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• How to improve Desktop capture performance and quality with ffmpeg [closed]

  6 novembre 2024, par Francesco Bramato

  I'm developing a game capture feature from my Electron app. I'm working on this since a while and tried a lot of different parameters combinations, now i'm running out of ideas :)

  


  I've read tons of ffmpeg documentation, SO posts, other sites, but i'm not really a ffmpeg expert or video editing pro.

  


  This is how it works now :

  


  The app spawn an ffmpeg command based on user's settings :

  


  

  • Output format (mp4, mkv, avi)

  


  • Framerate (12, 24, 30, 60)

  


  • Codec (X264, NVidia NVENC, AMD AMF)

  


  • Bitrate (from 1000 to 10000kpbs)

  


  • Presets (for X264)

  


  • Audio output (a dshow device like StereoMix or VB-Cable) and Audio input (a dshow device like the Microphone)

  


  • Final Resolution (720p, 1080p, 2K, Original Size)

  


  


  The command executed, as far, is :

  


  ffmpeg.exe -nostats -hide_banner -hwaccel cuda -hwaccel_output_format cuda -f gdigrab -draw_mouse 0 -framerate 60 -offset_x 0 -offset_y 0 -video_size 2560x1440 -i desktop -f dshow -i audio=@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{D61FA53D-FA37-4BE7-BE2F-4005F94790BB} -ar 44100 -colorspace bt709 -color_trc bt709 -color_primaries bt709 -c:v h264_nvenc -b:v 6000k -preset slow -rc cbr -profile:v high -g 60 -acodec aac -maxrate 6000k -bufsize 12000k -pix_fmt yuv420p -f mpegts -


  


  one of the settings is the recording mode : full game session or replay buffer.
In case of full game session, the output is a file, for replay buffer is stdout.

  


  The output format is mpegts because, as far i have read in a lot of places, the video stream can be cut in any moment.

  


  Replays are cutted with different past and future duration based on game events.

  


  In full game session, the replays are cutted directly from the mpegts.

  


  In replay buffer mode, the ffmpeg stdout is redirect to the app that record the buffer (1 or 2 minutes), when the replay must be created, the app saves on the disk the buffer section according to past and future duration and with another ffmpeg command, copy it to a mp4 or mkv final file.

  


  Generally speaking, this works reliably.

  


  There are few issues :

  


  

  • nonetheless i ask ffmpeg to capture at 60fps, the final result is at 30fps (using -r 60 will speed up the final result)

  


  • some user has reported FPS drops in-game, specially when using NVidia NVENC (and having a NVIDIA GPU), using X264 seems save some FPS

  


  • colors are strange compared to original, what i see on screen, they seem washed out - i could have solved this using -colorspace bt709 -color_trc bt709 -color_primaries bt709 but don't know if is the right choice

  


  • NVIDIA NVenc with any other preset that is not slow creates videos terribly laggy

  


  


  here two examples, 60 FPS, NVIDIA NVENC (slow, 6000kbs, MP4

  


  Recorded by my app : https://www.youtube.com/watch?v=Msm62IwHdlk

  


  Recorded by OB with nearly same settings : https://youtu.be/WuHoLh26W7E

  


  Hope someone can help me

  


  Thanks !

  


• input : Add a workaround for swscale overread bugs

  22 octobre 2017, par Henrik Gramner

  input : Add a workaround for swscale overread bugs
  swscale can read past the end of the input buffer, which may result in
  
  crashes if such a read crosses a page boundary into an invalid page.
  Work around this by adding some padding space at the end of the buffer when
  
  using memory-mapped input frames. This may sometimes require copying the
  
  last frame into a new buffer on Windows since the Microsoft memory-mapping
  
  implementation has very limited capabilities compared to POSIX systems.
  

  • [DH] input/input.c
  • [DH] input/input.h

• What is ffmpeg trying to do when fps is shown gradually decreasing for a given frame ?

  30 mars 2015, par eternalthinker

  I’ve been trying to create an animated overlay over an FLV video, and trying to get the output in MP4 format. I initially used ffmpeg version 1.26. But, as the filters seem to support better options with the latest format, I compiled ffmpeg version 2.61 from source.

  Now the encoding seems to work fine, but the command stays at one point for too long, where it is seen that the fps drops to smaller values, and the ’drop’ value changes accordingly. I used the fps filter to supply fps=25 option, and now the encoding is stuck at the same point, only the drop value remains 0, while fps is shown dropping to smaller values, taking a long time as before.

  

  In the screenshot above, all values remain same, while fps keep dropping to smaller values. After 10fps, it drops by 0.1 and continues past 1, to 0.9 etc. I didn’t wait until it went down further, as the whole thing was taking too much time.

  What can I do to avoid this, and tell ffmpeg to move on with one framerate ? That is, to finish encoding after the 21.45 seconds shown here, and not try to tweak fps or whatever it is trying to do here.

  The full command I am using is this :

  ffmpeg -y -i BaseVideo.flv  -loop 1 -i 1overlay.png  -loop 1 -filter_complex '[1:v] fade=out:20:20:alpha=1:start_time=4:d=3:c=white [V2]; [0:v][V2] overlay, fps=25' -c:v libx264 -strict -2 result.mp4