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• ffmpeg removes dead space in video but not audio

  10 juillet 2015, par Peter Becich

  I’m transferring a VHS tape on Ubuntu with ffmpeg, somagic-capture, the line-in jack and an EasyCap dongle.

  There is a big issue with audio drift that, I believe, is caused by ffmpeg removing dead space from the video stream but not the audio stream.

  The capture utility creates a stream :

  somagic-capture --ntsc -c --luminance=2 --lum-aperture=3 \
  
  2> $SOMAGIC_LOG |

  Which is piped into ffmpeg. ffmpeg also captures from alsa :

   ffmpeg -pixel_format uyvy422 -s:v 720x480 \
  
  -framerate 29.97 -f rawvideo -i -  -f alsa -thread_queue_size 1024 \
  
  -i hw:0,0 -vf scale=w=640:h=480 -vcodec libx264 -preset ultrafast \
  
  -shortest -c:a libfdk_aac -b:a 256k $OUTFILE

  Is it true that ffmpeg by default removes dead space from a stream ?

  If so, would ffmpeg trim both streams even if only one is "dead" — suppose the video is momentarily blank while the audio is noisy.

  If not, are these two streams incompatible with each other ? Is the ALSA input (line-in jack) on a different clock than the EasyCap video dongle ?

  Input #0, rawvideo, from 'pipe:':
  
    Duration: N/A, start: 0.000000, bitrate: 165722 kb/s
  
      Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 720x480, 
  
      165722 kb/s, 29.97 tbr, 29.97 tbn, 29.97 tbc
  
  Guessed Channel Layout for  Input Stream #1.0 : stereo
  
  
  
  Input #1, alsa, from 'hw:0,0':
  
    Duration: N/A, start: 1436492353.282796, bitrate: 1536 kb/s
  
    Stream #1:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s

  I think the -shortest flag only concerns killing the ffmpeg process.

  My prior, more general question didn’t solve the problem : http://video.stackexchange.com/questions/14809/sync-up-ffmpeg-rawvideo-recording-and-audacity-alsa-recording

  Thanks for any advice !

  The full script :

  #!/bin/sh
  
  
  
  PIPE=/tmp/somagic-pipe
  
  OUTFILEDIR=~/easycap/Videos/
  
  LOGDIR=~/.somagic-log/
  
  NOW=`date +"%m_%d_%Y_%H_%M_%S"`
  
  
  
  OUTFILE=${OUTFILEDIR}fpv_${NOW}_video.mp4
  
  
  
  mkdir $LOGDIR
  
  
  
  FFMPEG_LOG=${LOGDIR}ffmpeg_video.log
  
  SOMAGIC_LOG=${LOGDIR}somagic_video.log
  
  MPLAYER_LOG=${LOGDIR}mplayer_video.log
  
  
  
  rm $PIPE >/dev/null 2>&1
  
  rm $OUTFILE >/dev/null 2>&1
  
  
  
  rm $FFMPEG_LOG
  
  rm $SOMAGIC_LOG
  
  rm $MPLAYER_LOG
  
  
  
  mkfifo $PIPE >/dev/null 2>&1
  
  
  
  somagic-capture --ntsc -c --luminance=2 --lum-aperture=3 \
  
  2> $SOMAGIC_LOG | ffmpeg -pixel_format uyvy422 -s:v 720x480 \
  
  -framerate 29.97 -f rawvideo -i -  -f alsa -thread_queue_size 1024 \
  
  -i hw:0,0 -vf scale=w=640:h=480 -vcodec libx264 -preset ultrafast \
  
  -shortest -c:a libfdk_aac -b:a 256k $OUTFILE
  
  
  
  rm $PIPE >/dev/null 2>&1 

  Modified from here : https://gist.github.com/Brick85/0b327ac2d3d45e23ed33

• fbdev : Support the RGB565 colour space.

  11 juillet 2013, par Dan Flett

  fbdev : Support the RGB565 colour space.
  Tested on a Raspberry Pi.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavdevice/fbdev.c

• fbdev : Support the RGB565 colour space.

  11 juillet 2013, par Dan Flett

  fbdev : Support the RGB565 colour space.
  Tested on a Raspberry Pi.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavdevice/fbdev.c