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• difference overlay filter ffmpeg like photoshop/affinity photo

  14 janvier, par Owen Quinlan

  In photoshop and affinity photo there is a nice overlay filter that basically subtracts the overlaying layer from the one bellow to make a "difference map"

  


  Example :
Base image :
Screenshot Mario Kart 1

  


  Overlaying image :
Screenshot Mario Kart 2

  


  Resulting output :
Diff from two screenshots

  


  This is an example diff of overlaying a PNG with a JpegXL(I think) compressed image and then brightened :
Diff generated from image compression

  


  Location of filter in photoshop :
Photoshop screenshot

  


  Is there anyway to accomplish this with a filter in ffmpeg for an entire video ?

  


• What's the difference between avfilter_graph_parse_ptr() and avfilter_link() ?

  17 mai 2022, par Jeycri

  I use the same set of codec to verify different methods.For audio, there is little difference between the two methods. For video, the following situation will occur.
This is the way use avfilter_link(), but it can't trim video.

  


  ...
const AVFilter *trim = avfilter_get_by_name("trim");
char args[128] = { 0 };
snprintf(args, sizeof(args), "start=10:end=60");
AVFilterContext *trim_ctx;
avfilter_graph_create_filter(&trim_ctx, trim, "video_trim", args, NULL, videofilterGraph);
avfilter_link(videoBuffSrc, 0, trim_ctx, 0);
...
const AVFilter *setpts= avfilter_get_by_name("setpts");
char args[128] = { 0 };
snprintf(args, sizeof(args), "PTS-STARTPTS");
AVFilterContext *setpts_ctx;
avfilter_graph_create_filter(&setpts_ctx, setpts, "video_setpts", args, NULL, videofilterGraph);
avfilter_link(trim_ctx, 0, setpts_ctx, 0);
...
//Finally linked format and buffsink.


  


  This is the way use avfilter_graph_parse_ptr(), it works well.

  


  AVFilter* buffersrc = avfilter_get_by_name("buffer");
AVFilter* buffersink = avfilter_get_by_name("buffersink");
AVFilterInOut* inputs = avfilter_inout_alloc();
AVFilterInOut* outputs = avfilter_inout_alloc();
...
avfilter_graph_parse_ptr(videofilterGraph, "trim=start=10:end=60,setpts=PTS-STARTPTS", &inputs, &outputs, NULL)


  


• whats the difference between “&” and multiple terminals in Linux Multiprocessing [closed]

  11 mai 2022, par Ma XIaoyu

  I am using Linux for multi-task processing. Specifically, calling ffmpeg multiple times to transcoding multi source videos.

  


  Strangely, when I am using :
“
ffmpeg-cmds01 &
ffmpeg-cmds02 &
ffmpeg-cmds03 &
……
”
The ffmpeg process often get errors and stop after a few hours.

  


  However, if I open several terminals and using each terminal for only one ffmpeg cmd( i.e., terminal#1 only run ffmpeg-cmd01 ; ternimal#2 only for ffmpeg-cmd02, etc.) The transcoding procedure can last for dozens of days and no errors are reported.

  


  Could anyone kindly help us to analysis what’s there differences ? Opening multiple terminals is too difficult for managing especially when the number of video streams are up to 300+.

  


  Thanks a lot for help !