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• Converting GridFS file object to File object to upload via carriewave then process with ffmpeg in Rails

  20 juin 2014, par Ojash

  I have a GridFS file object

  Mongoid::GridFs::Fs::File _id: 53a277dc700ca7ac146f5797, length: 2237337, chunkSize: 261120, uploadDate: 2014-06-19 05:40:44 UTC, md5: "390968a8ef198f8537495468366f67b9", filename: "720p_5.MP4", contentType: "binary/octet-stream", aliases: nil, metadata: nil

  Now I need a Tempfile(or File will do) instance from that

  File:/tmp/fileupload20140620-4601-19via7k

  Since the file that I process is a video file i need to further process it with the ffmpeg to get different versions of the video file

  normally I could get a tmp file but the tempfile size seems to be quite low for a video file and the ffmpeg also gives error, may be the temp file created is not correct. I have no idea what did i do wrong.

• Missing reference frame, slice header decode error

  20 juin 2014, par AnilJ

  I split this (http://www.auby.no/files/video_tests/h264_720p_mp_3.1_3mbps_aac_shrinkage.mp4) video using mp4box command "MP4Box -split 1 shrinking.mp4" into slices of 1 second each. I have following questions :

  1. I got different sizes of the video although I sliced it evenly at 1 second. Not sure how this happened ?
  2. When I try to dump the information about the video slice file, I get the below message with an error. Can someone please help me understand what it is, and how possibly I can modify the command above to get rid of it ? This error occurs for every video slide generated. This error comes only on the sliced videos.

  Thanks,
  /anil.

  anilj@desk1:~/workspace/testprogs/shellscripts$ ffmpeg -i invideo/shrinking_01.mp4
  
  ffmpeg version N-36083-g2501f93-xuggle-5.5 Copyright (c) 2000-2012 the FFmpeg developers
  
    built on Jun  3 2014 13:43:04 with gcc 4.6.4
  
    configuration: --prefix=/home/anilj/workspace/xugglehome --extra-version=xuggle-5.5 --extra-cflags=-I/home/anilj/workspace/xuggle-xuggler/build/native/x86_64-unknown-linux-gnu/captive/stage/home/anilj/workspace/xugglehome/include --extra-ldflags=-L/home/anilj/workspace/xuggle-xuggler/build/native/x86_64-unknown-linux-gnu/captive/stage/home/anilj/workspace/xugglehome/lib --disable-shared --enable-pic --enable-gpl --enable-nonfree --enable-libx264 --enable-version3 --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libvo-aacenc --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librtmp --enable-openssl --enable-zlib --enable-libvpx
  
    libavutil      51. 46.100 / 51. 46.100
  
    libavcodec     54. 14.101 / 54. 14.101
  
    libavformat    54.  3.100 / 54.  3.100
  
    libavdevice    53.  4.100 / 53.  4.100
  
    libavfilter     2. 67.101 /  2. 67.101
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0. 10.100 /  0. 10.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  [h264 @ 0x1ddeac0] Missing reference picture
  
  [h264 @ 0x1ddeac0] decode_slice_header error
  
  [h264 @ 0x1ddeac0] Missing reference picture
  
  [h264 @ 0x1ddeac0] decode_slice_header error
  
  [h264 @ 0x1ddeac0] Missing reference picture
  
  [h264 @ 0x1ddeac0] decode_slice_header error
  
  [h264 @ 0x1ddeac0] Missing reference picture
  
  [h264 @ 0x1ddeac0] decode_slice_header error
  
  [h264 @ 0x1ddeac0] concealing 3600 DC, 3600 AC, 3600 MV errors
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'invideo/shrinking_01.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 1
  
      compatible_brands: isom
  
      creation_time   : 2014-06-19 20:21:02
  
    Duration: 00:00:00.90, start: 0.000000, bitrate: 38 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 30 kb/s, 29.96 fps, 29.96 tbr, 29956 tbn, 59.92 tbc
  
      Metadata:
  
        creation_time   : 2011-05-05 18:09:35
  
        handler_name    : ?Apple Video Media Handler
  
  At least one output file must be specified

• MPEG-DASH create initialization segment

  3 novembre 2014, par static

  I’m segmenting the video capture of the desktop using ffmpeg -segment and sending them over network in order to be served to clients and to be played using dash.js. The problem is that the player is searching for the initialization segment and i don’t seem to be able to figure out how to create it.
  I create the segments using this ffmpeg command :

  ffmpeg -rtbufsize 1500M -f dshow -r 15 -i video="UScreenCapture"
  
  -flags +global_header -vcodec libvpx -crf 10 -quality good -keyint_min 15 -g 15
  
  -cpu-used 3 -b:v 1000k -qmin 10 -qmax 42  -threads 2 -vf scale=-1:480 -bufsize 1
  
  500 -map 0 -f stream_segment -segment_time 2 -segment_format webm http://localho
  
  st:3000/stream/22/%03d

  The manifest that i create for the stream looks something like this :

  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" type="dynamic" availabilitystarttime="2014-06-19T07:47:40.079Z" minbuffertime="PT0S" profiles="urn:mpeg:dash:profile:isoff-live:2011" suggestedpresentationdelay="PT40S" maxsegmentduration="PT2.000S" minimumupdateperiod="PT1000M">
  
  <period bitstreamswitching="true" start="PT0S">
  
  <adaptationset mimetype="video/webm" segmentalignment="true" startwithsap="1" maxwidth="1280" maxheight="720" maxframerate="15">
  
  <contentcomponent contenttype="video"></contentcomponent>
  
  <segmenttemplate presentationtimeoffset="0" timescale="90000" media="$Number$/" duration="180000" startnumber="0"></segmenttemplate>
  
  <representation width="853" height="480" framerate="15" bandwidth="1000000" codecs="vp8"></representation>
  
  </adaptationset>
  
  </period>
  
  </mpd> 

  The player debugging mode prints the following things :

  Getting the request for time: 0 dash.all.js:2073
  
  Index for time 0 is 0 dash.all.js:2073
  
  Waiting for more video buffer before starting playback. dash.all.js:2073
  
  BufferController video seek: 0 dash.all.js:2073
  
  Marking a special seek for initial video playback. dash.all.js:2073
  
  Start searching for initialization. dash.all.js:2073
  
  Perform init search: stream/22/ dash.all.js:2073
  
  Getting the request for time: 0 dash.all.js:2073
  
  Index for time 0 is 0 dash.all.js:2073
  
  Data changed - loading the video fragment for time: 0 dash.all.js:2073
  
  Getting the request for time: 0 

  How can i create the initialization segment for the generated segments ? I can’t seem to be able to get it to work.