Sur d’autres sites (14865)

• Capturing FFmpeg output in python before storing it

  14 juin 2012, par tarrasch

  I am trying to capture output from ffmpeg and storing that in memory, deciding at a later stage if I want to write it to disk.

  Is it possible to analyze the output of ffmpeg before writing it onto the HDD ?

  Since I do not really know how to approach the thing, I cannot yet provide a code example.

  EDIT :
  Yes, I am trying to write small chunks of the captured avi/mp4 to RAM and analyze them before writing to disc.

• Why does use of H264 in sender/receiver pipelines introduce just HUGE delay ?

  24 janvier 2012, par Serguey Zefirov

  When I try to create pipeline that uses H264 to transmit video, I get some enormous delay, up to 10 seconds to transmit video from my machine to... my machine ! This is unacceptable for my goals and I'd like to consult StackOverflow over what I (or someone else) do wrong.

  I took pipelines from gstrtpbin documentation page and slightly modified them to use Speex :

  This is sender pipeline :
  # !/bin/sh

  gst-launch -v gstrtpbin name=rtpbin \
  
          v4l2src ! ffmpegcolorspace ! ffenc_h263 ! rtph263ppay ! rtpbin.send_rtp_sink_0 \
  
                    rtpbin.send_rtp_src_0 ! udpsink host=127.0.0.1 port=5000                            \
  
                    rtpbin.send_rtcp_src_0 ! udpsink host=127.0.0.1 port=5001 sync=false async=false    \
  
                    udpsrc port=5005 ! rtpbin.recv_rtcp_sink_0                           \
  
          pulsesrc ! audioconvert ! audioresample  ! audio/x-raw-int,rate=16000 !    \
  
                    speexenc bitrate=16000 ! rtpspeexpay ! rtpbin.send_rtp_sink_1                   \
  
                    rtpbin.send_rtp_src_1 ! udpsink host=127.0.0.1 port=5002                            \
  
                    rtpbin.send_rtcp_src_1 ! udpsink host=127.0.0.1 port=5003 sync=false async=false    \
  
                    udpsrc port=5007 ! rtpbin.recv_rtcp_sink_1

  Receiver pipeline :

   !/bin/sh

  gst-launch -v\
  
      gstrtpbin name=rtpbin                                          \
  
      udpsrc caps="application/x-rtp,media=(string)video, clock-rate=(int)90000, encoding-name=(string)H263-1998" \
  
              port=5000 ! rtpbin.recv_rtp_sink_0                                \
  
          rtpbin. ! rtph263pdepay ! ffdec_h263 ! xvimagesink                    \
  
       udpsrc port=5001 ! rtpbin.recv_rtcp_sink_0                               \
  
       rtpbin.send_rtcp_src_0 ! udpsink port=5005 sync=false async=false        \
  
      udpsrc caps="application/x-rtp,media=(string)audio, clock-rate=(int)16000, encoding-name=(string)SPEEX, encoding-params=(string)1, payload=(int)110" \
  
              port=5002 ! rtpbin.recv_rtp_sink_1                                \
  
          rtpbin. ! rtpspeexdepay ! speexdec ! audioresample ! audioconvert ! alsasink \
  
       udpsrc port=5003 ! rtpbin.recv_rtcp_sink_1                               \
  
       rtpbin.send_rtcp_src_1 ! udpsink host=127.0.0.1 port=5007 sync=false async=false

  Those pipelines, a combination of H263 and Speex, work fine enough. I snap my fingers near camera and micropohne and then I see movement and hear sound at the same time.

  Then I changed pipelines to use H264 along the video path.

  The sender becomes :
  # !/bin/sh

  gst-launch -v gstrtpbin name=rtpbin \
  
          v4l2src ! ffmpegcolorspace ! x264enc bitrate=300 ! rtph264pay ! rtpbin.send_rtp_sink_0 \
  
                    rtpbin.send_rtp_src_0 ! udpsink host=127.0.0.1 port=5000                            \
  
                    rtpbin.send_rtcp_src_0 ! udpsink host=127.0.0.1 port=5001 sync=false async=false    \
  
                    udpsrc port=5005 ! rtpbin.recv_rtcp_sink_0                           \
  
          pulsesrc ! audioconvert ! audioresample  ! audio/x-raw-int,rate=16000 !    \
  
                    speexenc bitrate=16000 ! rtpspeexpay ! rtpbin.send_rtp_sink_1                   \
  
                    rtpbin.send_rtp_src_1 ! udpsink host=127.0.0.1 port=5002                            \
  
                    rtpbin.send_rtcp_src_1 ! udpsink host=127.0.0.1 port=5003 sync=false async=false    \
  
                    udpsrc port=5007 ! rtpbin.recv_rtcp_sink_1

  And receiver becomes :
  # !/bin/sh

  gst-launch -v\
  
      gstrtpbin name=rtpbin                                          \
  
      udpsrc caps="application/x-rtp,media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264" \
  
              port=5000 ! rtpbin.recv_rtp_sink_0                                \
  
          rtpbin. ! rtph264depay ! ffdec_h264 ! xvimagesink                    \
  
       udpsrc port=5001 ! rtpbin.recv_rtcp_sink_0                               \
  
       rtpbin.send_rtcp_src_0 ! udpsink port=5005 sync=false async=false        \
  
      udpsrc caps="application/x-rtp,media=(string)audio, clock-rate=(int)16000, encoding-name=(string)SPEEX, encoding-params=(string)1, payload=(int)110" \
  
              port=5002 ! rtpbin.recv_rtp_sink_1                                \
  
          rtpbin. ! rtpspeexdepay ! speexdec ! audioresample ! audioconvert ! alsasink \
  
       udpsrc port=5003 ! rtpbin.recv_rtcp_sink_1                               \
  
       rtpbin.send_rtcp_src_1 ! udpsink host=127.0.0.1 port=5007 sync=false async=false

  This is what happen under Ubuntu 10.04. I didn't noticed such huge delays on Ubuntu 9.04 - the delays there was in range 2-3 seconds, AFAIR.

• File parameter substitution : Movie creation with png files

  9 mai 2012, par John Rumpel

  I've a simple question : I try to create a movie file like mentioned above (have a lot of png-files with name plt_.png). When I try to run the commandline input :

  ffmpeg -q:v 5 -r 2 -b:v 9600 -i plt_%d.png movie.mp4

  ... I receive the error message : "plt_d.png : No such file or directory".

  This is because XP tries to substitute % by command line paramenter 0, I think. But this substitution shouldn't be done here but one stage deeper by ffmpeg.

  Do you have an idea to fix this ?

  Thanks a lot !