Recherche avancée

Sur d’autres sites (15960)

• FFmpeg.swr_convert : audio to raw 16 bit pcm, to be used with xna SoundEffect. Audio cuts out when i convert

  21 mars 2019, par Robert Russell

  I want to resample mkv(vp8/ogg) and also raw 4 bit adpcm to raw 16bit pcm byte[] to be loaded into SoundEffect from xna library. So I can play it out while I’m using other code to display the frames (the video side is working).
  I can read a 16 bit wav file and play it. But when I goto resample something it doesn’t play 100%. One file is 3 mins and 15 secs. I only get 13 sec and 739 ms before it quits playing. I have been learning to do this by finding code samples in c++ and correcting it to work in c# using ffmpeg.autogen.

  the below is my best attempt at resampling.

              int nb_samples = Frame->nb_samples;
  
                      int output_nb_samples = nb_samples;
  
                      int nb_channels = ffmpeg.av_get_channel_layout_nb_channels(ffmpeg.AV_CH_LAYOUT_STEREO);
  
                      int bytes_per_sample = ffmpeg.av_get_bytes_per_sample(AVSampleFormat.AV_SAMPLE_FMT_S16) * nb_channels;
  
                      int bufsize = ffmpeg.av_samples_get_buffer_size(null, nb_channels, nb_samples,
  
                                                               AVSampleFormat.AV_SAMPLE_FMT_S16, 1);
  
  
  
                      byte*[] b = Frame->data;
  
                      fixed (byte** input = b)
  
                      {
  
                          byte* output = null;
  
                          ffmpeg.av_samples_alloc(&output, null,
  
                              nb_channels,
  
                              nb_samples,
  
                              (AVSampleFormat)Frame->format, 0);//
  
  
  
                          // Buffer input
  
  
  
                          Ret = ffmpeg.swr_convert(Swr, &output, output_nb_samples / 2, input, nb_samples);
  
                          CheckRet();
  
                          WritetoMs(output, 0, Ret * bytes_per_sample);
  
                          output_nb_samples -= Ret;
  
  
  
                          // Drain buffer
  
                          while ((Ret = ffmpeg.swr_convert(Swr, &output, output_nb_samples, null, 0)) > 0)
  
                          {
  
                              CheckRet();
  
                              WritetoMs(output, 0, Ret * bytes_per_sample);
  
                              output_nb_samples -= Ret;
  
                          }
  
                      }

  I changed that all to this but it cuts off sooner.

    Channels = ffmpeg.av_get_channel_layout_nb_channels(OutFrame->channel_layout);
  
                      int nb_channels = ffmpeg.av_get_channel_layout_nb_channels(ffmpeg.AV_CH_LAYOUT_STEREO);
  
                      int bytes_per_sample = ffmpeg.av_get_bytes_per_sample(AVSampleFormat.AV_SAMPLE_FMT_S16) * nb_channels;
  
  
  
                      if((Ret = ffmpeg.swr_convert_frame(Swr, OutFrame, Frame))>=0)
  
                          WritetoMs(*OutFrame->extended_data, 0, OutFrame->nb_samples * bytes_per_sample);
  
                      CheckRet();

  Both code use a function to set Swr it runs one time after the first frame is decoded.

          private void PrepareResampler()
  
      {
  
          ffmpeg.av_frame_copy_props(OutFrame, Frame);
  
          OutFrame->channel_layout = ffmpeg.AV_CH_LAYOUT_STEREO;
  
          OutFrame->format = (int)AVSampleFormat.AV_SAMPLE_FMT_S16;
  
          OutFrame->sample_rate = Frame->sample_rate;
  
          OutFrame->channels = 2;
  
          Swr = ffmpeg.swr_alloc();
  
          if (Swr == null)
  
              throw new Exception("SWR = Null");
  
          Ret = ffmpeg.swr_config_frame(Swr, OutFrame, Frame);
  
          CheckRet();
  
          Ret = ffmpeg.swr_init(Swr);
  
          CheckRet();
  
          Ret = ffmpeg.swr_is_initialized(Swr);
  
          CheckRet();
  
      }

  This is where I take the output and put it in the sound effect

  private void ReadAll()
  
      {
  
  
  
          using (Ms = new MemoryStream())
  
          {
  
              while (true)
  
              {
  
                  Ret = ffmpeg.av_read_frame(Format, Packet);
  
                  if (Ret == ffmpeg.AVERROR_EOF)
  
                      break;
  
                  CheckRet();
  
                  Decode();
  
              }
  
              if (Ms.Length > 0)
  
              {
  
                  se = new SoundEffect(Ms.ToArray(), 0, (int)Ms.Length, OutFrame->sample_rate, (AudioChannels)Channels, 0, 0);
  
                  //se.Duration; Stream->duration;
  
  
  
  
  
                  see = se.CreateInstance();
  
                  see.Play();
  
              } 
  
          }
  
      }

• How to detect a surge of activity in a video ?

  22 mars 2019, par Alain Collins

  I’d like to automatically detect a surge of activity in a video, e.g. basketball jump shot, hockey face-off, sprinters starting, etc., preferably using ffmpeg.

  In these instances, there’s some motion as the players assume their positions, followed by a pause as they wait for the ref to throw the ball or drop the puck, followed by a lot of motion as all players begin to react. It’s also typical that the camera will be still during this period and begin moving as the ball or puck changes position.

