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• Produce waveform video from audio using FFMPEG

  27 avril 2017, par RhythmicDevil

  I am trying to create a waveform video from audio. My goal is to produce a video that looks something like this

  

  For my test I have an mp3 that plays a short clipped sound. There are 4 bars of 1/4 notes and 4 bars of 1/8 notes played at 120bpm. I am having some trouble coming up with the right combination of preprocessing and filtering to produce a video that looks like the image. The colors dont have to be exact, I am more concerned with the shape of the beats. I tried a couple of different approaches using showwaves and showspectrum. I cant quite wrap my head around why when using showwaves the beats go past so quickly, but using showspectrum produces a video where I can see each individual beat.

  ShowWaves

  ffmpeg -i beat_test.mp3 -filter_complex "[0:a]showwaves=s=1280x100:mode=cline:rate=25:scale=sqrt,format=yuv420p[v]" -map "[v]" -map 0:a output_wav.mp4

  This link will download the output of that command.

  ShowSpectrum

  ffmpeg -i beat_test.mp3 -filter_complex "[0:a]showspectrum=s=1280x100:mode=combined:color=intensity:saturation=5:slide=1:scale=cbrt,format=yuv420p[v]" -map "[v]" -an -map 0:a output_spec.mp4

  This link will download the output of that command.

  I posted the simple examples because I didn’t want to confuse the issue by adding all the variations I have tried.

  In practice I suppose I can get away with the output from showspectrum but I’d like to understand where/how I am thinking about this incorrectly. Thanks for any advice.

  Here is a link to the source audio file.

• Aspect ratio problems at transcoding with ffmpeg [closed]

  19 novembre 2023, par udippel

  I have a huge collection of videos from the last 20+ years, videos in all sorts of formats. I use gerbera as open source UPnP-AV media server. Our TV handles only very limited of these formats. Therefore I use the transcoding feature of gerbera (I don't want to convert the 2000+ files ; thereby avoiding loss of multiple audio tracks, (multiple) subtitles, and so forth).

  


  This is my current unified argument line for ffmpeg :
-c:v mpeg2video -maxrate 20000k -vf setdar=16/9 -r 24000/1001 -qscale:v 4 -top 1 -c:a mp2 -f mpeg -y
It works pretty okay, except of the aspect ratios. Well, I don't understand this fully, because ffprobe for File A states :
Stream #0:0: Video: mpeg4 (Simple Profile) (XVID / 0x44495658), yuv420p, 624x464 [SAR 1:1 DAR 39:29], 1500 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
This file displays very well.
File B comes as :
Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 960x720, SAR 1:1 DAR 4:3, 23.98 fps, 23.98 tbr, 1k tbn, 180k tbc (default)
This file displays horribly squeezed vertically and doesn't fill the screen left and right neither, with the same settings of the TV. Also, playing this file (and others, naturally) the TV doesn't offer the 14:9 display option, which is available e.g. for the file further up.

  


  Both have same SAR, DAR, almost identical H:V ratios (1.345, 1.333) ; and almost identical DAR.

  


  My questions :

  


  

  1. Why, despite of almost identical pixel ratios, DAR and SAR are these files handled so differently in one and the same session on the same TV (SONY), please ?

  


  2. With which method could I instruct ffmpeg to display the second file properly, too, please ?
(I have already tried 'scale' ; but to no avail. Which could have been foreseen, since the ratios are already very close.)
My guess is, that the (tv, bt709, progressive) mess things up.
(I have already tried to add the yuv420p in the argument line, also to no avail.)

  


  


  Appreciate any help,

  


  Uwe

  


  I have already tried to add a 'scale' option ; but to no avail. Which could have been foreseen, since the ratios are already very close.
I have already tried to add the yuv420p in the argument line, also to no avail.
I have already tried force_original_aspect_ratio, but also here, nothing improving.
Also, I played with -aspect, but the aspects are okay, and would need individual corrections, which I can't and don't to do for 2000+ files. A simple 16:9 doesn't cut it.

  


• lavu : add an API function to return the Libav version string

  2 juillet 2015, par wm4

  lavu : add an API function to return the Libav version string
  This returns something like "v12_dev0-1332-g333a27c". This is much more
  
  useful than the individual library versions, of which there are too
  
  many, and which are very hard to map back to releases or git commits.
  Signed-off-by : Janne Grunau <janne-libav@jannau.net>
  

  • [DH] .gitignore
  • [DH] Makefile
  • [DH] cmdutils.c
  • [DH] doc/APIchanges
  • [DH] libavutil/avutil.h
  • [DH] libavutil/utils.c