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• converting a "gif" to video using swift

  3 décembre 2019, par James Woodrow

  I’ve looked around and found a few things here and there, mainly that I should be using AVAssetWriter to do this but I have 0 experience with this and video editing/creation so it doesn’t help me much since I can’t seem to find anything that does something I can modify easily (or not at my level of knowledge at least) so that it works as I intend it to.

  I have an app which takes n photos every cft (capture frame time which I get from a backend server) seconds (it’s a double for obvious reasons) I then display these frames using a UIImageView and the frames change every dft (display frame time which I also get from a backend server and can be different from cft). Up until this point nothing complicated.

  now what is currently the workflow is that these frames are sent back to a server with any relevant information I want and then the server would use imagemagick to create a real gif file and ffmpeg to create a 15 seconds video using said gif.

  the issue is this makes it so that my heroku server bills aren’t as low as I would like because of the limited memory on the dynos and the time it takes to generate these videos is of about 5-10 seconds I believe (not sure but it’s longer than I’d like)

  So the idea I had was to make the app create the video since he already has all the information he needs for this, and then simply upload it with the rest of the frames and relevant data. Using bandwidth nowadays is much cheaper than buying extra processing power on a server.

  • he has n frames to loop over
  • he has a float value representing how long each frame should last dft
  • he has a gpu or at least a much better cpu than the dynos heroku have to offer

  I’ve also looked around to see if anyone made an extensive tutorial on how to use ffmpeg in swift but I still didn’t find anything at my level and I didn’t even find a tutorial per se, only some GitHub projects which were partially completed and/or without the original tutorial linked to understand the thought process.

  I would appreciate any tips/code sample/tutorials on the subject.

  I’m adding the ffmpeg command line equivalent to what I would love to be able to do (if I could use ffmpeg directly with iOS this could be nice too)

  ffmpeg -framerate 100/13 -loop 1 -i frame%02d.png -c:v libx264 -r 100/13 -pix_fmt yuv420p -t 0:15 instagram.mp4

  where basically I did 100 / (dft * 100) for the input frame rate and just output at the same fps for 15 seconds. by the way if there are any ways to optimise this command to make it run faster without losing quality I might be able to keep the current way of functioning with heroku although I would still prefer some iOS solution.

• SegmentedIndexBox (SIDX) not generated when using WEBM over DASH

  11 juillet 2014, par Flock Dawson

  I’m trying to get the Industry Format DASH player to work with WEBM audio/video files. However, I’m running in the same error again and again, and Google doesn’t seem to give much help.

  To start with, I created different streams of the same file (different resolutions and bitrates) using this tutorial : https://developer.mozilla.org/en-US/docs/Web/HTML/DASH_Adaptive_Streaming_for_HTML_5_Video

  Then, I downloaded the Industry Format DASH player (http://dashif.org/software/) and pointed it to the DASH manifest I created. When I try to play the video in Chrome, I get the following log :

  Parsing complete: ( xml2json: 3ms, objectiron: 2ms, total: 0.005s) dash.all.js:3
  
  Manifest has loaded. dash.all.js:3
  
  MediaSource is open! dash.all.js:3
  
  Event {clipboardData: undefined, path: NodeList[0], cancelBubble: false, returnValue: true, srcElement: MediaSource…}
  
  dash.all.js:3
  
  Video codec: video/webm;codecs="vp8" dash.all.js:3
  
  No text tracks. dash.all.js:3
  
  Audio codec: audio/webm;codecs="vorbis" dash.all.js:3
  
  Duration successfully set to: 27.2 dash.all.js:3
  
  Perform SIDX load: https://*****/street_orig_125k_final.webm dash.all.js:3
  
  Perform SIDX load: https://*****/street_audio_final.webm dash.all.js:3
  
  Uncaught RangeError: Offset is outside the bounds of the DataView 

  From this log, I distilled that the manifest is fetched and processed correctly, but something goes wrong when trying to process the SIDX (SegmetIndexBox). I tried another (third-party) source, which works perfectly. I analysed the response returned by the server when trying to fetch the SIDX, and when converted to a readable presentation, the text ’Dsidx’ can be found in this response. So, I analyzed the WEBM file I provide (hexdump and grep), but I cannot find such a SIDX. My conclusion is that the SIDX is never added to the WEBM file.

  From the tutorial I used, I guess the generation of the SIDX is handled by the samplemuxer command, which does not offer any additional parameters. Is there anyone who has more experience in generating this SIDX ?

• batch file FOR %%f IN (*) DO

  13 juin 2017, par RyanMe321

  I’ve created a script based of this example however I don’t understand how to correctly implement the FOR %%f IN (*.mkv) DO (MY SCRIPT) component as when i do and replace video.mkv with "%%f" (contains the full file name and format ?) "%%~nf" (only the file name ?) in the same way the example code does it doesn’t seem to work. However when run on a test file called "video.mkv" works perfectly.

  ::ID FILE
  
  for /F "delims=" %%I in ('C:\ffmpeg\bin\ffprobe.exe -v error -show_entries format^=filename -of default^=noprint_wrappers^=1:nokey^=1 video.mkv') do set "FILENAME=%%I"
  
  
  
  for /F "delims=" %%I in ('C:\ffmpeg\bin\ffprobe.exe -v error -select_streams v:0 -show_entries stream^=codec_name -of default^=noprint_wrappers^=1:nokey^=1 video.mkv') do set "Vcodec=%%I"
  
  
  
  for /F "delims=" %%I in ('C:\ffmpeg\bin\ffprobe.exe -v error -select_streams a:0 -show_entries stream^=codec_name -of default^=noprint_wrappers^=1:nokey^=1 video.mkv') do set "Acodec=%%I"
  
  
  
  echo %FILENAME% is using %Vcodec% and %Acodec% codecs
  
  
  
  if %Vcodec% == h264 (echo DO NOT CONVERT VIDEO) else (echo CONVERT VIDEO) 
  
  if %Acodec% == ac3 (echo DO NOT CONVERT AUDIO) else (echo CONVERT AUDIO)
  
  timeout /t 5
  
  
  
  :: COPY V FIX A
  
  if %Vcodec% == h264 if not %Acodec% == ac3 (echo Copying Video, Converting Audio
  
  timeout /t 5
  
  C:\ffmpeg\bin\ffmpeg.exe -i video.mkv -map 0 -vcodec copy -scodec copy -acodec ac3 -b:a 640K video-AC3.mkv)
  
  
  
  :: FIX V COPY A
  
  if not %Vcodec% == h264 if  %Acodec% == ac3 (echo Converting Video, Copying Audio
  
  timeout /t 5
  
  C:\ffmpeg\bin\ffmpeg.exe -i video.mkv -map 0 -vcodec libx264 -scodec copy -acodec copy video-h264.mkv)
  
  
  
  :: FIX V FIX A
  
  if not %Vcodec% == h264 if not %Acodec% == ac3 (echo Converting Video, Converting Audio
  
  timeout /t 5
  
  C:\ffmpeg\bin\ffmpeg.exe -i video.mkv -map 0 -vcodec libx264 -scodec copy -acodec ac3 -b:a 640K video-h264-AC3.mkv)
  
  
  
  :: COPY V COPY A
  
  if %Vcodec% == h264 if %Acodec% == ac3 (echo "Doesn't require any Conversion")
  
  
  
  pause

  I’ve limited programming experience and have come up short trying to find what is wrong with using this implementation of FOR %%f IN of what to search to get me to an answer.

  Also I’d be interested if there is a way to recognise a list of file types i.e. *.mp4 and *.mkv and *.avi etc not just MKV to be processed.