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• FFmpeg : negative video duration

  19 octobre 2020, par quento

  FFmpeg is used to combine images into video and then duration is taken out of this video.

  


  Surprisingly I found out that FFmpeg could return negative duration.

  


  Command to get duration. This command is the most reliable according to this spec

  


  


  You can also use ffmpeg to get the duration by fully decoding the file. The null muxer is used so no output file is created. Refer to time= in the next-to-last line of the console output. In this example the input has a duration of 00:57:28.87.

  


  


  ffmpeg -i input.webm -f null -  


  


  Output ex :

  


  frame=206723 fps=1390 q=-0.0 Lsize=N/A time=00:57:28.87 bitrate=N/A speed=23.2x


  


  Actual example

  


  Generation of mp4 of screenshots :

  


  `/usr/bin/ffmpeg' -framerate 30 -pattern_type glob -i '/app/tmp/ecc0fe7b5ca4d7b20ea54d3ba757cfbf_b4581272-c485-4be2-a210-cbc99d71bd14_0/*.jpeg' -c:v libx264 -vf 'scale=trunc(iw/2)*2:trunc(ih/2)*2' -pix_fmt yuv420p -filter:v 'setpts=1.11*PTS' '/app/tmp/ecc0fe7b5ca4d7b20ea54d3ba757cfbf_b4581272-c485-4be2-a210-cbc99d71bd14_0/ecc0fe7b5ca4d7b20ea54d3ba757cfbf.mp4`


  


  Next, extracting duration :

  


  /usr/bin/ffmpeg' -i '/app/tmp/ecc0fe7b5ca4d7b20ea54d3ba757cfbf_b4581272-c485-4be2-a210-cbc99d71bd14_0/ecc0fe7b5ca4d7b20ea54d3ba757cfbf.mp4  -f null


  


  Output :

  


  time=-577014:32:22.77


  


  Unfortunately I can't reproduce this issue on local machine so far, so there are not many details to share. However, such cases appear on other machines quite frequently. Different videos get exactly the same broken time. There are also enough other inconsistent cases.

  


  One of the suggestions is to parse extraction out of first command, which generates video. I'm not sure that I won't also face negative numbers there, though.

  


  Most probably I miss much more easier solution. The only requirement is that is must be 100% precise.

  


  Thanks in advance !

  


• WebRTC predictions for 2016

  17 février 2016, par silvia

  I wrote these predictions in the first week of January and meant to publish them as encouragement to think about where WebRTC still needs some work. I’d like to be able to compare the state of WebRTC in the browser a year from now. Therefore, without further ado, here are my thoughts.

  WebRTC Browser support

  I’m quite optimistic when it comes to browser support for WebRTC. We have seen Edge bring in initial support last year and Apple looking to hire engineers to implement WebRTC. My prediction is that we will see the following developments in 2016 :

  • Edge will become interoperable with Chrome and Firefox, i.e. it will publish VP8/VP9 and H.264/H.265 support
  • Firefox of course continues to support both VP8/VP9 and H.264/H.265
  • Chrome will follow the spec and implement H.264/H.265 support (to add to their already existing VP8/VP9 support)
  • Safari will enter the WebRTC space but only with H.264/H.265 support

  Codec Observations

  With Edge and Safari entering the WebRTC space, there will be a larger focus on H.264/H.265. It will help with creating interoperability between the browsers.

  However, since there are so many flavours of H.264/H.265, I expect that when different browsers are used at different endpoints, we will get poor quality video calls because of having to negotiate a common denominator. Certainly, baseline will work interoperably, but better encoding quality and lower bandwidth will only be achieved if all endpoints use the same browser.

  Thus, we will get to the funny situation where we buy ourselves interoperability at the cost of video quality and bandwidth. I’d call that a “degree of interoperability” and not the best possible outcome.

  I’m going to go out on a limb and say that at this stage, Google is going to consider strongly to improve the case of VP8/VP9 by improving its bandwidth adaptability : I think they will buy themselves some SVC capability and make VP9 the best quality codec for live video conferencing. Thus, when Safari eventually follows the standard and also implements VP8/VP9 support, the interoperability win of H.264/H.265 will become only temporary overshadowed by a vastly better video quality when using VP9.

