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• How to contribute to open source, for companies

  18 octobre 2010, par Dark Shikari — development, open source, x264

  I have seen many nigh-incomprehensible attempts by companies to contribute to open source projects, including x264. Developers are often simply boggled, wondering why the companies seem incapable of proper communication. The companies assume the developers are being unreceptive, while the developers assume the companies are being incompetent, idiotic, or malicious. Most of this seems to boil down to a basic lack of understanding of how open source works, resulting in a wide variety of misunderstandings. Accordingly, this post will cover the dos and don’ts of corporate contribution to open source.

  Do : contact the project using their preferred medium of communication.

  Most open source projects use public methods of communication, such as mailing lists and IRC. It’s not the end of the world if you mistakenly make contact with the wrong people or via the wrong medium, but be prepared to switch to the correct one once informed ! You may not be experienced using whatever form of communication the project uses, but if you refuse to communicate through proper channels, they will likely not be as inclined to assist you. Larger open source projects are often much like companies in that they have different parts to their organization with different roles. Don’t assume that everyone is a major developer !

  If you don’t know what to do, a good bet is often to just ask someone.

  Don’t : contact only one person.

  Open source projects are a communal effort. Major contributions are looked over by multiple developers and are often discussed by the community as a whole. Yet many companies tend to contact only a single person in lieu of dealing with the project proper. This has many flaws : to begin with, it forces a single developer (who isn’t paid by you) to act as your liaison, adding yet another layer between what you want and the people you want to talk to. Contribution to open source projects should not be a game of telephone.

  Of course, there are exceptions to this : sometimes a single developer is in charge of the entirety of some particular aspect of a project that you intend to contribute to, in which case this might not be so bad.

  Do : make clear exactly what it is you are contributing.

  Are you contributing code ? Development resources ? Money ? API documentation ? Make it as clear as possible, from the start ! How developers react, which developers get involved, and their expectations will depend heavily on what they think you are providing. Make sure their expectations match reality. Great confusion can result when they do not.

  This also applies in the reverse — if there’s something you need from the project, such as support or assistance with development of your patch, make that explicitly clear.

  Don’t : code dump.

  Code does not have intrinsic value : it is only useful as part of a working, living project. Most projects react very negatively to large “dumps” of code without associated human resources. That is, they expect you to work with them to finalize the code until it is ready to be committed. Of course, it’s better to work with the project from the start : this avoids the situation of writing 50,000 lines of code independently and then finding that half of it needs to be rewritten. Or, worse, writing an enormous amount of code only to find it completely unnecessary.

  Of course, the reverse option — keeping such code to yourself — is often even more costly, as it forces you to maintain the code instead of the official developers.

  Do : ignore trolls.

  As mentioned above, many projects use public communication methods — which, of course, allow anyone to communicate, by nature of being public. Not everyone on a project’s IRC or mailing list is necessarily qualified to officially represent the project. It is not too uncommon for a prospective corporate contributor to be turned off by the uninviting words of someone who isn’t even involved in the project due to assuming that they were. Make sure you’re dealing with the right people before making conclusions.

  Don’t : disappear.

  If you are going to try to be involved in a project, you need to stay in contact. We’ve had all too many companies who simply disappear after the initial introduction. Some tell us that we’ll need an NDA, then never provide it or send status updates. You may know why you’re not in contact — political issues at the company, product launch crunches, a nice vacation to the Bahamas — but we don’t ! If you disappear, we will assume that you gave up.

  Above all, don’t assume that being at a large successful company makes you immune to these problems. If anything, these problems seem to be the most common at the largest companies. I didn’t name any names in this post, but practically every single one of these rules has been violated at some point by companies looking to contribute to x264. In the larger scale of open source, these problems happen constantly. Don’t fall into the same traps that many other companies have.

  If you’re an open source developer reading this post, remember it next time you see a company acting seemingly nonsensically in an attempt to contribute : it’s quite possible they just don’t know what to do. And just because they’re doing it wrong doesn’t mean that it isn’t your responsibility to try to help them do it right.

• Switching between multiple m3u8 playlist

  25 janvier 2018, par formatkaka

  In a live stream setup, I have 2 cameras and each one sends RTMP stream to one different application which is on my Nginx-RTMP server. On the browser I am using Videojs Hls plugin.

  Now my question is how can I load these two streams one after another in the same hlsplayer player instance. For example, I want to load the first 15 seconds in my first source and the next 15 seconds from my second source in the same player. Since the .ts files are named incrementally and if I have 5sec chunks of .ts files in each .m3u8 file, I want to load the first 3 .ts files to be loaded from the first source(.m3u8 file) and the next 3 from another source(.m3u8 file). How can I achieve that ?

  Can I generate some kind of master M3U8 file which has the list of these other .M3U8 files or can I develop a plugin in videojs to load the appropriate ts files directly ?

  source1.m3u8
  1.ts
  2.ts
  3.ts

  source2.m3u8
  1.ts
  2.ts
  3.ts

  I want to load 1.ts from source1.m3u8 and 2.ts from source2.m3u8 but with no delay or lag.

• ffmper with vlc - too heavy screen grabbing, resulting injumpy file, frame loss

  15 mai 2016, par OGP

  I’m using ’vlc/ffmpeg’ package to grab the screen and convert it to H.264 file.

  The problem arises when the host is heavily loaded. I need to maintain correct time stamps and use the 5 fps (relatively low frame rate). Yet sometimes the resulting file jumps few seconds forward, apparently due to frame loss.
  I can deal with the frame loss, it’s OK, but I need to duplicate lost frames to maintain correct timing.

  My configuration file :

  vlc.exe screen :// -I dummy —verbose=2 —one-instance :screen-fps=5 :screen-caching=10000 :sout=#transcodevenc=x264preset=ultrafast,tune=zerolatency,vcodec=h264,fps=5,vb=3000,width=1024,height=576,acodec=none:filedst="C :\tmp\output.mp4"

  What should I add/config to preserve proper time stamps and clip duration ?

  Many thanks for your help.