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• Correct way of recutting HLS playlist with FFMPEG

  4 juillet 2020, par somerandomusername

  I'm recording a stream on my server and after it finished I need to trim x seconds from the beginning of my video. My stream has master.m3u8 playlist and then 3 sub index_[0|1|2].m3u8 playlists.

  


  I'm trying different methods, they all seem to generate a result, but nothing as I expect.

  


  For example this :

  


  


  ffmpeg -i index_0.m3u8 -ss 30 -strict -2 -hls_time 6 output_0.m3u

  


  


  Seems to generate the correct nr. of *.ts files, but playlist is is only 30s long. Original #EXT-X-TARGETDURATION was set to 6, now it is 8, but actual size is a floating 8.3333...

  


  I'm definitely missing something.

  


  Update 1 :

  


  OK, so I figured out why my *.m3u8 file was to small, by default it only loads last few records in the list so setting -hls_list_size 0 resolved that. Now I need to figure out how to get rid of floating point video sizes.

  


  Update 2 :

  


  It seems that I need -hls_flags split_by_time flag for HLS transmuxer not to ignore my hls_time option. Now my output is even closer to correct result, still have that floating point video size problem.

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:6
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:5.933333,
output_clip0.ts
#EXTINF:6.033333,
output_clip1.ts
#EXTINF:5.933333,
output_clip2.ts
#EXTINF:6.000000,
output_clip3.ts
#EXTINF:3.000000,
output_clip3.ts
#EXT-X-ENDLIST


  


• What is a correct way of ffmpeg dshow webcamera properties save and load ?

  12 juin 2020, par C0oo1D

  Command (PS == Windows PowerShell) :

  



  PS D:\> ffmpeg -f dshow -show_video_device_dialog True -video_device_save some_profile.txt -i 'video=MicrosoftR LifeCam Studio(TM)'


  



  FFmpeg Header :

  



  ffmpeg version git-2020-06-04-7f81785 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200523
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 49.100 / 56. 49.100
  libavcodec     58. 90.100 / 58. 90.100
  libavformat    58. 44.100 / 58. 44.100
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 84.100 /  7. 84.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100


  



  Error after OK/Cancel/Close in camera settings dialog (empty file was created). Also tried without dialog - the same problem :

  



  [dshow @ 0715de40] Query for IPersistStream failed.
video=Microsoft® LifeCam Studio(TM): I/O error


  



  I assume that problem at the camera side, but I don't exclude my blindness (didn’t find any examples of saving settings or required command options in the documentation).

  



  Perhaps there is another way to save / load webcamera properties ?

  


• Cutting HEVC video results in parts stating with no video (black image) but correct audio for a few seconds

  8 juin 2020, par Oliver

  i have large HEVC video files and want to cut out parts of them. I use ffmpeg for that with the following command :

  



  ffmpeg -i input.mp4 -ss 01:18:47.040 -c:v copy -c:a copy -to 01:18:42.640 output.mp4


  



  i know that there can be problems when copy is used and no re-encoding, that is why i checked before that the frames specified in the -ss and -to parameters where keyframes (i-frames).

  



  So iam expecting to get a clean cut at the beginning and at the end. But what i get is 10 seconds of black image with normal audio in the beginning until the video starts. To make this clear : 10 seconds of video are missing in the beginning but the audio is fine.

  



  Btw : when moving the -ss part before the -i there seem to be no problems with the video (at least in the beginning). I know about the differences of putting -ss before and after the -i, but i also know, that using -ss after the -i should be slower (and was more accurate in the past) but should not make any differences in the final result. That is why I am so irritated.