  The Enterprise Boundary

  Like all video conferencing technology, WebRTC is having a hard time dealing with the corporate boundary : firewalls and proxies get in the way of setting up video connections from within an enterprise to people outside.

  The telco world has come up with the concept of SBCs (session border controller). SBCs come packed with functionality to deal with security, signalling protocol translation, Quality of Service policing, regulatory requirements, statistics, billing, and even media service like transcoding.

  SBCs are a total overkill for a world where a large number of Web applications simply want to add a WebRTC feature – probably mostly to provide a video or audio customer support service, but it could be a live training session with call-in, or an interest group conference all.

  We cannot install a custom SBC solution for every WebRTC service provider in every enterprise. That’s like saying we need a custom Web proxy for every Web server. It doesn’t scale.

  Cloud services thrive on their ability to sell directly to an individual in an organisation on their credit card without that individual having to ask their IT department to put special rules in place. WebRTC will not make progress in the corporate environment unless this is fixed.

  We need a solution that allows all WebRTC services to get through an enterprise firewall and enterprise proxy. I think the WebRTC standards have done pretty well with firewalls and connecting to a TURN server on port 443 will do the trick most of the time. But enterprise proxies are the next frontier.

  What it takes is some kind of media packet forwarding service that sits on the firewall or in a proxy and allows WebRTC media packets through – maybe with some configuration that is necessary in the browsers or the Web app to add this service as another type of TURN server.

  I don’t have a full understanding of the problems involved, but I think such a solution is vital before WebRTC can go mainstream. I expect that this year we will see some clever people coming up with a solution for this and a new type of product will be born and rolled out to enterprises around the world.

  Summary

  So these are my predictions. In summary, they address the key areas where I think WebRTC still has to make progress : interoperability between browsers, video quality at low bitrates, and the enterprise boundary. I’m really curious to see where we stand with these a year from now.

  —

  It’s worth mentioning Philipp Hancke’s tweet reply to my post :

  https://datatracker.ietf.org/doc/draft-ietf-rtcweb-return/ … — we saw some clever people come up with a solution already. Now it needs to be implemented

  The post WebRTC predictions for 2016 first appeared on ginger’s thoughts.

• Museum of Multimedia Software, Part 1

  14 août 2010, par Multimedia Mike — Software Museum

  Many years ago, I found a boneyard of old software, much of it related to the creation and processing of multimedia. I was permitted to liberate anything of my choosing from this cache. This is the same pile where I found this Apple QuickTime format spec as well as this perfect form factor floppy disc box. So I have been sitting on the stuff for awhile.

  I thought I might get the chance to study it a bit more closely one day. But now I’m interested in getting rid of it. Before I do, it’s more or less traditional for me to photograph it and post it on one blog or another. Also, if you know of any software collection groups who would be interested in taking this stuff off my hands, do let me know.

  As usual, click a picture for a much larger image.

  Paracomp FilmMaker
  This is easily the most distinctive piece in this collection and it’s easy to see why— the software is packaged in a film cannister. Still sealed, and I don’t have a good reason to open it now.

  
  
  

  "The Professional Animation/Presentation Program for the Macintosh." No copyright date on the packaging, though the front does mention a 1990 award. System requirements : Mac OS 6.0.5, 5 MB RAM, 32-bit QuickDraw, math coprocessor.

  Strata VideoShop
  Version 4.5 (and not for resale), still shrink-wrapped. "The Digital Video Editor for Creative Professionals."

  
  
  

  System requirements : PowerMac with 5 MB RAM (8 MB recommended), Mac OS 7.5.

  BeatWare e-Picture
  "The Professional’s Choice for Designing Animated Web Graphics." Claims a best of show award for 1999 MacWorld New York Expo.

  
  
  

  System requirements : PowerMac with Mac OS 8, 32MB RAM, 10 MB of HD space and a 256-color adapter.

  BeatWare eZ-Motion
  Another offering from BeatWare. "The fastest and easiest way to create animations and graphics for the Web."

  
  
  

  This one is for either Mac or Windows. 32 MB RAM and 25 MB HD space required. Works with Mac OS 8.5, 8.6, or 9.0, or Windows 98, NT, or 2000.

  Much more to come...