Author Archives: Fredrik Mellbin

Positive Thinking – How to Convince Yourself That You Can Code

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Previously I’ve discussed how computers work so now it’s time to take a look at how humans work. I personally think this is something programming textbooks neglect to take into consideration, for example humans generally work very badly when confronted with binary operations and bit-wise shifts the first time. It can also be somewhat detrimental to their mental state. So this post is about negative thinking and what You Can Do To Break The Pattern! My personal trick is to always keep the law of attraction in mind when I code and so should you! Get the positive thinking going by putting some comments telling yourself that YOU CAN DO IT! or maybe that it’s simple. See this example from Avisynth:

if (!(audio && video)) { // Hey - simple!!
if (audio) {
  return new DirectShowSource(filename, _avg_time_per_frame, seekmode, true , false,
    args[5].AsBool(false), _media, _timeout, _frames, log, env);

And indeed that is simple! Just imagine what this technique can do for your mental health. No more feeling like a rejected PHP coder, instead you’ll be the coolest PHP coder in a basement within two blocks. Guaranteed or your money back!

Personally I prefer to apply the law of attraction in a slightly different way. For example I write my goal in every single comment. See this code snippet:

// Buy milk
for (int x = 0; x < width; x++) {
// Clean thoughts
// (representing my desire to have a clean toilet)
  dstp[x] = srcp[x-1] + srcp[x+1] + srcp[x-1-stride] + srcp[x+1-stride] + srcp[x-1+stride] + srcp[x+1+stride];
  // For loops are trivial and even my grandma could do them...
  // if she was still alive

Sometimes I try this but I have had less success with it:

// Hire Fredrik Mellbin, he's awesome

I’m currently experimenting with writing it every 10 lines in my code just to see what happens. I’ll post a follow-up later and tell you all how it works out.

Finally Using the Bug Tracker

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I’ve added link to the bug tracker on Google Code and I will be checking it a lot more often. It’s the best way of submitting documentation corrections as well. Just remember to quickly check the closed reports too because I usually only upload a new documentation revision when a new version is released of VapourSynth. You can find the link in the sidebar.

R16 – The Slightly Less Broken Release

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R15 had a serious issue that prevented the Avisynth compatibility stuff from working with anything except YV12, this release mainly fixes it. There isn’t much else new of interest in this release.

If you need more stuff to fidget with then go try the new resizers for VapourSynth too. They will most likely replace swscale once they become stable so testing is appreciated. They’re based on the dither tools code.

Next on my own todo list is a plugin to evaluate expressions at run-time, think mt_lutxy(z) but without insane memory requirements for 16bit formats. The other thing on the list mostly is about VSFS and that is to improve error handling and adapt the code to the latest Pismo File Mount API.

R15 – API Improvements

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The time has come to break the API slightly to add some missing features. It also ends the alpha support discussion. The proper (and only) way to handle alpha is to return it as a separate mask clip. To make this easier filters now have a reasonably simple API to return more than one clip.

The new filters this time try to fill in some of the biggest feature holes, they are Merge, MaskedMerge and AVISource. MaskedMerge is very similar to masktool’s mt_merge in terms of functionality and the other two are very similar to the internal Avisynth filters with the same name. AVISource can of course open both VapourSynth and Avisynth scripts for import too.

There are also minor changes that need to be done to make plugins compile (binary compatibility with old plugins is however preserved). Previously the VSNodeRef type was always declared as const, this superfluous const declaration has now been removed everywhere in the API. Below are examples of the other two changes needed.

vsapi->setVideoInfo(a, b);
Change it to:
vsapi->setVideoInfo(a, 1, b);

The other construct that needs changing is filter creation which now automatically assigns itself to the out map:

cref = vsapi->createFilter(in, out, "Invert", invertInit, invertGetFrame, invertFree, fmParallel, 0, data, core);
vsapi->propSetNode(out, "clip", cref, 0);
vsapi->freeNode(cref);
Change it to:
vsapi->createFilter(in, out, "Invert", invertInit, invertGetFrame, invertFree, fmParallel, 0, data, core);

And don’t forget to check out my previous post with suggested tasks if you want to help out.

VapourSynth Tasks

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I’ve hinted that there are plenty of things left to do before. Especially in my forum posts. Repeatedly. So in this post I’ll list some tasks I think should be done. Not all of them are programming either.

  • Proofread the documentation — most it was written after midnight so suggest clarifications too
  • Write testcases to cover more parts of the code — testing the python bindings is important too so only some scripting knowledge needed to help out with it
  • Add override file support to VIVTC (good entry level programming task)
  • Convert the EEDI3 port to pure C (simple if you know the difference between C and C++)
  • Port your favorite function/plugin from Avisynth — there’s something for everyone here
  • Port your favorite Avisynth script
  • Make a nice editor with preview — think AvsP
  • Write some simple getting started examples or maybe a quick introduction for Avisynth users
  • Add support for more output formats in vfw — clean up the output code too a bit
  • Write a good implementation of edge detection filters — canny, sobel and friends for higher depths would be nice
  • Your own ideas here

Minimum Requirements

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I never mentioned the minimum requirements for VapourSynth. I completely forgot about it. It wasn’t until a poor ancient Athlon user reported crashes I remembered that I actually do have minimum requirements. So what are they? and why?

  • A CPU with SSE2 support (may be disregarded if not running on an x86 CPU)
  • XP SP3 or later (may be disregarded if not a windows user of course)

That’s it! Not so bloody. The rationale for only supporting XP and later mostly comes down to testing. There’s simply no one who uses older systems around to provide testing. Maybe my code will run,  maybe it won’t, but there’s no way to justify spending time testing it myself.

SSE2 on the other hand requires a bit more motivation. It’s very good to have when optimizing filters. Also, most CPUs support it today, it has reached the levels MMX support had 10 years ago or so. Every single x64 CPU must also support it. It’s everywhere.  And it’s good. For example the transpose function in VapourSynth runs a bit over 10 times faster with SSE2 optimizations.

I think that’s all I have to say about the minimum requirements. There’s always Avisynth for the few who don’t qualify.

R14 – Improved Packaging

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It’s time for another release. The main highlights are bug fixes and the possibility to set the max cache size. The default max is 1GB everywhere to prevent running out of address space in 32bit applications. I’ve also decided to start bundling some potentially useful filters:

  • TemporalSoften – C code restored from inline asm
  • Histogram – with support for higher bitdepths in the default mode
  • VIVTC – think TIVTC but less features and portable
  • EEDI3 – improved to work on all 8bit formats

Since this project’s success depends a lot on good plugins being available I’ve also included all files needed to start developing in the installer. Just check out the SDK directory and the example invert filter to get started.

It’s now time for me to start spending more time porting/rewriting some useful Avisynth things…