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• What is “interoperable TTML” ?

  19 septembre 2012, par silvia

  I’ve just tried to come to terms with the latest state of TTML, the Timed Text Markup Language.

  TTML has been specified by the W3C Timed Text Working Group and released as a RECommendation v1.0 in November 2010. Since then, several organisations have tried to adopt it as their caption file format. This includes the SMPTE, the EBU (European Broadcasting Union), and Microsoft.

  Both, Microsoft and the EBU actually looked at TTML in detail and decided that in order to make it usable for their use cases, a restriction of its functionalities is needed.

  EBU-TT

  The EBU released EBU-TT, which restricts the set of valid attributes and feature. “The EBU-TT format is intended to constrain the features provided by TTML, especially to make EBU-TT more suitable for the use with broadcast video and web video applications.” (see EBU-TT).

  In addition, EBU-specific namespaces were introduce to extend TTML with EBU-specific data types, e.g. ebuttdt:frameRateMultiplierType or ebuttdt:smpteTimingType. Similarly, a bunch of metadata elements were introduced, e.g. ebuttm:documentMetadata, ebuttm:documentEbuttVersion, or ebuttm:documentIdentifier.

  The use of namespaces as an extensibility mechanism will ascertain that EBU-TT files continue to be valid TTML files. However, any vanilla TTML parser will not know what to do with these custom extensions and will drop them on the floor.

  Simple Delivery Profile

  With the intention to make TTML ready for “internet delivery of Captions originated in the United States”, Microsoft proposed a “Simple Delivery Profile for Closed Captions (US)” (see Simple Profile). The Simple Profile is also a restriction of TTML.

  Unfortunately, the Microsoft profile is not the same as the EBU-TT profile : for example, it contains the “set” element, which is not conformant in EBU-TT. Similarly, the supported style features are different, e.g. Simple Profile supports “display-region”, while EBU-TT does not. On the other hand, EBU-TT supports monospace, sans-serif and serif fonts, while the Simple profile does not.

  Thus files created for the Simple Delivery Profile will not work on players that expect EBU-TT and the reverse.

  Fortunately, the Simple Delivery Profile does not introduce any new namespaces and new features, so at least it is an explicit subpart of TTML and not both a restriction and extension like EBU-TT.

  SMPTE-TT

  SMPTE also created a version of the TTML standard called SMPTE-TT. SMPTE did not decide on a subset of TTML for their purposes – it was simply adopted as a complete set. “This Standard provides a framework for timed text to be supported for content delivered via broadband means,…” (see SMPTE-TT).

  However, SMPTE extended TTML in SMPTE-TT with an ability to store a binary blob with captions in another format. This allows using SMPTE-TT as a transport format for any caption format and is deemed to help with “backwards compatibility”.

  Now, instead of specifying a profile, SMPTE decided to define how to convert CEA-608 captions to SMPTE-TT. Even if it’s not called a “profile”, that’s actually what it is. It even has its own namespace : “m608 :”.

  Conclusion

  With all these different versions of TTML, I ask myself what a video player that claims support for TTML will do to get something working. The only chance it has is to implement all the extensions defined in all the different profiles. I pity the player that has to deal with a SMPTE-TT file that has a binary blob in it and is expected to be able to decode this.

  Now, what is a caption author supposed to do when creating TTML ? They obviously cannot expect all players to be able to play back all TTML versions. Should they create different files depending on what platform they are targeting, i.e. a EBU-TT version, a SMPTE-TT version, a vanilla TTML version, and a Simple Delivery Profile version ? Should they by throwing all the features of all the versions into one TTML file and hope that the players will pick out the right things that they require and drop the rest on the floor ?

  Maybe the best way to progress would be to make a list of the “safe” features : those features that every TTML profile supports. That may be the best way to get an “interoperable TTML” file. Here’s me hoping that this minimal set of features doesn’t just end up being the usual (starttime, endtime, text) triple.

  UPDATE :

  I just found out that UltraViolet have their own profile of SMPTE-TT called CFF-TT (see UltraViolet FAQ and spec). They are making some SMPTE-TT fields optional, but introduce a new @forcedDisplayMode attribute under their own namespace “cff :”.

• Use ffmpeg to convert FLAC to AAC using the aac_mf encoder

  19 juin 2022, par dstaley

  I'm using ffmpeg to convert audio from FLAC to AAC and I'd like to use the aac_mf encoder, which uses Microsoft Media Foundation. If I use the native AAC encoder built into ffmpeg it works with the following command :

  


  ffmpeg -i input.flac -acodec aac -vn output.m4a


  


  However, the following command gives an error :

  


  > ffmpeg -i input.flac -acodec aac_mf -vn output.m4a
ffmpeg version 5.0.1-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 11.2.0 (Rev7, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
Input #0, flac, from '.\input.flac':
  Duration: 00:04:09.17, start: 0.000000, bitrate: 833 kb/s
  Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
Stream mapping:
  Stream #0:0 -> #0:0 (flac (native) -> aac (aac_mf))
Press [q] to stop, [?] for help
[aac_mf @ 000001bad81c6400] MFT name: 'Microsoft AAC Audio Encoder MFT'
[ipod @ 000001bad81fb640] track 0: codec frame size is not set
Output #0, ipod, to 'output.m4a':
  Stream #0:0: Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, s16, 128 kb/s
    Metadata:
      encoder         : Lavc59.18.100 aac_mf
[aac_mf @ 000001bad81c6400] nb_samples (4096) != frame_size (0)
Audio encoding failed
Conversion failed!


