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• How to use the ffmpeg library to transpose a video ?

  12 décembre 2013, par beni

  I'm trying to develop an video recorder and playback app in Android. So, I'm using the ffmpeg library and I've compiled the library to use in the project.

  I record a video and when I playback, in some devices don't recognize the orientation matrix, so I want to develop with the ffmpeg library a C method to do this order :

  ffmpeg -i f.mp4 -vf "transpose=1" -r 24 -sameq f2.mp4"

  I found this documentation but don't help me, because don't use the AVFilter and AVFilterContext classes.

  http://dranger.com/ffmpeg/tutorial01.html

  http://cekirdek.pardus.org.tr/ ismail/ffmpeg-docs/structAVFilterContext.html

  http://ffmpeg.org/doxygen/trunk/api-example_8c-source.html

  Now I only have the opening and closing video file

  Here my code :

  /*open the video file*/
  
  if ((lError = av_open_input_file(&gFormatCtx, gFileName, NULL, 0, NULL)) !=0 ) {
  
      LOGE(1, "Error open video file: %d", lError);
  
      return; //open file failed
  
  }
  
  /*retrieve stream information*/
  
  if ((lError = av_find_stream_info(gFormatCtx)) < 0) {
  
      LOGE(1, "Error find stream information: %d", lError);
  
      return;
  
  } 
  
  /*find the video stream and its decoder*/
  
  gVideoStreamIndex = av_find_best_stream(gFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &lVideoCodec, 0);
  
  if (gVideoStreamIndex == AVERROR_STREAM_NOT_FOUND) {
  
      LOGE(1, "Error: cannot find a video stream");
  
      return;
  
  } else {
  
  LOGI(10, "video codec: %s", lVideoCodec->name);
  
  }
  
  if (gVideoStreamIndex == AVERROR_DECODER_NOT_FOUND) {
  
      LOGE(1, "Error: video stream found, but no decoder is found!");
  
      return;
  
  }   
  
  /*open the codec*/
  
  gVideoCodecCtx = gFormatCtx->streams[gVideoStreamIndex]->codec;
  
  LOGI(10, "open codec: (%d, %d)", gVideoCodecCtx->height, gVideoCodecCtx->width);
  
  #ifdef SELECTIVE_DECODING
  
  gVideoCodecCtx->allow_selective_decoding = 1;
  
  #endif
  
  if (avcodec_open(gVideoCodecCtx, lVideoCodec) < 0) {
  
  LOGE(1, "Error: cannot open the video codec!");
  
      return;
  
  }
  
  LOGI(10, "get video info ends");

  How can I transpose the video using the ffmpeg library ?

• How to achive better quality with libav on android surface ?

  16 novembre 2018, par iLobanov

  Playing video from RTSP stream on Android surface using solution from this repo
  https://github.com/alexandruc/android-ffmpeg-player/blob/master/android-ffmpeg-player/jni/ffmpeg-player.c

  Video is playng but have a lot of glitches especially when something moving.
  Have not enought expirience using libav.
  Will be happy if someone can help or give links on some tutorials or community.

  Here is the function to display video on surface.

  void* decodeAndRender(void *voidArgs) {
  
  auto *args = (decode_args*)voidArgs;
  
  CamCon* cc = getCamCon(args->name);
  
  
  
  ANativeWindow_Buffer    windowBuffer;
  
  AVPacket                packet;
  
  int                     i=0;
  
  int                     frameFinished;
  
  int                     lineCnt;
  
  
  
  int counter = 0;
  
  while(av_read_frame(cc->formatCtx, &packet)>=0 && cc->isConnect) {
  
      counter = 1;
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index==cc->videoStreamIdx) {
  
          // Decode video frame
  
          avcodec_decode_video2(cc->codecCtx, cc->decodedFrame, &frameFinished, &packet);
  
          // Did we get a video frame?
  
          if(frameFinished) {
  
              // RECORD video
  
              if(cc->isRecord)
  
                  recordMP4(packet, cc);
  
  
  
              // DISPLAY video
  
              // Convert the image from its native format to RGBA
  
              sws_scale (
  
                      cc->sws_ctx,
  
                      (uint8_t const * const *)cc->decodedFrame->data,
  
                      cc->decodedFrame->linesize,
  
                      0,
  
                      cc->codecCtx->height,
  
                      cc->frameRGBA->data,
  
                      cc->frameRGBA->linesize
  
              );
  
              // lock the window buffer
  
              if (ANativeWindow_lock(cc->window, &windowBuffer, NULL) < 0) {
  
                  LOGE("cannot lock window");
  
              } else {
  
                  // draw the frame on buffer
  
                  LOGI("copy buffer %d:%d:%d", cc->displayWidth, cc->displayHeight, cc->displayWidth * cc->displayHeight*4);
  
                  LOGI("window buffer: %d:%d:%d", windowBuffer.width,
  
                       windowBuffer.height, windowBuffer.stride);
  
                  memcpy(windowBuffer.bits, cc->buffer,  cc->displayWidth * cc->displayHeight * 4);
  
                  // unlock the window buffer and post it to display
  
                  ANativeWindow_unlockAndPost(cc->window);
  
                  // count number of frames
  
                  ++i;
  
              }
  
          }
  
      }
  
      // Free the packet that was allocated by av_read_frame
  
      av_free_packet(&packet);
  
  }
  
  LOGI("total No. of frames decoded and rendered %d", i);
  
  finish(args->env, args->name);

  }

• Anomalie #3714 : squelette article : documents dupliqués en cas de majuscule

  22 février 2016, par b b

  Niveau "ergo", les modèles proposés dans les boîtes des documents de l’objet en cours d’édition sont bien présentés en minuscules. D’ailleurs, un double clic sur le modèle souhaité l’insert automatiquement dans le texte à la position du curseur. Peut-être est-ce point que tu as oublié de montrer à ton "élève" lors de la "formation" ?