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• Handbreak ffmpeg encode vs decode speed (x265)

  10 février 2023, par Demian

  I'm encoding videos in x265 to save same storage (Gopro, DJI, etc.). This is working well for me with Handbreak and I got some good CRF values for my use cases.

  


  My question is about the encoding preset. The slower it is the better Qualitiy per Bitrate you get, but the encoding time increases.

  


  But how the decoding time. Does it also consume more CPU power to watch (decode) a video which was created with a slow prestet then a fast preset ?

  


  Thank you !

  


• YouTube Live Broadcast silence detect

  12 mai 2020, par Markus

  I'm trying to monitor a YouTube live broadcast for silence to be able to restart ffmpeg broadcast. How would you achieve that without breaking the YouTube ToS ?

  



  I tried with the YouTube API, but health.status is only supported for Live streams but not for broadcast.

  



  I came up with the idea of youtube-dl, grabing the m3u8 and the run ffmpeg with silencedetect but now I'm somehow stuck.

  



  Get the formats

  



  youtube-dl --list-formats https://www.youtube.com/watch?v=BiHequcIiNw


  



  Get the m3u8 manifest

  



  youtube-dl -f 91 -g https://www.youtube.com/watch?v=BiHequcIiNw


  



  Run ffprobe

  



  ffprobe -v quiet -print_format json -show_streams https://manifest.googlevideo.com/api/manifest/hls_playlist/expire/1588936061/ei/Hem0Xp35EZLl1wLLhYaYCA/ip/2a02:1205:c6bb:4590:301f:6186:c624:f2ba/id/BiHequcIiNw.0/itag/91/source/yt_live_broadcast/requiressl/yes/ratebypass/yes/live/1/goi/160/sgoap/gir%3Dyes%3Bitag%3D139/sgovp/gir%3Dyes%3Bitag%3D160/hls_chunk_host/r3---sn-nfpnnjvh-9and.googlevideo.com/playlist_duration/30/manifest_duration/30/vprv/1/playlist_type/DVR/initcwndbps/13630/mh/GY/mm/44/mn/sn-nfpnnjvh-9and/ms/lva/mv/m/mvi/2/pl/48/dover/11/keepalive/yes/fexp/23882513/mt/1588914375/disable_polymer/true/sparams/expire,ei,ip,id,itag,source,requiressl,ratebypass,live,goi,sgoap,sgovp,playlist_duration,manifest_duration,vprv,playlist_type/sig/AOq0QJ8wRgIhALApv3H2YEE2GLTXIyRxw8Fu8espLgRThUfhi97DIS6-AiEAsT_4bwAfsihK6zsrKgaxMYTemlAr8BXnBTwuhwe3aAE%3D/lsparams/hls_chunk_host,initcwndbps,mh,mm,mn,ms,mv,mvi,pl/lsig/AG3C_xAwRQIgRG3c1ww23Jokzk6vfAfeZlhwEanWG_9GmwRip81v65cCIQDg1Y9pXWS4bUjpKpZ90c3icp4slmAzhQJPn2gqW0UOeQ%3D%3D/playlist/index.m3u8


  



  But I haven't found a difference in the json if the stream is up or down. Any hint how I could monitor the m3u8 if it's up or down ?

  


• Issue with MJPEG stream playback speed when encoding with FFmpeg

  6 janvier, par Arciiix

  I'm working with a MJPEG stream source

  


  Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 1280x720 [SAR 1:1 DAR 16:9], 25 tbr, 25 tbn

  


  I want to capture this stream and save it to an MP4 file using FFmpeg, but I am running into a weird issue.

  


  The only way it works fine is when I just copy the stream without reencoding and using wallclock as timestamps (cmd 1) :

  


  ffmpeg -use_wallclock_as_timestamps 1 -i "http://IP/video/1280x720" -c:v copy output_good.mp4


  


  However, when I try encoding the stream with libx264, the playback speed of the resulting video becomes slower than 100%, causing the video to gradually fall out of sync with real-time. This happens even when I use any encoding, also when I explicitly set the frame rate or vsync. For example, these commands fail :

  


  

  • CMD 2 : ffmpeg -i "http://IP/video/1280x720" -c:v libx264 -r 30 -preset fast output_bad1.mp4

  


  • CMD 3 : ffmpeg -use_wallclock_as_timestamps 1 -i "http://IP/video/1280x720" -c:v libx264 output.mp4

  


  


  https://www.youtube.com/watch?v=PF0fuCu7Xao

  


  As you can see in the comparison of the resulting videos, the playback gradually slows down with CMD 2 and CMD 3, while it's alright with CMD 1.

  


  What I've noticed is that on the FFmpeg stdout, when using encoding, the speed= and FPS= go up and up, e.g. to 31 FPS even though my source is technically at 25 FPS.

  


  What I've tried :

  


  

  • different encoding codecs (e.g. libvpx)

  


  • -re

  


  • preset ultrafast on encoding

  


  • vsync (fps_mode), both ctr and vfr

  


  • fps=30 filter

  


  


  Has anyone encountered a similar issue or know how to force FFmpeg to preserve the correct playback speed while encoding or enforcing a frame rate ? Thanks !