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• Incorrect length of video produced with ffmpeg libraries [closed]

  28 mars, par ivan.ukr

  I'm writing a C program that takes series of PNG images and converts them into a video. Video consists of the initial black screen and then each of those images, shown for the same constant amount of time, say 200 ms. I'm using libx264 as codec and mp4 as output format. I'm compiling my program with GCC 12 on Ubuntu 22.04 LTS. I'm using ffmpeg version from Ubuntu repositories. In order to achieve above behavior I've set time base to 1/5 in the both stream and codec.

  // assume imageDuration = 200
  AVRational timeBase;
  av_reduce(&timeBase.num, &timeBase.den, imageDuration, 1000, INT_MAX);
  
  const AVCodec *c = avcodec_find_encoder(codecId);
  AVStream *s = avformat_new_stream(fc, c);
  s->time_base = timeBase;
  s->nb_frames = numImages + 1; // inital black screen + images
  s->duration = numImages + 1;
  
  AVCodecContext *cc = avcodec_alloc_context3(c);
  cc->width = width;
  cc->height = height;
  cc->pix_fmt = pixelFormat;
  cc->time_base = timeBase;
  
  // ffmpeg headers suggest: Set to time_base ticks per frame.
  // Default 1, e.g., H.264/MPEG-2 set it to 2.
  cc->ticks_per_frame = 2;
  
  cc->framerate = av_inv_q(timeBase);
  if (fc->oformat->flags & AVFMT_GLOBALHEADER) {
      cc->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  }
  
  

  Then I'm encoding 11 frames.

  Finally, I'm getting video with the following characteristics:

  $ ffprobe v.mp4
  
  ....
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'v.mp4':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      encoder         : Lavf58.76.100
    Duration: 00:00:00.01, start: 0.000000, bitrate: 68414 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360, 69073 kb/s, 10333.94 fps, 10240 tbr, 10240 tbn, 10 tbc (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  
  

  Please pay attention to:

  Duration: 00:00:00.01
  

  and

  10333.94 fps
  

  That's totally NOT what I've expected (2.2s video length and 5 fps frame rate).

  Note: The content of video is correct, this can be verified by looking into the generated video file frame-by-frame in some program like Avidemux. But video length and frame rate are incorrect.

  Please advise, how to fix this?

• How to initialize video decoder with a already decoded frame ?

  27 mars, par Ragdoll Car

  Let's say I have an FFmpeg video decoder x264 initially initialized with some parameters. I am using C++ in my scenario. In normal conditions we push an encoded I-frame into such decoder and then referencing encoded P-frames.

  I have a special case where my I-frame is already decoded. So in my case I want to:

  • push already decoded I-frame into my decoder
  • push referencing encoded P-frames into my decoder

  How can I initialize the decoder state with already decoded I-frame? Currently to bypass these limitations I have to:

  • create a new temporary encoder
  • encode already decoded I-frame
  • decode encoded I-frame
  • and then I am able to push referencing encoded P-frames

• FFMPEG compile with x264 support for Android

  10 mars, par Pecana

  I am trying to build ffmpeg extensions for media3 (ExoPlayer) for Android

  https://github.com/androidx/media/tree/release/libraries/decoder_ffmpeg

  Using the default settings everything is fine but if I try to add support to libx264 the build failed. I compiled x264 for Android locally and it worked so the .so file for arm64 is present, I added it to the pkg-config with :

  export PKG_CONFIG_PATH=/build/x264/arm64/lib/pkgconfig:$PKG_CONFIG_PATH

  but when I try to build ffmpeg with the following command it fails :

  ./configure \
  --prefix=/build/ffmpeg \
  --enable-gpl \
  --enable-libx264 \
  --enable-static \
  --enable-pic \
  --arch=arm64 \
  --target-os=android \
  --cross-prefix=$TOOLCHAIN/bin/aarch64-linux-android21- \
  --sysroot=$SYSROOT
  

  Error : ERROR: x264 not found using pkg-config

  But it is not due to pkg-config as the command:

  pkg-config --cflags --libs x264
  

  reports : -DX264_API_IMPORTS -I/build/x264/arm64/include -L/build/x264/arm64/lib -lx264

  Any idea on how to fix it ?

