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Multi-rate HEVC with x265 for adaptive HTTP streaming

15 Aug

Another in-depth look into multi-rate video encoding by my friend Damien Schroeder.


Version 2.0 of x265 has recently been tagged. It has been more than two years of work since version 1.0. Since then, HEVC has become more visible with wide adoption on devices and in software. From a streaming perspective, adaptive HTTP streaming is now the most common streaming technology to watch live or on-demand content on the web, for example with the DASH standard.

Remember, adaptive HTTP streaming requires a video to be encoded at different representations, that is, different qualities, which is generally achieved by encoding the same video at different (spatial) resolutions and different signal qualities. Depending on the encoder and on the encoding mode, the signal quality can be tuned by varying the quantization parameter (QP), or varying the target bitrate when using rate-control. In the case of x265, the so-called constant rate factor (CRF) can also be used to tune the quality of the…

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Postgres troubles

16 Mar

Hi everyone!

I am reposting this as the lovely people at MusicBrainz are having really serious issues with their server at the moment, and they are looking for help from anyone savvy with similar software.

Cheers and spread the info!

Update (19/03/2015): The problem was recently fixed. Good on MusicBrainz for their transparency, and thanks to all the helpers! Now let’s get back to editing! :)

MetaBrainz Blog

(Regular readers of this blog, please ignore this post. We’re casting a wide net to try and find help for our problems.)

Dear Postgres gurus:

We at MusicBrainz have been very happy postgres users for over a decade now and Postgres is something that gives is very few headaches compared to all the other things that we run. But last week we started having some really vexing issues with our server. Here is some back-story:

When our load spiked, we did the normal set of things that you do:

  • Check for missing indexes, made some new ones, no change. (see details below)
  • Examined for new traffic; none of our web front end servers showed an increase in traffic.
  • Eliminated non-mission-critical uses of the DB server: stop building indexes for search, turn off lower priority sites. No change.
  • Review the performance settings of the server. Debate each setting as a…

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Comparison of open-source HEVC encoders

13 Oct


High Efficiency Video Coding (HEVC) or H.265 is a quite recent video coding standard which has been ratified in 2013. It can achieve much better rate-distortion performance (and promises 50% bitrate reduction at same subjective video quality) than its predecessor H.264/AVC, which is the dominant video codec currently. However, this performance enhancement comes at the price of a significantly increased encoding complexity.

The “Joint Collaborative Team on Video Coding” has been working on an open-source reference implementation called HM, that can be found on the Fraunhofer HHI website.

On the other hand, probably everybody has heard of the popular x264, an open-source encoder for H.264, which is widely used in various projects, ranging from video software such as ffmpeg to major companies such as YouTube. The success story of x264 had to be continued with HEVC, and thus, the x265 project was started. In order to be able…

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Reset the Net

5 Jun

Reset the Net is happening today, the 5th of June 2014. It is a global day of action to make government surveillance on the Internet more difficult. It was instigated by the American organisation Fight for the Future, “a nonprofit advocacy group in the area of digital rights founded in 2011″ (see the Wikipedia article). This effort is scheduled a year after Edward Snowden started revealing the NSA’s, and more generally the Five Eyes members’ global surveillance activities. The day of action echoes others like The Day We Fight Back, organised by Aaron Swartz’ Demand Progress in February this year.

Reset the Net is a great event, and I really hope it has a lasting effect on the Internet. However, this kind of change is one that needs to be durable, and this probably means that it won’t be done in a day. I will try and write posts related to government surveillance and general online privacy in the next few day to show examples of how we can switch to safer options, and report on the efforts I made myself. This will be my little contribution towards giving people ideas and making this issue more visible.

For the moment, have a look at the Reset the Net “privacy pack” to get you started on this. There is quite an array of actions you can take, from a simple switch from one app to another, to more elaborate geeky things: everyone can find something that looks doable to them.


Colgate: Liars!

28 May

Colgate: Liars!

We are no fools, Colgate!
– Stéphane Guillou 2014, CC-By-SA

Ubuntu for Phones + Fair Phone?

13 Mar

Ubuntu for Phones

This is an article I posted a while ago on my other blog. Now that goFLOSS! exists, it really belongs here, in an updated extended version!

Days ago, Ubuntu for Phones was announced to the masses. If for some reason you dodged the constant flow of articles and videos about it, you can start from the official launch keynote in which Mark Shuttleworth presents the product in order to start working with phone manufacturers.

