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• Stream specifier '' in filtergraph description [0][1]concat=a=1:n=1:v=1[s0] matches no streams

  9 août 2020, par Tanmoy Bhowmick

  i am trying to concatenate two audio files in django with ffmpeg but getting this error Stream specifier '' in filtergraph description [0][1]concat=a=1:n=1:v=1[s0] matches no streams.`

  


  here is my function

  


  def audiomarge(request):
    recorded_audio = request.FILES['audio']
    new = tempSong(tempSongFile=recorded_audio)
    new.tempSongFile.name = 'test.wav'
    new.save()
    record_file_path = new.tempSongFile.path
    record_file_path = str(record_file_path)
    recorded_audio = request.POST.get('audio')
    songslug = request.POST.get('songslug')
    current_song = Song.objects.filter(slug=songslug)[0]
    current_song_path = current_song.songFile.url 
    current_song_path = '.'+(str(current_song_path))
    
    input_first = ffmpeg.input(current_song_path)
    input_second = ffmpeg.input(record_file_path)


    ffmpeg.concat(input_first, input_second, v=1, a=1).output('./finished_video.wav').run()
    return HttpResponse('okay')


  


  i have also tried .compile() instead of .run() in this case nothing is happening

  


• tf.contrib.signal.stft returns an empty matrix

  9 décembre 2017, par matt-pielat

  This is the piece of code I run :

  import tensorflow as tf
  
  
  
  sess = tf.InteractiveSession()
  
  
  
  filename = 'song.mp3' # 30 second mp3 file
  
  SAMPLES_PER_SEC = 44100
  
  
  
  audio_binary = tf.read_file(filename)
  
  
  
  pcm = tf.contrib.ffmpeg.decode_audio(audio_binary, file_format='mp3', samples_per_second=SAMPLES_PER_SEC, channel_count = 1)
  
  stft = tf.contrib.signal.stft(pcm, frame_length=1024, frame_step=512, fft_length=1024)
  
  
  
  sess.close()

  The mp3 file is properly decoded because print(pcm.eval().shape) returns :

  (1323119, 1)

  And there are even some actual non-zero values when I print them with print(pcm.eval()[1000:1010]) :

  [[ 0.18793298]
  
   [ 0.16214484]
  
   [ 0.16022217]
  
   [ 0.15918455]
  
   [ 0.16428113]
  
   [ 0.19858395]
  
   [ 0.22861415]
  
   [ 0.2347789 ]
  
   [ 0.22684409]
  
   [ 0.20728172]]

  But for some reason print(stft.eval().shape) evaluates to :

  (1323119, 0, 513) # why the zero dimension?

  And therefore print(stft.eval()) is :

  []

  According to this the second dimension of the tf.contrib.signal.stft output is equal to the number of frames. Why are there no frames though ?

• Saving Raw Uncompressed Video Files using OpenCv, Gstreamer, and/or FFMPEG ?

  20 septembre 2022, par adav0033

  I have been trying to implement the cv::VideoWriter function from OpenCV to generate a an uncompressed (raw) video file. I started this because of a statement within the OpenCV Documentation which I will link here along with the statement.

  


  cv::VideoWriter::VideoWriter    (   const String &  filename,
int     fourcc,
double  fps,
Size    frameSize,
bool    isColor = true 
)       


  


  "If FFMPEG is enabled, using codec=0 ; fps=0 ; you can create an uncompressed (raw) video file."

  


  Ref. https://docs.opencv.org/3.4/dd/d9e/classcv_1_1VideoWriter.html

  


  However whilst troubleshooting the function I came across the refuting statement,

  


  " VideoCapture and VideoWriter do not provide interface to access raw compressed video stream, except maybe MJPEG in some cases.
Make sure you actually use FFmpeg backend by setting apiPreference parameter : VideoWriter("outfile.avi", cv2.CAP_FFMPEG, ...)"

  


  Ref. https://github.com/opencv/opencv/issues/14573

  


  I am now confused about how I go about writing the cv::VideoWriter function to satisfy the requirements to create a raw uncompressed video file (.avi) and if it is even possible. If it is not possible how do I achieve the outcome of saving an raw uncompressed video file, as I assume it would use some combination of FFMPEG, OpenCV,or Gstreamer.

  


  Note : My code is implemented in c++