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• DTS and PTS are different, despite not having B-frames (ffmpeg)

  7 août 2018, par Damian

  Just a quick question in regards to video encoding/muxing a video file with ffmpeg. Basically, I have my muxer functioning and I’m trying to have my packets output the correct PTS/DTS.

  This is a portion of my code that encodes my AVFrame, muxing it to an output file :

  int ret;
  
  int got_packet = 0;
  
  
  
  AVPacket pkt = { 0 };
  
  av_init_packet(&pkt);
  
  
  
  pkt.data = NULL;
  
  pkt.size = 0;
  
  
  
  /* encode the image */
  
  ret = avcodec_encode_video2(cc, &pkt, frame, &got_packet);
  
  if (ret < 0)
  
  {
  
      fprintf(stderr, "error encoding video frame: %s\n", av_err2str(ret));
  
      exit(EXIT_FAILURE);
  
  }
  
  
  
  if (got_packet)
  
  {
  
      av_packet_rescale_ts(&pkt, cc->time_base, st->time_base);
  
  
  
      fprintf(stderr, "\npkt.pts     = %ld\n", pkt.pts);
  
      fprintf(stderr,   "pkt.dts     = %ld\n", pkt.dts);
  
      fprintf(stderr, "writing frame\n");
  
  
  
      ret = av_interleaved_write_frame(fmt_ctx, &pkt);
  
      av_packet_unref(&pkt);
  
  }
  
  else
  
  {
  
      ret = 0;
  
  }
  
  
  
  ...

  I’m then getting an output of the following :

  pkt.pts     = 0
  
  pkt.dts     = 0
  
  writing frame
  
  
  
  pkt.pts     = 1502
  
  pkt.dts     = 0
  
  writing frame
  
  
  
  pkt.pts     = 3003
  
  pkt.dts     = 1502
  
  writing frame
  
  
  
  pkt.pts     = 4505
  
  pkt.dts     = 3003
  
  writing frame
  
  
  
  ...

  My goal is to have my PST and DST both with the pattern : 1502, 3003, 4505, 6006, 7508, ...

  But it seems that the first DTS value is repeating once, and thus being off-sync with it’s corresponding PTS value. It’s also worth mentioning that the codec context was configured to have no b-frames, so only i- and p- frames are present here.

  Does anyone with more experience have some insight on this ?

  Addition :

  I ran the following command in terminal to check if my DTS and PTS values were consistent to my print statements :

  sudo ./ffprobe -show_packets -print_format json mux_test.ts | less

  And I got the following :

  {
  
      "packets": [
  
          {
  
              "codec_type": "video",
  
              "stream_index": 0,
  
              "pts": 0,
  
              "pts_time": "0.000000",
  
              "dts": -1501,
  
              "dts_time": "-0.016678",
  
              "duration": 1501,
  
              "duration_time": "0.016678",
  
              "convergence_duration": "N/A",
  
              "convergence_duration_time": "N/A",
  
              "size": "55409",
  
              "pos": "564",
  
              "flags": "K"
  
          },
  
          {
  
              "codec_type": "video",
  
              "stream_index": 0,
  
              "pts": 1502,
  
              "pts_time": "0.016689",
  
              "dts": 0,
  
              "dts_time": "0.000000",
  
              "duration": 1501,
  
              "duration_time": "0.016678",
  
              "convergence_duration": "N/A",
  
              "convergence_duration_time": "N/A",
  
              "size": "46574",
  
              "pos": "60160",
  
              "flags": "_"
  
          },
  
          {
  
              "codec_type": "video",
  
              "stream_index": 0,
  
              "pts": 3003,
  
              "pts_time": "0.033367",
  
              "dts": 1502,
  
              "dts_time": "0.016689",
  
              "duration": 1501,
  
              "duration_time": "0.016678",
  
              "convergence_duration": "N/A",
  
              "convergence_duration_time": "N/A",
  
              "size": "2544",
  
              "pos": "110356",
  
              "flags": "_"
  
          },
  
  
  
          ...

  Which doesn’t show my first DTS value repeated, but continues to show my DTS one cycle behind my PTS.

• what codec to specify to accessing my HDMI-to-USB adaptor, under Linux ? [closed]

  14 mai 2022, par David

  A week or so ago,I bought a HDMI-to-USB adapter, to use to capture video
TV content from my TV's set-top box. (Xfinity, if it matters. Box generically is :
"XiD X1"...I have both the Pace and the Cisco models available here in this house.)

