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• FFMpeg + OpenAL

  24 juillet 2013, par Dekowta

  I've been having a problem decoding different codecs into PCM 16 little-endian which is the supported format for OpenAL (I believe that is correct).

  I am using the windows pre-compiled libraries for FFMpeg (dont know if that effects anything).

  The code I have so far is here http://pastebin.com/T4wGL72a

  I have aiff and wav working (though with single channel OpenAL wants to have half the frequency and im not really sure why).

  The main problem is encoded audio files.

  mp3 files play sometimes (sometime get missing header) but end up stuttering with noise and are high pitched.

  ac3 files played the first preloaded buffers and then the frame would not have any more decoded data in the data array (did not check to see if the packet fetched encoded data or not).

  ogg files are the same as ac3

  m4a files would never finish the frame so I have no idea what happens when they do.

  wma files stutter and have a lot of noise but it is not high pitched like mp3 files

  I don't work with audio very often so its difficult for me to get my head round it and this is also the first time I've worked with FFMpeg.

  I'm sure there is something i'm doing very wrong I just need a hand on pointing out where it is.

  Thanks

  Chris.

• Add PNG image overlay to video starting with non-key frame

  8 mai 2020, par RamRick

  Alright, so I'm trying to edit a bunch of short to very long videos.
The goal is to mute a 1 minute part within each video and overlay that small part with a PNG image for the full duration.

  



  Because this all has to be done as fast as possible, I figured it would be the best idea to split every video into 3 parts, then mute and add the overlay to part #2 and put all 3 parts back together.

  



  The first problem I ran into was that part #2 and #3 always started with a 1-2 second freeze in video, while the audio was fine.

  



  I found out that this was caused by me cutting at key frames and ignoring non-key frames at the beginning.

  



  I fixed that by adding the -copyinkf parameter to also copy all non-key frames, like so :

  



  ffmpeg -i "in.mp4" \
-to 0:04:00 -c:v copy -c:a copy -copyinkf "p1.mp4" \
-ss 0:04:00 -to 0:05:00 -c:v copy -c:a copy -copyinkf "p2.mp4" \
-ss 0:05:00 -c:v copy -c:a copy -copyinkf "p3.mp4"


  



  So I went on and proceeded to mute part #2, like so :

  



  ffmpeg -i "p2.mp4" -af "volume=0" -c:v copy -copyinkf "p2_muted.mp4"


  



  All fine until this point, and IF I put the parts back together right now it would also be quick and accurate, like so :

  



  --parts.txt
file 'p1.mp4'
file 'p2_muted.mp4'
file 'p3.mp4'

ffmpeg -f concat -safe 0 -i parts.txt -c copy "out.mp4"


  



  But now comes the problem :

  



  Since I have to re-encode part #2 to overlay the PNG image, I get the 1-2 seconds freeze frame problem at the beginning again and I can't for the life of me figure out the "equivalent" of -copyinkf for re-encoding a video.

  



  Right now I'm overlaying the PNG image like so :

  



  ffmpeg -i "p2_muted.mp4" -i "../banner.png" -filter_complex "[1][0]scale2ref[i][v];[v][i]overlay" -c:a copy "p2_edited.mp4"


  



  So my question is, what would the equivalent to -copyinkf be, or in case there is a better way than mine, what would that be to achieve my task.

  


• avisynth : corrected interlace detection

  24 mai 2021, par emcodem

  avisynth : corrected interlace detection
  AviSynth works on frame-based video by default, which can
  
  be either progressive or interlaced. Some filters can break
  
  frames into half-height fields, at which point it considers
  
  the clip to be field-based (avs_is_field_based can be used
  
  to check for this situation).
  To properly detect the field order of a typical video clip,
  
  the frame needs to have been weaved back together already,
  
  so avs_is_field_based should actually report 'false' when
  
  checked.
  Signed-off-by : Stephen Hutchinson <qyot27@gmail.com>
  

  • [DH] libavformat/avisynth.c