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• ffmpeg or sox write text file with frequency response

  12 décembre 2016, par esposito

  I need some command line for ffmpeg, sox or other that can write a text file with peak response frequency.

  Actually I use these lines :

  ffmpeg.exe -i input.flac -y -filter_complex  ""[0:a]showfreqs=mode=line:colors=white|white:averaging=0:fscale=log,format=yuv420p[v]""  -map ""[v]"" -t 00:04:24  -filter:a ""atempo=2"" -r 1 -map 0:a out.mp4
  
  
  
  ffmpeg.exe -i output.mp4 -y -ss 00:04:23 out.png

  and this is the result :

  http://www.pro-software.it/inglese.png

  this is good for show graph but I need a numeric values. Example :

  10 Hz = -5.0 dB

  50 hz = -5.8 dB

  1000 Hz = -9.7 dB

  1100 Hz = -9.8 dB

  There is a way to write a text file with numeric value like this ?

• FFmpeg : Create a Video Slideshow from PNG Images for MS PowerPoint

  20 septembre 2016, par Klaidonis

  I am using FFmpeg on Windows 7 to create a video from PNG image sequence for Microsoft PowerPoint.

  The best results I have achieved so far, is by using the following command :

  ffmpeg -framerate 10 -start_number 3 -i .\folder\name_%d.png -q:v 0 -c:v libx264 -pix_fmt yuv420p output-video.avi

  It seems perfect, 50 images of total size 30 MB are converted into 200 KB video with no loss in the quality. Placing it in PowerPoint also seems right, but there is a slight color shift (yellow appears darker and possibly more orangish). By using some other conversion options, I obtained a video in PowerPoint where the first image of the video (like album cover art) is exactly as the original but the rest of the video plays with the mentioned color shift.

  When I play this file in VLC, it’s good. Although, if in the settings "Use hardware YUV->RGB conversions" is enabled, colors appear a bit washed out, and white color is a bit gray.

  I also tried to convert the images to a GIF file and at first it seems good but outer edges and numbers from the left and top side are blurred, and the background has turned from white to a bit gray color, although, white segments not on the background are white. The output size is 18 MB. I ended up with a way better GIF 600 KB by converting from the first video file ; just it is slightly more dotted, and the background again is grayish.

  ffmpeg -i output-video.avi output-video.gif

  Could someone help ?

• screen recording and video encoding with ffmpeg

  2 septembre 2016, par Alexander M.

  1.we need to record screenshots into video with 2-3 fps. Quality - the minimum possible to make text on the screen readable, 256 colors. It is important to reduce the output video file size as much as possible.

  2.we’ve made a lot of tests, and currently the most suitable way is to make screenshots every 300-500msec, save them in PNG, then run ffmpeg to encode to H.267 with these params :

  ffmpeg -f image2 -i "C:\png5min\image%04d.png" -y -an -vcodec libx264 -preset veryfast -crf 30 "C:\output.mp4"

  3.is it the best way to get minimum output size with 2-3fps screencast ?

  4.the output file plays very quickly, codec by default concerns that images represent 25fps. But they are 2fps actually.
  Ok, but if we try to decrease the output frame rate, output file size increases for about twice !! (from 3mb to 6mb for a 3m:26s video). And if we set the output frame rate as 2 - video does not play frames at all or plays just 2 frames for 3mins... :

  -r 2 -f image2 -i "C:\png5min\image%04d.png" -y -an -vcodec libx264 -preset veryfast -crf 30 -r 2 "C:\image5min_2fps_crf30_test__R2-2.mp4"

  so, how can we just add some latency after each frame without increasing the output file size ???