jb, 28y

VLC 1.2

Introduction

As promised in my last major post, I will try to discuss about features that are getting shaped for VLC 1.2.0.

This post is therefore the first of the series.

Be careful, this post is a bit technical.

tl;dr version: VLC 1.2.0 will be awesome, faster and have better display quality.

Video Output Rework

When I joined the VideoLAN project and the VLC development team, something like 5 years ago, people were already speaking about the Video Output rework.

This Arlésienne was, to me, a bit like our DNF.

However, during the development of VLC 1.1, VLC guru Laurent Aimar, aka 'fenrir' started to work on it. The VLC 1.1.x series has had part of this work in it, but most of the nice features were hidden to the users.

Vout Rework features

VLC 1.2.0 has seen enormous amount of work to go on this project and this work is almost finished.

This means:

1. Most of the Video Outputs have been rewritten in a way or another, and their priority revised;
2. Other Video Outputs were just dropped, like gapi, omapfb, hd1000v;
3. OpenGL output has now got shaders to do YUV->RGB conversions in the GPU,
4. Most video filters were ported to the new API, and most of them should be transcodable and streamable now.

New features

But this also means new features, like:

1. Sharper subtitles rendering,
2. New Video Outputs were written, notably for Direct2D, for iOS and Android,
3. Important changes for the deinterlacers,
4. New filter for debanding videos,
5. New filter for anti-flickering of videos,
6. New posterize and sepia filters for more fun.

I would like to speak about 2 of those features, in the following parts of this post.

Subtitles rendering in VLC

Definitions

• What we call source size is the original size in pixels of the video in the file. It is often what people call video definition, like 480x640, 576x720, 720x1280, 1080x1920.

• What we call window size is the display size in pixels of the video in the file. It is often what people call window resolution. It depends on the size of your VLC window, whether you resize it or not or if you are in full-screen mode or not.

• What we call text OSD are text subtitles and OSD were the text is rendered on the screen. Using a renderer, like Freetype, it converts the text into an image.

• What we call blending of 2 images, if what people would call merging.

How does VLC display subtitles

Those days, to display subtitles, we have the following steps:

1. the text OSD is rendered to the source size,
2. the rendered OSD is blended into the source image,
3. the resulting image is passed to the video output, that scales to the window size and does it usually in your hardware GPU.

As you can imagine, if your source is 640x480 and your monitor is full HD, the text will be badly scaled.

However, doing this that way is better for your resources, because the most costly operation (scaling) is done in your hardware.

How will VLC display subtitles

But those days, with very powerful GPUs, can't we do differently?

Yes, we can. Using Direct3D or OpenGL.

To display subtitles, we will have the following steps:

1. the text OSD is rendered to the window size,
2. the rendered OSD passed to the video output in a texture,
3. the source image is passed to the video output in a texture,
4. the video output scales the source texture from source size to window size,
5. the video output blends both textures.

You can see quickly that the new way is sharper (you might need to click on the images)

Before people scream, yes, it isn't exactly the same frame which is why the colors are different and yes, white on white isn't very readable. But this is beyond the point. The point is the difference in sharpness. I'll do better screenshots, when I got time (never :D).

Compatible Video Outputs

At the time of this writing, the video outputs that can do this blending are:

• Direct3D, default on Vista and 7
• OpenGL,
• x11.

However, notable video outputs like DirectDraw and Xv are not able to work in this mode.

Deinterlacers

In addition to this work, an important amount of work was done on the VLC deinterlacers by Juha.

Notably, he has written new deinterlacer modes, fixed bugs, cleaned the code and written an impressive documentation.

The most notable parts of the work include:

• a complete InVerse TeleCine deinterlacer, very useful for old NTSC anime,
• a framerate doubling CRT TV simulator mode, named Phosphor.

And all of them are properly documented on our .

Moreover, as previously told, all modes of deinterlacing should be transcodable or streamable.

Thanks for the support. To be continued...

Read: Update of this article

Apple OS X 10.6 is out

If you have missed the news, then you are not on the same techy blogs than I am.

So, Apple new operating system Mac OS X.6, named Snow Leopard is out, and it improves a lot the speed, and ports most of its application to 64bits, but doesn’t introduce any important new feature. Learn more about it !

VLC and 64bits

Do you really need 64bits for a video application? I seriously doubt it. But well, you might want/need it in the future.

Linux

VLC 64bits runs on 64bits linux since a long time, and I use it a lot. No majors problems since Linux is cleverly engineered.

Windows

VLC runs on Windows 64 as a Win32 application, but we haven’t finished the port to Win64, especially because of external libraries issues. It will come eventually.

Mac OS X

Since the WWDC ‘08, we know we have to remove all Carbon code, and we have mostly done it.

Leopard

VLC 64bits runs on 32bits Leopard without issues.

Snow Leopard

As one of our OSX developers says: I’ve you had asked me a month ago, I had said that everything is cool and VLC64 will be released the same day as Snow Leopard.

BUT

It doesn’t work now, because of a change in the Cocoa runtime. VLC stopped working in the last two seeds (the GM and the one prior to it).

Launching VLC results in crashes in a low level function called _NSBundleCreate, which is triggered by a whole bunch of Cocoa and IOKit methods. Basically every method of these frameworks results in a crash on Snow Leopard. This is strange, as exactly the same code runs nicely in 64bit on Leopard and prior seeds of Snow Leopard.

The problem is that VLC is not an ordinary NSApplication, but a plain C app, that loads a Cocoa plugin, which instantiates NSApp itself. Therefore, you cannot reproduce the crashes in normal Cocoa apps.

Conclusion

Apple, once again, breaks everything with a new OS, as it happens often, or when a new version of Xcode gets out. Last version of Xcode forced us to drop X.4 if we wanted to go 64bits and compatible with Snow Leopard. Seriously, I don’t get it.

I have applications that are running on the Win7 64bit setup that are Win98 games!

Anyway, to not finish on a bad note, Snow Leopard looks gorgeous!