Recherche avancée

Sur d’autres sites (9868)

• avformat/mpegtsenc : fix incorrect PCR selection with multiple programs

  2 août 2019, par Marton Balint

  avformat/mpegtsenc : fix incorrect PCR selection with multiple programs
  The MPEG-TS muxer had a serious bug related to the use of multiple programs :
  
  in that case, the PCR pid selection was incomplete for all services except one.
  
  This patch solves this problem and selects a stream to become PCR for each
  
  service, preferably the video stream.
  This patch also moves pcr calculation attributes to MpegTSWriteStream from
  
  MpegTSService. PCR is a per-stream and not per-service thing, so it was
  
  misleading to refer to it as something that is per-service.
  Also remove *service from MpegTSWriteStream because a stream can belong to
  
  multiple services so it was misleading to select one for each stream.
  You can check the result with this example command :
  ./ffmpeg -loglevel verbose -y -f lavfi -i \
  
    "testsrc=s=64x64:d=10,split=2[out0][tmp1] ;[tmp1]vflip[out1] ;sine=d=10,asetnsamples=1152[out2]" \
  
    -flags +bitexact -fflags +bitexact -sws_flags +accurate_rnd+bitexact  \
  
    -codec:v libx264 -codec:a mp2 -pix_fmt yuv420p \
  
    -map '0:v:0' \
  
    -map '0:v:1' \
  
    -map '0:a:0'  \
  
    -program st=0:st=2 -program st=1:st=2 -program st=2 -program st=0 -f mpegts out.ts
  You should now see this :
  [mpegts @ 0x37505c0] service 1 using PCR in pid=256
  
  [mpegts @ 0x37505c0] service 2 using PCR in pid=257
  
  [mpegts @ 0x37505c0] service 3 using PCR in pid=258
  
  [mpegts @ 0x37505c0] service 4 using PCR in pid=256
  Fixes ticket #8039.
  v2 : a video is stream is preferred if there are no programs, just like before
  
  the patch.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavformat/mpegtsenc.c

• How to read raw audio data using FFmpeg ?

  6 juin 2020, par Yousef Alaqra

  I'm trying to use this command to get the audio stream using UDP :

  



  ffmpeg -i udp://192.168.1.1:6980 -acodec copy


  



  I got an error when I execute it, which says :

  



  [udp @ 00000157a76b9a40] bind failed: Error number -10048 occurred
udp://192.168.1.1:6980: I/O error


  



  What's the meaning of this error ?

  



  Update :

  



  I was able to read raw audio data using FFmpeg and output into a wave file, using the following command :

  



  ffmpeg -f u16be -ar 44100 -ac 2 -i 'udp://127.0.0.1:1223' output.wav


  



  The problem now, Sine there is surrounding metadata in the network packets being received, it needs to be stripped out or it will result in noise.

  



  In C# I used Skip() to trim the first 28 bytes of the received packet, how would I achieve this using FFmpeg ?

  



  Update :

  



  I was able to read the raw bytes from UDP packets using by executing child process in node js :

  



  var http = require("http");
var port = 8888;
var host = "localhost";
var children = require("child_process");

http
  .createServer(function (req, res) {
    //ffmpeg -f s16le -ar 48000 -ac 2 -i 'udp://192.168.1.230:65535' -b:a 128k -f webm -
    var ffm = children.spawn(
      "ffmpeg",
      "-f s16le -ar 48000 -ac 2 -i udp://192.168.1.230:65535 -b:a 128k -f webm -".split(
        " "
      )
    );

    res.writeHead(200, { "Content-Type": "audio/webm" });
    ffm.stdout.on("data", (data) => {
      console.log(data);
      res.write(data);
    });
  })
  .listen(port, host);

console.log("Server running at http://" + host + ":" + port + "/");


  



  As you can see in the code sample above, I'm trying to pipe the output of the child process into the response, so I would be able to hear the audio in the browser.

  



  I'm receiving the data, after executing the child process, but the browser unable to play audio for some reason that I need to figure it out.

  



  Do you have an idea of what am I missing ?

  


• Extract motion vectors from x265 (HVEC) encoded video with ffmepg/libavcodec ?

  16 novembre 2017, par John Allard

  I know that one can extract the motion vectors from an h264 encoded via by first setting the flag

  av_dict_set(&opts, "flags2", "+export_mvs", 0);

  then you can query the side-data for the motion vectors by doing this

  sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);

  When I looked online to see if you can do something similar with HVEC encoded videos, I wasn’t able to find any information. All I found was this by the definition of "AV_FRAME_DATA_MOTION_VECTORS"

  Motion vectors exported by some codecs (on demand through the
  export_mvs flag set in the libavcodec AVCodecContext flags2 option).

  The data is the AVMotionVector struct defined in
  libavutil/motion_vector.h.

  but there was no information on exactly which codecs export this motion vector information. How would I go about finding this out ?