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• Will ffmpeg transcoding change the media's duration ?

  6 juillet 2012, par MaiTiano

  For example, I have a example flv media : 1775818137_1775828481_10344.flv. Only audio data has contained in it. (No video data)

  The major properties of this flv are :

  _____________________________________________________________________
  
  Format                                   : Flash Video
  
  
  
  File size                                : 87.4 KiB
  
  
  
  Duration                                 : 494 hours
  
  
  
  Overall bit rate mode                    : CBR
  
  
  
  Overall bit rate                         : 0 bps
  
  
  
  Writing application                      : Lavf53.4.0
  
  
  
  Audio
  
  
  
  Format                                   : MPEG Audio
  
  
  
  Format version                           : Version 1
  
  
  
  Format profile                           : Layer 3
  
  
  
  Mode                                     : Joint stereo
  
  
  
  Mode extension                           : MS Stereo
  
  
  
  Codec ID                                 : 2
  
  
  
  Codec ID/Hint                            : MP3
  
  
  
  Duration                                 : 49hours
  
  
  
  Bit rate mode                            : CBR
  
  
  
  Bit rate                                 : 64.0 Kbps
  
  
  
  Channel(s)                               : 2 channels
  
  
  
  Sampling rate                            : 44.1 KHz
  
  
  
  Compression mode                         : Lossy
  
  
  
  Stream size                              : 13.3 GiB
  
  
  
  _____________________________________________________________________

  Because this is the flv piece generated from the Suse10.0 server, the timestamp may be not correctly wrote into the flv metadata. Therefore, the Duration item listed above is not the real time of it.
  I has record the time in its file name.
  So, the beginning time is 1775818137 ms
  the ending time of this flv is 1775828481 ms
  The actual duation of this flv is 10344 ms which is about 10 seconds.

  **HERE IS MY QUESTION -.- **

  When I use ffmpeg to transcode flv fromat into ts format, like this,

  ./ffmpeg -i 1775818137_1775828481_10344.flv -f mpegts -vn -acodec libfaac -ar 44100 -ab 48k 1775818137_1775828481_10344.ts

  Is there possibility that the duration of final gotten ts file is not equal to the duation of original flv file ? In other words, the ts file's duration is not 10344ms.

• FFMPEG best practice ?

  26 avril 2013, par HighFlyingFantasy

  I'm trying to write a wrapper class for FFMPEG. I have 4 classes within the wrapper, Stream, Demux, Encode, Decode. All of these classes use avcodec, avformat, etc. My question is, can I use the avcodec_register_all, av_register_all and avformat_network_init in my top level wrapper after initializing the lower level classes, or should I call each one individually in the lower level init methods ?

• runtime error when linking ffmpeg libraries in qt creator

  6 juillet 2012, par dxthegreat

  I'm quite new around here but i hear that if you want a question answered, stackoverflow is the place to ask it >.<. So i hope that my question isn't too trivial that everyone will get annoyed at my lack of research (I've tried googling for two days already D= no progress !)
  I've also asked this question in the Qt forums, but i figured i'd ask here too.

  so...

  For the last few days I’ve been fiddling around with opengl and the like, trying to write a video player.

  However, when i try to import the ffmpeg libraries (avcodec, avformat, avutils etc), an error occurs on runtime (the program compiles fine). When compiled and run in debug mode, the error message gives me only a memory address and error code 135 (DLL not found).

  This error occurs when i include a function from those libraries in my code (e.g. av_register_all()) and it occurs regardless of whether the function is actually called.

  So i’m thinking that I’m doing something wrong when linking these libraries.
  I’m currently using :
  Windows vista (32bit),
  Qt creator 2.4.1 based on Qt 4.7.4 (32bit),
  Zeranoe’s FFmpeg build git-3233ad4 (2012-06-30)

  My .pro file consists of :

  QT       += core gui opengl
  
  
  
  TARGET = test
  
  TEMPLATE = app
  
  
  
  
  
  SOURCES += main.cpp\
  
          mainwindow.cpp \
  
      glwidget.cpp
  
  
  
  HEADERS += mainwindow.h \
  
      glwidget.h \
  
  
  
  FORMS    += mainwindow.ui
  
  
  
  
  
  LIBS += -L"$$_PRO_FILE_PWD_/libraries/ffmpeg/libs/" -lavcodec -lavformat -lavutil
  
  INCLUDEPATH += libraries/ffmpeg/includes

  I’ve tried many variations to the LIBS += line and checked my filepath many times. However, the DLL not found error occurs in all of these variations =(.

  Is there something I’m forgetting when doing these includes ?

  Thanks in advance >.<,
  (young and naive) aspiring dev