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• How to make a MPEG-DASH MPD which starts the playback in the middle of the first segment ?

  18 septembre 2018, par ravin.wang

  Here are the reproduce steps :

  1. Normalize an H.264 video stream

     ffmpeg -i 2.h264 -c:v libx264 -intra -r 25 -vf scale=640x360,setdar=16:9 2@25fps@intra@640x360.h264

     (*) After that, I got an H.264 stream where all pictures are H.264 IDR frames, and fps is 25, resolution is 640x360, aspect-ratio is 16:9.

  2. Generate an MP4 file

     MP4Box -add 2@25fps@intra@640x360.h264:timescale=1000 -fps 25 2@25fps@intra@640x360.mp4

  3. Make dash MP4 fragmented content, including init mp4, .m4s files and one .mpd file

     MP4Box -dash 5000 -frag 5000 -dash-scale 1000 -frag-rap -segment-name ’seg_second$Number$’ -segment-timeline -profile live 2@25fps@intra@640x360.mp4

  4. Copy and publish all these files to a folder under one HTTPD server

  5. I want to play from 4s of the first segment, and don’t display any frames before 4s, so I changed the .MPD file to modify the fields "SegmentTemplate@presentationTimeOffset", "SegmentTimeline:S@d/t", like as :
     

     <?xml version="1.0"?>
<mpd xmlns="urn:mpeg:dash:schema:mpd:2011" minbuffertime="PT1.500S" type="static" mediapresentationduration="PT0H0M26.000S" maxsegmentduration="PT0H0M5.000S" profiles="urn:mpeg:dash:profile:isoff-live:2011">
<period duration="PT0H0M26.000S">
<adaptationset segmentalignment="true" maxwidth="640" maxheight="360" maxframerate="25" par="16:9" lang="und">
 <segmenttemplate presentationtimeoffset="4000" media="seg_second$Number$.m4s" timescale="1000" startnumber="1" initialization="seg_secondinit.mp4">
   <segmenttimeline>
       <s d="1000" t="4000"></s>
       <s d="5000" r="4"></s>
   </segmenttimeline>
  </segmenttemplate>
<representation mimetype="video/mp4" codecs="avc3.64101E" width="640" height="360" framerate="25" sar="1:1" startwithsap="1" bandwidth="2261831">
</representation>
</adaptationset>
</period>
</mpd>

     
     

  6. Play the MPD url from VLC player, or Edge browser, it always starts the the first frame of the first segment, the frames between 0s 4s are also displayed unexpectedly.

  What’s wrong with my steps ? Or any other options for it ?

• Ble with record video

  24 juillet 2017, par Vitaly

  I’m working on rpi3.
  When I try to run the command :

  sudo ffmpeg -f video4linux2 -i /dev/video0 -video_size 640x480 -r 25 output.avi

  to record a video using ffmpeg.

  In this time,I try to connect with Bluetooth.

  The BT cannot connect.

  the exception I get is :
  A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

  top result :

  1156 root 20 0 299860 197172 137736 S 80.6 20.9 40:21.35 ffmpeg

  80.6 % cpu and 20.9 % mem.

  all the other processes take less than 1%.

  Did you encounter with this ?
  Do you have a clue what can be done ?

  Thanks

• av_interleaved_write_frame hang forver when network broken

  8 octobre 2019, par DJI_lover

  I am using ffmpeg to stream video to rtmp server.But when network broken,my streaming program seem to hang on in av_interleaved_write_frame() and there is no error output.if I recover the network within seconds,the program resume to work within seconds.But if I recover the network after 20 seconds or even longer，my program freeze forever with no error.I want to interupt the av_interleaved_write_frame() when it hang up for a period of time and restart my whole streaming program.Could someone tell me how to do ,thanks !!