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• How to add arbitrary or custom metadata in MP4 ?

  13 avril 2021, par 大大大大萝卜凉

  The MP4 muxer in ffmpeg only allows certain metadata by default. I would like to add :

  


  com.android.model: Mi 10 Pro
xyz: +22.9835+113.3621/
com.android.version: 1
com.android.manufacturer: Xiaomi


  


  How can I add this with ffmpeg ?

  


• How would I assign multiple MMAP's from single file descriptor ?

  9 juin 2011, par Alex Stevens

  So, for my final year project, I'm using Video4Linux2 to pull YUV420 images from a camera, parse them through to x264 (which uses these images natively), and then send the encoded stream via Live555 to an RTP/RTCP compliant video player on a client over a wireless network. All of this I'm trying to do in real-time, so there'll be a control algorithm, but that's not the scope of this question. All of this - except Live555 - is being written in C. Currently, I'm near the end of encoding the video, but want to improve performance.

  To say the least, I've hit a snag... I'm trying to avoid User Space Pointers for V4L2 and use mmap(). I'm encoding video, but since it's YUV420, I've been malloc'ing new memory to hold the Y', U and V planes in three different variables for x264 to read upon. I would like to keep these variables as pointers to an mmap'ed piece of memory.

  However, the V4L2 device has one single file descriptor for the buffered stream, and I need to split the stream into three mmap'ed variables adhering to the YUV420 standard, like so...

  buffers[n_buffers].y_plane = mmap(NULL, (2 * width * height) / 3,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset);
  
  buffers[n_buffers].u_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 1) /
  
                                      sysconf(_SC_PAGE_SIZE));
  
  buffers[n_buffers].v_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 
  
                                      width * height / 6 + 1) / 
  
                                      sysconf(_SC_PAGE_SIZE));

  Where "width" and "height" is the resolution of the video (eg. 640x480).

  From what I understand... MMAP seeks through a file, kind of like this (pseudoish-code) :

  fd = v4l2_open(...);
  
  lseek(fd, buf.m.offset + (2 * width * height) / 3);
  
  read(fd, buffers[n_buffers].u_plane, width * height / 6);

  My code is located in a Launchpad Repo here (for more background) :
  http://bazaar.launchpad.net/ alex-stevens/+junk/spyPanda/files (Revision 11)

  And the YUV420 format can be seen clearly from this Wiki illustration : http://en.wikipedia.org/wiki/File:Yuv420.svg (I essentially want to split up the Y, U, and V bytes into each mmap'ed memory)

  Anyone care to explain a way to mmap three variables to memory from the one file descriptor, or why I went wrong ? Or even hint at a better idea to parse the YUV420 buffer to x264 ? :P

  Cheers ! ^^

• ffmpeg - continuous file streaming over RTMP

  1er mai 2013, par Sébastien Renauld

  I've been looking around for a simple (or perhaps not-so-simple) walkaround for a problem I am having in my set up for a simple test case : video streaming over red5 media server.

  I have built a small-ish library of FLV files scraped from YouTube and managed to play them in succession with the following perl script :

  use Cwd;
  
  use strict;
  
  use warnings;
  
  use DBI;
  
  use DBD::mysql;
  
  
  
  our $db = DBI->connect();
  
  my $dst = "/home/seb/youtube/";
  
  sub streamFile {
  
      my $r = $db->prepare("SELECT name FROM music_flvs ORDER BY RAND() LIMIT 1");
  
      $r->execute();
  
      my @data = $r->fetchrow_array();
  
      my $filename = $data[0]
  
      my $t = `ffmpeg -re -i '${dst}${filename}' -ab 48k -ac 1 -vcodec libx264 -crf 30 -s "640x480" -acodec libfaac -ar 44100 -threads 4 -f flv 'rtmp://server/oflaDemo/music'`;
  
      return 1;
  
  }
  
  while (&streamFile()) {
  
  }

  This script does its purpose extremely well : it plays files one by one through ffmpeg. However, it does so with a crucial problem : it causes an Unpublish event every time it swaps songs, which causes all the clients to disconnect. I would like to prevent this. The event manifests itself in ActionScript as this :

   16:33:54:209 - Playback - NetStream.Play.UnpublishNotify
  
   16:33:54:209 - Playback - NetStream.Play.PublishNotify

  I have seen the concat demuxer and believe that it might somewhat help me. The question is pretty simple : what is the best way to make ffmpeg stream a playlist to a RTMP server without ever causing an Unpublish event ?