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• Codec not found while H.264 encoding using FFMPEG in iOS

  12 juin 2013, par Sukhpal Singh

  I am trying to encode video in h.264 format using FFMpeg in iOS. Actually I am receiving sample buffer from iPhone Camera and then converting it AVFrame and further from AVFrame to H.264 video. But while h.264 encoding if I use :

  codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);

  Then codec is found but if I use :

  codec = avcodec_find_encoder(CODEC_ID_H264);

  Then codec is nil means codec not found. Full code is as below :

  static void encode(AVFrame *picture)
  
   {
  
       AVCodec *codec;
  
       AVCodecContext *c= NULL;
  
       int i, out_size, size,  outbuf_size;
  
       uint8_t *outbuf, *picture_buf;
  
  
  
       printf("Video encoding\n");
  
  
  
       /* find the mpeg1 video encoder */
  
  
  
       //avcodec_init() ; // Also tried this but giving warning and not worked
  
       avcodec_register_all();
  
  
  
       codec = avcodec_find_encoder(CODEC_ID_H264);
  
       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  = 352;
  
       c->height = 288;
  
       /* 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);
  
       }
  
  
  
           /* alloc image and output buffer */
  
       outbuf_size = 100000;
  
       outbuf = malloc(outbuf_size);
  
       size = c->width * c->height;
  
       picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
  
  
  
       out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
  
  
  
       NSLog(@"NSdada===%@",[NSData dataWithBytes:(const void *)outbuf length:out_size]);
  
  
  
       free(picture_buf);
  
       free(outbuf);
  
  
  
       avcodec_close(c);
  
       av_free(c);
  
       av_free(picture);
  
       printf("\n");
  
   }

• When rTorrent finishes, run FFmpeg and convert audio track in mkv to ac-3 5.1

  11 septembre 2021, par miniHessel

  What is the best approach for this ? I saw the following answer, is that still a valid approach ? If so, how do you execute that when a torrent finishes ? I mostly want to convert dts-hd either 5.1 or 7.1. Sometimes also Atmos.

  


• x264 Downsides of a high CRF (22) intermediary codec between conversions instead of lossless

  18 décembre 2019, par bobtheencoder

  I have a huge collection of video files that are in the range of CRF 16-20 taking up TB’s of space. The only need I have for these originals is that I have to encode them from time to time but the CRF of these final encodes is very low (CRF 26-28).

  I understand that a lossy to lossy converstion ALWAYS results in some quality loss but my question is what if the intermediate file is almost visually lossless compared to the final output.

  So to sum up, what quality difference should I expect from the following routes ?

  CRF 18 (original) -----> CRF 28 (final)
  
  CRF 18 (original) -----> CRF 22 (long-term storage) -----> Lossy  CRF 28 (final)