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• How to avoid a growing delay with ffmpeg between sound and raw video data ?

  13 novembre 2011, par roland

  Hello everybody and thank you for reading !

  Here is my problem : I have a program piping raw video frames to the standard output. This program is using OpenCV to capture and process the video and outputs directly the processed frames. The loop is synced to the framerate I chose. I'm using ffmpeg to read from the standard input and everything works fine for the video.
  But now that I added the sound I have a big problem : a growing delay is occuring and I really need to get rid of it. So here is my idea, but I really need your help :

  I have to find a way to include a timestamp information to the raw video. To be understandable by ffmpeg, it needs to be a known raw video compatible container. And then I will need to use the container API and pipe it to the standard output in my program. I really do not know what to use in the jungle of video formats and codecs, and I don't event know how to enable timestamp synchronizing in ffmpeg...

  If anyone has an idea, i am really interested here. For information, here is the command line i use to pipe the raw video :

  ./myprogram | ffmpeg -y -f alsa -i pulse -ac 2  -f rawvideo -vcodec rawvideo -r 24 -s 640x480 -pix_fmt bgr24 -i - -vcodec libx264 -pix_fmt yuv420p -r 24 -f flv -ar 44100 out.flv;

  Thand you very much,

  Roland

• ffmpeg resize down larger video to fit desired size and add padding

  5 février 2017, par misterjinx

  I’m trying to resize a larger video to fit an area that I have. In order to achieve this I calculate first the dimensions of the resized video so That it fits my area, and then I try to add padding to this video so that the final result will have the desired dimension, keeping the aspect ratio as well.

  So let’s say that I have the original video dimensions of 1280x720 and to fit my area of 405x320 I need first to resize the video to 405x227. I do that. Everything is fine at this point. I do some math and I find out that I have to add 46 pixels of padding at the top and the bottom.

  So the padding parameter of the command for that would be -vf "pad=405:320:0:46:black". But each time I run the command I get an error like Input area 0:46:405:273 not within the padded area 0:0:404:226.

  The only docs for padding that I found is this http://ffmpeg.org/libavfilter.html#pad.

  I don’t know what I’m doing wrong. Anyone had this problem before ? Do you have any suggestions ?

• Use FFMPEG to create video from jpeg, and index using vlc

  16 novembre 2011, par Greg

  OpenSuse 11.4
  FFMEG 0.8.5

  I'm using FFMPEG to create a 5 minute mpeg from about 2100 individual jpegs (7fps). I've been using the following command (OpenSuse 11.4)
  /usr/bin/ffmpeg -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 Event-3692-r1-s1-3.mpg

  Now I Try to open the file (In windows XP with VLC 1.1.11 Player).
  Media->AdvancedFileOpen
  *I select "Show more options" and set StartTime to 5s. I expect that the video should start 5 seconds in, but instead it starts at a seemingling random (although consistent) time of 30 seconds in.

  I also tried changing ffmpeg command to :
  /usr/bin/ffmpeg -sameq -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 Event-3692-r1-s1-3.mpg
  *This result in about a constant 2x offset (5sec => 10sec) (10s => 20s) etc. But filesize is also about 6x larger, which is a strain on my storage.

  I also tried
  /usr/bin/ffmpeg -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 -f mpegts Event-3692-r1-s1-3.mpg
  *This result in vlc not indexing at all into my video. Also not desired. Anybody have any clues what is going on here. It is very important for me to be able to use this VLC feature and have it work correctly.

  Thanks in advance