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• C flags which gives priority to quality for decoded images in ffmpeg

  18 janvier 2016, par Tank2005

  I’m trying to decode h.264 streaming with ffmpeg(latest version) on Android NDK.

  I succeeded to get a decoded frame. But, an aquired image is very dirty even if low latency flag is disabled.

  If I want to give priority to quality over decoding speed, which flags should I specify ?

  bool initCodec(bool low_latency)
  
  {
  
      av_register_all();
  
  
  
      codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
      if(!codec) return false;
  
  
  
      context = avcodec_alloc_context3(codec);
  
      if(!context) return false;
  
  
  
      if(codec->capabilities & CODEC_CAP_TRUNCATED) context->flags |= CODEC_FLAG_TRUNCATED;
  
      if(low_latency == true) context->flags |= CODEC_FLAG_LOW_DELAY;
  
  
  
      frame = av_frame_alloc();
  
  
  
      int res = avcodec_open2(context, codec, NULL);
  
      if (res < 0) {
  
          qDebug() << "Coundn't open codec :" << res;
  
          return false;
  
      }
  
  
  
      av_init_packet(&avpkt);
  
      return true;
  
  }
  
  
  
  void sendBytes(unsigned char *buf, int buflen)
  
  {
  
      avpkt.size = buflen;
  
      avpkt.data = buf;
  
  
  
      int got_frame, len;
  
      while (avpkt.size > 0) {
  
          len = avcodec_decode_video2(context, frame, &got_frame, &avpkt);
  
          if (len < 0) {
  
              qDebug() << "Error while decoding : " << len;
  
              break;
  
          }
  
          if (got_frame) {
  
              onGotFrame(frame);
  
          }
  
          avpkt.size -= len;
  
          avpkt.data += len;
  
      }
  
  }

  

  Ex : I heard that it made a problem while compiling the library. So I write a compile option here(I built it on OpenSUSE Linux).

  #!/bin/bash
  
  NDK=/home/ndk
  
  SYSROOT=$NDK/platforms/android-9/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
  
  function build_one
  
  {
  
  ./configure \
  
  --prefix=$PREFIX \
  
  --enable-shared \
  
  --disable-static \
  
  --disable-avdevice \
  
  --disable-doc \
  
  --disable-symver \
  
  --disable-encoders \
  
  --disable-decoders \
  
  --enable-decoder=h264 \
  
  --enable-decoder=aac \
  
  --disable-protocols \
  
  --disable-demuxers \
  
  --disable-muxers \
  
  --disable-filters \
  
  --disable-network \
  
  --disable-parsers \
  
  --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
  --target-os=linux \
  
  --arch=arm \
  
  --enable-asm --enable-yasm \
  
  --enable-cross-compile \
  
  --sysroot=$SYSROOT \
  
  --extra-cflags="-Os -marm -march=armv7-a -mfloat-abi=softfp -mfpu=neon" \
  
  --extra-ldflags="-Wl,--fix-cortex-a8" \
  
  $ADDITIONAL_CONFIGURE_FLAG
  
  make clean
  
  make
  
  make install
  
  }
  
  CPU=armv7-a
  
  PREFIX=$(pwd)/android/$CPU
  
  build_on

• ffmpeg and php to get an image out of a video and convert video to ogg

  6 mars 2016, par sonam Sharma

  I have a video hosting site and have successfully installed ffmpeg on my local server. Things work overall, but I cannot get the video duration and don’t know how to convert videos to the ogg format. I can convert videos to mp4 but am unsure if the same code can also convert to ogg.

  One more thing is that I can get a thumbnail out of the video at the start of the video but I want it after 50 seconds.

     $base = basename($uploadfile, $safe_file['ext']);
  
                  $new_file = $base.'mp4';
  
                  $new_image = $base.'jpg';
  
                  $new_image_path = $live_img.$new_image;
  
                  $new_flv = $live_dir.$new_file;
  
  
  
    equire 'vendor/autoload.php';
  
          //ececute ffmpeg generate mp4
  
          exec('ffmpeg -i '.$uploadfile.' -f mp4 -s 896x504 '.$new_flv.'');
  
          //execute ffmpeg and create thumb
  
          exec('ffmpeg  -i '.$uploadfile.' -f mjpeg -vframes 71 -s 768x432 -an '.$new_image_path.''); 

• What is the recommended method to get metadata from files uploaded with ffmpeg.wasm ? [closed]

  28 novembre 2023, par Palma Dulce

  I'm developing an app using vite react.js and ffmpeg.wasm and I'm having trouble to find out how to get the duration time of a file. I need to writeFile to the FS, read the metadata, get the time duration, store it in a variable so I can use it to encode other things.

  


  I've tried to get it through log and process calls, but the time in log always shows different results, and the time in progress shows me how long the process it's taking to finish, not the file duration time. I've tried to readFile in countless ways as well. I guess I could maybe do that by local directory reading methods, but I wish to do that only with ffmpeg.wasm. I'm currently running ffmpeg/core from its API, in the latest 12.4.0 version, and the ffmpeg/ffmpeg in its latest 12.7.0.

  


  I'm a beginner, so maybe the answer it's right in my face, but I spent a good amount of time trying and can't see to find a solution.