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• How do I use ffmpeg to create an audio-synced cut from a single file ?

  1er octobre 2017, par AlaShiban

  I have 1 large file (lets call it test.mp4), and I’d like to create a new file (out.mp4) that takes 3 segments that are 1 second apart :

  Seg1: 00:01:00 - 00:02:00
Seg2: 00:03:00 - 00:04:00
Seg3: 00:06:00 - 00:07:00

  And merge them into out.mp4

  I’ve tried various concat filters, or using the textfile.txt with instructions in it :

  file file-1.wav
duration 20.0

  But various methods produce glitchy video with the x264 codec (green artifacts, choppy out-of-sync audio)

  Cutting each segment into its own file and then merging is not applicable because that approach would produce thousands of files and seems quite slow processing wise.

  Does anyone have thoughts on how this can be done properly with ffmpeg ? Is there an alternative API/CLI tool I could use thats known to work better for these cases ?

• How to create a panning video with a specific duration from a single panoramic image using ffmpeg

  4 janvier 2019, par Introspectre

  I have a panoramic landscape image (30000x1025) generated using sox input.flac -n remix 2 spectrogram -r -l -x 30000 -y 1030 -o output.png. I’d like to use ffmpeg to create a panning video of this spectrogram and I’d like it to match the exact length of input.flac. I’ve tried variations of ffmpeg -loop 1 -r 60 -i input.png -vf crop=1822:1025:n:0 -frames:v 20000 output.mkv, alternating the frame rate (30-60) and total frame count (10000-60000) to get a video of the exact length of the audio, but this has yet to yield the correct panning duration in output.mkv. To clarify, I’m having a problem with video overflow/underflow : either the video ends before panning the entire spectrogram or it runs off for some time after the image comes to an end.

  What I can’t calculate are the number of frames being panned from the original image. If the original image is split evenly on the x axis there should be a total of 16.46 slices measuring 1822x1025. So how do I tell ffmpeg to pan x frames/second per image slice ? If input.flac is 306 seconds, how do I instruct ffmpeg to take exactly 18.59 (306/16.46) seconds to pan each image slice ?

  Note that I’m not aiming to trim the video overflow and scaling the result using setpts afterwords. I’ve tried this and while it does work it has also produced certain unintended visual artifacts. I’d like to solve this issue with a single straightforward command or set of commands ; without unecessary re-encoding, if at all possible.

  If there’s a simpler solution that doesn’t involve ffmpeg, I’d be open to learning about that as well.

• rtpproto : Check the source IP if one single source has been specified

  18 juillet 2013, par Martin Storsjö

  rtpproto : Check the source IP if one single source has been specified
  If another peer is sending unicast packets to the same port that
  
  we are listening on, those packets can end up being received despite
  
  using source specific multicast. For those cases, manually check the
  
  source address of received packets against the intended source address.
  This only handles the case when the source list is one single IP
  
  address for now, which probably is the most common case.
  Based on a patch by Ed Torbett.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/rtpproto.c