[FFmpeg-devel] [PATCH 2/3] avutil/timecode: fix av_timecode_get_smpte_from_framenum with 50/60 fps
Marton Balint
cus at passwd.hu
Tue Jul 21 13:42:03 EEST 2020
On Tue, 21 Jul 2020, lance.lmwang at gmail.com wrote:
> On Tue, Jul 21, 2020 at 11:07:29AM +0200, Marton Balint wrote:
>>
>>
>> On Tue, 21 Jul 2020, lance.lmwang at gmail.com wrote:
>>
>> > On Mon, Jul 20, 2020 at 11:04:38PM +0200, Marton Balint wrote:
>> > > 50/60 fps timecode is using the field bit (which is the same 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.
>> > >
>> > > Let's add support for this by using the recently added av_timecode_get_smpte
>> > > function which handles this properly.
>> > >
>> > > This change affects DV and MXF encoder, MXF has no fate for 50/60fps content,
>> > > DV does, therefore the changes. It also affects decklink indev.
>> > >
>> > > MediaInfo (a recent version) confirms that half-frame timecode must be
>> > > inserted. (although MediaInfo does not seem to check the field flag).
>> > > MXFInspect confirms valid timecode insertion to the System Item of MXF files.
>> > >
>> > > Signed-off-by: Marton Balint <cus at passwd.hu>
>> > > ---
>> > > libavutil/timecode.c | 15 +--------------
>> > > libavutil/timecode.h | 7 +++----
>> > > tests/ref/vsynth/vsynth1-dv-hd | 2 +-
>> > > tests/ref/vsynth/vsynth2-dv-hd | 2 +-
>> > > tests/ref/vsynth/vsynth3-dv-hd | 2 +-
>> > > tests/ref/vsynth/vsynth_lena-dv-hd | 2 +-
>> > > 6 files changed, 8 insertions(+), 22 deletions(-)
>> > >
>> > > diff --git a/libavutil/timecode.c b/libavutil/timecode.c
>> > > index cca53d73c4..cb916970ef 100644
>> > > --- a/libavutil/timecode.c
>> > > +++ b/libavutil/timecode.c
>> > > @@ -65,20 +65,7 @@ uint32_t av_timecode_get_smpte_from_framenum(const AVTimecode *tc, int framenum)
>> > > ss = framenum / fps % 60;
>> > > mm = framenum / (fps*60) % 60;
>> > > hh = framenum / (fps*3600) % 24;
>> > > - return 0 << 31 | // color frame flag (0: unsync mode, 1: sync mode)
>> > > - drop << 30 | // drop frame flag (0: non drop, 1: drop)
>> > > - (ff / 10) << 28 | // tens of frames
>> > > - (ff % 10) << 24 | // units of frames
>> > > - 0 << 23 | // PC (NTSC) or BGF0 (PAL)
>> > > - (ss / 10) << 20 | // tens of seconds
>> > > - (ss % 10) << 16 | // units of seconds
>> > > - 0 << 15 | // BGF0 (NTSC) or BGF2 (PAL)
>> > > - (mm / 10) << 12 | // tens of minutes
>> > > - (mm % 10) << 8 | // units of minutes
>> > > - 0 << 7 | // BGF2 (NTSC) or PC (PAL)
>> > > - 0 << 6 | // BGF1
>> > > - (hh / 10) << 4 | // tens of hours
>> > > - (hh % 10); // units of hours
>> > > + return av_timecode_get_smpte(tc->rate, drop, hh, mm, ss, ff);
>> >
>> > av_timecode_get_smpte() is used by the h264/hevc, and the specs reserved more bits for ff, so in case it's
>> > > 30fps, so av_timecode_get_smpte() will divide ff by 2 to get frame pair. But for SMPTE ST 12 specs, the
>> > ff reserved 2 bits for tens, so for > 30fps, it's supported by frame pair and ff
>> > is divide by 2 already by the spec, so you'll get unexpected results if divide
>> > by 2 again(four frame pair if test)
>>
>> I don't understand what you want to say. av_timecode_get_smpte_from_framenum
>> is a function for which the number of frames (as a single integer) is
>> passed. Clearly the number of frames as a single integer is not divided by
>> anything, so there cannot be double division when
>> av_timecode_get_smpte_from_framenum() calls av_timecode_get_smpte().
