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• ffplay : remove global video state

  4 décembre 2011, par Marton Balint

  ffplay : remove global video state

• how to improve the quality of resultant video when merging audio-video with ffmpeg ?

  6 novembre 2015, par R.S

  When merging an audio and video with ffmpeg, the quality of the resultant video goes down. How to we improve the quality(esp. the audio quality) ?

  The audio quality gets degraded to quite an extent with random screeches in between.
  I’ve tried converting the audio to mp3 and video to mp4 before merging them, tried various audio-video parameters like bitrate, sample-rate, qscale etc but still unsuccessful.
  Any help would be greatly appreciated !

• Why doesn't this FFmpeg code create a video from a series of images ?

  20 octobre 2011, par user551117

  I have successfully compiled the FFmpeg library for use in an iOS application. I would like to use it for encoding a video from a series of images, but I can't seem to make it work.

  The following is the code that I am using to encode this video :

  AVCodec *codec;
  
  AVCodecContext *c= NULL;
  
  int i, out_size, size, outbuf_size;
  
  FILE *f;
  
  AVFrame *picture;
  
  uint8_t *outbuf;
  
  
  
  printf("Video encoding\n");
  
  
  
  /// find the mpeg video encoder
  
  codec=avcodec_find_encoder(CODEC_ID_MPEG4);
  
  //codec = avcodec_find_encoder(CODEC_ID_MPEG4);
  
  if (!codec) {
  
      fprintf(stderr, "codec not found\n");
  
      exit(1);
  
  }
  
  
  
  c= avcodec_alloc_context();
  
  picture= avcodec_alloc_frame();
  
  
  
  // put sample parameters 
  
  c->bit_rate = 400000;
  
  /// resolution must be a multiple of two 
  
  c->width = 320;
  
  c->height = 480;
  
  //frames per second 
  
  c->time_base= (AVRational){1,25};
  
  c->gop_size = 10; /// emit one intra frame every ten frames
  
  c->max_b_frames=1;
  
  c->pix_fmt = PIX_FMT_YUV420P;
  
  
  
  //open it
  
  if (avcodec_open(c, codec) < 0) {
  
      fprintf(stderr, "could not open codec\n");
  
      exit(1);
  
  }
  
  
  
  f = fopen([[NSTemporaryDirectory() stringByAppendingPathComponent:filename] UTF8String], "w");
  
  if (!f) {
  
      fprintf(stderr, "could not open %s\n",[filename UTF8String]);
  
      exit(1);
  
  }
  
  
  
  // alloc image and output buffer
  
  outbuf_size = 100000;
  
  outbuf = malloc(outbuf_size);
  
  size = c->width * c->height;
  
  
  
  #pragma mark -
  
  AVFrame* outpic = avcodec_alloc_frame();
  
  int nbytes = avpicture_get_size(PIX_FMT_YUV420P, c->width, c->height);
  
  
  
  //create buffer for the output image
  
  uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes);
  
  
  
  #pragma mark -  
  
  for(i=1;i<48;i++) {
  
      fflush(stdout);
  
  
  
      int numBytes = avpicture_get_size(PIX_FMT_YUV420P, c->width, c->height);
  
      uint8_t *buffer = (uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
  
  
  
      UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"%d.png", i]];
  
      CGImageRef newCgImage = [image CGImage];
  
  
  
      CGDataProviderRef dataProvider = CGImageGetDataProvider(newCgImage);
  
      CFDataRef bitmapData = CGDataProviderCopyData(dataProvider);
  
      buffer = (uint8_t *)CFDataGetBytePtr(bitmapData);   
  
  
  
      avpicture_fill((AVPicture*)picture, buffer, PIX_FMT_RGB24, c->width, c->height);
  
      avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, c->width, c->height);
  
  
  
      struct SwsContext* fooContext = sws_getContext(c->width, c->height, 
  
                                                     PIX_FMT_RGB24, 
  
                                                     c->width, c->height, 
  
                                                     PIX_FMT_YUV420P, 
  
                                                     SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
  
  
      //perform the conversion
  
      sws_scale(fooContext, picture->data, picture->linesize, 0, c->height, outpic->data, outpic->linesize);
  
      // Here is where I try to convert to YUV
  
  
  
      // encode the image
  
  
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, outpic);
  
      printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, out_size, f);
  
  
  
      free(buffer);
  
      buffer = NULL;      
  
  
  
  }
  
  
  
  // get the delayed frames
  
  for(; out_size; i++) {
  
      fflush(stdout);
  
  
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
      printf("write frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, outbuf_size, f);      
  
  }
  
  
  
  // add sequence end code to have a real mpeg file
  
  outbuf[0] = 0x00;
  
  outbuf[1] = 0x00;
  
  outbuf[2] = 0x01;
  
  outbuf[3] = 0xb7;
  
  fwrite(outbuf, 1, 4, f);
  
  fclose(f);
  
  free(outbuf);
  
  
  
  avcodec_close(c);
  
  av_free(c);
  
  av_free(picture);
  
  printf("\n");

  What could be wrong with this code ?