[FFmpeg-user] exponential decay, is it possible?

[Michael Koch]

> luminance = 0.95 * luminance_in_last_frame;     // exponential decay

I'm trying to do the following:
Read image temp0000.jpg, set luminance to 90%, write as temp0001.jpg
Read image temp0001.jpg, set luminance to 90%, write as temp0002.jpg
and so on in an iterative process, until 10 images are written.
But it works only for the first image and then stops. I think the 
problem is that ffmpeg wants to read the next image before the first 
image was written. Below is the full console output.

Michael


F:\xxx>c:/ffmpeg/ffmpeg -i temp%4d.jpg -vf lutyuv="y=0.9*val"
-frames 10 -q:v 1 -start_number 1 temp%4d.jpg
ffmpeg version N-91565-g1940c27c82 Copyright (c) 2000-2018 the FFmpeg 
developers

   built with gcc 7.3.1 (GCC) 20180722
   configuration: --enable-gpl --enable-version3 --enable-sdl2 
--enable-bzlib --e
nable-fontconfig --enable-gnutls --enable-iconv --enable-libass 
--enable-libblur
ay --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb 
--enable-
libopencore-amrwb --enable-libopenjpeg --enable-libopus 
--enable-libshine --enab
le-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame 
--enable-li
bvpx --enable-libwavpack --enable-libwebp --enable-libx264 
--enable-libx265 --en
able-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp 
--enable-
libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa 
--enabl
e-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf 
--enabl
e-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc 
--enable-nvdec --enab
le-dxva2 --enable-avisynth
   libavutil      56. 18.102 / 56. 18.102
   libavcodec     58. 22.100 / 58. 22.100
   libavformat    58. 17.101 / 58. 17.101
   libavdevice    58.  4.101 / 58.  4.101
   libavfilter     7. 26.100 /  7. 26.100
   libswscale      5.  2.100 /  5.  2.100
   libswresample   3.  2.100 /  3.  2.100
   libpostproc    55.  2.100 / 55.  2.100
Input #0, image2, from 'temp%4d.jpg':
   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 
5472x3648,
  25 tbr, 25 tbn, 25 tbc
Stream mapping:
   Stream #0:0 -> #0:0 (mjpeg (native) -> mjpeg (native))
Press [q] to stop, [?] for help
Output #0, image2, to 'temp%4d.jpg':
   Metadata:
     encoder         : Lavf58.17.101
     Stream #0:0: Video: mjpeg, yuvj422p(pc), 5472x3648, q=2-31, 200 
kb/s, 25 fps
, 25 tbn, 25 tbc
     Metadata:
       encoder         : Lavc58.22.100 mjpeg
     Side data:
       cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
frame=    1 fps=0.0 q=1.0 Lsize=N/A time=00:00:00.04 bitrate=N/A 
speed=0.122x

video:783kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB 
muxing o
verhead: unknown