>
> For example, when I'm print out the tc from timecode->GetString(&decklink_tc) in
> decklink_dec.cpp for fps = 50, the tc will be:
>
> 00:00:00:00
> 00:00:00:00 -> repeat TC for frame pair
> 00:00:00:01
> 00:00:00:01 -> repeat
> ....
>
> 00:00:00:24
> 00:00:00:24 -> repeat, 50 frame now
>
> 00:00:00:00
> 00:00:00:00 -> repeat
That's because your input is containing the wrong timecode, as I suggested
in the other thread.
>
> If the av_timecode_get_smpte_from_framenum(), the ff will be divided by 2 after change, you'll get below:
>
> 00:00:00:00
> 00:00:00:00
> 00:00:00:00
> 00:00:00:00
> 00:00:00:01
> 00:00:00:01
> 00:00:00:01
> 00:00:00:01
> ....
>
> 00:00:00:12
> 00:00:00:12
> 00:00:00:12
> 00:00:00:12 -> 50 frame now, repeat 4 times
>
> 00:00:00:00
> 00:00:00:00
> 00:00:00:00
> 00:00:00:00
And this is because av_timecode_make_smpte_tc_string does not handle 50fps
timecodes properly.
Regards,
Marton
>
> I'm not sure whether it's clear to explain my meaning.
>
>
>>
>> Regards,
>> Marton
>>
>> >
>> >
>> > > }
>> > >
>> > > uint32_t av_timecode_get_smpte(AVRational rate, int drop, int hh, int mm, int ss, int ff)
>> > > diff --git a/libavutil/timecode.h b/libavutil/timecode.h
>> > > index 5801330921..e54b116e93 100644
>> > > --- a/libavutil/timecode.h
>> > > +++ b/libavutil/timecode.h
>> > > @@ -66,11 +66,11 @@ int av_timecode_adjust_ntsc_framenum2(int framenum, int fps);
>> > > * the format description as follows:
>> > > * bits 0-5: hours, in BCD(6bits)
>> > > * bits 6: BGF1
>> > > - * bits 7: BGF2 (NTSC) or PC (PAL)
>> > > + * bits 7: BGF2 (NTSC) or FIELD (PAL)
>> > > * bits 8-14: minutes, in BCD(7bits)
>> > > * bits 15: BGF0 (NTSC) or BGF2 (PAL)
>> > > * bits 16-22: seconds, in BCD(7bits)
>> > > - * bits 23: PC (NTSC) or BGF0 (PAL)
>> > > + * bits 23: FIELD (NTSC) or BGF0 (PAL)
>> > > * bits 24-29: frames, in BCD(6bits)
>> > > * bits 30: drop frame flag (0: non drop, 1: drop)
>> > > * bits 31: color frame flag (0: unsync mode, 1: sync mode)
>> > > @@ -78,8 +78,7 @@ int av_timecode_adjust_ntsc_framenum2(int framenum, int fps);
>> > > * @note Frame number adjustment is automatically done in case of drop timecode,
>> > > * you do NOT have to call av_timecode_adjust_ntsc_framenum2().
>> > > * @note The frame number is relative to tc->start.
>> > > - * @note Color frame (CF), binary group flags (BGF) and biphase mark polarity
>> > > - * correction (PC) bits are set to zero.
>> > > + * @note Color frame (CF) and binary group flags (BGF) bits are set to zero.
