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• 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 ! ^^

• Anomalie #3014 : Chaines de langue de "Forums" utilisées dans la "dist"

  24 décembre 2017, par b b

  Pour info, voici les occurrences de chaînes de langue de forum dans la dist à ce jour :

  grep -nHIirF —exclude=*.svn-base — :forum : .
  ./404.html:36 :            [(#ENVfond_erreur|==forum|oui)
  
  <:forum:aucun_message_forum :>
  
  ]
  
  ./article.html:56 :            [
  <:forum:form_pet_message_commentaire :>
  ./inclure/forum.html:17 :                [(#CONFIGforums_titre| !=non|oui)#COMPTEUR_BOUCLE.
  
  ./inclure/forum.html:42 :                        [(#CONFIGforums_titre| !=non|oui)#COMPTEUR_BOUCLE.
  
  ./forum.html:11 :    
  
  ./forum.html:25 :
  
  <:accueil_site :> &gt ; ... &gt ; <:forum:forum :> #ID_FORUM
  
  ./forum.html:28 :                [
  (#TITRE|sinon<:forum:forum :> #ID_FORUM)
  ]
  
  ./forum.html:38 :
  <:forum:forum_avez_selectionne :> #TITRE
  
  ./forum.html:41 :            [
  <:forum:form_pet_message_commentaire :>
  ./breve.html:43 :            [
  <:forum:form_pet_message_commentaire :>
  
  

• Getting "Error while decoding stream #0:0 : Invalid data found when processing input" when using ffmpeg to convert tga to mp4

  22 juin 2020, par Calvin Godfrey

  I've used ffmpeg to convert a bunch of tga files into an mp4 just fine for a few weeks, but it broke for no apparent reason earlier today. I have a pastebin with -loglevel debug here, but the command I use is the same as the one that has worked before — ffmpeg -framerate 60 -i triangle%03d.tga output.mp4, and now it's broken.

  


  The tga files are manually created by a C program that I wrote, but I don't think it's a problem with the file header/format because it hasn't been a problem with ffmpeg before before and I can open the tga files fine with eog and a tga viewer on Windows. Just in case it matters, here's the start of a hexdump for one of the files :

  


  0000000 0000 0002 0000 0000 0000 0000 0780 0438
0000010 2018 ceeb eb87 87ce ceeb eb87 87ce ceeb
0000020 eb87 87ce ceeb eb87 87ce ceeb eb87 87ce
0000030 ceeb eb87 87ce ceeb eb87 87ce ceeb eb87
0000040 87ce ceeb eb87 87ce ceeb eb87 87ce ceeb
0000050 eb87 87ce ceeb eb87 87ce ceeb eb87 87ce
0000060 ceeb eb87 87ce ceeb eb87 87ce ceeb eb87
0000070 87ce ceeb eb87 87ce ceeb eb87 87ce ceeb
0000080 eb87 87ce ceeb eb87 87ce ceeb eb87 87ce
0000090 ceeb eb87 87ce ceeb eb87 87ce ceeb eb87


  


  Would appreciate any help on fixing the ffmpeg (or alternative ways to convert tga to mp4).