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• C++ h264 ffmpeg/libav encode/decode(lossless) issues

  1er février 2017, par MrSmith

  Insights to encode/decode video with ffmpeg h264 (lossless)

  So I got something working on the encoding part, encode an avi in 264 however VLC wont play it, however Totem will.
  Decoding the same file proves troublesome. (I want the exact same data/frame going in as going out), I get these ;

  saving frame   5
  
  Video decoding
  
  [h264 @ 0x1d19880] decode_slice_header error
  
  frame :6
  
  saving frame   6
  
  Video decoding
  
  [h264 @ 0x1d19880] error while decoding MB 15 7, bytestream -27
  
  [h264 @ 0x1d19880] concealing 194 DC, 194 AC, 194 MV errors in I frame
  
  frame :7
  
  saving frame   7
  
  Video decoding
  
  [h264 @ 0x1d19880] decode_slice_header error

  and ultimatly this

  [H264 Decoder @ 0x7f1320766040] frame :11
  
  Broken frame packetizing
  
  [h264 @ 0x1d19880] SPS changed in the middle of the frame
  
  [h264 @ 0x1d19880] decode_slice_header error
  
  [h264 @ 0x1d19880] no frame!
  
  Error while decoding frame 11

  GAME OVER.

  Now I suspect that I have to go back to 1. the encoding part, there is problary a good reason VLC wont play it !

  I encode like this.

  void encode(char *Y,char *U,char *V){
  
  av_init_packet(&pkt);
  
  pkt.data = NULL;    // packet data will be allocated by the encoder
  
  pkt.size = 0;
  
  fflush(stdout);
  
  
  
  frame->data[0] = (uint8_t*)Y;
  
  frame->data[1] = (uint8_t*)U;
  
  frame->data[2] = (uint8_t*)V;
  
  frame->pts = ++i;
  
  
  
  ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
  if (ret < 0) {
  
      fprintf(stderr, "Error encoding frame\n");
  
      exit (EXIT_FAILURE);
  
  }
  
  if (got_output) {
  
      printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
      fwrite(pkt.data, 1, pkt.size, f);
  
      av_free_packet(&pkt);
  
  }
  
  }

  And the codec is setup like this :

  AVCodecID dasd = AV_CODEC_ID_H264;
  
  codec = avcodec_find_encoder(dasd);
  
  c = avcodec_alloc_context3(codec);
  
  c->bit_rate = 400000;
  
  c->width = 320;
  
  c->height = 240;
  
  c->time_base= (AVRational){1,25};
  
  c->gop_size = 10; 
  
  c->max_b_frames=1;
  
  c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  av_opt_set(c->priv_data, "preset", "slow", 0);
  
  avcodec_open2(c, codec, NULL);

  Since I am going for lossless i am not dealing with delayed frames(is this a correct assumption ?)
  I may not actually be encoding lossless, it seems like I may have to go with something like

  AVDictionary *param;
  
  av_dict_set(&param, "qp", "0", 0);

  And then open...

  So I guess me questions is these :

  • What are the correct codec params for lossless encoding (and advice if h264 is a terrible idea in this regard).
  • Do I need to handle delayed frames when going for lossless ?
  • Why is VLC mad at me ?

  Thanks.

• ffmpeg - Making a Clean WAV file

  24 septembre 2016, par Edward

  I’m looking to batch convert a number of files to audio files using ffmpeg for a game called Star Wars: Jedi Knight: Dark Forces II. The problem I’m having is that ffmpeg seems to be doing something that does so that Jedi Knight can’t play the sound file.

  Jedi Knight accepts plain old PCM WAV files of various ranges, from 5khz to 96khz, 8 and 16 bit, mono and stereo. This sounds plain and simple. Except for that if one were to create a WAV file using MS Sound Recorder, Jedi Knight could not play it. Speculation was that it added something extra to header or something. But it can play a WAV file created by Audacity, GoldWave or ModPlug Tracker to name a few.

  So why not ffmpeg ? Am I using the wrong codec or params ? I took an original sound file from the game and performed the following :

  ffmpeg -i "orig_thrmlpu2.wav" -f wav -acodec pcm_s16le -ar 22050 -ac 1 "ffmpeg_thrmlpu2.wav"

  The ffmpeg version does not play in the game. ffprobe shows that the ffmpeg version has some Metadata which the original doesn’t have. What params should I use to try and get the same WAV format as the original ? Mind you, -ar, -ac and bits aren’t the important parts.

  Here are the files for you to examine : http://www.edwardleuf.org/Games/JK/thrmlpu2.zip

• Capturing video over USB/HDMI/Thunderbolt

  12 novembre 2016, par Yatko

  Looking for a solution for capturing video over USB/HDMI/Thunderbolt from a digital output (e.g. digital camera) to a computer, Mac and/or Windows.

  The goal is to have an URL to a real-time video stream (e.g. IP/PATH/ ?.mp4) that we can further process/transcode/send to a media server.

  I’m looking for tips and ideas -similar to the method below-, maybe someone met a new project that’s focusing on capture-cards and devices, that does’n need a custom FFmpeg build. Something different.

  • we can capture the HDMI stream form a GoPro, using a Blackmagic Intensity Shuttle and DeckLink SDK with custom FFmpeg build using --extra-cflags and --extra-ldflags and the rest is straightforward

  Is there any tool, open-source project, something that’s made for this purpose ? Maybe something that also supports the Elgato Game Capture HD60 as well ? Any experimental projects for capturing and processing the incoming video over USB/HDMI/Thunderbolt ?

  The ultimate goal is live streaming to Wowza, using Cameleon live and a Sony Alpha a7S.