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• How to send ffmpeg AVPacket through WebRTC (using libdatachannel)

  14 novembre 2022, par mike

  I'm encoding a video frame with the ffmpeg libraries, generating an AVPacket with compressed data.

  


  Thanks to some recent advice here on S/O, I am trying to send that frame over a network using the WebRTC library libdatachannel, specifically by adapting the example here :

  


  https://github.com/paullouisageneau/libdatachannel/tree/master/examples/streamer

  


  I am seeing problems inside h264rtppacketizer.cpp (part of the library, not the example) which are almost certainly to do with how I'm providing the sample data.
(I don't think that this is anything to do with libdatachannel specifically, it will be an issue with what I'm sending)

  


  The example code reads each encoded frame from a file, and populates a sample by setting the content of the file to the contents of the file :

  


  sample = *reinterpret_cast *>(&fileContents);

  


  sample is just a std::vector<byte>;</byte>

  


  I have naively copied the contents of an AVPacket->data pointer into the sample vector :

  


  sample.resize(pkt->size);
memcpy(sample.data(), pkt->data, pkt->size * sizeof(std::byte));    


  


  but the packetizer is falling over when trying to get length values out of that data.
Specifically, in the following code, the first iteration gets a length of 1, but the second, looking up index 5, gives 1119887324. This is way too big for my data, which is only 3526 bytes (the whole frame is a single colour so likely to be small once encoded) :

  


  while (index &lt; message->size()) {&#xA;assert(index &#x2B; 4 &lt; message->size());&#xA;auto lengthPtr = (uint32_t *)(message->data() &#x2B; index);&#xA;uint32_t length = ntohl(*lengthPtr);&#xA;auto naluStartIndex = index &#x2B; 4;&#xA;auto naluEndIndex = naluStartIndex &#x2B; length;&#xA;assert(naluEndIndex &lt;= message->size());    &#xA;        &#xA;auto begin = message->begin() &#x2B; naluStartIndex;&#xA;auto end = message->begin() &#x2B; naluEndIndex;&#xA;nalus->push_back(std::make_shared<nalunit>(begin, end));&#xA;index = naluEndIndex;&#xA;}&#xA;</nalunit>

  


  Here is a dump of

  


  uint32_t length = ntohl(*lengthPtr);


  


  for the first few elements of the message (*lengthPtr in parentheses) :

  


  [2022-03-29 15:12:01.182] [info] index 0: 1  (16777216)
[2022-03-29 15:12:01.183] [info] index 1: 359  (1728118784)
[2022-03-29 15:12:01.184] [info] index 2: 91970  (1114046720)
[2022-03-29 15:12:01.186] [info] index 3: 23544512  (3225577217)
[2022-03-29 15:12:01.186] [info] index 4: 1732427807  (532693607)
[2022-03-29 15:12:01.187] [info] index 5: 1119887324  (3693068354)
[2022-03-29 15:12:01.188] [info] index 6: 3223313413  (98312128)
[2022-03-29 15:12:01.188] [info] index 7: 534512896  (384031)
[2022-03-29 15:12:01.188] [info] index 8: 3691315291  (1526728156)
[2022-03-29 15:12:01.189] [info] index 9: 83909537  (2707095557)
[2022-03-29 15:12:01.189] [info] index 10: 6004992  (10574592)
[2022-03-29 15:12:01.190] [info] index 11: 1537277952  (41307)
[2022-03-29 15:12:01.190] [info] index 12: 2701131779  (50331809)
[2022-03-29 15:12:01.192] [info] index 13: 768  (196608)


  


  (I know I should post a complete sample, I am working on it)

  


  


  • I am fairly sure I am just missing something basic. E.g. am I supposed to do something with the AVPacket side_data, does AVPacket have or miss some header info ?

