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• FFmpeg : MD5 hash of M3U8 playlists generated from same input video with different segment durations (after applying video filter) don't match

  30 juillet 2020, par Saurabh P Bhandari

  Here are a few commands I am using to convert and transize a video in MP4 format to a M3U8 playlist.

  


  For a given input video (MP4 format), generate multiple video segments with segment duration 30 seconds.

  


  ffmpeg -loglevel error -i input.mp4 -dn -sn -an -c:v copy -bsf:v h264_mp4toannexb -copyts -start_at_zero -f segment -segment_time 30 30%03d.mp4 -dn -sn -vn -c:a copy audio.aac


  


  Apply a video filter (in this case scaling) on each segment and convert it to a M3U8 format.

  


  ls 30*.mp4 | parallel 'ffmpeg -loglevel error -i {} -vf scale=-2:144 -hls_list_size 0 {}.m3u8'


  


  Store the list of m3u8 files generated in list.txt in this format file 'segment-name.m3u8'

  


  for f in 30*.m3u8; do echo "file '$f'" >> list.txt; done


  


  Using concat demuxer, combine all segment files (which are in M3U8 format) and the audio to get one final m3u8 playlist pointing to segments with duration of 10 seconds.

  


  ffmpeg -loglevel error -f concat -i list.txt -i audio.aac -c copy -hls_list_size 0 -hls_time 10 output_30.m3u8


  


  ---

  


  I can change the segment duration in the first step from 30 seconds to 60 seconds, and compare the MD5 hash of the final M3U8 playlist generated in both the cases using this command :

  


  ffmpeg -loglevel error -i <input m3u8="m3u8" playlist="playlist" /> -f md5 -&#xA;

  


  The MD5 hash of the output files differ, i.e., video streams of output_30.m3u8 and output_60.m3u8 are not the same.

  


  Can anyone elaborate on this ?

  


  (I expected the MD5 hash to be the same)

  


• How to keep personally identifiable information safe

  23 janvier 2020, par Joselyn Khor
  The protection of personally identifiable information (PII) is important both for individuals, whose privacy may be compromised, and for businesses that may have their reputation ruined or be liable if PII is wrongly accessed, used, or shared.

  Curious about what PII is ? Here’s your introduction to personally identifiable information.

  Due to hacking, data leaks or data thievery, PII acquired can be combined with other pieces of information to form a more complete picture of you. On an individual level, this puts you at risk of identity theft, credit card theft or other harm caused by the fraudulent use of your personal information.

  On a business level, for companies who breach data privacy laws – like Cambridge Analytica’s harvesting of millions of FB profiles – the action leads to an erosion of trust. It can also impact your financial position as heavy fines can be imposed for the illegal use and processing of personally identifiable information.

  So what can you do to ensure PII compliance ?

  On an individual level :

  1. Don’t give your data away so easily. Although long, it’s worthwhile to read through privacy policies to make sure you know what you’re getting yourself into.
  2. Don’t just click ‘agree’ when faced with consent screens, as consent screens are majorly flawed. Users mostly always opt in without reading and without being properly informed what they opt in to.
  3. Did you know you’re most likely being tracked from website to website ? For example, Google can identify you across visits and websites. One of the things you can do is to disable third party cookies by default. Businesses can also use privacy friendly analytics which halt such tracking. 
  4. Use strong passwords.
  5. Be wary of public wifi – hackers can easily access your PII or sensitive data. Use a VPN (virtual private network), which lets you create a secure connection to a server of your choosing. This allows you to browse the internet in a safe manner.

  A PII compliance checklist for businesses/organisations :

  1. Identify where all PII exists and is stored – review and make sure this is in a safe environment.
  2. Identify laws that apply to you (GDPR, California privacy law, HIPAA) and follow your legal obligations.
  3. Create operational safeguards – policies and procedures for handling PII at an organisation level ; and building awareness to focus on the protection of PII.
  4. Encrypt databases and repositories where such info is kept.
  5. Create privacy-specific safeguards in the way your organisation collects, maintains, uses, and disseminates data so you protect the confidentiality of the data.
  6. Minimise the use, collection, and retention of PII – only collect and keep PII if it’s necessary for you to perform your legal business function.
  7. Conduct privacy impact assessments (PIA) to find and prevent privacy risks (identify what and why it’s to be collected ; how the information will be secured etc.).
  8. De-identify within the scope of your data collection and analytics tools.
  9. Anonymise data.
  10. Keep your privacy policy updated.
  11. Pseudonymisation.
  12. A more comprehensive guide for businesses can be found here : https://iapp.org/media/pdf/knowledge_center/NIST_Protecting_PII.pdf

  Unsure of what information could be considered PII ? Check out this list of examples.

