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• How do I make Ffmpeg work for subtitles in flutter ?

  19 juillet 2024, par Mohammed Bekele

  I'm trying to burn subtitles in a video. I'm going to show you the manual command I used :

  


  String newCmd =
          '-i /storage/emulated/0/ffmpeg/video.avi -vf subtitles=\'/storage/emulated/0/ffmpeg/caption.srt\':force_style=\'Fontsize=24\' /storage/emulated/0/ffmpeg/apt.mp4';
      


  


  When I use the above command it just fail, but the following code works.

  


   String newCmd =
          '-i /storage/emulated/0/ffmpeg/video.avi /storage/emulated/0/ffmpeg/apt.mp4';


  


  When I run ffmpeg on my pc this is the command

  


  ffmpeg -i F:\ffmpeg\video.avi -vf subtitles='F\:\\ffmpeg\\caption.srt':force_style='Fontsize=24' F:\ffmpeg\new.mp4


  


  So when using in subtitles we need to provide extra backslashes to the paths. So does this mean Flutter expects the same ? Or should I have to include a font file to it ?

  


  I'm using ffmpeg_kit_flutter package.

  


• ffmpeg does not respect the -t option and keeps recording [closed]

  21 juillet 2024, par Naman Muley

  The command I use is :

  


   ffmpeg -f avfoundation -framerate 30 -i "2:0" -vcodec libx264 -pix_fmt yuv420p -acodec aac -strict experimental -t 10 ./recordings/tmp.mp4


  


  With the above command, I expect the recording output to stop after 10 seconds. But the ffmpeg command keeps running and does not stop.
Feels like I am missing something basic but I have now spent 3 hours debugging and cannot figure out why.

  


  Usecase :
I need to record my screen's video as well as audio for a specifiable amount of time.

  


  According to the manual, putting -t before -i limits the input recording and putting it after -i limits the output recording. I believe after the -i is the correct way to go.

  


  Output of list devices :

  


   ffmpeg -v verbose -f avfoundation -list_devices true -i ""
ffmpeg version 7.0.1 Copyright (c) 2000-2024 the FFmpeg developers
  built with Apple clang version 15.0.0 (clang-1500.1.0.2.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/7.0.1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox
  libavutil      59.  8.100 / 59.  8.100
  libavcodec     61.  3.100 / 61.  3.100
  libavformat    61.  1.100 / 61.  1.100
  libavdevice    61.  1.100 / 61.  1.100
  libavfilter    10.  1.100 / 10.  1.100
  libswscale      8.  1.100 /  8.  1.100
  libswresample   5.  1.100 /  5.  1.100
  libpostproc    58.  1.100 / 58.  1.100
[AVFoundation indev @ 0x7fdc48f047c0] AVFoundation video devices:
[AVFoundation indev @ 0x7fdc48f047c0] [0] FaceTime HD Camera (Built-in)
[AVFoundation indev @ 0x7fdc48f047c0] [1] Screwdriver Desk View Camera
[AVFoundation indev @ 0x7fdc48f047c0] [2] Capture screen 0
[AVFoundation indev @ 0x7fdc48f047c0] [3] Capture screen 1
[AVFoundation indev @ 0x7fdc48f047c0] AVFoundation audio devices:
[AVFoundation indev @ 0x7fdc48f047c0] [0] Built-in Microphone
[AVFoundation indev @ 0x7fdc48f047c0] [1] Screwdriver Microphone
[in#0 @ 0x7fdc49904080] Error opening input: Input/output error
Error opening input file .
Error opening input files: Input/output error


  


  

  • I tried using different codecs and pix_fmt options.

  


  • Tried moving the -t before the -i option and after. no change.

  


  


  Works with only audio input :
The below command that records only the audio works out just fine.

  


  ffmpeg -f avfoundation -i ":0" -acodec libmp3lame -t 10 ./recordings/tmp.mp3


  


• ffmpeg fast seek not working for MP4 over HTTP

  27 juillet 2024, par Gmanicus

  I'm attempting to download snapshots from a video provided by the U.S House of Representatives :

  


  https://houseliveprod-f9h4cpb9dyb8gegg.a01.azurefd.net/east/2024-04-11T08-55-12_Download/video_3000000_1.mp4


  


  I am using fluent-ffmpeg in Node to execute this command :

  


  ffmpeg('https://houseliveprod-f9h4cpb9dyb8gegg.a01.azurefd.net/east/2024-04-11T08-55-12_Download/video_3000000_1.mp4')
  .inputOption(`-ss 03:33:33`)
  .outputOptions([
     '-vframes 1'
  ])
  .output('test.png')

// Effectively:
// ffmpeg -ss 03:33:33 -i  -y -vframes 1 test.png


  


  My intention is to fast-seek to the desired timestamp and take a snapshot over HTTP. However, when doing so, the performance is not great. A snapshot takes about 10s per 3hrs of video and seems to increase fairly linearly at that rate.

  


  However, when using ffmpeg on the same video locally, it's super fast ! Sub-500ms regardless of the desired timestamp.

  


  Is there some magic that could be done via ffmpeg options or perhaps some sort of technique with manual requests to get a snapshot at the desired segment of video more efficiently ?