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• ffmpeg : VLC won’t open .sdp files generated by ffmpeg

  8 mai 2020, par tiredamage42

  TLDR : VLC or Quicktime won’t open .sdp video stream files generated by ffmpeg, even though ffplay does.

  



  Web development and ffmpeg noob, so apologies if I’m using the wrong terminology :

  



  I’m trying to stream my desktop capture (on OSX) using ffmpeg, sending it out via rtp protocol. 
As of right now I’m just testing it out by streaming it over a port in my localhost (4000). And trying to play it locally.

  



  The problem is that when I try and open the .sdp file generated by the ffmpeg command, VLC opens it and immediately stops, no errors or anything, and shows that it has a duration of 0:00. Quicktime won’t event open the file in the first place.

  



  ffplay does play the stream and I can see my desktop in the player window (with a significant loss in quality though). Even so there are a ton of warning and errors that show up intermittently (outlined below)

  



  I’m not sure if it’s a problem in the way I start the ffmpeg stream, the command is after a ton of iterations of trying to just make it work, so my options might be way wrong.

  



  command to 'serve' the desktop capture :

  



  ./ffmpeg -f avfoundation -s 1920x1080 -r 60 -i "1" -an \
-vcodec libx264 -preset ultrafast -tune zerolatency -pix_fmt yuv420p \
-sdp_file video.sdp -rtsp_transport tcp -f rtp rtp://127.0.0.1:4000


  



  SDP file that’s generated with the ffmpeg command :

  



  SDP:
v=0
o=- 0 0 IN IP4 127.0.0.1
s=No Name
c=IN IP4 127.0.0.1
t=0 0
a=tool:libavformat 58.29.100
m=video 4000 RTP/AVP 96
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1


  



  ffplay command used to play the stream :

  



  ./ffplay -probesize 32 -analyzeduration 0 -sync ext \
-fflags nobuffer -fflags discardcorrupt -flags low_delay -framedrop \
-strict experimental -avioflags direct \
-protocol_whitelist file,rtp,udp -I video.sdp


  



  For a while before ffplay starts I see a bunch of these errors repeating (in red) :

  



  [h264 @ 0x7ff6b788de00] non-existing PPS 0 referenced
[h264 @ 0x7ff6b788de00] decode_slice_header error
[h264 @ 0x7ff6b788de00] no frame!


  



  then the window seems to 'catch up' to the stream and actually shows the desktop capture, and I get these errors and warnings on a regular interval :

  



  1- in a yellow warning color :

  



  [sdp @ 0x7fc85b830600] RTP: missed 4 packets
[sdp @ 0x7fc85b830600] max delay reached. need to consume packet


  



  2-in a red error color :

  



  [h264 @ 0x7fc85b02aa00] out of range intra chroma pred mode
[h264 @ 0x7fc85b02aa00] error while decoding MB 132 32


  



  (I have a feeling that the above errors have to do with previewing the desktop capture in the desktop I’m capturing and causing pixels in the display to overflow)

  



  Edit :
So, I solved the issue soon after posting, but will leave this up in case anyone runs into the same problem.

  



  The solution was to remove the top line in the .sdp file that said SDP:

  


• Merge commit ’e481458bc308ee838deaeacac51929514762e7a7’

  26 avril 2016, par Derek Buitenhuis

  Merge commit ’e481458bc308ee838deaeacac51929514762e7a7’
  * commit ’e481458bc308ee838deaeacac51929514762e7a7’ :
  
    h264 : factor out pred weight table parsing into a separate file
  Merged-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavcodec/Makefile
  • [DH] libavcodec/dxva2_h264.c
  • [DH] libavcodec/h264.c
  • [DH] libavcodec/h264.h
  • [DH] libavcodec/h264_mb.c
  • [DH] libavcodec/h264_mc_template.c
  • [DH] libavcodec/h264_parse.c
  • [DH] libavcodec/h264_parse.h
  • [DH] libavcodec/h264_parser.c
  • [DH] libavcodec/h264_refs.c
  • [DH] libavcodec/h264_slice.c
  • [DH] libavcodec/vaapi_h264.c

• libav :0: : cabac decode of qscale diff failed at 4 26 ? While UDP Streaming in Gstreamer

  28 juin 2016, par Prasanth Kumar Arisetti

  I would like to stream the webcam data over UDP in mpegts format.

  At Sending End: :

  gst-launch-1.0 -v v4l2src device=/dev/video1 ! videoconvert ! video/x-raw,width=720,height=576,framerate=25/1,format=I420 ! videoparse width=720 height=576 framerate=25/1 ! x264enc bitrate=2048 ref=4 key-int-max=20 byte-stream=true tune=zerolatency speed-preset=3 sliced-threads=true threads=4  ! video/x-h264,stream-format=byte-stream,profile=main ! queue ! mpegtsmux ! rtpmp2tpay ! udpsink host=192.168.2.149 port=8888 sync=true async=false qos=true qos-dscp=46

  At Receiving End: :

  GST_DEBUG=4 gst-launch-1.0 -v udpsrc port=8888 caps=application/x-rtp,media=video,encoding-name=MP2T buffer-size=524288 ! rtpmp2tdepay ! tsdemux name=demuxer  demuxer. !  queue max-size-buffers=0 max-size-time=0 ! h264parse ! avdec_h264 ! videoconvert ! xvimagesink qos=true sync=true async=false 

  For few seconds, video is coming good, but after that it is getting disturbed, and not at all coming, struck at single frame.

  And when i used GST_DEBUG=4, i observed below error :

  0:00.000000000, position 0:00:10.397114020, duration 99:99:99.999999999
  
  0:00:10.396195300   536 0x7f1328001300 ERROR                  libav :0:: cabac decode of qscale diff failed at 4 26
  
  0:00:10.396212221   536 0x7f1328001300 ERROR                  libav :0:: error while decoding MB 4 26, bytestream -1
  
  0:00:10.396255836   536       0xe03320 INFO                   libav :0:: concealing 1215 DC, 1215 AC, 1215 MV errors

  But, if I stream the Data to localhost, then it is perfectly working.

  After setting cabac=false on x264enc,

  0:00.000000000, position 0:00:14.796602703, duration 99:99:99.999999999
  
  0:00:15.020440888 15449 0x7f69dc4fe2c0 ERROR                  libav :0:: out of range intra chroma pred mode at 18 14
  
  0:00:15.020464168 15449 0x7f69dc4fe2c0 ERROR                  libav :0:: error while decoding MB 18 14
  
  0:00:15.020694828 15449      0x2513320 INFO                   libav :0:: concealing 1215 DC, 1215 AC, 1215 MV errors

  What is the problem here ? is this because of network bandwidth or any other else ? And how to solve this problem ?