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• Expand (extend) a video to an specific duration

  8 février 2013, par BorrajaX

  Do VLC or FFmpeg (or AVconv) have any feature to force the duration of a video to a certain number of seconds ?

  Let's say I have a... 5 minutes .mp4 video (without audio). Is there a way to have any of the aforementioned tools "expanding" the video to a longer duration ? The video comes from a Power Point slideshow, but it's too short (running too fast, to say so). The idea would be automatically inserting frames so it reaches an specified duration. It looks like something pretty doable (erm... for a total newbie in video encoding/transcoding as I am) : A 5 minutes video, at 30fps means I have 9000 frames... To make it be 10 times longer, get the first "real" frame, copy it ten times, then get the second "real" frame, copy it ten times... and so on.

  I'm using Ubuntu 12.04, but I can install/compile any required software, if needed. So far, I have VLC, AVConv and FFmpeg (FFmpeg in an specific folder, so it won't conflict with AVConv)

  Thank you in advance.

• Making changes on a video before a download [on hold]

  1er février 2016, par Chris Russo

  We have a website with lots of videos (>10,000) and lots of users (>50,000). Each video might be around 1,2 Gbs.

  The goal is to generate a unique video for each one of the members or users of the website making a small variation either on the audio track of the video, or the keyframes on the video itself, using low frequency beeps, or a few random pixels on specific keyframes.

  I understand that this operation can be done using SoX for the audio track, or FFmpeg in the case of the video, manipulating the keyframes.

  Here’s my question, as we have to choose between 2 options at this point :

  In terms of resources : would it be convenient or even possible to generate in real time a clone of the video and make this variations at the moment that the user’s request the download (please considerate the big volume of videos and users).

  Or it would be convenient to face this problem using HDD, pre-generating and storing the already manipulated videos ready to be served ?

  I understand that storing all this data will require a few many Tera’s but I’m not sure about how much RAM and Microprocessing could be demanded to perform this operations in real time, over videos that might be as big as 1Gbs.

• filesize is not growing as expected

  29 juillet 2019, par Oracy Martos

  I am trying to record a stream here on my machine to study ffmpeg library,
  but with(out) success.

  I have a file watcher to clean up bugged streams, that cleanup each 3 minutes files that have been not changed less then 3 minutes.

  The real problem is, if I use the command below :

  /usr/bin/ffmpeg -i http://sysrad.net:10090/ -y test.mp3

  this command doesn’t have any kind of codec or audio transformation, so my target file (test.mp3) become 256k quickly, but, if I use this command below :

  /usr/bin/ffmpeg -i http://sysrad.net:10090/ -y -b:a 8k -ac 1 -ar 11025 test.mp3

  My target file (test.mp3) keep 0k until the record has 256k, I am not sure if this is an Unix problem or ffmpeg problem.

  Other information, if I run in loop :

  while true; do wc -l teste.mp3; sleep 0.5; done;

  test.mp3 file keeps 0 rows, until has 256k size...

  I have no idea how to workaround that, to get the real time file size for each 1k that ffmpeg get from stream with those codecs, does you guys have any idea how can I handle that ?

  Thanks !!!!