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• Why decoding frames from avi container and encode them to h264/mp4 doesn't work ?

  28 novembre 2013, par theateist

  I started using ffmpeg and I want to convert avi file to mp4/h264 file. I've read many posts including this, but I couldn't find any good example how to save frames to mp4 file. The code below is simplified one that decodes frames from avi file and encode it to H264/mp4 file, but when I save the frames the mp4 file cannot be played. I think I do somethinkg wrong in encoding

  I will appreciate if you could tell me what is wrong and how to fix it.

  const char* aviFileName = "aviFrom.avi";
  
  const char* mp4FileName = "mp4To.mp4";
  
  
  
  // Filling pFormatCtx by open video file and Retrieve stream information
  
  // ...
  
  // Retrieving codecCtxDecode and opening codecDecode 
  
  //...
  
  
  
  
  
  // Get encoder
  
  codecCtxEncode = avcodec_alloc_context();   
  
  codecCtxEncode->qmax = 69; 
  
  codecCtxEncode->max_qdiff = 4;
  
  codecCtxEncode->bit_rate = 400000;
  
  codecCtxEncode->width = codecCtxDecode->width;
  
  codecCtxEncode->height = codecCtxDecode->height;
  
  codecCtxEncode->pix_fmt = AV_PIX_FMT_YUV420P;   
  
  codecEncode = avcodec_find_encoder(CODEC_ID_H264);
  
  if(codecEncode == NULL)
  
      return -1;  
  
  if(avcodec_open2(codecCtxEncode, codecEncode, NULL))
  
      return -1;
  
  
  
  SwsContext *sws_ctx = sws_getContext(codecCtxDecode->width, codecCtxDecode->height, codecCtxDecode->pix_fmt,
  
                              codecCtxDecode->width, codecCtxDecode->height, AV_PIX_FMT_YUV420P,
  
                              SWS_BILINEAR, NULL, NULL, NULL);
  
  
  
  // Allocate an AVFrame structure    
  
  frameDecoded = avcodec_alloc_frame();
  
  frameEncoded = avcodec_alloc_frame();    
  
  
  
  avpicture_alloc((AVPicture *)frameEncoded, AV_PIX_FMT_YUV420P, codecCtxDecode->width, codecCtxDecode->height);
  
  
  
  while(av_read_frame(pFormatCtx, &packet)>=0)
  
  {       
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index==videoStreamIndex) {
  
          avcodec_decode_video2(codecCtxDecode, frameDecoded, &frameFinished, &packet);
  
          // Did we get a video frame?
  
          if(frameFinished)
  
          {           
  
              fwrite(packet.data, packet.size,
  
              sws_scale(sws_ctx, frameDecoded->data, frameDecoded->linesize, 0, codecCtxDecode->height, 
  
                          frameEncoded->data, frameEncoded->linesize);
  
  
  
  
  
  
  
              int64_t pts = packet.pts;
  
              av_free_packet(&packet);
  
              av_init_packet(&packet);
  
              packet.data = NULL;
  
              packet.size = 0;    
  
              frameEncoded->pts = pts;                
  
  
  
              int failed = avcodec_encode_video2(codecCtxEncode, &packet, frameEncoded, &got_output);
  
              if(failed)
  
              {
  
                  exit(1);
  
              }
  
              fwrite(packet.data,1,packet.size, mp4File);
  
          }
  
      }
  
  
  
      av_free_packet(&packet);
  
  }

• Encode image to video using ffmpeg (sws_scale)

  26 septembre 2012, par bahar_p

  I'm trying to encode an image to video using ffmpeg library.
  I have these global params :

  //Global params
  
  AVCodec         *codec;
  
  AVCodecContext  *codecCtx;
  
  uint8_t         *output_buffer;
  
  int             output_buffer_size;

  I divided the encoding to 3 methods :
  Initialize the encoder :

  jint Java_com_camera_simpledoublewebcams2_CameraPreview_initencoder(JNIEnv* env,jobject thiz){
  
  avcodec_register_all();
  
  avcodec_init();
  
  av_register_all();
  
  
  
  int fps = 30;
  
  
  