  


  Specifically, here's the adapter I bought,from Amazon :
https://www.amazon.com/gp/product/B09FLN63B3

  


  So, I'm fluent in both Windows (Win-11) and Linux (Debian 'Bullseye', on my chromebook).

  


  The adapter does not come with any recommendations for what software/drivers to (try to) use, but I was prepared for that.
After some google searches, I decided to first try using the cmd-line
'ffmpeg' program, because I'm
quite familiar with that (excellent !) piece of open-source software !

  


  So, after a day or two of (mostly) success recordings under Win-11, using
ffmpeg's Microsoft-based 'dshow' (aka 'DirectShow'), I decided to attempt to get
up to the same level of accomplishment on my Chromebook, under Linux, also
using 'ffmpeg'.

  


  [Ok...a very brief explanation of 'mostly' successful. I'll
post another separate question here, about the specifics of my glitches,
using 'dshow' on Windows. But, essentially, when I try to record to a MP4
file, I get 2 scenarios of glitch : #1 : Suddenly, dropped packets surges up,
and I get "1000 dropped' yellow msg #2 : On other trials, I get '...contains
no image...'.) So, I figured I should first give a Linux a chance,
before spending more effort trying to resolve the glitches on Windows.]

  


  My first snag, was learning that 'dshow' seems to be specific to 'Windows',
and thus ffmpeg is getting 'unknown' for my reference to 'dshow'. After more hours of 'guessing', I've finally learned/concluded that there are other things
(something call "DeckLink" is one such alternative ?) for Linux, but I'm unclear
what extra Linux packages might exist for ffmpeg support, or whether I will need to built a more complete 'ffmpeg' (e.g. from source code), to get things going under Linux ?

  


  Is my device able to be accessed from some tools other than 'ffmpeg' ?
(e.g. VLC or Handbrake or whatever ?) more easily, on the Linux platform ?

  


  [If I had to, I'd probably invest another $20-$50 in some other hardware
device that goes from HDMI-to-USB (USB-A/B), if it were ]

  


  All ideas are welcome...(TIA)

  


  — Dave

  


• Send stream from hdhomerun to AWS EC2 instance

  13 novembre 2018, par icalvete

  I’m trying something odd to get fun. Send stream from hdhomerun to AWS EC2 instance.

  First aproach. Read stream with ffmpeg
  (tested locally successfully)

  hdhomerun_config discover sya my device have ip 192.168.1.200 so I open port on my router in this way

  <my home="home" public="public" ip="ip">:5005 -> 192.168.1.200:80
  
  <my home="home" public="public" ip="ip">:5004 -> 192.168.1.200:5004
  
  </my></my>

  w3m and telnet say everything is ok.

  But...

  from EC2 instance I do

  /usr/bin/ffmpeg -y -i 'http://<my home="home" public="public" ip="ip">:5004/auto/v5057?transcode=internet240' -t 12 -vn -acodec pcm_s16le -ar 16000 -ac 1 '/tmp/test.wav'
  
  </my>

  In tuner1 I can see...

  Virtual Channel none
  
  Frequency   698.000 MHz
  
  Program Number  186
  
  Modulation Lock t8qam64
  
  Signal Strength 89%
  
  Signal Quality  100%
  
  Symbol Quality  100%
  
  Streaming Rate  none
  
  Resource Lock   <ec2 public="public" ip="ip">
  
  </ec2>

  In hdhomerun system logs...

  19700102-10:27:25 Tuner: tuner0 tuning 5057 Telecinco (t8qam64:698MHz-186)
  
  19700102-10:27:25 Tuner: tuner0 streaming http to <ec2 public="public" ip="ip">:34124
  
  </ec2>

  Everything seems ok but ffmpeg don’t get any data.

  Seccond aproach. Send stream to wowza

  I have a wowza server running in EC2 instance

  From a linux box at my home I do.

  root# /usr/bin/hdhomerun_config 1250D7B2 scan /tuner1 scan.log
  
  root# /usr/bin/hdhomerun_config 1250D7B2 set /tuner1/channel auto:651000000
  
  root# /usr/bin/hdhomerun_config 1250D7B2 get /tuner1/streaminfo
  
  root# /usr/bin/hdhomerun_config 1250D7B2 get /tuner1/program 190
  
  root# /usr/bin/hdhomerun_config 1250D7B2 set /tuner1/target rtp://<wowza server="server" public="public" ip="ip">:1935/TEST/hdhr
  
  root# echo $?
  
  root# 0
  
  </wowza>

  Ends without error buy doesn’t work
  This was a long shot but ....

  Any ideas to do this.

  Thanks !!!