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• FFMPEG GOP Extraction

  29 mars 2015, par user3601375

  I have an MPEG -4 video and I would like to extract a one GOP (Group of pictures ) at a time to BMPs (using FFMPEG and c++ (code block) ) rather than the whole video in one go, since now all my code writing is stuck there I use to sketch everything in my mind then program and I can’t imagine how to do this, I searched the net for something like that but of no use.. any command line or any library used to do that (I have no full experience on FFMPEG I have read the documentation but that thing was not there). I will appreciate any kind help and thanks for reading y post.

  Regards,

• FFmpeg : jpeg scaling on amazone linux

  8 août 2016, par Vovik

  I have a need to rescale a jpg image in command line. And I use ffmpeg for that :

  ffmpeg -loglevel debug -i photo.jpg -vf scale=1920:1080 photo_scaled.jpg

  It works perfectly on my work Mac and gives following output :

  Splitting the commandline.
  
  Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'. 
  
  Reading option '-i' ... matched as input file with argument 'photo.jpg'. 
  
  Reading option '-vf' ... matched as option 'vf' (set video filters) with argument 'scale=1920:1080'. 
  
  Reading option 'photo_scaled.jpg' ... matched as output file. Finished splitting the commandline. 
  
  Parsing a group of options: global . 
  
  Applying option loglevel (set logging level) with argument debug. Successfully parsed a group of options. 
  
  Parsing a group of options: input file photo.jpg. Successfully parsed a group of options. 
  
  Opening an input file: photo.jpg. 
  
  [png_pipe @ 0x7fd221810600] Format png_pipe probed with size=2048 and score=99 
  
  [png_pipe @ 0x7fd221810600] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0 
  
  [png_pipe @ 0x7fd221810600] After avformat_find_stream_info() pos: 303755 bytes read:303755 seeks:0 frames:1 Input #0, png_pipe, from 'photo.jpg':   
  
  Duration: N/A, bitrate: N/A
  
  
  
  Stream #0:0, 1, 1/25: Video: png, 1 reference frame, rgb24(pc), 905x509 (0x0), 1/25, 25 tbr, 25 tbn, 25 tbc 
  
  Successfully opened the file. 
  
  Parsing a group of options: output file photo_scaled.jpg. 
  
  Applying option vf (set video filters) with argument scale=1920:1080. Successfully parsed a group of options. 
  
  Opening an output file: photo_scaled.jpg

  But on amazone server it gives me the following :

  Splitting the commandline.
  
  Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
  
  Reading option '-i' ... matched as input file with argument 'photo.jpg'.
  
  Reading option '-vf' ... matched as option 'vf' (set video filters) with argument 'scale=1920:1080'.
  
  Reading option 'photo_scaled.jpg' ... matched as output file.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option loglevel (set logging level) with argument debug.
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input file photo.jpg.
  
  Successfully parsed a group of options.
  
  Opening an input file: photo.jpg.
  
  [AVIOContext @ 0x372f700] Statistics: 303755 bytes read, 0 seeks
  
  [mjpeg @ 0x372c6a0] marker=f9 avail_size_in_buf=303444
  
  [mjpeg @ 0x372c6a0] marker parser used 0 bytes (0 bits)
  
  [mjpeg @ 0x372c6a0] marker=de avail_size_in_buf=303438
  
  [mjpeg @ 0x372c6a0] marker parser used 0 bytes (0 bits)
  
  [mjpeg @ 0x372c6a0] marker=fd avail_size_in_buf=302501
  
  [mjpeg @ 0x372c6a0] marker parser used 0 bytes (0 bits)
  
  [mjpeg @ 0x372c6a0] marker=f3 avail_size_in_buf=298342
  
  [mjpeg @ 0x372c6a0] marker parser used 0 bytes (0 bits)
  
  [mjpeg @ 0x372c6a0] marker=f8 avail_size_in_buf=297965
  
  [mjpeg @ 0x372c6a0] invalid id 248
  
  [image2 @ 0x372b880] decoding for stream 0 failed
  
  [image2 @ 0x372b880] Could not find codec parameters for stream 0 (Video: mjpeg): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  photo.jpg: could not find codec parameters

  As I checked, the configuration of ffmpeg is different.
  On linux :

  ffmpeg version N-63893-gc69defd
  
  built on Jul 16 2014 05:38:01 with gcc 4.6 (Debian 4.6.3-1)
  
  configuration: --prefix=/root/ffmpeg-static/64bit --extra-cflags='-I/root/ffmpeg-static/64bit/include -static' --extra-ldflags='-L/root/ffmpeg-static/64bit/lib -static' --extra-libs='-lxml2 -lexpat -lfreetype' --enable-static --disable-shared --disable-ffserver --disable-doc --enable-bzlib --enable-zlib --enable-postproc --enable-runtime-cpudetect --enable-libx264 --enable-gpl --enable-libtheora --enable-libvorbis --enable-libmp3lame --enable-gray --enable-libass --enable-libfreetype --enable-libopenjpeg --enable-libspeex --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-version3 --enable-libvpx
  
  libavutil      52. 89.100 / 52. 89.100
  
  libavcodec     55. 66.101 / 55. 66.101
  
  libavformat    55. 43.100 / 55. 43.100
  
  libavdevice    55. 13.101 / 55. 13.101
  
  libavfilter     4.  8.100 /  4.  8.100
  
  libswscale      2.  6.100 /  2.  6.100
  
  libswresample   0. 19.100 /  0. 19.100
  
  libpostproc    52.  3.100 / 52.  3.100

  On Mac :

  ffmpeg version 2.8.5 Copyright (c) 2000-2016 the FFmpeg developers
  
  built with Apple LLVM version 7.0.2 (clang-700.1.81)
  
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.8.5 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
  
  libavutil      54. 31.100 / 54. 31.100
  
  libavcodec     56. 60.100 / 56. 60.100
  
  libavformat    56. 40.101 / 56. 40.101
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 40.101 /  5. 40.101
  
  libavresample   2.  1.  0 /  2.  1.  0
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.101 /  1.  2.101
  
  libpostproc    53.  3.100 / 53.  3.100

  But what is specific to image scaling in the difference ? And how to make amazone linux’s version of ffmpeg work same way as Mac’s version (at least, in the case) ?

• configure : Disable linker warnings for common symbols

  23 février 2024, par Andreas Rheinhardt

  configure : Disable linker warnings for common symbols
  Common symbols are not part of ISO-C and therefore not used
  
  by FFmpeg at all. Yet linker warnings to ensure it stays
  
  that way are nevertheless wrong, because the existence of
  
  common symbols does not imply that there is a bug in our code.
  More precisely, Clang's ASAN implementation uses a common symbol
  
  ___asan_globals_registered when used on Elf targets with
  
  the -fsanitize-address-globals-dead-stripping option ;
  
  said option is the default since Clang 17 [1].
  
  This leads to 1883 warnings about ___asan_globals_registered
  
  when linking here.
  
  (Even without that option there were warnings like
  
  _ZN14__interception10real_vforkE being overridden.)
  Said warning is also unnecessary : The proper way to ensure
  
  that our code is free of common symbols is to let the compiler
  
  enforce this. But this is already the default since GCC 10
  
  and Clang 11, so there is no risk of introducing our own
  
  common symbols.
  [1] : https://reviews.llvm.org/D152604
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] configure