Recherche avancée

Sur d’autres sites (4167)

• Inconsistent Rotation of Output Video OpenCV

  27 avril 2021, par user530316

  I am reading in mobile videos shot on an iphone (.MOV format). When the video is shot upright, ffmpeg meta data states the video frames are rotated 90 clockwise. When I read the video in with opencv as a .MOV and then outwrite again with opencv as a .mp4, both the input and output videos appear upright. Note I display the video frames using opencv via a while loop :
 cap = cv2.VideoCapture("video.MOV")

  


  ret,frame=cap.read()

  


  while ret:
    cv2.imshow('',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    ret,frame = cap.read()
cap.release()
cv2.destroyAllWindows() 


  


  This is not the problem. The problem is that when the same video is run on another machine with the same os and same virtual environment, the videos come out rotated by 90 degrees. Any reason this should happen ?

  


  Both machines are using opencv-python version 4.5.1, ffmpeg 4.2.2, and ffmpeg-python 0.2.0.

  


• "Smooth" the ffmpeg showwaves video filter output

  24 décembre 2019, par goodytx

  I think I’m close to what I’m after, thanks to excellent answers like : FFMPEG : Fill/Change (part of) audio waveform color as per actual progress with respect to time progress ...but not quite there !

  I’m scripting the generation of a waveform video with showwaves, and overlaying that onto a static image background, turning the whole thing into video. All is well, except I’d like to "smooth" the waveform. In most tutorials/answers you will see jagged "peaks" in the waveform animation, as of course the audio data varies widely into peaks and troughs. (The differences expressed between the lowest and highest amplitude (I think) in each audio frame sample.) I’d like to get more of a consistent "flowing wave", without the sharp spikes up and down.

  Currently using the filter much as described in the previous link :

  [1:a]aformat=channel_layouts=mono,asplit[red][white]; \
  
  [red]showwaves=s=1280x100:rate=15:mode=cline:scale=sqrt:colors=0xff0000[red]; \

  Which results in the following (ignoring the red on white overlay, which I may drop) :

  Current v desired

  This generates the type of wave plot I want (solid vs a sine, for example), but I think I need to either tweak the audio stream or...possibly post filter the showwaves video stream (but I think the former) to get the effect I want. I tried to reduce the rate of showwaves but that just results in juddery video. So to me that feels like the audio data needs to be the changed factor.

  My limited audio knowledge leads me to think I should gain, compress, normalize, or all of the above, the audio input, which I have tried, but can’t seem to nail it. Keep in mind the audio stream in this filter chain is purely feeding the showwaves filter, so I can "trash" it as much as needed in order to get the visualization I want.

  I hope this all makes sense, and if I need to provide more info, please let me know. Thanks !

• 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.