  I’ve tried using the ’select’ filter select='gt(scene,0.4)', but that seems to be more concerned with scene changes (i.e., more dramatic changes) even with low thresholds.

  I also tried exporting the scene information and examining it manually, but couldn’t find a clear pattern that correlated with motion in the video.

  UPDATE : I ran a mestimate on the video. Processing took a long time, but there was definitely a change in activity before and at point of interest. Is there a way to export this information to a file, or otherwise detect the amount of motion seen my mestimate ?

• Decoding YUYV422 raw images using FFmpeg

  12 avril 2019, par user373864q

  I have a collection of sequential YUYV422 raw images that I wish to turn into a video. The problem seems to be that when the frame is created in the avcodec_receive_frame. The frame only contains one channel instead of four in the YUYV format. This results in Input picture width <640> is greater then stride (0) since only the zeroth index of data and linesize is set in the frame. I don’t know if this is a ffmpeg bug or a misconfiguration on my part.

  #include "icsFfmpegImageDecoder.h"
  
  #include <stdexcept>
  
  
  
  ImageDecoder::ImageDecoder(std::string filename)
  
  {
  
      AVInputFormat* iformat;
  
      if (!(iformat = av_find_input_format("image2")))
  
          throw std::invalid_argument(std::string("input Codec not found\n"));
  
  
  
      this->fctx = NULL;
  
      if (avformat_open_input(&amp;this->fctx, filename.c_str(), iformat, NULL) &lt; 0)
  
      {
  
          std::string error = "Failed to open input file ";
  
          error += filename;
  
          error += "\n";
  
          throw std::invalid_argument(error);
  
      }
  
  #ifdef LIB_AVFORMAT_STREAM_CODEC_DEPRECATED
  
      if (!(this->codec = avcodec_find_decoder(this->fctx->streams[0]->codecpar->codec_id)))
  
          throw std::invalid_argument(std::string("Failed to find codec\n"));
  
  
  
      if (!(this->cctx = avcodec_alloc_context3(this->codec)))
  
          throw std::invalid_argument(std::string("could not create image read context codec"));
  
  
  
      if (avcodec_parameters_to_context(this->cctx, this->fctx->streams[0]->codecpar) &lt; 0)
  
          throw std::invalid_argument(std::string("could not get contest codec from stream"));
  
  #else
  
      this->cctx = this->fctx->streams[0]->codec;
  
      if (!(this->codec = avcodec_find_decoder(this->cctx->codec_id)))
  
          throw std::invalid_argument(std::string("Failed to find codec\n"));
  
  #endif
  
  
  
      if (this->cctx->codec_id == AV_CODEC_ID_RAWVIDEO) {
  
          // TODO Make Dynamic
  
          this->cctx->pix_fmt = AV_PIX_FMT_YUYV422 ;
  
          this->cctx->height = 800;
  
          this->cctx->width = 1280;
  
      }
  
  
  
      if (avcodec_open2(this->cctx, this->codec, NULL) &lt; 0)
  
          throw std::invalid_argument(std::string("Failed to open codec\n"));
  
  
  
  #ifdef USING_NEW_AVPACKET_SETUP
  
      if (!(this->pkt = av_packet_alloc()))
  
          throw std::invalid_argument(std::string("Failed to alloc frame\n"));
  
  #else
  
      this->pkt = new AVPacket();
  
      av_init_packet(this->pkt);
  
  #endif
  
      read_file();
  
  }
  
  
  
  ImageDecoder::~ImageDecoder()
  
  {
  
      avcodec_close(this->cctx);
  
      avformat_close_input(&amp;this->fctx);
  
  #ifdef USING_NEW_AVPACKET_SETUP
  
      av_packet_free(&amp;this->pkt);
  
  #else
  
      av_free_packet(this->pkt);
  
      delete this->pkt;
  
  #endif
  
  }
  
  
  
  void ImageDecoder::read_file()
  
  {
  
      if (av_read_frame(this->fctx, this->pkt) &lt; 0)
  
          throw std::invalid_argument(std::string("Failed to read frame from file\n"));
  
  
  
      if (this->pkt->size == 0)   
  
          this->ret = -1;
  
  }
  
  
  
  #ifdef LIB_AVCODEC_USE_SEND_RECEIVE_NOTATION
  
  void ImageDecoder::send_next_packet() {
  
  
  
      if ((this->ret = avcodec_send_packet(this->cctx, this->pkt)) &lt; 0)
  
          throw std::invalid_argument("Error sending a packet for decoding\n");
  
  }
  
  
  
  bool ImageDecoder::receive_next_frame(AVFrame* frame)
  
  {
  
      if (this->ret >= 0)
  
      {
  
          this->ret = avcodec_receive_frame(this->cctx, frame);
  
          if (this->ret == AVERROR_EOF)
  
              return false;
  
          else if (this->ret == AVERROR(11))//11 == EAGAIN builder sucks
  
              return false;
  
          else if (this->ret &lt; 0)
  
              throw std::invalid_argument("Error during decoding\n");
  
          return true;
  
      }
  
      return false;
  
  }
  
  #else
  
  void ImageDecoder::decode_frame(AVFrame* frame)
  
  {
  
      int got_frame = 0;
  
      if (avcodec_decode_video2(this->cctx, frame, &amp;got_frame, this->pkt) &lt; 0) 
  
          throw std::invalid_argument("Error while decoding frame %d\n");
  
  }
  
  #endif
  
  </stdexcept>