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• MSVC fatal error LNK1120 : 1 unresolved externals with FFMPEG libs

  16 août 2019, par Jared

  I am trying to utilize the ffmpeg libraries in a program of my own and am having trouble linking them. Specifically, In my a basic program I am receiving fatal error LNK1120: 1 unresolved externals errors. The program is :

  #include <iostream>
  
  #include <libswresample></libswresample>swresample.h>
  
  
  
  int main()
  
  {
  
      std::cout &lt;&lt; "Hello World!\n";
  
      struct SwrContext* swr_ctx = swr_alloc();
  
      if (!swr_ctx) {
  
          std::cout &lt;&lt; "Could not allocate resampler context";
  
      }
  
  }
  
  </iostream>

  I downloaded prebuild libraries from https://ffmpeg.zeranoe.com/builds/, specifically the Windows x64 dev package which includes the .def/.lib as well as .dll files.

  I originally tried (and intend to ultimately use) cmake to generate the MSVC sln files. The cmake file is :

  cmake_minimum_required(VERSION 3.5)
  
  
  
  project(ffmpeg_jni)
  
  
  
  # Find the JNI bits
  
  find_package(JNI)
  
  
  
  # Search for the ffmpeg libraries
  
  set(ffmpeg_include_hint "ffmpeg-dev/include")
  
  set(ffmpeg_lib_hint "ffmpeg-dev/lib")
  
  
  
  find_path(SWRESAMPLE_INCLUDE_DIR libswresample/swresample.h PATHS ${ffmpeg_include_hint})
  
  find_library(SWRESAMPLE_LIBRARY swresample PATHS ${ffmpeg_lib_hint})
  
  add_library(swresample SHARED IMPORTED)
  
  set_target_properties(swresample PROPERTIES
  
      IMPORTED_LOCATION "${SWRESAMPLE_LIBRARY}"
  
      IMPORTED_IMPLIB "${SWRESAMPLE_LIBRARY}"
  
      INTERFACE_INCLUDE_DIRECTORIES "${SWRESAMPLE_INCLUDE_DIR}"
  
  )
  
  
  
  # Setup basic include dirs
  
  set(includeDIRS
  
          src/main/cpp
  
          ${JAVA_INCLUDE_PATH})
  
  
  
  # Setup windows specific includes
  
  set(includeDIRS
  
          ${includeDIRS}
  
          ${JAVA_INCLUDE_PATH}/Win32)
  
  
  
  include_directories(${includeDIRS})
  
  
  
  set(WRAPPER_SRC
  
          src/main/cpp/logging.c
  
          src/main/cpp/logging.h
  
          src/main/cpp/main.cpp)
  
  
  
  add_library(ffmpeg_jni SHARED ${WRAPPER_SRC})
  
  target_link_libraries(ffmpeg_jni PRIVATE swresample)

  The generated solution compiles and has proper access to the include files (Visual Studio can even take me to the declarations). The issue comes in the linking phase of the build where I receive :

  error LNK2019 : unresolved external symbol "struct SwrContext * __cdecl
  swr_alloc(void)" (?swr_alloc@@YAPEAUSwrContext@@XZ) referenced in
  function main

  Thinking that I perhaps had something wrong in cmake since I am still pretty new with it I tried making a simple demo as a pure visual studio project following what I have found in countless online demos for adding an external library to a project. Specifically this included :

  • Adding the directory containing the header files to Properties->C/C++->General->Additional Include Directories
  • Adding the directory containing the .lib files to Properties->Linker->General->Additional Library Directories (Note that the cmake path did not do this but instead added the lib file via a relative path)
  • Adding the .lib file to Properties->Linker->Input->Additional Dependencies

  At this point any searching efforts I undertake show me different people doing the same things which tells me I’ve been looking at this too long to find the answer myself and its something trivial that I’m missing/not understanding.

• ffmpeg - Audio Issues with TS File

  5 décembre 2020, par MeaningOfLife

  I am new to the world of ffmpeg, so I apologize in advance if this is a stupid question or request.

  


  I'm in the process of trying to convert a .ts file to a h264/mp4. I was able to successfully convert the video, however whenever I go to play the output file, the audio is weird. Most of the audio is only coming through the left channel. I noticed that the audio has multiple channels - 6 to be exact. And there are two audio streams as well. I'm assuming that this has something to do with it, but I am not sure what exactly to put in the command line to fix it.

  


  I was hoping there would be a way to copy the video stream from the mp4 I had already made with ffmpeg, and then replace the audio from that mp4 with the audio from the source ts file - preferably mixed down into regular stereo audio. It is quite a big file, so I would like to not have to convert the video stream again if I don't have to.

  


  Here is the media information from the source video.

