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• Gnuplot how to set a variable to standard-input if not passed

  27 août 2020, par DDS

  I have a gnuplot script (plot.script) that is invoked like

  


  C:> ffmpeg -i '.\my_awesome_audio_file.wav' -filter_complex aformat=channel_layouts=mono -acodec pcm_s16le -ar 4000 -f data - | gnuplot -e "fileout='plot';fileformat='png';wid=500;" .\plot.script        


  


  Now I'd want to default filein variable to stdin if it is not passed as argument. This because I want to be able to call this script as a 1-liner command with ffmpeg data generation and also as step-by-step procedure

  


  My idea was to use

  


  if(!exists('filein')){
filein = '-';
}


  


  but this throws warning: Skipping data file with no valid points

  


  if i print the variable datafile I got - (I expected something like stdin).

  


  this is the plot.script script :

  


  
if(!exists('filein')){
    filein = '-';
    }

if (!exists("hei")){
    hei = 4444;
    }
if (!exists("wid")){
    wid = 5555;
    }
if(!exists("fileformat")){
     fileformat = 'png';
     }
if(!exists("fileout")){
     fileout = 'risultato';
   }
   
fileout = fileout . '.' . fileformat;
   
if(!exists("dataformat")){
    dataformat = '%int16';
    }
if(fileformat eq 'png'){
  set terminal png transparent size larghezza,altezza;
  
  }else{
  set terminal fileformat size wid,hei;
  }
  set output fileout;
  unset key;
  unset tics;
  unset border;
  set lmargin 0;
  set rmargin 0;
  set tmargin 0;
  set bmargin 0;


print filein;
plot filein binary filetype=bin format=dataformat endian=little array=1:0 with lines linecolor "0x009900";


  


  But I also want to call this command-by-command :
generate the data-file :

  


  c:> ffmpeg -i '.\my_awesome_audio_file.wav' -filter_complex aformat=channel_layouts=mono -acodec pcm_s16le -ar 4000 -f data audio.dat


  


  plot the data :

  


  c:> gnuplot -e "filein='audio.dat';fileout='plot';fileformat='png';wid=500;" .\plot.script


  


• Convert wav to mp3 using Meteor FS Collections on Startup

  28 juillet 2015, par TheBetterJORT

  I’m trying to transcode all wav files into a mp3 using Meteor and Meteor FS Collections. My code works when I upload a wav file to the uploader — That is it will convert the wav to a mp3 and allow me to play the file. But, I’m looking for a Meteor Solution that will transcode and add the file to the DB if the file is a wav and exist in a certain directory. According to the Meteor FSCollection it should be possible if the files have already been stored. Here is their example code : *GM is for ImageMagik, I’ve replaced gm with ffmpeg and installed ffmpeg from atmosphereJS.

  Images.find().forEach(function (fileObj) {
  
    var readStream = fileObj.createReadStream('images');
  
    var writeStream = fileObj.createWriteStream('images');
  
    gm(readStream).swirl(180).stream().pipe(writeStream);
  
  });

  I’m using Meteor-CollectionFS [https://github.com/CollectionFS/Meteor-CollectionFS]-

  if (Meteor.isServer) {
  
    Meteor.startup(function () {
  
          Wavs.find().forEach(function (fileObj) {
  
        var readStream = fileObj.createReadStream('.wavs/mp3');
  
        var writeStream = fileObj.createWriteStream('.wavs/mp3');
  
        this.ffmpeg(readStream).audioCodec('libmp3lame').format('mp3').pipe(writeStream);
  
        Wavs.insert(fileObj, function(err) {
  
        console.log(err);
  
      });
  
        });
  
        });
  
  }

  And here is my FS.Collection and FS.Store information. Currently everything resides in one JS file.

  Wavs = new FS.Collection("wavs", {
  
    stores: [new FS.Store.FileSystem("wav"),
  
      new FS.Store.FileSystem("mp3",
  
  
  
      {
  
        path: '~/wavs/mp3',
  
        beforeWrite: function(fileObj) {
  
          return {
  
            extension: 'mp3',
  
            fileType: 'audio/mp3'
  
          };
  
        },
  
        transformWrite: function(fileObj, readStream, writeStream) {
  
          ffmpeg(readStream).audioCodec('libmp3lame').format('mp3').pipe(writeStream);
  
        }
  
      })]
  
  });

  When I try and insert the file into the db on the server side I get this error : MongoError : E11000 duplicate key error index :

  Otherwise, If I drop a wav file into the directory and restart the server, nothing happens. I’m new to meteor, please help. Thank you.

• Stream OpenCV frames to http using ffmpeg

  15 mars 2023, par Christoph Meyer

  I have a small Python OpenCV project and would like to stream my processed frames to HTTP using ffmpeg.

  


  For this I used the following sources :
Pipe and OpenCV to FFmpeg with audio streaming RTMP in Python
and
https://github.com/kkroening/ffmpeg-python/blob/master/examples/README.md#stream-from-a-local-video-to-http-server

  


  To make things more readable I used the ffmpeg-python library but as far as I understand, it doesn't matter if I open a pipe using subprocess or use the library.

  


  The problem that I have is, that I always get a broken pipe or "Connection refused" when I open the stream with ffplay.

  


  import ffmpeg
import cv2

video_format = "flv"
server_url = "http://localhost:8080"

cap = cv2.VideoCapture(1)
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))


process = (
    ffmpeg
    .input('pipe:', format='rawvideo',codec="rawvideo", pix_fmt='bgr24', s='{}x{}'.format(width, height))
    .output(
        server_url,
        #codec = "copy", # use same codecs of the original video
        listen=1, # enables HTTP server
        codec="libx264",
        pix_fmt="yuv420p",
        preset="ultrafast",
        f=video_format)
    .overwrite_output()
    .run()
)

while True:
    ret, frame = cap.read()
    if not ret:
        break
    print("Sending frame")
    process.stdin.write(frame.tobytes())


  


  I also tried to stream using only ffmpeg and FaceTime and that works as i expected.

  


  My operation system is MacOS 12.3

  


  Maybe someone knows how to fix this.

  


  Thanks for your help

  


  Chris