  /* find the H263 video encoder */
  
  codec = avcodec_find_encoder(CODEC_ID_H263);
  
  if (!codec) {
  
      LOGI("avcodec_find_encoder() run fail.");
  
      return -5;
  
  }
  
  
  
  //allocate context
  
  codecCtx = avcodec_alloc_context();
  
  
  
  /* put sample parameters */
  
  codecCtx->bit_rate = 400000;
  
  /* resolution must be a multiple of two */
  
  codecCtx->width = 176;
  
  codecCtx->height = 144;
  
  /* frames per second */
  
  codecCtx->time_base = (AVRational){1,fps};
  
  codecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  codecCtx->codec_id = CODEC_ID_H263;
  
  codecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
  
  
  
  /* open it */
  
  if (avcodec_open(codecCtx, codec) < 0) {
  
      LOGI("avcodec_open() run fail.");
  
      return -10;
  
  }
  
  
  
  //init buffer
  
  output_buffer_size = 500000;
  
  output_buffer = malloc(output_buffer_size);
  
  
  
  return 0;

  }

  Encoding the image :

  jint Java_com_camera_simpledoublewebcams2_CameraPreview_encodejpeg(JNIEnv* env,jobject thiz,jchar* cImage, jint imageSize){
  
  int             out_size;
  
  AVFrame         *picture;
  
  AVFrame         *outpic;
  
  uint8_t         *outbuffer;
  
  
  
  //allocate frame    
  
  picture = avcodec_alloc_frame();    
  
  outpic = avcodec_alloc_frame();
  
  
  
  int nbytes = avpicture_get_size(PIX_FMT_YUV420P, codecCtx->width, codecCtx->height);
  
  outbuffer = (uint8_t*)av_malloc(nbytes);
  
  outpic->pts = 0;
  
  
  
  //fill picture with image
  
  avpicture_fill((AVPicture*)picture, (uint8_t*)cImage, PIX_FMT_RGBA, codecCtx->width, codecCtx->height);
  
  //fill outpic with empty image
  
  avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, codecCtx->width, codecCtx->height);
  
  
  
  //rescale the image 
  
  struct SwsContext* fooContext = sws_getContext(codecCtx->width, codecCtx->height, 
  
                                                         PIX_FMT_RGBA, 
  
                                                         codecCtx->width, codecCtx->height, 
  
                                                         PIX_FMT_YUV420P, 
  
                                                         SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
  sws_scale(fooContext, picture->data, picture->linesize, 0, codecCtx->height, outpic->data, outpic->linesize);   
  
  
  
  //encode the image
  
  out_size = avcodec_encode_video(codecCtx, output_buffer, output_buffer_size, outpic);
  
  out_size += avcodec_encode_video(codecCtx, output_buffer, output_buffer_size, outpic);
  
  
  
  //release pictures
  
  av_free(outbuffer);
  
  av_free(picture);
  
  av_free(outpic);
  
  
  
  return out_size;

  }

  And closing the encoder :

  void Java_com_camera_simpledoublewebcams2_CameraPreview_closeencoder(JNIEnv* env,jobject thiz){
  
  free(output_buffer);
  
  avcodec_close(codecCtx);
  
  av_free(codecCtx);

  }

  When I send the first image, I get a result from the encoder. When I try to send another image the program crashes.
  I tried calling init once and then the images, then the close - didn't work.
  I tried calling the init and the close for every image - didn't work.

  Any suggestions ?

  Thanks !

  EDIT : After further research I found that the problem is at sws_scale method.
  Still don't know what is causing this issue...

• screenrecorder appliaction. video output size issues [closed]

  25 juin 2022, par jNc

  Having working github project
https://github.com/abdullahfarwees/screen-recorder-ffmpeg-cpp

  


  All works perfectly fine, but output video resolution is not correct
I need to change output video resolution

  


  Using ubuntu/gcc/opencv/

  


  [...]
outAVCodecContext->bit_rate = 400000; // 2500000
outAVCodecContext->width = 1920; // <- change this one
outAVCodecContext->height = 1080; // <- and also this one
outAVCodecContext->gop_size = 3;
[...]