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• vframes option ignored in ffmpeg ?

  25 mars 2016, par cooper

  I have a directory that contains 2001 PNG files. I can convert all of the frames to an mp4 video using ffmpeg and the following command :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -c:v libx264 -r 30 \
  
  -pix_fmt yuv420p input1ia.mp4

  This works fine. However, I am creating a more complicated application that needs to read only the first 1020 files in the directory (specifically 0 thru 1019). Some googling around led me to the -vframes option. My problem is — it seems to get ignored or at least interpreted differently than I expect.

  My modified command looks like :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -vframes 1020 -c:v libx264 
  
  -r 30 -pix_fmt yuv420p input1.mp4

  It seems like many other people doing the same thing as me do not encounter this issue. So I did some more digging. I tried changing vframes from 1020 to -vframes 20, and this seemed to work properly. So now I am thinking it might be some kind of mismatch between -framerate and -r ?

  The full resultant video is 33 sec long... which makes sense mathematically.

   1 sec
  
   ---------   x  2001 frames = 33.35 seconds
  
   60 frames

  That’s why I thought that specifying 1/2 of the PNGs as the ’end point’ would result in a video of the first 16-17 seconds. But I always get the full length video from using the -vframes option.

  I assume my input to -vframes must be incorrect mathematically, since a small number of frames seems to work. However, I do not understand why.

  The most educated guess I can seem to make is that it is reading the PNGs as 60fps (-framerate), but the -r makes the output video 30fps or something ? However, then I would assume that the full output video would not be 33 seconds long.

• vframes option ignored in ffmpeg ?

  25 mars 2016, par cooper

  I have a directory that contains 2001 PNG files. I can convert all of the frames to an mp4 video using ffmpeg and the following command :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -c:v libx264 -r 30 \
  
  -pix_fmt yuv420p input1ia.mp4

  This works fine. However, I am creating a more complicated application that needs to read only the first 1020 files in the directory (specifically 0 thru 1019). Some googling around led me to the -vframes option. My problem is — it seems to get ignored or at least interpreted differently than I expect.

  My modified command looks like :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -vframes 1020 -c:v libx264 
  
  -r 30 -pix_fmt yuv420p input1.mp4

  It seems like many other people doing the same thing as me do not encounter this issue. So I did some more digging. I tried changing vframes from 1020 to -vframes 20, and this seemed to work properly. So now I am thinking it might be some kind of mismatch between -framerate and -r ?

  The full resultant video is 33 sec long... which makes sense mathematically.

   1 sec
  
   ---------   x  2001 frames = 33.35 seconds
  
   60 frames

  That’s why I thought that specifying 1/2 of the PNGs as the ’end point’ would result in a video of the first 16-17 seconds. But I always get the full length video from using the -vframes option.

  I assume my input to -vframes must be incorrect mathematically, since a small number of frames seems to work. However, I do not understand why.

  The most educated guess I can seem to make is that it is reading the PNGs as 60fps (-framerate), but the -r makes the output video 30fps or something ? However, then I would assume that the full output video would not be 33 seconds long.

• Framerate live streaming webm with dash and ffmpeg

  14 mai 2016, par Jones

  I am streaming a live video with ffmpeg and dash.js using
  these instructions. It works well except that the video is playing at a too high framerate. No framerate is specified in the manifest.
  Creating the Chunks :

  SET VP9_LIVE_PARAMS=-speed 6 -threads 8 -static-thresh 0 -max-intra-rate 300 -deadline realtime -lag-in-frames 0 -error-resilient 1
  
  ffmpeg -re -r 25 -i tcp://localhost:8891 ^
  
  -map 0:0 ^
  
    -pix_fmt yuv420p ^
  
    -c:v libvpx-vp9 ^
  
      -s 800x600 -keyint_min 25 -g 25 %VP9_LIVE_PARAMS% ^
  
      -f webm_chunk ^
  
      -header "webm_live/glass_360.hdr" ^
  
      -chunk_start_index 1 ^
  
    webm_live\glass_360_%%d.chk ^

  Creating the Manifest :

  ffmpeg ^
  
    -f webm_dash_manifest -live 1 ^
  
     -r 25 ^
  
    -i webm_live/glass_360.hdr ^
  
    -c copy ^
  
    -map 0 ^
  
    -r 25 ^
  
    -framerate 25 ^
  
    -f webm_dash_manifest -live 1 ^
  
      -adaptation_sets "id=0,streams=0" ^
  
      -chunk_start_index 1 ^
  
      -chunk_duration_ms 1000 ^
  
      -time_shift_buffer_depth 7200 ^
  
      -minimum_update_period 7200 ^
  
    webm_live/glass_live_manifest.mpd

  Manifest :

  <?xml version="1.0" encoding="UTF-8"?>
  
  <mpd xmlns="urn:mpeg:DASH:schema:MPD:2011" type="dynamic" minbuffertime="PT1S" profiles="urn:mpeg:dash:profile:isoff-live:2011" availabilitystarttime="2016-03-30T13:02:53Z" timeshiftbufferdepth="PT7200S" minimumupdateperiod="PT7200S">
  
  <period start="PT0S">
  
  <adaptationset mimetype="video/webm" codecs="vp9" bitstreamswitching="true" subsegmentalignment="true" subsegmentstartswithsap="1">
  
  <contentcomponent type="video"></contentcomponent>
  
  <segmenttemplate timescale="1000" duration="1000" media="glass_$RepresentationID$_$Number$.chk" startnumber="1" initialization="glass_$RepresentationID$.hdr"></segmenttemplate>
  
  <representation bandwidth="1000000" width="800" height="600" codecs="vp9" mimetype="video/webm" startswithsap="1"></representation>
  
  </adaptationset>
  
  </period>
  
  </mpd>

  Any Ideas how to fix this ?