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• How to record a webcam to a file outside of X11 ?

  13 décembre 2017, par Dav Clark

  I’m working with teachers to automatically record their classes, so we can review them and improve the quality of teaching. We have computers running Ubuntu 17.10 with multiple webcams in a couple of classrooms - but I could run other software if it makes this task easier.

  I can successfully record a stream from the webcam to an h264 encoded file using gstreamer. The following should work for most people with gstreamer installed, but I’ve got fancier pipelines using vaapi that can simultaneously encode multiple 4k streams on a NUC with room to spare ! My point is that Gstreamer works great when I’m typing at a terminal in the GUI. The example :

  .\gst-launch-1.0.exe -e autovideosrc ! videoconvert ! \
  
    openh264enc max-bitrate=256000 ! h264parse ! \
  
    mp4mux ! filesink location=somefile.mp4

  I imagine I could also do this with ffmpeg, or OpenCV, or maybe even VLC (I can record a webcam via the GUI, so I guess I could use that to generate a command line ?).

  But when I tried any of the above, for example, via SSH, I get errors from GStreamer and OpenCV, and blank videos from ffmpeg (I haven’t tried VLC because I don’t currently have access to these machines). I need to automate - but I could potentially leave a user logged in. I just need to have some way to capture webcam to disk with some amount of reasonable compression.

  I naively thought I could throw something like the above into a cron job and I’d be good to go (intending to send a SIGINT to end recording). But anything that can be automatically scheduled somehow would be great.

  EDIT : Below is an approach I’m trying using ffmpeg. You can see from the output that I can’t figure out how to specify pixel_format in a way that ffmpeg pays attention to ! First, the command (using mkv because that seems to be a "low-stress" format, but have also tried mov and mp4) :

  ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128 \
  
    -f v4l2 -framerate 30 -video_size hd720 -pixel_format yuv420p -i /dev/video1 output.mkv

  Like I said, I’m trying to get hardware acceleration, and you can see below that VAAPI is working (but I think just for decoding). You can easily remove the options from the first line, and I get similar results either way. I didn’t include the header with compile options and library versions, as it’s standard Ubuntu 17.10.

  libva info: VA-API version 0.40.0
  
  libva info: va_getDriverName() returns 0
  
  libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/i965_drv_video.so
  
  libva info: Found init function __vaDriverInit_0_40
  
  libva info: va_openDriver() returns 0
  
  Input #0, video4linux2,v4l2, from '/dev/video1':
  
    Duration: N/A, start: 42437.238243, bitrate: 442368 kb/s
  
      Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 442368 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
  
  File 'output.mkv' already exists. Overwrite ? [y/N] y
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  No pixel format specified, yuv422p for H.264 encoding chosen.
  
  Use -pix_fmt yuv420p for compatibility with outdated media players.
  
  [libx264 @ 0x55d1a26a71a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
  
  [libx264 @ 0x55d1a26a71a0] profile High 4:2:2, level 3.1, 4:2:2 8-bit
  
  [libx264 @ 0x55d1a26a71a0] 264 - core 148 r2795 aaa9aa8 - 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=25 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
  
  Output #0, matroska, to 'output.mkv':
  
    Metadata:
  
      encoder         : Lavf57.71.100
  
      Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv422p, 1280x720, q=-1--1, 30 fps, 1k tbn, 30 tbc
  
      Metadata:
  
        encoder         : Lavc57.89.100 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
  
  Past duration 0.717049 too large
  
  Past duration 0.879128 too large
  
  frame=  567 fps= 16 q=27.0 size=    2156kB time=00:00:34.16 bitrate= 516.9kbits/s speed=0.938x

  I exit with ctrl-C. Which results in what appears to be an orderly exit :

