPTE timecode is
using the field bit (which is the same bit as the phase correction bit) to
signal the least significant bit of a 50/60 fps timecode. See SMPTE ST
12-1:2014 section 12.1.
Therefore we slightly change the format of the return value of
av_timecode_get_smpte_from_framenum and AV_FRAME_DATA_S12M_TIMECODE and start
using the previously unused Phase Correction bit as Field bit. (As the SMPTE
standard suggests)
We add 50/60 fps support to av_timecode_get_smpte_from_framenum by calling the
recently added av_timecode_get_smpte function in it which already handles this
properly.
This change affects the decklink indev and the DV and MXF muxers. MXF has no
fate test for 50/60fps content, DV does, therefore the changes.
MediaInfo (a recent version) confirms that half-frame timecode must be inserted
to DV. MXFInspect confirms valid timecode insertion to the System Item of MXF
files. For MXF, also see EBU R122.
Note that for DV the field flag is not used because in the HDV specs (SMPTE
370M) it is still defined as biphase mark polarity correction flag. So it
should not matter that the DV muxer overrides the field bit.
Signed-off-by: Marton Balint <cus@passwd.hu>
Fixes the following warning:
libavutil/timecode.c:103:60: warning: '%02d' directive output may be truncated writing between 2 and 10 bytes into a region of size between 0 and 7
Some demuxers set a timecode in the format or streams metadata. The
muxers now make use of this metadata instead of a duplicated private
option.
This makes possible transparent copy of the timecode when transmuxing
and transcoding.
-timecode option for MPEG1/2 codec is also renamed to -gop_timecode. The
global ffmpeg -timecode option will set it anyway so no option change
visible for the user.
Marton Balint
Limin Wang
Carl Eugen Hoyos
Stefano Sabatini
Clément Bœsch
Matthieu Bouron