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• How to use sexagesimal syntax in arguments of FFmpeg or if impossible how to convert it in Windows CMD shell

  6 décembre 2020, par Link-akro

  Question updated 2020-12-06 to enlarge the scope without discarding the prior answer which applies to both prior and larger cases.

  


  I had trouble to provide a sexagesimal time (HH:MM:SS.mm) to a filter option that was not an expression. For instance trim filter.
It happens there is an escaping rule i did not know yet when i first asked, and was addressed in the first comment by @Gyan.

  


  The problem is universal, but the solution may depend on the shell if we go the scripting route... and i am currently stuck with Windows's CMD.exe.

  


  For instance the following skips one minute and 4 tenths of seconds in all streams as accurately as it can seek each, then invokes the trim filter to keep the segment between one and two minutes of the remaining duration, and do so with two different syntaxes. This example happens to be compatible with both CMD and BASH shells so no escaping hell.

  


  ffmpeg -ss "1:00.4" -i INPUT -vf "trim=start='1\:00':end='120'" OUTPUT


  


  Then how do we achieve the same in the expressions within the filters ?
If we cannot avoid using the scripting of the shell, i am looking for a Windows CMD solution.
I had posted one answer with a piece of script to convert a textual sexagesimal time to a textual decimal fractional time in seconds, which was not useful for the original case, but may apply to more generic cases and in particular to the expressions.

  


  Example of failed attempt with one expression in the select filter.

  


  ffmpeg -ss "1:00.4" -i INPUT -vf "select='between(t,1\:00',120)'" OUTPUT


  


  The sexagesimal notation seems to not be supported by ffmpeg filter expressions as i found no reference of it in the documentation nor in SO/web.

  


  I browsed through the list of functions defined in ffmpeg expression library but did not find any way to parse the sexagesimal input there yet, nor any way to use text in its semantics.

  


  However i found some unrelated example that hard-coded some arithmetical expression to provide the numerical decimal amount of seconds equivalent to what was intended, such as 2*60+2 to mean 2:02.

  


  The polynome used above to compute seconds may use preprocessing of shell variable, whichever shell it is, but we need to parse the components of HH:MM:SS.mm to put them in those variable first. You know, using bash $var or cmd %var%/%~1 styles. Otherwise we may compute the polynome completely in the shell instead of the expression but it is so much trouble for little gain.

  


  So while CMD still exists like an undead and becomes really dead , and while i do not have the opportunity yet to replace it, i wish for an answer that either :

  


  

  • does not need the shell/script at all, OR

  


  • provide a solution in Windows CMD, although relying on it as little as possible.

  


  


  Reminder and clarification, the use case assumes that we are given a textual sexagesimal time as input and intend to use it in an expression of ffmpeg filter with as little shell dependency as possible or otherwise satisfy Windows CMD.

  


• Merge Audio and Video on Uno Platform

  27 mars 2021, par trungnt2910

  I am trying to merge an audio stream and a video stream into a single file, on the Uno Platform, particularly for WebAssembly.
  
I already know that the normal, desktop-only way is by calling ffmpeg, and I also found a C# only way for UWP here.
  
However, the code used Windows.Media.Editing which is not implemented in Uno.
  
I know there is a ffmpeg library port for WASM here, but I don't know how to call it from my Uno web application.

  


  So are there any ways to merge an audio stream and a video stream to a single file, on the Uno platform for WASM ?

  


• HTML5 Video Compatibility (MP4, WEBM, OGG) in 2021

  19 juillet 2021, par William

  The support of HTML5 video has evolved a lot over the years. I am trying to understand whether the <video></video> element still needs to have three sources : MP4, WEBM, and OGG.

  


  There are a lot of answers throughout StackOverflow with deeply conflicting information - some of which say that you just need MP4 now, others say, MP4 and WEBM are enough, and then finally many say that you need all three (although many of those article are 10 years old).

  


  W3 suggests that either MP4 or WEBM alone would have universal support (Even though I found a 2011 article from Google saying that they would be removing support for MP4/H.264). Wikipedia paints a more complicated picture (as well as listing that Google Chrome does indeed support MP4/H.264). Azure Media services ONLY seems to allow output in MP4, which would suggest to me that MP4 must have widespread compatibility.

  


  Also see Example 1, Example 2, Example 3.

  


  Is there any definitive information on what video types to include in an HTML5 video player to achieve widespread compatibility ?

  


  Background : I am building a Content Management Platform that allows uploading videos. When a new video is uploaded, a conversion process kicks off to convert the video into the required formats. This takes time and CPU/Memory, so if it is possible I would like to convert uploaded videos into as few formats as possible.

  


  p.s. This question HAS been asked before, however, the fundamentals of playing video on the web continually evolve and most of the answers out there have become irrelevant.