>> > > */
>> > > uint32_t av_timecode_get_smpte_from_framenum(const AVTimecode *tc, int framenum);
>> > >
>> > > diff --git a/tests/ref/vsynth/vsynth1-dv-hd b/tests/ref/vsynth/vsynth1-dv-hd
>> > > index e22f28c704..a93ce50ec0 100644
>> > > --- a/tests/ref/vsynth/vsynth1-dv-hd
>> > > +++ b/tests/ref/vsynth/vsynth1-dv-hd
>> > > @@ -1,4 +1,4 @@
>> > > -77f146c73a24495495c649f1e0d26fee *tests/data/fate/vsynth1-dv-hd.dv
>> > > +ce9f887af2391edbfcb21675962db54c *tests/data/fate/vsynth1-dv-hd.dv
>> > > 14400000 tests/data/fate/vsynth1-dv-hd.dv
>> > > 34b78cf725346c7f819c9d6209b8299a *tests/data/fate/vsynth1-dv-hd.out.rawvideo
>> > > stddev: 4.30 PSNR: 35.45 MAXDIFF: 74 bytes: 7603200/ 7603200
>> > > diff --git a/tests/ref/vsynth/vsynth2-dv-hd b/tests/ref/vsynth/vsynth2-dv-hd
>> > > index 5c4ed86fe7..9552c31948 100644
>> > > --- a/tests/ref/vsynth/vsynth2-dv-hd
>> > > +++ b/tests/ref/vsynth/vsynth2-dv-hd
>> > > @@ -1,4 +1,4 @@
>> > > -168f80951daf5eeefacac33fd06db87d *tests/data/fate/vsynth2-dv-hd.dv
>> > > +c152c7c3f9ef8f404b4bb7a388b947be *tests/data/fate/vsynth2-dv-hd.dv
>> > > 14400000 tests/data/fate/vsynth2-dv-hd.dv
>> > > 15dbe911532aca81c67bdd2846419027 *tests/data/fate/vsynth2-dv-hd.out.rawvideo
>> > > stddev: 1.75 PSNR: 43.26 MAXDIFF: 34 bytes: 7603200/ 7603200
>> > > diff --git a/tests/ref/vsynth/vsynth3-dv-hd b/tests/ref/vsynth/vsynth3-dv-hd
>> > > index ed94d08155..d0420d6f07 100644
>> > > --- a/tests/ref/vsynth/vsynth3-dv-hd
>> > > +++ b/tests/ref/vsynth/vsynth3-dv-hd
>> > > @@ -1,4 +1,4 @@
>> > > -1211b843d8dde81c583023e15beff35a *tests/data/fate/vsynth3-dv-hd.dv
>> > > +973b0856d1d94793bd6e8951284e642d *tests/data/fate/vsynth3-dv-hd.dv
>> > > 14400000 tests/data/fate/vsynth3-dv-hd.dv
>> > > a038ad7c3c09f776304ef7accdea9c74 *tests/data/fate/vsynth3-dv-hd.out.rawvideo
>> > > stddev: 0.00 PSNR:999.99 MAXDIFF: 0 bytes: 86700/ 86700
>> > > diff --git a/tests/ref/vsynth/vsynth_lena-dv-hd b/tests/ref/vsynth/vsynth_lena-dv-hd
>> > > index 6764f03c35..8b87da40ba 100644
>> > > --- a/tests/ref/vsynth/vsynth_lena-dv-hd
>> > > +++ b/tests/ref/vsynth/vsynth_lena-dv-hd
>> > > @@ -1,4 +1,4 @@
>> > > -fa8df53531f9e58f90bc9a33e5c78ca8 *tests/data/fate/vsynth_lena-dv-hd.dv
>> > > +30652b3740a32fa8bcee3b06a66b1dd2 *tests/data/fate/vsynth_lena-dv-hd.dv
>> > > 14400000 tests/data/fate/vsynth_lena-dv-hd.dv
>> > > 4db4175c80ea1f16b7ec303611b8873a *tests/data/fate/vsynth_lena-dv-hd.out.rawvideo
>> > > stddev: 1.49 PSNR: 44.66 MAXDIFF: 27 bytes: 7603200/ 7603200
>> > > --
>> > > 2.26.2
>> > >
>> > > _______________________________________________
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>> > >
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>> >
>> > --
>> > Thanks,
>> > Limin Wang
>> > _______________________________________________
>> > ffmpeg-devel mailing list
>> > ffmpeg-devel at ffmpeg.org
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>> >
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>
> --
> Thanks,
> Limin Wang
> _______________________________________________
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