Recherche avancée

Sur d’autres sites (5725)

• Decoding of 4k video causing overflow of buffer in a multi process application

  15 octobre 2016, par mkreddy

  I am quite new in working with FFMPEG. Please excuse me if I made any mistake while explaining my problem.

  I am working on an application where PCAP captures 1316 bytes of data split that into 188 bytes and writes it into it to corresponding shared memory. The other process reads the data and decode using ffmpeg and process it.

  This whole process is working fine with H264 and HEVC video.
  The problem comes with 4k video. While decodig the 4k video I am encountering buffer overflow.
  I have observed that on a machine with high CPU frequence the overflow rate was less. Hence If I can reduce the time taken to decode and process the video data at ffmpeg might solve my problem. I am not able to find a good solution for my problem.

  Is there any way to speed up the process at ffmpeg decoder ?, is thre any other way to supress the overflows ?

• ffmpeg -vg -filtercomplex, create gif with color kway and limited fps

  3 février 2020, par daniel

  I need to create a gif file with color key (greenscreen) with 10FPS and specified size. I try to combine -vg and -filter_complex :

  ffmpeg -i testdatei-c.avi -vf "fps=10,scale=320:-1:flags=lanczos" -filter_complex "[0:v]chromakey=0xFFFFFF,split[v0][v1];[v0]palettegen[p];[v1][p]paletteuse" output.gif

  I get the error :

  Filtergraph 'fps=10,scale=320:-1:flags=lanczos' was specified through the -vf/-af/-filter option for output stream 0:0, which is fed from a complex filtergraph.
  
  -vf/-af/-filter and -filter_complex cannot be used together for the same stream.

• Color spot in FFmpeg output

  2 juin 2022, par Fabian Garcia

  I work in a company that serves multimedia content to different clients and one of these requests that the videos contain the following specifications :

  


  

  • Codec : H264 High@4.0

  


  • Mode : CBR 1 pass

  


  • Window Buffer : 5 secs

  


  • Frame Rate : 29.97/23.97

  


  • Key Frame Interval : 2 secs

  


  • Bitrate : 4000 Kbps

  


  • Size : 1920x1080

  


  • Window Buffer : 5 secs

  


  • GOP : closed

  


  • GOP size : fixed (no scene change detection)

  


  • Window Buffer : 5 secs

  


  • B Frames : As needed

  


  


  For the above, i build following script :

  


  ffmpeg -hide_banner -nostats -loglevel error -y
-init_hw_device cuda=cuda -hwaccel cuda -hwaccel_device cuda
-i 'video_source.mxf' -filter_hw_device cuda
-filter_complex '[0:v]format=nv12,hwupload,yadif_cuda,scale_cuda=1920:1080[v0]'
-map '[v0]' -c:v h264_nvenc -rc cbr -b:v 4M -bufsize 8M -x264-params "keyint=60:min-keyint=48:no-scenecut" -r '30000/1001' -profile:v high -level:v 4
-map 0:1 -c:a libfdk_aac -b:a 96k -ar 44100 -ac 2 -sample_fmt s16
'output.mp4'


  


  The inconvenience is that the generated output presents some color spots in the scene changes (it's a fade) as can be seen in the attached image.

  


  I could notice that in the output video, the time does not match the input precisely, the output is a few milliseconds ahead, I think that the color spot corresponds to the image that should be shown at that moment in the original video.

  


  Can you see something wrong in script ? Or maybe some concept that i don't know is causing a conflict with the output (This is my first time using ffmpeg).

  


  Thank for your help !