A few days later, I discovered – via a post on Diaspora* – the FairPhone, an amazing project that aims at delivering a smartphone that is sustainably and ethically produced.

FairPhone | FairPhone brings a fair smartphone to the market – one made of parts produced and utilised without harming individuals or the environment..

As I read on the project’s website’s FAQ, they are considering selling it with Firefox OS but state that it is more likely that it will end up with Android preinstalled, as they are looking for a rock-solid operating system. Here is what they say:

We think transparency and open source design/hard/software are key to create a fair phone. Our approach though is a growing model. We have to take these things step-by-step and that means we have to work pragmatically. We can’t say how open the first model will be, as we don’t have that much influence (yet) as a small player on the design and manufacturing, but it is in our roadmap to make it radically open.

Regarding the OS we were thinking about launching it with Firefox OS, but we also have to balance between stability and openness. As we are a new product, we don’t want to take too many risks on this. We want to offer a very stable product for our customers, so we might wait until Firefox has proven itself and probably use Android for the first model. We also want a system that supports Dual Sim (Android does; Firefox doesn’t), as this is in line with our vision (less phones, more value in second-life markets like Africa).

FairPhone concept

As I try to promote sustainable practices as well as OpenSource alternatives, I was very excited about those two stories, and I started imagining a FairPhone running Ubuntu for Phones. In order to know more about it, I decided to send them an email concerning the recent news that thrilled most of the Ubuntu community. Here is the response I got from Joe Mier, their Community Manager:

Hey Stéphane,

Thanks for your support!

That’s a good question about Ubuntu and what operating system we will use. It’s something we are still considering but let me tell you what we’re thinking about so far.

You’ve probably already read on our website how we are considering Firefox OS, but prefer Android because of its emphasis on stability and openness for our initial run of smartphones. Aside from that, we are planing to launch the phone with root access for the user, so they can decide for themselves which operating system they want to install (though, apart from the custom Android ROMs, they will probably have to write some code themselves to make it work with the hardware). Another option we are currently looking into is to launch the phone with Android, but fully prepare the FairPhone for Ubuntu. Ubuntu uses the same linux kernel as Android and can therefore be “easily” installed on any Android device.

Here’s a quick news item about some things to keep in mind about Ubuntu on mobile:

Thanks again for your questions! If you haven’t already, sign up for future news on the FairPhone:

All the best,

FairPhone Community Manager

It is good to hear that the Fair Phone will be designed with openness in mind, and that it will be very hackable in order to let the user choose their favourite OS.

They plan to start the production of the FairPhone in the third quarter of 2013, with a limited number of phones pre-sold before then. If you don’t want to miss out, make sure you subscribe to their newsletter on their website.


On the 28th of February, Tessa Wernink from Fair Phone posted some news about Fair Phone’s quest for an operating system on their website, as they were visiting the Mobile World Congress held in Barcelona.

In fact, they made it clear that their choice will be Android for their first device in order to deliver a very stable product. But they did meet people from Mozilla, Jolla and Canonical and are definitely looking into working with them to deliver a product that is compatible with those new OSes.

Here’s to the future of smartphones! A more open, ethical and sustainable future.

goFLOSS! – Yet another blog about Free, Libre and Open Source stuff

12 Mar

Hello world!

Welcome on my new blog!

I will obviously be talking about the Open Source ecosystem and try to promote it as much as possible by writing about tips, news, tutorials and hopefully some philosophical nonsense too.

I will probably be writing in English, as it is the de facto international language, and as I am currently living in Australia. However, I might write a few posts in French – my mother tongue – or in Spanish – my heritage/couple tongue – or even in German one day – the FLOSS tongue I reckon! -, who knows. Anyway, it doesn’t really matter as the Interwebs can translate everything in no time already. ¡Entonces no importa el idioma! N’est-ce pas ?

Hopefully you will enjoy reading the stuff I publish. If you do enjoy it, don’t hesitate in telling me, it always feels awesome. I you think it’s utter rubbish, please say so too. If something is plain wrong or my grammar is crap, I would appreciate if you could point it out – we are here to learn from our mistakes. And I dislike being wrong.

And hopefully, I will actually DO this thing. Making it a fun experience will probably help.

So there you go!

Thank you for visiting!