  


  General
ID : 1 (0x1)
Complete name : D:\88th Annual Christmas in Rockefeller Center.ts
Format : MPEG-TS
File size : 9.80 GiB
Duration : 2 h 7 min
Overall bit rate mode : Variable
Overall bit rate : 11.0 Mb/s
Law rating : None

Video
ID : 101 (0x65)
Menu ID : 1 (0x1)
Format : MPEG Video
Format version : Version 2
Format profile : Main@High
Format settings : BVOP
Format settings, BVOP : Yes
Format settings, Matrix : Default
Format settings, GOP : Variable
Format settings, picture structure : Frame
Codec ID : 2
Duration : 2 h 7 min
Bit rate mode : Variable
Bit rate : 9 851 kb/s
Maximum bit rate : 80.0 Mb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Active Format Description : Full frame 16:9 image
Frame rate : 29.970 (30000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Top Field First
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.159
Time code of first frame : 00:00:00;00
Time code source : Group of pictures header
Stream size : 8.80 GiB (90%)

Audio #1
ID : 102 (0x66)
Menu ID : 1 (0x1)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : 129
Duration : 2 h 7 min
Bit rate mode : Constant
Bit rate : 384 kb/s
Channel(s) : 6 channels
Channel layout : L R C LFE Ls Rs
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Compression mode : Lossy
Delay relative to video : 32 ms
Stream size : 351 MiB (3%)
Language : English
Service kind : Complete Main

Audio #2
ID : 7543 (0x1D77)
Menu ID : 1 (0x1)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : 129
Duration : 2 h 7 min
Bit rate mode : Constant
Bit rate : 192 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Compression mode : Lossy
Delay relative to video : 11 ms
Stream size : 176 MiB (2%)
Language : Spanish
Service kind : Complete Main

Text #1
ID : 101 (0x65)-CC1
Menu ID : 1 (0x1)
Format : EIA-608
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 2 h 7 min
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)
CaptionServiceName : CC1

Text #2
ID : 101 (0x65)-1
Menu ID : 1 (0x1)
Format : EIA-708
Muxing mode : A/53 / DTVCC Transport
Muxing mode, more info : Muxed in Video #1
Duration : 2 h 7 min
Bit rate mode : Constant
Stream size : 0.00 Byte (0%)


  


• Troll spirit

  15 juin 2013, par Mans — Law and liberty

  Last week’s announcements from the White House of steps being taken to begin fighting back against patent trolls, along with legislation passed in Vermont for the same purpose, are worthy of praise. Whether they prove effective or not, they are a sign of the problem finally having been recognised by the highest authorities. That said, only one aspect of the issue is addressed, that of non-practising entities or trolls. Little effort is being made to stymie troll-like behaviour from otherwise legitimate actors. While a stake is driven through the heart of the troll, its spirit remains free to roam the corporate world, and like a demon of darkness it possesses companies, compelling them to engage in the very practices we seek to eradicate.

  The demon

  The most damaging, when wielded by a troll, are those patents with vague or overly broad claims. These can easily be asserted against large numbers of alleged infringers, many of which likely choose to settle out of court rather than risk an expensive litigation process with uncertain outcome. Such negotiations are frequently subject to non-disclosure agreements prohibiting publication of details in any deals, or even the existence thereof. As a result, an accused has no way of assessing a fair price for a licence (assuming the patent is in fact valid), and the patent holder can thus extract from each would-be infringer precisely as much as they are willing or able to pay to avoid a lawsuit.

  At the root of this problem is the ease with which applications for the patents in question are granted. Given the volume of patent applications, it is hardly reasonable to demand a hugely more extensive examination process than currently takes place (although some improvements here are no doubt possible) ; after all, a speedy decision is in the best interest of all parties. The solution must evidently be found elsewhere.

  The exorcism

  An obvious cure to the problem is the abolishment of the patent system. As this is clearly not feasible today, more practical, albeit less effective, remedies must be sought. A few ideas follow.

  Make patent validity all or nothing

  Change the rules such that any claim being found invalid cancels the patent its entirety. With the full patent at stake in this manner, companies would be discouraged from gambling on frivolous claims and encouraged to conduct a more thorough background investigation before filing.

  Maintain a registry of licences

  Require that all patent licence agreements be filed in an open, easily searchable registry. This would hopefully increase fairness in licensing deals.

  Mandate reimbursement of licence fees for invalidated patents

  If a patent is challenged and found invalid, require that the owner reimburse any licence fees previously collected for the patent in question. Apart from being morally right, this could act as a deterrent to over-charging. The amount requested for a licence would likely be balanced against the risk of being made to pay it all back later, resulting in lower licence fees for low-confidence patents.

  These suggestions, alone or together, will not completely eradicate the problems of patent abuse. They are but small steps towards a more thorough overhaul of a system increasingly ill-suited to the nature and pace of modern technological development.