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• Trim / Cut video on Android using FFMpeg's Copy

  6 août 2012, par Kevin P

  We're trying to replicate the functionality of this command line ffmpeg directive using the FFMpeg c api through JNI calls on Android.

  ffmpeg -ss 2 -t 120 -vcodec copy -acodec copy -i input.file output.file

  Basically, given a start and end time, we wish to copy (not re-encode) a small(er) segment of video from the larger (input) video source.

  We've been using the wonderful JavaCv wrapper to openCv and FFMpeg, but we just cannot figure out how to do this simple bit of work. We've been scouring the ffmpeg.c and related sources and while I now understand that it switches to stream_copy and remuxing rather than re-encoding when the codec is specified as copy I cannot for the life of me identify what series of method calls to make to replicate this through the C api. Does anyone have an example JNI file for doing this ? Or are there rockstar C types that can explain how I get from that command line to api calls ? We've spent the better part of two weeks working on this (we're not native C guys) and we're at the point where we just need to ship some code. Any example code, especially JNI code or method call maps etc. would be greatly appreciated !

• avdevice/decklink_enc : Add support for compressed AC-3 output over SDI

  7 avril 2023, par Devin Heitmueller

  avdevice/decklink_enc : Add support for compressed AC-3 output over SDI
  Extend the decklink output to include support for compressed AC-3,
  
  encapsulated using the SMPTE ST 377:2015 standard.
  This functionality can be exercised by using the "copy" codec when
  
  the input audio stream is AC-3.  For example :
  ./ffmpeg -i /foo.ts -codec:a copy -f decklink 'UltraStudio Mini Monitor'
  Note that the default behavior continues to be to do PCM output,
  
  which means without specifying the copy codec a stream containing
  
  AC-3 will be decoded and downmixed to stereo audio before output.
  Thanks to Marton Balint for providing feedback.
  Signed-off-by : Devin Heitmueller <dheitmueller@ltnglobal.com>
  
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavdevice/decklink_enc.cpp

• Can't maintain desired fps with ffmpeg live stream when overlay is added

  1er avril 2019, par jawsware

  I’m attempting to produce a 4K live stream for YouTube.

  I’m capturing 2160p30 frames from a BlackMagic Design DeckLink Mini Recorder. I’m passing those frames to ffmpeg in their raw 8-bit 4:2:2 format. I’m able to achieve 30 fps encoding ( 16kbits/s and q= in the high 20s to low 30s) with my current parameters which are :

  ffmpeg -threads:v 2 -threads:a 8 -filter_threads 2
  
  -f rawvideo -framerate 30 -pixel_format uyvy422 -video_size 3840x2160 -i \\.\pipe\videopipe
  
  -f s16le -ac 2 -ar 44100 -i \\.\pipe\audiopipe
  
  -r 30 -g 60 -c:v h264_nvenc -pix_fmt yuv420p -preset fast -profile main
  
  -b:v 16000K -maxrate 24000k -bufsize 6000k
  
  -f flv "rtmp://a.rtmp.youtube.com/live2/xxxx-xxxx-xxxx-xxxx"

  I’m dilemma is that once I introduce an overlay graphic, my encoding fps drops to 28 at best. Which leads me to believe I’m barley achieving the 30 fps without the overlay. I’m only adding these parameters to include the overlay :

  -i logo.png
  
  
  
  -filter_complex "overlay=100:100"

  I further diminish the encoding fps (20 fps max) when I introduce a dynamic overlay which I feed to ffmpeg through an additional pipe.

  My questions are 1.) is there a better set a parameters I could be using to encode the 4K stream ? 2.) is there a better way to include the overlay ?