  


• Need help to compile FFmpeg with MSVC tools

  30 janvier 2018, par Antwane

  I need to compile FFmpeg on Windows 10 using MSVC 2017 compiler. I followed some guides from :

  • https://trac.ffmpeg.org/wiki/CompilationGuide/MSVC
  • https://www.ffmpeg.org/platform.html#Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows
  • https://pracucci.com/compile-ffmpeg-on-windows-with-visual-studio-compiler.html

  I installed current stable version of MSYS, fixed link.exe and use of PATH environment, installed make diffutils gcc pkg-config and downloaded c99-to-c89, nasm, and inttypes.h

  I think my environment is now correctly set up, I ran MSYS shell from MSVC Command prompt and have everything reachable.

  $ which cl
  
  /c/Program Files (x86)/Microsoft Visual Studio/2017/Professional/VC/Tools/MSVC/14.12.25827/bin/HostX64/x64/cl
  
  
  
  $ which link
  
  /c/Program Files (x86)/Microsoft Visual Studio/2017/Professional/VC/Tools/MSVC/14.12.25827/bin/HostX64/x64/link
  
  
  
  $ which yasm
  
  /home/Antoine/bin/yasm
  
  
  
  $ which c99conv
  
  /home/Antoine/bin/c99conv
  
  
  
  $ which c99wrap
  
  /home/Antoine/bin/c99wrap

  Now I configure the build

  $ ./configure --toolchain=msvc
  
  install prefix            /usr/local
  
  source path               .
  
  C compiler                cl
  
  C library                 msvcrt
  
  ARCH                      x86 (generic)
  
  big-endian                no
  
  runtime cpu detection     yes
  
  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
  
  XOP enabled               yes
  
  FMA3 enabled              yes
  
  FMA4 enabled              yes
  
  i686 features enabled     yes
  
  CMOV is fast              yes
  
  EBX available             no
  
  EBP available             no
  
  debug symbols             yes
  
  strip symbols             no
  
  optimize for size         no
  
  optimizations             yes
  
  static                    yes
  
  shared                    no
  
  postprocessing support    no
  
  network support           yes
  
  threading support         w32threads
  
  safe bitstream reader     yes
  
  texi2html enabled         no
  
  perl enabled              no
  
  pod2man enabled           no
  
  makeinfo enabled          no
  
  makeinfo supports HTML    no
  
  
  
  External libraries:
  
  schannel                 xlib
  
  
  
  External libraries providing hardware acceleration:
  
  cuda                     cuvid                    d3d11va                  dxva2                    nvenc
  
  
  
  Libraries:
  
  avcodec                  avdevice                 avfilter                 avformat                 avutil                   swresample               swscale
  
  
  
  Programs:
  
  ffmpeg                   ffprobe
  
  
  
  [...]
  
  Hundreds of modules, library, etc.
  
  [...]
  
  
  
  License: LGPL version 2.1 or later
  
  Creating configuration files ...
  
  config.h is unchanged
  
  config.asm is unchanged
  
  libavutil/avconfig.h is unchanged
  
  libavcodec/bsf_list.c is unchanged
  
  libavformat/protocol_list.c is unchanged

  But when I run make it stops very quickly

  $ make
  
  Makefile:47: la cible « qt-faststart » ne correspond pas au motif de cible
  
  Makefile:47: la cible « trasher » ne correspond pas au motif de cible
  
  Makefile:47: la cible « uncoded_frame » ne correspond pas au motif de cible
  
  Makefile:91: ffbuild/library.mak: No such file or directory
  
  make: *** Aucune règle pour fabriquer la cible « ffbuild/library.mak ». Arrêt.

  Sorry for the french wording, I don’t know how to tell MSVC print its output in english. Basically, the error means :

  Makefile:47: target « qt-faststart » doesn't match the target pattern
  
  make: *** No rule to make target « ffbuild/library.mak ». Stopped.

  Side notes :

  $ tree ffbuild
  
  ffbuild
  
  ├── config.fate
  
  ├── config.log
  
  ├── config.mak
  
  └── config.sh

  That’s right, library.mak were not generated into ffbuild, but I don’t know why, and configure script didn’t output any error message...

  Does anybody can help me to find out what am I doing wrong ?

  Edit :

  make distclean doesn’t help

  $ make distclean
  
  Makefile:47: la cible « qt-faststart » ne correspond pas au motif de cible
  
  Makefile:47: la cible « trasher » ne correspond pas au motif de cible
  
  Makefile:47: la cible « uncoded_frame » ne correspond pas au motif de cible
  
  Makefile:91: ffbuild/library.mak: No such file or directory
  
  make: *** Aucune règle pour fabriquer la cible « ffbuild/library.mak ». Arrêt.