Moritz Barsnick wrote:
On Mon, Jul 27, 2015 at 15:19:01 +0100, Andy Furniss wrote:
The overhead is a bit high! but the framerate looks good.
:-)
Anyway players will play the vid but think it's 1000 fps ffmpeg -i
below.
I tried to reproduce, and noticed that indeed the y4m header (very
easy to read, check here:
http://wiki.multimedia.cx/index.php?title=YUV4MPEG2) says 1000 fps.
If I run ffmpeg with "-r 60" as an output option, the framerate is
recorded correctly in the y4m header, see this text diff of the two
output files, which are otherwise identical:
+YUV4MPEG2 W3840 H2160 F1000:1 Ip A1:1 C420jpeg XYSCSS=420JPEG
-YUV4MPEG2 W3840 H2160 F60:1 Ip A1:1 C420jpeg XYSCSS=420JPEG
So, that's your workaround.
If I dare to stab at the root cause of the problem: It might be this
code in libavformat/yuv4mpegenc.c, in yuv4_generate_header():
// TODO: should be avg_frame_rate av_reduce(&raten, &rated,
st->time_base.den, st->time_base.num, (1UL << 31) - 1);
It shows that the time base of the input stream "st" is being used,
and not the frame rate. (av_reduce() creates numerator and
denominator, to be able to create the quoted string "F1000:1".) And
the time base of the input is indeed "1k", as seen in your logs. This
may be a bug, and the "TODO" may have something to do (excuse the
pun) with that.
That was quick - thanks for looking -r 60 it will be - I would count
it as a bug especially as the output says 60fps.
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