  Additional resources :

  • https://www.umassmed.edu/it/security/compliance/what-is-pii/
  • http://www.osec.doc.gov/opog/privacy/PII_BII.html

• Statically built FFMPEG binary segmentation fault

  12 février 2020, par stevendesu

  I want to create a custom build of FFMPEG which rips out everything except for the ability to transmux HLS videos to MP4, and I need this build to be 100% static with no external dependencies

  I tried using the following configuration :

  ./configure \
  
      --extra-cflags='-static -static-libstdc++ -static-libgcc' \
  
      --extra-cxxflags='-static -static-libstdc++ -static-libgcc' \
  
      --extra-ldflags='-static -static-libstdc++ -static-libgcc' \
  
      --pkg-config-flags='--static' \
  
      --enable-static \
  
      --disable-shared \
  
      --disable-runtime-cpudetect \
  
      --disable-autodetect \
  
      --disable-ffplay \
  
      --disable-ffprobe \
  
      --disable-doc \
  
      --disable-avdevice \
  
      --disable-swresample \
  
      --disable-swscale \
  
      --disable-postproc \
  
      --disable-pthreads \
  
      --disable-w32threads \
  
      --disable-os2threads \
  
      --enable-network \
  
      --disable-dct \
  
      --disable-dwt \
  
      --disable-error-resilience \
  
      --disable-lsp \
  
      --disable-lzo \
  
      --disable-mdct \
  
      --disable-rdft \
  
      --disable-fft \
  
      --disable-faan \
  
      --disable-pixelutils \
  
      --disable-encoders \
  
      --disable-decoders \
  
      --disable-hwaccels \
  
      --disable-muxers \
  
      --enable-muxer=mov \
  
      --enable-muxer=mp4 \
  
      --disable-demuxers \
  
      --enable-demuxer=hls \
  
      --enable-demuxer=mpegts \
  
      --enable-demuxer=h264 \
  
      --enable-demuxer=aac \
  
      --disable-parsers \
  
      --enable-parser=h264 \
  
      --enable-parser=aac \
  
      --disable-bsfs \
  
      --disable-protocols \
  
      --enable-protocol=tcp \
  
      --enable-protocol=tls \
  
      --enable-protocol=http \
  
      --enable-protocol=https \
  
      --enable-protocol=hls \
  
      --disable-indevs \
  
      --disable-outdevs \
  
      --disable-devices \
  
      --disable-filters \
  
      --disable-alsa \
  
      --disable-appkit \
  
      --disable-avfoundation \
  
      --disable-bzlib \
  
      --disable-coreimage \
  
      --disable-iconv \
  
      --disable-lzma \
  
      --enable-openssl \
  
      --disable-sndio \
  
      --disable-sdl2 \
  
      --disable-securetransport \
  
      --disable-xlib \
  
      --disable-zlib \
  
      --disable-amf \
  
      --disable-audiotoolbox \
  
      --disable-cuda-llvm \
  
      --disable-cuvid \
  
      --disable-d3d11va \
  
      --disable-dxva2 \
  
      --disable-ffnvcodec \
  
      --disable-nvdec \
  
      --disable-nvenc \
  
      --disable-v4l2-m2m \
  
      --disable-vaapi \
  
      --disable-vdpau \
  
      --disable-videotoolbox \
  
      --disable-debug

  This looked about like what I wanted :

  install prefix            /usr/local
  
  source path               .
  
  C compiler                gcc
  
  C library                 glibc
  
  ARCH                      x86 (generic)
  
  big-endian                no
  
  runtime cpu detection     no
  
  standalone assembly       yes
  
  x86 assembler             nasm
  
  MMX enabled               yes
  
  MMXEXT enabled            yes
  
  3DNow! enabled            yes
  
  3DNow! extended enabled   yes
  
  SSE enabled               yes
  
  SSSE3 enabled             yes
  
  AESNI enabled             yes
  
  AVX enabled               yes
  
  AVX2 enabled              yes
  
  AVX-512 enabled           yes
  
  XOP enabled               yes
  
  FMA3 enabled              yes
  
  FMA4 enabled              yes
  
  i686 features enabled     yes
  
  CMOV is fast              yes
  
  EBX available             yes
  
  EBP available             yes
  
  debug symbols             no
  
  strip symbols             yes
  
  optimize for size         no
  
  optimizations             yes
  
  static                    yes
  
  shared                    no
  
  postprocessing support    no
  
  network support           yes
  
  threading support         no
  
  safe bitstream reader     yes
  
  texi2html enabled         no
  
  perl enabled              yes
  
  pod2man enabled           yes
  
  makeinfo enabled          no
  
  makeinfo supports HTML    no
  
  
  
  External libraries:
  
  openssl
  
  
  
  External libraries providing hardware acceleration:
  
  
  
  Libraries:
  
  avcodec                 avfilter                avformat                avutil
  
  
  
  Programs:
  
  ffmpeg
  
  
  
  Enabled decoders:
  
