When displaying a frame count number in the drawtext filter, the varying height
of the characters can make the text jitter vertically as they count. Its
possible to stop this by applying the ‘ascent' value to the y coordinate.
However when the drawtext filter contains a box, this element also jitters
vertically and there doesn’t appear to be a way to apply the same method of
using the ‘ascent’ value to stabilise it.
Here is an example command (font is relevant to macOS):
ffmpeg -f lavfi -i "color=red:size=1280x720:rate=24" -y -t 12 -c:v mjpeg
-qscale:v 4 -huffman default -pix_fmt yuvj422p -vf
"drawtext=fontfile=/System/Library/Fonts/Geneva.dfont: fontcolor=white:
fontsize=150: box=1: boxcolor=black: boxborderw=5: x=640: y=500-ascent:
text=%{n}: start_number=0" output.mov
In the above example, including ‘-ascent' in the y coordinate value stops the
number characters from being jittery as they count. However you can see the box
is still jittery and does not seem to support having the ‘-ascent’ value
applied to it.
Is there any way to negate this jitter when using a box? Thanks.
Full uncut command:
ffmpeg version N-93020-g3224d6691c-tessus https://evermeet.cx/ffmpeg/
Copyright (c) 2000-2019 the FFmpeg developers
built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg
--extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl
--enable-libaom --enable-libass --enable-libbluray --enable-libdav1d
--enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame
--enable-libmysofa --enable-libopencore-amrnb --enable-libopencore-amrwb
--enable-libopenh264 --enable-libopenjpeg --enable-libopus
--enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr
--enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab
--enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack
--enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs
--enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi
--enable-version3 --pkg-config-flags=--static --disable-ffplay
libavutil 56. 26.100 / 56. 26.100
libavcodec 58. 44.100 / 58. 44.100
libavformat 58. 26.100 / 58. 26.100
libavdevice 58. 6.101 / 58. 6.101
libavfilter 7. 48.100 / 7. 48.100
libswscale 5. 4.100 / 5. 4.100
libswresample 3. 4.100 / 3. 4.100
libpostproc 55. 4.100 / 55. 4.100
Input #0, lavfi, from 'color=red:size=1280x720:rate=24':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720 [SAR
1:1 DAR 16:9], 24 tbr, 24 tbn, 24 tbc
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> mjpeg (native))
Press [q] to stop, [?] for help
[swscaler @ 0x7fce5b00d800] deprecated pixel format used, make sure you did set
range correctly
Output #0, mov, to 'output.mov':
Metadata:
encoder : Lavf58.26.100
Stream #0:0: Video: mjpeg (jpeg / 0x6765706A), yuvj422p(pc), 1280x720 [SAR
1:1 DAR 16:9], q=2-31, 200 kb/s, 24 fps, 12288 tbn, 24 tbc
Metadata:
encoder : Lavc58.44.100 mjpeg
Side data:
cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
frame= 288 fps=0.0 q=4.0 Lsize= 7103kB time=00:00:11.95
bitrate=4865.5kbits/s speed=19.7x
video:7101kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing
overhead: 0.027039%
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