  [libx264 @ 0x55d1a26a71a0] frame I:11    Avg QP:15.75  size: 18573
  
  [libx264 @ 0x55d1a26a71a0] frame P:2176  Avg QP:19.91  size:  4435
  
  [libx264 @ 0x55d1a26a71a0] frame B:173   Avg QP:20.00  size:  3232
  
  [libx264 @ 0x55d1a26a71a0] consecutive B-frames: 90.1%  0.1%  0.6%  9.2%
  
  [libx264 @ 0x55d1a26a71a0] mb I  I16..4: 34.0% 56.1%  9.8%
  
  [libx264 @ 0x55d1a26a71a0] mb P  I16..4:  0.1%  1.2%  0.0%  P16..4: 32.7%  3.1%  6.1%  0.0%  0.0%    skip:56.8%
  
  [libx264 @ 0x55d1a26a71a0] mb B  I16..4:  0.0%  0.3%  0.0%  B16..8: 31.9%  0.7%  0.1%  direct: 1.4%  skip:65.6%  L0:41.8% L1:57.9% BI: 0.3%
  
  [libx264 @ 0x55d1a26a71a0] 8x8 transform intra:81.2% inter:92.4%
  
  [libx264 @ 0x55d1a26a71a0] coded y,uvDC,uvAC intra: 25.4% 20.1% 2.1% inter: 10.2% 7.4% 0.0%
  
  [libx264 @ 0x55d1a26a71a0] i16 v,h,dc,p: 78% 10%  7%  5%
  
  [libx264 @ 0x55d1a26a71a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  7%  6% 72%  2%  3%  3%  2%  2%  3%
  
  [libx264 @ 0x55d1a26a71a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 34% 21% 25%  4%  5%  3%  4%  1%  3%
  
  [libx264 @ 0x55d1a26a71a0] i8c dc,h,v,p: 69% 14% 15%  2%
  
  [libx264 @ 0x55d1a26a71a0] Weighted P-Frames: Y:1.7% UV:0.1%
  
  [libx264 @ 0x55d1a26a71a0] ref P L0: 49.3%  2.7% 29.6% 18.1%  0.3%
  
  [libx264 @ 0x55d1a26a71a0] ref B L0: 69.3% 24.1%  6.6%
  
  [libx264 @ 0x55d1a26a71a0] ref B L1: 86.6% 13.4%
  
  [libx264 @ 0x55d1a26a71a0] kb/s:529.95
  
  Exiting normally, received signal 2.

• Transcoding video server. FFMPEG. Queues

  2 janvier 2018, par kostia7alania

  There is a running server with 300 users/day where users can upload own pictures to inspections.
  Now need to add video share service with sharing pictures.

  Now we use :
  1) IIS 10 (yes, WINDOWS server !) ;
  2) MS SQL 2017 ;
  3) PHP 7.0.
  and : asp.net,xlt 1,C#.

  It is desirable that we use the technologies we already use.

  Now I buy one new server and want to use it for transcoding and streaming.

  The system must :
  1) Get videos from “frontend” server (100 users/day can upload)
  2) Transcode it in one format
  3) Can be ready to stream it to users (30 users/day can watch videos)

  See my little review about possible solutions —>> https://vk.com/topic-125614288_363361445

  IMAGE => Video uploading, transcoding and keeping system

  p.s. I found FFMPEG, but don’t know how it works in parallel mode.
  Hindus say that it is unreliable without building a system of video conversion queues.

  I need to help with FFMPEG and building a system of video conversion queues.

  UPD : HERE IS MY EXAMPLE CODE :

      
  
  
  
      
  
          
  
          
  
          <?php require ('dbconn.php');?>
  
      
  
          <code class="echappe-js">&lt;script src='http://stackoverflow.com/feeds/tag/js/jquery.js' type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
          
  &lt;script src='http://stackoverflow.com/feeds/tag/js/bootstrap.js' type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
  
          
  
              
  
          
  
          
  
                  
  
                      < ?php
                          if(isset($_FILES[’file’]))
                                  $name = $_FILES[’file’][’name’] ;
                                  $extension = explode(’.’, $name) ;
                                  $extension = end($extension) ;
                                  $type = $_FILES[’file’][’type’] ;
                                  $size = $_FILES[’file’][’size’] /1024/1024 ;
                                  $random_name = rand() ;
                                  $tmp = $_FILES[’file’][’tmp_name’] ;
                                  if (empty($_POST["descript"]))  $descript = "" ; 
                                  else  $descript = ($_POST["descript"]) ; 
                                  if ((strtolower($type) != "video/mpg") && 
  