    


  


  • If I just fwrite the pkt->data for a single frame to disk, I can read the codec information with ffprobe :

    


  


  


  Input #0, h264, from 'encodedOut.h264':
Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (Constrained Baseline), yuv420p(progressive), 1280x720, 30 tbr, 1200k tbn


  


  Update : This issue is solved by changing the H264RtpPacketizer separator setting from H264RtpPacketizer::Separator::Length to H264RtpPacketizer::Separator::LongStartSequence, many thanks to author of libdatachannel paullouisageneau (see answer below)

  


  I have issues related to settings for the libx264 encoder, but can happily encode with h264_nvenc and h264_mf

  


• Android Java — Using and building FFMPEG library in Android Studio(Cmake)

  12 septembre 2017, par y3k00000

  As title, I’m trying to use the ffmpeg source code as library in Android Studio on Ubuntu Linux, but meeting some trouble in compilation stage. I think I must be missing some compile option but having no idea what I miss, can somebody lend a hand ?

  My codes & settings are below :

  A simple auto-generated .cpp

  #include 
  
  #include <string>
  
  #include "libavcodec/aacenc.h"
  
  
  
  extern "C"
  
  JNIEXPORT jstring JNICALL
  
  Java_y3k_testffmpegnative_MainActivity_stringFromJNI(
  
          JNIEnv *env,
  
          jobject /* this */) {
  
      std::string hello = "Hello from C++";
  
      return env->NewStringUTF(hello.c_str());
  
  }
  
  
  
  AACEncContext * aacEncContext; // Just trying by adding this.
  
  </string>

  I’ve tried these Gradle setting and it didn’t help :

  android {
  
      ....
  
      externalNativeBuild {
  
          cmake {
  
              arguments "-DANDROID_TOOLCHAIN=clang"
  
              cFlags "-std=c99"
  
              cppFlags "-frtti","-fexceptions"
  
          }
  
      }
  
  }
  
  ....

  CMakeLists.txt

  (Android Studio generated)
  
  ....
  
  include_directories( /home/y3k/ffmpeg )

  Error message while compiling :

  /home/y3k/ffmpeg/libavutil/float_dsp.h
  
  Error:(164, 50) error: expected ')'
  
  Information:(164, 30) to match this '('
  
  Error:(164, 50) error: expected ')'
  
  Information:(164, 30) note: to match this '('
  
  /home/y3k/ffmpeg/libavutil/fixed_dsp.h
  
  Error:(153, 44) error: expected ')'
  
  Information:(153, 30) to match this '('
  
  Error:(153, 44) error: expected ')'
  
  Information:(153, 30) note: to match this '('
  
  /home/y3k/ffmpeg/libavcodec/mpeg4audio.h
  
  Error:(44, 8) error: unknown type name 'av_export'
  
  Error:(44, 18) error: expected unqualified-id
  
  Error:(44, 8) error: unknown type name 'av_export'
  
  Error:(44, 18) error: expected unqualified-id
  
  /home/y3k/ffmpeg/libavcodec/aac.h
  
  Error:(294, 21) error: expected member name or ';' after declaration specifiers
  
  Error:(294, 21) error: expected member name or ';' after declaration specifiers

  FFMpeg config.h generated by this script :

  NDK=/home/y3k/Android/Sdk/ndk-bundle
  
  SYSROOT=$NDK/platforms/android-23/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
  
  function build_one
  
  {
  
  ./configure \
  
   --prefix=$PREFIX \
  
   --disable-shared \
  
   --enable-static \
  
   --disable-doc \
  
   --disable-ffmpeg \
  
   --disable-ffplay \
  
   --disable-ffprobe \
  
   --disable-ffserver \
  
   --disable-avdevice \
  
   --disable-doc \
  
   --disable-symver \
  
   --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
   --target-os=linux \
  
   --arch=arm \
  
   --enable-cross-compile \
  
   --sysroot=$SYSROOT \
  
   --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
  
   --extra-ldflags="$ADDI_LDFLAGS" \
  
   $ADDITIONAL_CONFIGURE_FLAG
  
  make clean
  
  make
  
  make install
  
  }
  
  CPU=arm
  
  PREFIX=$(pwd)/android/$CPU
  
  ADDI_CFLAGS="-marm"
  
  build_one

  By tracing the errors I found these lines :

  in float_dsp.h, fixed_dsp.h :

  void (*butterflies_float)(float *av_restrict v1, float *av_restrict v2, int len);

  av_restrict defined in config.h

  #define av_restrict restrict

  in aac.h :