  
  
  Enabled encoders:
  
  
  
  Enabled hwaccels:
  
  
  
  Enabled parsers:
  
  aac                     h264
  
  
  
  Enabled demuxers:
  
  aac                     h264                    hls                     mpegts
  
  
  
  Enabled muxers:
  
  mov                     mp4
  
  
  
  Enabled protocols:
  
  hls                     http                    https                   tcp                     tls
  
  
  
  Enabled filters:
  
  aformat                 anull                   atrim                   format                  hflip                   null                    transpose               trim                    vflip
  
  
  
  Enabled bsfs:
  
  null
  
  
  
  Enabled indevs:
  
  
  
  Enabled outdevs:
  
  
  
  License: LGPL version 2.1 or later

  It included several filters which I won’t ever need or use, but these filters are pulled in automatically if you don’t specify --disable-avfilter, and specifying --disable-avfilter prevents the ffmpeg binary from being produced. So I’m stuck with those.

  Using these parameters and then running make, I received a binary that was about 5.9 MB in size and looked right :

  $> ldd ffmpeg
  
          not a dynamic executable

  But when I try to run it :

  $> ./ffmpeg -version
  
  Segmentation fault

  Using valgrind to try and inspect the cause of the segmentation fault :

  $> valgrind ./ffmpeg -version
  
  .... lots of stuff ...
  
  ==61362== Jump to the invalid address stated on the next line
  
  ==61362==    at 0x0: ???
  
  ==61362==    by 0x70BB1B: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x70B2E6: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x4033F9: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x1FFF000677: ???
  
  ==61362==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
  
  ==61362==
  
  ==61362==
  
  ==61362== Process terminating with default action of signal 11 (SIGSEGV)
  
  ==61362==  Bad permissions for mapped region at address 0x0
  
  ==61362==    at 0x0: ???
  
  ==61362==    by 0x70BB1B: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x70B2E6: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x4033F9: ??? (in /src/FFmpeg/ffmpeg)
  
  ==61362==    by 0x1FFF000677: ???
  
  ==61362==
  
  ==61362== HEAP SUMMARY:
  
  ==61362==     in use at exit: 0 bytes in 0 blocks
  
  ==61362==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
  
  ==61362==
  
  ==61362== All heap blocks were freed -- no leaks are possible
  
  ==61362==
  
  ==61362== For counts of detected and suppressed errors, rerun with: -v
  
  ==61362== Use --track-origins=yes to see where uninitialised values come from
  
  ==61362== ERROR SUMMARY: 93 errors from 90 contexts (suppressed: 0 from 0)
  
  Segmentation fault

  Attempting to access memory at location 0x0 sounds like trying to follow a null pointer. But I’m not sure how to fix this.

  gdb backtrace

  When I first ran gdb ./ffmpeg gdb immediately gave me a segmentation fault and I wasn’t kicked into the gdb REPL, so I couldn’t investigate

  After rebuilding ffmpeg I was able to get in this time :

  $> gdb ./ffmpeg
  
  
  
  GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
  
  Copyright (C) 2018 Free Software Foundation, Inc.
  
  License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
  
  This is free software: you are free to change and redistribute it.
  
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  
  and "show warranty" for details.
  
  This GDB was configured as "x86_64-linux-gnu".
  
  Type "show configuration" for configuration details.
  
  For bug reporting instructions, please see:
  
  /www.gnu.org/software/gdb/bugs/>.
  
  Find the GDB manual and other documentation resources online at:
  
  /www.gnu.org/software/gdb/documentation/>.
  
  For help, type "help".
  
  Type "apropos word" to search for commands related to "word"...
  
  Reading symbols from ffmpeg...done.
  
  (gdb) r
  
  Starting program: /src/FFmpeg/ffmpeg
  
  warning: Error disabling address space randomization: Operation not permitted
  
  
  
  Program received signal SIGSEGV, Segmentation fault.
  
  0x0000000000000000 in ?? ()
  
  (gdb) bt
  
  #0  0x0000000000000000 in ?? ()
  
  #1  0x0000000000f9a8d5 in __register_frame_info_bases.part.6 ()
  
  #2  0x00000000004445fd in frame_dummy ()
  
  #3  0x0000000000000001 in ?? ()
  
  #4  0x0000000000ebd20c in __libc_csu_init ()
  
  #5  0x0000000000ebc9d7 in __libc_start_main ()
  
  #6  0x000000000044451a in _start ()
  
  (gdb)

  I tried grep’ing the code base for __register_frame_info_bases and found nothing. So I’m not really sure where to go from here

  A fix, but not an explanation

  By randomly removing configuration parameters and rebuilding I discovered that --disable-pthreads was causing the segmentation fault. When I remove this, ffmpeg runs just fine

  I don’t know why this is the case, though. Why would they make it possible to remove something that you need to run ?