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• Combining audio and video streams in ffmpeg in nodejs

  10 juillet 2015, par LouisK

  This is a similar question to Merge WAV audio and WebM video but I’m attempting to deal with two streams instead of static files. It’s kind of a multi-part question.

  It may be as much an ffmpeg question as a Node.js question (or more). I’ve never used ffmpeg before and haven’t done a ton of streaming/piping.

  I’m using Mauz-Khan’s MediaStreamCapture (an expansion on RecordRTC) in conjunction with Socket.io-stream to stream media from the browser to the server. From webkit this delivers independent streams for audio and video which I’d like to combine in a single transcoding pass.

  Looking at FFmpeg’s docs it looks like it’s 100% capable of using and merging these streams simultaneously.

  Looking at these NPM modules :

  https://www.npmjs.com/package/fluent-ffmpeg and https://www.npmjs.com/package/stream-transcoder

  Fluent-ffmpeg’s docs suggest it can take a stream and a bunch of static files as inputs, while stream-transcoder only takes a single stream.

  I see this as a use case that just wasn’t built in (or needed) by the module developers, but wanted to see if anyone had used either (or another module) to accomplish this before I get on with forking and trying to add the functionality ?

  Looking at the source of stream-transcoder it’s clearly setup to only use one input, but may not be that hard to add a second to. From the ffmpeg perspective, is adding a second input as simple as adding an extra source stream and an extra ’-i’ in the command ? (I think yes, but can foresee a lot of time burned trying to figure this out through Node).

  This section of stream-transcoder is where the work is really being done :

  /* Spawns child and sets up piping */
  
  Transcoder.prototype._exec = function(a) {
  
  
  
      var self = this;
  
  
  
      if ('string' == typeof this.source) a = [ '-i', this.source ].concat(a);
  
      else a = [ '-i', '-' ].concat(a);
  
  
  
      var child = spawn(FFMPEG_BIN_PATH, a, {
  
          cwd: os.tmpdir()
  
      });
  
      this._parseMetadata(child);
  
  
  
      child.stdin.on('error', function(err) {
  
          try {
  
              if ('object' == typeof self.source) self.source.unpipe(this.stdin);
  
          } catch (e) {
  
              // Do nothing
  
          }
  
      });
  
  
  
      child.on('exit', function(code) {
  
          if (!code) self.emit('finish');
  
          else self.emit('error', new Error('FFmpeg error: ' + self.lastErrorLine));
  
      });
  
  
  
      if ('object' == typeof this.source) this.source.pipe(child.stdin);
  
  
  
      return child;
  
  
  
  };

  I’m not quite experienced enough with piping and child processes to see off the bat where I’d add the second source - could I simply do something along the lines of this.source2.pipe(child.stdin) ? How would I go about getting the 2nd stream into the FFmpeg child process ?

• How to add Qt to an existing C program and compile ?

  26 juin 2015, par El Sampsa

  I have a small Qt program I have compiled with qmake and make. When I launch make, I get the following commands for compilation :

  g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++-64 -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I/usr/lib/x86_64-linux-gnu -I/usr/include/SDL -I. -o simpleqt.o simpleqt.cpp

  (.. lets call that (**)) and

  g++ -m64 -Wl,-O1 -o qt simpleqt.o -L/usr/lib/x86_64-linux-gnu -lSDL -lX11 -lQtGui -lQtCore -lpthread

  .. and the program is compiled without problems.

  On the other hand, I have the ffmpeg library which has the "ffplay" program. I want to put some Qt things into ffplay. In the ffmpeg config files I tell to the make process (using "common.mak") that it should be verbose and when issuing "make ffplay", it gives me the following monster :

  gcc -I. -I./ -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -DZLIB_CONST -I/home/sampsa/ffmpeg/build/include -std=c99 -fomit-frame-pointer -pthread -I/usr/include/freetype2 -I/usr/include/fribidi -I/usr/include/freetype2 -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -g -Wdeclaration-after-statement -Wall -Wdisabled-optimization -Wpointer-arith -Wredundant-decls -Wwrite-strings -Wtype-limits -Wundef -Wmissing-prototypes -Wno-pointer-to-int-cast -Wstrict-prototypes -Wempty-body -Wno-parentheses -Wno-switch -Wno-format-zero-length -Wno-pointer-sign -O3 -fno-math-errno -fno-signed-zeros -fno-tree-vectorize -Werror=format-security -Werror=implicit-function-declaration -Werror=missing-prototypes -Werror=return-type -Werror=vla -Wformat -Wno-maybe-uninitialized -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -MMD -MF ffplay.d -MT ffplay.o -c -o ffplay.o ffplay.c

  (lets call that monster (++)).

  So far, so good, I have two commands, one (**) for compiling Qt programs and another one (++) for another project (in this case, ffmpeg’s ffplay)

  How do I combine these two ?

  I have tried merging the flags in (**) into command (++). It compiles OK, but the moment I am adding

  #include <qtgui> 
  
  </qtgui>

  into "ffplay.c", all hell breaks loose and the compiler tells me (among many other things) :

  In file included from /usr/include/qt4/QtCore/qobjectdefs.h:45:0,
  from /usr/include/qt4/QtCore/qobject.h:47,
  from /usr/include/qt4/QtCore/qabstracteventdispatcher.h:45,
  from /usr/include/qt4/QtCore/QtCore:3,
  from /usr/include/qt4/QtGui/QtGui:3,
  from ffplay2.c:61 :
  /usr/include/qt4/QtCore/qnamespace.h:51:1 : warning : return type defaults to ‘int’ [enabled by default]
  QT_MODULE(Core)
  ^
  /usr/include/qt4/QtCore/qnamespace.h:51:1 : warning : function declaration isn’t a prototype [-Wstrict-prototypes]
  /usr/include/qt4/QtCore/qnamespace.h : In function ‘QT_MODULE’ :
  /usr/include/qt4/QtCore/qnamespace.h:54:1 : error : unknown type name ‘namespace’
  namespace
  ^
  ...
  ...

  If I combine flags in (**) to (++) and change the compiler from "gcc" to "g++", I get all kinds of errors, this time related to the "ffplay.c" source code.

  What is going on ?

• cant convert webm to gif with node.js

  5 février 2015, par asafg

  I want to convert a .webm file to .gif

  I’m using the gifify module.

  var fs = require('fs');
  
  var gifify = require('gifify');
  
  var path = require('path');
  
  
  
  var input = path.join('./inputs', 'mov.webm');
  
  var output = path.join('./outputs', 'mov.gif');
  
  
  
  var gif = fs.createWriteStream(output);
  
  
  
  var options = {
  
    resize: '200:-1',
  
    from: 30,
  
    to: 35
  
  };
  
  
  
  gifify(input, options).pipe(gif);

  I keep getting this error

  events.js:53
  
  EventEmitter.prototype.emit = function emit(type) {
  
                                             ^
  
  RangeError: Maximum call stack size exceeded

  I think it has to do with the ffmpeg module dependency because when im trying to convert via shell I also get an error

  $ gifify inputs/mov.webm -o outputs/mov.gif --resize 800:-1
  
  [Error: Could not find ffmpeg on your system]

  Which is odd because i installed ffmpeg and I can require it.

  Does anyone know of to make gifify work ?
  Thank you !