  ....
  
  struct AACContext {
  
      AVClass        *class;
  
  ....

  in mpeg4audio.h :

  extern av_export const int avpriv_mpeg4audio_sample_rates[16];

  So I’m guessing it’s because the compiler misrecognized the C code as C++, I tried adding these :

  arguments "-DANDROID_TOOLCHAIN=clang"
  
  cFlags "-std=c99"

  to my build.gradle but didn’t help. Having no idea where to move on. :(

  I’m using the latest stable version of Android Studio on Ubuntu desktop. Please don’t be hesitate to ask if any extra information is required.

  Also I’ve been tried edit my native-lib.cpp into .c (Surely with the code contents changed), but wasn’t working either.

  Appreciate for any help.

• Anomalie #4495 (Nouveau) : migration 3.2.7 vers 3.3.0

  24 mai 2020, par josiane aletto

  test 1-
  j’ai installée en local un site qui était en SPIP 3.2.7 [24473] pour le migrer en SPIP 3.3.0-dev [24578].
  fichier mesoptions.php avec
  

  <span class="CodeRay"><span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_HEIGHT</span><span class="delimiter">'</span></span>,<span class="integer">1200</span>); <span class="comment">// largeur en pixels</span>
  <span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_WIDTH</span><span class="delimiter">'</span></span>, <span class="integer">1024</span>);  <span class="comment">// hauteur en pixels</span>
  <span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_SIZE</span><span class="delimiter">'</span></span>,  <span class="integer">650</span>);   <span class="comment">// taille en kilo-octets</span>
  </span>
  Télécharger

  
  Des logos de taille superieure a _IMG_MAX_SIZE’, 650 ne sont plus dans IMG Pas non plus dans logo_erreur non plus.
  par exemple rubon3 : 1630 × 648 pixels
  Plugins :
  Adaptive Images 1.9.2 -
  Agenda 3.26.0 -
  API de vérification 1.8.1 - stable
  Centre image 0.10.4 - dev
  Couleur de rubrique 2.3.8
  Facteur 3.6.2 - stable
  Formidable 3.34.3 - stable
  Insérer Modèles 1.3.3 - stable
  Massicot 0.8.1 -
  Mini Calendrier 2.4.1 - stable
  oEmbed 2.0.10 - stable
  Owl Carousel 1.0.18
  Carousel responsive avec support du multi-touch.
  Palette 4.0.7
  pdf.js 0.6.3
  Picto mod avec FontAwesome 2.1.0
  Saisies pour formulaires 3.11.1
  SPIP Bonux 3.4.6
  YAML 2.0.10
  test2
  Pour mieux voir J’ai recommencé installation /migration en désinstallant le plugin massicot et en le supprimant du repertoire plugin et en mettant dans mes_options.php
  define(’_IMG_MAX_HEIGHT’,800) ; // largeur en pixels
  define(’_IMG_MAX_WIDTH’, 500) ; // hauteur en pixels
  define(’_IMG_MAX_SIZE’, 400) ; // taille en kilo-octets

  je constate ; que les logos de taille >400Ko sont présent mais retaillé, rubon3 qui avait 1630 × 648 pixels a maintenant à 500 × 199 pixels 221 ko dans logo/IMG alors qu’il n’ y a pas massicot.
  si je supprime ce rubon3 par logo de la rubrique et télécharge l’image originale j’obtiens une image retaillé avec du noir en plus. mais si je clique dessus l’image est retaillée mais ok et elle est bien en 500*199 dans IMG sans le noir.

  • les images migrées ont bien gardées leurs dimensions*.

  test3
  je telecharge le logo rubon3 de 1630 × 648 pixels comme un document d’un article —> il est enregistré directement en 500 × 199 pixels 221 ko . Ce mécanisme a changé, en mieux, car dans la version 3.2 j’avais un message "Les images doivent obligatoirement faire moins de 650 ko (ce fichier fait 847.5 ko)".