  Thank you :-)

• avcodec_find_encoder(AV_CODEC_ID_H264) returns null

  22 janvier, par Monjura Rumi

  I am building an android application which will encode image captured from camera preview and later decode it. I am using ffmpeg library to encode and decode. To build static library with x264 I have used this tutorial. http://dl.dropbox.com/u/22605641/ffmpeg_android/main.html. As a source code of ffmpeg if I use the one downloaded from the link given in tutorial I can built it but can't build library if i use source code downloaded from here git clone git://source.ffmpeg.org/ffmpeg.git ffmpeg. I have built library in ubuntu and using it in windows 7 in Eclipse. As I need only h264 encoder and decoder I have used following code for ffmpeg, slightly modified from tutorial.

  #!/bin/bash
  
  NDK=~/Documents/android-ndk-r8e
  PLATFORM=$NDK/platforms/android-8/arch-arm
  PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  PREFIX=/home/android-ffmpeg
  
  function build_one
  {
      ./configure --target-os=linux --prefix=$PREFIX \
      --enable-cross-compile \
      --enable-runtime-cpudetect \
      --disable-asm \
      --arch=arm \
      --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
      --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
      --disable-stripping \
      --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
      --sysroot=$PLATFORM \
      --enable-nonfree \
      --enable-version3 \
      --disable-everything \
      --enable-gpl \
      --disable-doc \
      --enable-avresample \
      --disable-ffplay \
      --disable-ffserver \
      --enable-ffmpeg \
      --disable-ffprobe \
      --enable-avcodec \
      --enable-libx264 \
      --enable-encoder=libx264 \
      --enable-encoder=libx264rgb \
      --enable-decoder=h263 \
      --enable-decoder=h264 \
      --enable-decoder=svq3 \   
      --enable-zlib \
      --enable-gpl \
      --enable-pic \
      --disable-devices \
      --disable-avdevice \
      --extra-cflags="-I/home/android-ffmpeg/include -fPIC -DANDROID -D__thumb__ -mthumb -Wfatal-errors -Wno-deprecated -mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=armv7-a" \
      --extra-ldflags="-L/home/android-ffmpeg/lib"
  make -j4 install
  $PREBUILT/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o
  $PREBUILT/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -L$PREFIX/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libavresample/libavresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a -lc -lm -lz -ldl -llog -lx264 --warn-once --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a
  }
  
  build_one
  

  After building library I have been able to build android ndk. A little part of my JNI code is here.

  JNIEXPORT jint JNICALL Java_com_example_testjava_TestjniActivity_initencoder(JNIEnv* env,jobject obj){
  
      av_register_all();
      avcodec_register_all();
      codec = avcodec_find_encoder(AV_CODEC_ID_H264);
      if (!codec) {
        __android_log_write(ANDROID_LOG_INFO, "debug", "not found");                
         return -1;
      }
  .
  .
  .
  }
  

  When I run my java source code that calls initencoder() I get -1 as return value and logcat prints "not found". That means avcodec_find_encoder() returns null and if condition is being ok. I don't know what's wrong. Why this function is returning null? I have searched a lot but did not find any solution that could guide me to right direction. some says to use avcodec_init(). But ndk-build command fails and shows error saying undefined reference to 'avcodec_init()'. I have started with library build because I thought may be I am doing wrong from the first stage. Did I make any mistake in library building like not enabling things that I should? Please help me here. This is kind of urgent for me.

• Per macroblock encoding in libx264

  12 janvier, par Wei.M

  I know that in x264 encoding, the process is going on with the unit of macroblock. However, is that possible to set the parameters for each macroblocks? For example, if I want to let the QP of some specific area to be smaller than others. Is that possible? If I need to modify the functions and Apis in libx264, where should I begin?