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• Capture Video with opencv, save to ffmpeg pipe and live stream

  9 mars 2018, par Chris

  The goal is to stream an analysed live video over RTSP to some media server. To make the edits/analysis I use opencv, save the edited frames as JPEG in an FFMPEG image pipe and use the same FFMPEG to create a RTSP stream. Sorry if the terminology is not that accurate, I find it still quite confusing.

  I have the following code after quite some struggle :

  import cv2
  
  from subprocess import Popen, PIPE
  
  from PIL import Image
  
  
  
  # open pipe
  
  p = Popen('ffmpeg -y -f image2pipe -vcodec mjpeg -r 24 -i - -vcodec h264 -f rtsp -rtsp_transport tcp rtsp://localhost:8081/test.sdp', stdin=PIPE)
  
  
  
  video = cv2.VideoCapture(0)
  
  i = 0
  
  while video.isOpened():
  
      i=i+1
  
      ret, frame = video.read()
  
      if ret:
  
          #[...do some analysis stuff]
  
          im = Image.fromarray(frame)
  
          im.save(p.stdin, 'JPEG')
  
  
  
          """
  
          alternatively
  
          img_str = cv2.imencode('.jpg', frame)[1].tostring()
  
          p.stdin.write(img_str)
  
          """
  
  
  
      else:
  
          break
  
  
  
      print (i)
  
      if(i==1000):
  
          break
  
  
  
  
  
  p.stdin.close()
  
  p.wait()
  
  video.release()
  
  cv2.destroyAllWindows()
  
  print("done streaming video")

  This runs for 124 frames (i=124) then the loop hangs and I get some message from ffmpeg where I am not sure what it is about, however it does not look like an error :

  push frame
  
  122
  
  push frame
  
  123
  
  push frame
  
  124
  
  Input #0, image2pipe, from 'pipe:':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 640x480 [SAR 1:1 DAR 4:3], 24 fps, 24 tbr, 24 tbn, 24 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
  
  [libx264 @ 000002076650d980] using SAR=1/1
  
  [libx264 @ 000002076650d980] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 000002076650d980] profile High, level 3.0
  
  [libx264 @ 000002076650d980] 264 - core 155 r2893 b00bcaf - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=24 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  push frame

  The webcam seems to continue running but no more frames are pushed into the pipe. It looks like some buffer is filled or something. If I write directly to a video file instead of rtsp, it works. If I open the rtsp stream simultaneously with ffplay, it also works (although with a 5 seconds lag).
  Anyone an idea where this is coming from and how to solve it ?

• how do I set speed rate (ex:double speed) in FFmpeg library ?

  19 avril 2018, par geeeek

  I’m working on rtsp live video from ffmpeg and rendering it on the screen.

  However, the image is displayed after 1 to 2 seconds.

  to reduce video delay, So I want to increase the playback speed in my program.

  int64_t duration = m_formatCtx-> duration;
  
  duration = duration * 1000;
  
  av_seek_frame (m_formatCtx, m_videoStream, duration, AVSEEK_FLAG_ANY);
  
  av_seek_frame (m_formatCtx, m_audioStream, duration, AVSEEK_FLAG_ANY);
  
  while (av_read_frame (m_formatCtx, & m_packet)> = 0)

  I can not get the result I want in this way.

• Anomalie #4465 (Nouveau) : Table principale enlevée de la requête sur double jointure avec mots et...

  24 mars 2020, par Mathieu Lopes

  Bug découvert avec l’aide de marcimat sur IRC.

  Sur ces boucles
  TEST
  depot #ID_DEPOT

  depot2 #ID_DEPOT

  depot3 #ID_DEPOT
  

  Une erreur est levée :
  Erreur SQL 1054
  Unknown column ’depots.id_depot’ in ’on clause’
  SELECT L2.id_objet, L2.id_objet AS id_depot FROM spip_auteurs_liens AS `L2` INNER JOIN spip_mots_liens AS L1 ON ( L1.id_objet = depots.id_depot AND L1.objet=’depot’) WHERE (L1.id_mot = 1) AND (L2.id_auteur = 1) GROUP BY L2.id_objet

  Dans la boucle test3 : la table principale est virée de la clause FROM (alors que le debug indique que tout est bon).

  Bug découvert en essayant de créer un nouvel objet éditorial.

  Pas de soucis avec les objets ARTICLES ou BREVES " (mais il y a un champ statut dessus, qui ajoute un champ)" (dixit marcimat)

  "pareil avec : #ID_MESSAGE

  qui crée une mauvaise requête
  WHERE (L1.id_mot = 1)
  alors qu’il faudrait WHERE (L1.id_mot = 1) AND (L1.objet = ’message’)"