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• how to use libavcodec/ffmpeg to find duration of video file

  14 août 2016, par Kunal Vyas

  I needed a library to perform basic functions such as length, size, etc of a video file (i’m guessing through the metadata or tags) so I chose ffmpeg. Valid video formats are primarily those prevalent in movie files viz. wmv, wmvhd, avi, mpeg, mpeg-4, etc. If you can, please help me with the method(s) to be used for knowing the duration the video file. I’m on a Linux platform.

• Cannot Play Video Output of Libavcodec (ffmpeg) Encoding Example

  29 octobre 2019, par user3707763

  From FFMPEG’s GitHub, I use the encode_video.c to generate a 1 second video. Here is the example in question : https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/encode_video.c

  I compile with : gcc -Wall -o ffencode encode_video.c -lavcodec -lavutil -lz -lm

  Clean compile, zero warnings.

  I test the program by running : ./ffencode video.mp4 libx264

  Lots of stats printed out (expected based on source code) as well as ffmpeg logs, but ultimately no errors or warnings.

  However, then the generated output video.mp4, can only be played by ffplay, and VLC Player (as well as Google Chrome) fail to play the video.

  Playing it via vlc command line actually prints :

  [00007ffd3550fec0] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
  
  TagLib: MP4: Invalid atom size
  
  TagLib: MP4: Invalid atom size
  
  TagLib: MP4: Invalid atom size

  Looking at ffprobe output, the bitrate and duration fields are empty :

  Input #0, h264, from 'video.mp4':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264 (High), yuv420p(progressive), 352x288, 25 fps, 25 tbr, 1200k tbn, 50 tbc

  I am using ffmpeg 4.1 with the following configuration :

  ffprobe version 4.1 Copyright (c) 2007-2018 the FFmpeg developers
  
    built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gpl --enable-libmp3lame --enable-libopus --enable-libsnappy --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-opencl --enable-videotoolbox
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100

  Any ideas how to fix this ? It is pretty surprising to see an API’s official example to be lacking such basic information.

• StdioURLProtocolHandlerTest failed while Xuggler build under Windows

  26 mars 2012, par Dims

  Trying to build Xuggler under Windows. My Windows is x64 Win 7 prof, but all used libraries are 32bit. I am running build procedure under MinGW/MSys, from under Msys shell with the followinf script :

  #!/bin/sh
  
  export JAVA_HOME=/C/Program\ Files\ \(x86\)/Java/jdk1.6.0_25
  
  export XUGGLE_HOME=/C/Xuggler
  
  
  
  PATH=$XUGGLE_HOME/bin:/C/Program\ Files\ \(x86\)/Java/jdk1.6.0_25/bin:/d/APPS/msysgit/msysgit/bin/git:/D/APPS/MinGW/bin:/bin:/D/APPS/apa    che-ant-1.8.2/bin:/D/Users/Dims/Design/MinGW/Util:$PATH
  
  ant -Dbuild.m64=no run-tests

  The error follows

   [exec] Running 6 tests..
  
   [exec] In StdioURLProtocolHandlerTest::testRead:
  
   [exec] ../../../../../../../../../test/csrc/com/xuggle/xuggler/io/StdioURLProtocolHandlerTest.cpp:108: Error: Expected (4546420 == totalBytes), found (4546420 != 1042)
  
   [exec] In StdioURLProtocolHandlerTest::testReadWrite:
  
   [exec] ../../../../../../../../../test/csrc/com/xuggle/xuggler/io/StdioURLProtocolHandlerTest.cpp:185: Error: Expected (4546420 == totalBytes), found (4546420 != 1042)
  
   [exec] In StdioURLProtocolHandlerTest::testSeek:
  
   [exec] ../../../../../../../../../test/csrc/com/xuggle/xuggler/io/StdioURLProtocolHandlerTest.cpp:139: Error: Expected (4546420 == totalBytes), found (4546420 != 1042)
  
   [exec] .
  
   [exec] Failed 3 of 6 tests
  
   [exec] Success rate: 50%
  
   [exec] FAIL: xugglerioTestStdioURLProtocolHandler.exe

  My questions is : did anybody did this on Windows and did he/she have this test passed ? :)

  UPDATE 1

  The test code is follows :

  int32_t totalBytes = 0;
  
  do {
  
      unsigned char buf[2048];
  
      retval = handler->url_read(buf, (int)sizeof(buf));
  
      if (retval > 0)
  
           totalBytes+= retval;
  
  } while (retval > 0);
  
  VS_TUT_ENSURE_EQUALS("", 4546420, totalBytes);

  While the url_read code is follows :

  int
  
  StdioURLProtocolHandler :: url_read(unsigned char* buf, int size)
  
  {
  
      if (!mFile)
  
          return -1;
  
      return (int) fread(buf, 1, size, mFile);
  
  }

  I don't understand, under what circumstances it can return 1042 ??? May be 64 bits play here somehow ?

  UPDATE 2

  I printed out filename used and it was

  d:/......./../../../test/fixtures/testfile.flv

  the path is correct, but started with d:/ not with /d/

  Can this play a role under Msys ?