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• Concatenate chunk containg headers to another chunk in h264

  18 novembre 2014, par Ortixx

  I’m trying to extract thumbnails from a torrent stream by downloading the first couple of chunks to get the headers, another set of chunks from the middle and then concat them to have a single video file.

  For this I’m using nodejs but I’m having trouble with the concatenation part. Obviously the headers include the length of the video so if I simply concat another chunk to the end of the headers chunk, it won’t work.

  In other words, I have 2 chunks of a video file : The first one contains the headers and some material and the other one is fully composed of a video stream. I want to combine the two to form a single video file
  So my question is how can I make this work properly if at all ?

• Find video resolution and video duration of remote mediafile

  22 février 2012, par osgx

  I want to write an program which can find some metainformation of mediafile. I'm interested in popular video formats, such as avi, mkv, mp4, mov (may be other popular too). I want basically to get :

  • Video size (720, 1080, 360 etc)
  • Total runtime of video (may be not very exact)
  • Number of audio streams
  • Name of video codec
  • Name of audio codec

  There is already the mediainfo, but in my program I want to get information about remote file, which may be accessed via ftp, http, samba ; or even torrent (there are some torrent solutions, which allows to read not-yet downloaded file).

  MediaInfo library have no support of samba (smb ://) and mkv format (for runtime).

  Also, I want to know, how much data should be downloaded to get this information. I want not to download full videofile because I have no enough disk space.

  Is this information in the first 1 or 10 or 100 KiloBytes of the file ? Is it at predictable offset if I know the container name and total file size ?

  PS : Platform is Linux, Language is C/C++

• Creating MOV from PNGs with ffmpeg : playback issue in older quicktime (7.6.6)

  15 avril 2013, par Jim Lindstrom

  I'm using ffmpeg to create a MOV file from a series of images. When I view the movie in Quicktime 7.7.x, it looks great (left image). When I view in Quicktime 7.6.6 I get this weird issue (on the right) :

  
  

  Any idea even what this is, much less how to fix it ?

  Details

  My source images are a mix of PNGs and JPGs that I pre-process with ImageMagick (to draw text, captions, etc). I store intermediate results as MPCs, and final frames as PNMs.

  To draw the above frame, I'm doing this :

  convert -background none -fill white -font my_font.ttf -pointsize 132 -gravity \
  
          center -size 945x550 caption:"Stills Demo" background-template.png     \
  
          +swap -composite -resize 1920x1080! /tmp/title_screen4338355.png
  
  convert -auto-orient /tmp/title_screen4338355.png -resize 100% -type TrueColor \
  
          /tmp/1b2764754ce6e420986ed74b942bcf67.mpc
  
  convert /tmp/1b2764754ce6e420986ed74b942bcf67.mpc -set option:distort:viewport \
  
          1920x1080+0+0  +distort SRT '960.0,540.0 1.0 0 960.0,540.0'            \
  
          /tmp/stills-project-6224/video_frames/img_0000.pnm

  I render frames with ffmpeg like so :

  ffmpeg -y -f image2 -i /tmp/stills-project-6224/video_frames/img_%04d.pnm      \
  
         -i /tmp/soundtrack_8702693.wav -vcodec libx264 -pix_fmt yuvj444p        \
  
         -b:v 2200k  -r 25 -strict experimental                                  \
  
         /tmp/stills-project-6224/video_rendered/output.mov

  The rest of the video is fine. The other images are photos (jpgs or pngs) that I process in the same way. I have also noticed that if I don't apply text to this background-template, the image shows up fine, so I think the issue has something to do with either how I'm processing or saving that image.