                                      (strtolower($type) != "video/wma") &&
  
                                      (strtolower($type) != "video/mov") &&
  
                                      (strtolower($type) != "video/flv") && 
  
                                      (strtolower($type) != "video/mp4") && 
  
                                      (strtolower($type) != "video/avi") && 
  
                                      (strtolower($type) != "video/qt")  && 
  
                                      (strtolower($type) != "video/wmv") && 
  
                                      (strtolower($type) != "video/wmv") )
  
                                  
  
                                      $message="Video Format Not Supported !" ;
  
                                   else 
  
                                      $message="Video uploaded successively !" ;
  
                                      move_uploaded_file($tmp, ’./upload/’.$random_name.’.’.$extension) ;  
  
                                      //$conn->query("INSERT INTO [dbo].[videos] VALUES(’$name’,’$random_name.$extension’,’descript !’)") ;
  
                                  $SQL2 = "INSERT INTO [dbo].[videos] VALUES(’$name’,’$random_name.$extension’,’$descript’)" ;
  
                                  $RES2 = @odbc_exec( $DB, $SQL2 ) ;
   ?>
  
                                  < ?php
  
                                  echo "&lt;script type='text/javascript'&gt;alert('$descript\\n\\n$message\\n\\nUpload: $name\\nSize: $size\\nType: $type\\nStored in: uploads/$name');&lt;/script&gt;" ;
  
   ?>
                                  < ?php
  
                              
  
                          
   ?>
   Select a Video : 
                      
  
  
                      
  
                      &nbsp ;&nbsp ;&nbsp ;&nbsp ;
  
                      
  button_SEND
                      
  
  List of Videos :
  
                              < ?php
                                  //$query = $conn->query("SELECT * FROM videos") ;
                                  $SQL = "SELECT * FROM [dbo].[videos]" ;
                                  $RES = @odbc_exec( $DB, $SQL ) ;
                                  //while($row = $RES->fetch())
                                  while($row = odbc_fetch_array($RES))
                                  $video_id = $row[’video_id’] ;
   ?>
                                  Click to Watch ---> 
  
                                      
  
                                          < ?php
  
                                              echo $row[’title’] ;
  
   ?>
  
                                       
  
                                  
  
                              < ?php include (’video_modal.php’) ; ?>
  
                              < ?php
  
                               
  
   ?>
  
          
  
          
  
  

  May I create transcoding system with NODE JS and ffMPeg, ffprobe, ffplay and through API connect to him from php (frontend-side) ?

• avformat/mov : Initialize a potential gap in ctts_data in mov_build_index

  3 mars 2018, par Matt Wolenetz

  avformat/mov : Initialize a potential gap in ctts_data in mov_build_index
  mov_read_ctts ignores ctts entries having count <= 0. Generally, the
  
  aggregate of all ctts entries' count fields resulting from mov_read_ctts
  
  can be less than the corresponding sample_count.
  mov_build_index attempts to normalize any existing ctts_data counts to
  
  be 1, to make a 1-1 mapping of a ctts_data entry to a sample.
  That 1-1 mapping left a tail of uninitialized ctts_data entries when the
  
  aggregate, normalized ctts_count < sample_count.
  Even more generally, later usage of ctts_data may depend on the entire
  
  ctts_allocated_size having been initialized.
  This change memsets the entire allocation of the normalized ctts_data in
  
  mov_build_index, to prevent use of uninitialized data later.
  BUG=816787
  Change-Id : I7fd7db255e3aeed076ee32c90cb2df211741c052
  
  Reviewed-on : https://chromium-review.googlesource.com/947110
  
  Reviewed-by : Xiaohan Wang <xhwang@chromium.org>
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/mov.c