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• What is faster, Raw PCM audio files, or mp3 files decoded with FFmpeg ?

  8 janvier 2020, par Matthew Strom

  I’m pretty deep into the development of my Android app, and as I mess around with my audio files a second time to try longer audio clips (1000ms long), I am now getting audio glitches again. Before I was not getting any glitches with 160ms long files.

  • Background : I’m making a metronome, so imagine roughly 100 lines of code in the callback to constantly figure out what audio file to play and for how long.

  Without getting into my code, I was just wondering if file size or file type has any impact on performance ? I believe I’m using the sample Player rendering class (source) (for Raw file input) which seems to load the audio data of the file each callback. This would Perhaps loading data from a larger array would slow it down ? Although, It could also be the new features/logic that I’m adding to the callback.

  I know it is talked about frequently about using mp3’s and decoding with FFmpeg. Has anyone done any bench-marking between mp3 and raw, and is there any performance advantage to using mp3’s, or is it mainly to cut down on your APK size ?

  Sorry if this has been discussed somewhere, however, I wasn’t able to find any articles mentioning this aspect between the two file types. Looking more closely at the rendering class, my gut tells me that file size "shouldn’t" be a factor... Otherwise I’ll continue to debug and maybe get some systraces in if I can.

• Matplotlib - Why is my saved animation video blank ?

  4 juillet 2022, par Pat X

  This should be pretty simple but I just don't know.

  



  A newbie to Python and FFmpeg. Just trying to save a test video from ArtistAnimation but got blank video.

  



  Before I tried to produce the video, I can see the animation by plt.show() (without "matplotlib.use("Agg")" ). I have already installed FFmpeg in Anaconda as well.

  



  To ensure my FFmpeg is functioning, I used the code from matplotlib example and produced a video that looks perfect. (I guess this means my FFmpeg will work fine from now on ?)

  



  Then, I only changed the figure to my version. Having compared the figure part, I didn't see anything wrong obviously. But in the saved video of my version, it's blank.

  



  import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.animation as ani
import numpy as np
import pandas as pd


fig = plt.figure()
ims = []
for i in range(10):
    ax1 = plt.subplot2grid((2, 2), (0, 0), colspan=2, rowspan=2)
    data = np.random.normal(0, 1, i+1)
    pd.DataFrame(data).plot(kind='bar', ax=ax1)
    ims.append([ax1])



# Set up formatting for the movie files
Writer = ani.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)

anim = ani.ArtistAnimation(fig, ims, interval=500, repeat_delay=3000, blit=True)
anim.save('textmovie.mp4', writer=writer)
plt.show()


  


• Enreco Video Rotation in Asp.Net Virtual Machine is not completing

  24 juillet 2014, par Sreeraj

  I am developing an ASP.NET Web Api in which I need to concatenate some video clips and rotate them. I could achieve the same when I tried in my local system. When I deployed the same project to an Azure Virtual Machine I am not getting response. I am pretty sure that there isn’t any issue till video concatenation because I could see the concatenated video in the expected folder. Here is the code snippet.

   var ffMpeg = new NReco.VideoConverter.FFMpegConverter();
  
              NReco.VideoConverter.ConcatSettings set = new NReco.VideoConverter.ConcatSettings();
  
              ffMpeg.GetVideoThumbnail(_fileNames[0], imageRootPath + tobename + ".jpg");
  
    if (_fileNames.Count() > 1)
  
              {
  
                  ffMpeg.ConcatMedia(_fileNames, videoRootPath + tobename + "_r.mp4", NReco.VideoConverter.Format.mp4, set);
  
  
  
                  string path = HttpContext.Current.Server.MapPath("~\\bin\\");
  
                  System.Diagnostics.Process ffmpeg = new System.Diagnostics.Process();
  
                  ffmpeg.StartInfo.FileName = path + "\\" + "ffmpeg.exe";
  
                  ffmpeg.StartInfo.Arguments = "-i " + videoRootPath + tobename + "_r.mp4" + " -c copy -metadata:s:v:0 rotate=90 " + videoRootPath + tobename + ".mp4";
  
                  ffmpeg.Start();
  
                  ffmpeg.WaitForExit();
  
              }

  ffmpeg.ConcateMedia is working fine. I can’t figure out why the External process that I have invoked does not complete. The same piece is working fine in my local Visual Studio.

  Thank you in advance