Hello,
I want to add a +-10 pixels random horizontal jitter to video lines.
This is the first test:
c:\ffmpeg\ffmpeg -f lavfi -i testsrc2=size=vga -vf
format=gray,geq=lum='lum(X-10+20*random(0),Y)' -t 3 -y out1.mp4
This works, but it's a pixel-wise jitter and that's not what I want. I
want that all pixels in the same line get the same random jitter.
The idea is to set a seed value for the random generator. The seed value
is a function of N and Y.
c:\ffmpeg\ffmpeg -f lavfi -i testsrc2=size=vga -vf
format=gray,geq=lum='st(0,N+Y);lum(X-10+20*random(0),Y)' -t 3 -y out2.mp4
This doesn't work, no jitter is visible at all.
May be the seed value must be in the [0..1] range? Let's test it:
c:\ffmpeg\ffmpeg -f lavfi -i testsrc2=size=vga -vf
format=gray,geq=lum='st(0,mod(0.001*(N+Y),1));lum(X-10+20*random(0),Y)'
-t 3 -y out3.mp4
Same result as before, no jitter is visible at all.
It seems that either I have totally misunderstood how the random
generator works, or it's impossible to set seed values, or it's a bug.
The console output for the last command line is shown below.
Michael
C:\Users\mKoch\Desktop>c:\ffmpeg\ffmpeg -f lavfi -i testsrc2=size=vga
-vf format
=gray,geq=lum='st(0,mod(0.001*(N+Y),1));lum(X-10+20*random(0),Y)' -t 3
-y out3.m
p4
ffmpeg version git-2020-04-12-f1894c2 Copyright (c) 2000-2020 the FFmpeg
develop
ers
built with gcc 9.3.1 (GCC) 20200328
configuration: --enable-gpl --enable-version3 --enable-sdl2
--enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d
--enable-libb
luray --enable-libfreetype --enable-libmp3lame
--enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus
--enable-libshine --e
nable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora
--enable-lib
twolame --enable-libvpx --enable-libwavpack --enable-libwebp
--enable-libx264 --
enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma
--enable-zlib --e
nable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis
--enable-libvo
-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid
--enable-libaom
--disable-w32threads --enable-libmfx --enable-ffnvcodec
--enable-cuda-llvm --ena
ble-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2
--enable
-avisynth --enable-libopenmpt --enable-amf
libavutil 56. 42.102 / 56. 42.102
libavcodec 58. 78.102 / 58. 78.102
libavformat 58. 42.100 / 58. 42.100
libavdevice 58. 9.103 / 58. 9.103
libavfilter 7. 77.101 / 7. 77.101
libswscale 5. 6.101 / 5. 6.101
libswresample 3. 6.100 / 3. 6.100
libpostproc 55. 6.100 / 55. 6.100
Input #0, lavfi, from 'testsrc2=size=vga':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480
[SAR 1:1
DAR 4:3], 25 tbr, 25 tbn, 25 tbc
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 00000000035a1880] using SAR=1/1
[libx264 @ 00000000035a1880] using cpu capabilities: MMX2 SSE2Fast SSSE3
SSE4.2
AVX FMA3 BMI2 AVX2
[libx264 @ 00000000035a1880] profile High, level 3.0, 4:0:0, 8-bit
[libx264 @ 00000000035a1880] 264 - core 159 - H.264/MPEG-4 AVC codec -
Copyleft
2003-2019 - http://www.videolan.org/x264.html - options: cabac=1 ref=3
deblock=1
:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1
me_rang
e=16 chroma_me=0 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1
chroma_qp_
offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1
interla
ced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2
b_adapt=1 b_bias
=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25
scenecut=40
intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60
qpmin=0 qpma
x=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'out3.mp4':
Metadata:
encoder : Lavf58.42.100
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), gray,
640x480 [SAR 1
:1 DAR 4:3], q=-1--1, 25 fps, 12800 tbn, 25 tbc
Metadata:
encoder : Lavc58.78.102 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame= 14 fps=0.0 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A
speed=
frame= 28 fps= 26 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A
speed=
frame= 42 fps= 26 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A
speed=
frame= 56 fps= 26 q=28.0 size= 0kB time=00:00:00.12 bitrate=
3.2kbits/
frame= 70 fps= 26 q=28.0 size= 0kB time=00:00:00.68 bitrate=
0.6kbits/
frame= 75 fps= 24 q=-1.0 Lsize= 244kB time=00:00:02.88 bitrate=
694.6kbits
/s speed=0.928x
video:243kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing o
verhead: 0.687764%
[libx264 @ 00000000035a1880] frame I:1 Avg QP:16.21 size: 5580
[libx264 @ 00000000035a1880] frame P:21 Avg QP:20.55 size: 4059
[libx264 @ 00000000035a1880] frame B:53 Avg QP:30.86 size: 2959
[libx264 @ 00000000035a1880] consecutive B-frames: 1.3% 5.3% 24.0% 69.3%
[libx264 @ 00000000035a1880] mb I I16..4: 37.8% 46.9% 15.3%
[libx264 @ 00000000035a1880] mb P I16..4: 4.2% 4.1% 4.6% P16..4:
6.1% 3.1
% 1.4% 0.0% 0.0% skip:76.5%
[libx264 @ 00000000035a1880] mb B I16..4: 0.0% 0.1% 1.3% B16..8:
13.8% 3.2
% 0.8% direct: 1.1% skip:79.5% L0:49.5% L1:43.1% BI: 7.4%
[libx264 @ 00000000035a1880] 8x8 transform intra:31.3% inter:20.8%
[libx264 @ 00000000035a1880] coded y intra: 32.6% inter: 4.2%
[libx264 @ 00000000035a1880] i16 v,h,dc,p: 88% 11% 1% 0%
[libx264 @ 00000000035a1880] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20% 14% 65%
0% 0%
0% 0% 0% 0%
[libx264 @ 00000000035a1880] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 16% 31%
3% 4%
4% 4% 4% 6%
[libx264 @ 00000000035a1880] i8c dc,h,v,p: 100% 0% 0% 0%
[libx264 @ 00000000035a1880] Weighted P-Frames: Y:0.0%
[libx264 @ 00000000035a1880] ref P L0: 59.3% 5.8% 21.6% 13.2%
[libx264 @ 00000000035a1880] ref B L0: 70.8% 23.4% 5.8%
[libx264 @ 00000000035a1880] ref B L1: 92.0% 8.0%
[libx264 @ 00000000035a1880] kb/s:660.44
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