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• 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 ?

• 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

• ffmpeg Concatention - negative pad values

  15 décembre 2015, par mmmyum

  I’m relatively new to ffmpeg and having an issue concatenating some videos.

  Occasionally, I’m running into an issue with my command that is producing negative pad values, preventing the concat from completing. Check out this gist for details and the command output.

  Brief summary is that I’m using filter_complex to scale down and/or pad videos. You can see the full commands in the above links, but here are examples of the filter text :

  [$count:v]scale=if(gt(ih\,iw)\,-2\,$VID_WIDTH):if(gt(ih\,iw)\,$VID_HEIGHT\,-2),pad=$VID_WIDTH:$VID_HEIGHT:(ow-iw)/2:(oh-ih)/2,setsar=sar=1/1[v$count];

  where $VID_WIDTH and $VID_HEIGHT are the smallest dimensions of the inputs.

  I’m concatenating hundreds of videos (in different groups), the vast majority of which work without issue - but occasionally I run into this negative pad values issue. I assume it’s because the input width/height is larger than the output width/height, so it produces a negative value, but I’m not sure how to fix this - I need the videos to be centered.

  Other details :

  • most videos are shot on a cell phone, in a portrait orientation (some in landscape, but I’d like to stitch them in portrait anyways)

  • very rarely I run into a video rotated 90 degrees (larger width than height) - not sure how I should handle this, but one issue at a time

  • usually all videos have the same dimensions, but occasionally one or more videos in a group will have slightly different dimensions, sometimes just by a couple pixels (see attached gist for example)

  • scripting everything in bash right now