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• Audio output with video processing with opencv

  22 février 2012, par victor1234

  I am processing video with opencv, but at the same time I need to play audio and simply control it, like loud or current frame number.

  I think I should create a parallel process with ffmpeg, but I don't know how to do so. Can you explain what to do ?

  Or do you know another solution ?

• split video (avi/h264) on keyframe

  30 novembre 2012, par m.sr

  Hallo.

  I have a big video file. ffmpeg, tcprobe and other tool say, it is an h264-stream in an AVI-container.

  Now i'd like to cut out small chunks form the video.

  1. Problem : The index of the video seam corrupted/destroyed. I kind of fixed this via mplayer -forceidx -saveidx <indexfile> <bigvideofile></bigvideofile></indexfile>. The Problem here is, that I'm now stuck with mplayer/mencoder which can use this index file via -loadidx <indexfile></indexfile>. I have tried correcting the index like described in man aviindex (mplayer -frames 0 -saveidx mpidx broken.avi ; aviindex -i mpidx -o tcindex ; avimerge -x tcindex -i broken.avi -o fixed.avi), but this didn't fix my video - meaning that most tools i've tested couldn't search in the video file.

  2. Problem : I cut out parts of the video via following command : mencoder -loadidx in.idx -ss 8578 -endpos 20 -oac faac -ovc x264 -sws 9 -lavfopts format=mp4 -x264encopts <lotsofopts> -of lavf -vf scale=800:-10,harddup in.avi -o out.mp4</lotsofopts>. Now here the problem is, that some videos are corrupted at the beginning. I think this is because the fact, that i do not necessarily cut at keyframe.

  Questions :

  1. What is the best way to fix the index of an avi "inline" so that every tool can again work as expected with it ?

  2. How can i split at the keyframes ? Is there an mencoder-option for this ?

  3. Are Keyframes coming in a frequency ? How to find out this frequency ? (So with a bit of math it should be possible to calculate the next keyframe and cut there)

  4. Is ther perhaps some completely other way to split this movie ? Doing it by hand is no option, i've to cut out 1000+ chunks ...

  Thanks a lot !

• ffmpeg images-to-video script anyone ?

  3 février 2014, par danja

  I'm wanting to take a bunch of images and make a video slideshow out of them. There'll be an app for that, right ? Yup, quite a few it seems. The problem is I want the slides synced to a piece of music, and all the apps I've seen only allow you to show each slide for a multiple of a whole second. I want them to show for multiples of 1.714285714 seconds to fit with 140 bpm.

  The tools I've seen generally seem to have ffmpeg under the hood, so presumably this kind of thing could be done with a script. But ffmpeg has sooo many options...I'm hoping someone will have something close.

  I'll have up to about 100 slides, the ones that have to show for 3.428571428 secs or whatever I guess I can simply show twice.