Oleg E. Vorobiov isnullxbh

Introduction

This post describes how to add a custom attribute to LLVM and Clang. Why would you want to do such a thing?

You have semantic information of which the front-end is aware, but the back-end discards in the Intermediate Representation (IR), and an existing attribute can't be used to retain this information. Adding the attribute using the front-end analysis preserves the information into the back-end generated IR.
You've considered using the GCC/LLVM annotate attribute to hold arbitrary strings, but you also need to add a parameter (or more!) to that annotation.

The Clang Internals Manual discusses how to do this, but not with the detail you might like to see. Its description is high-level, and only lists one file that needs to be modified. Tracking down all of the other files that must be changed is left as a frustrating exercise to the reader.

Conventions used i

Git Commands

Getting & Creating Projects

Command	Description
`git init`	Initialize a local Git repository
`git clone ssh://[email protected]/[username]/[repository-name].git`	Create a local copy of a remote repository

C++ links: Coroutines

https://github.com/MattPD/cpplinks / C++ Standard / C++20 / Coroutines

(draft; work in progress)

#coroutines (C++ Slack): https://cpplang.slack.com/archives/C5JS5JXT5

About YUV formats

First of all: YUV pixel formats and Recommended 8-Bit YUV Formats for Video Rendering. Chromium's source code contains good documentation about those formats too: chromium/src/media/base/video_types.h and chromium/src/media/base/video_frame.cc (search for RequiresEvenSizeAllocation(), NumPlanes() and those kinds of functions).

YUV?

You can think of an image as a superposition of several planes (or layers in a more natural language). YUV formats have three planes: Y, U, and V.

Y is the luma plane, and can be seen as the image as grayscale. U and V are reffered to as the chroma planes, which are basically the colours. All the YUV formats have these three planes, and differ by the different orderings of them.

Most GStreamer examples found online are either for Linux or for gstreamer 0.10.

This particular release note seems to have covered important changes, such as:

ffmpegcolorspace => videoconvert
ffmpeg => libav

Applying -v will print out useful information. And most importantly the negotiation results.

	ffmpeg -i MVI_2595.MOV -sample_fmt u8 mov_u8.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt s16 mov_s16.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt s32 mov_s32.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt flt mov_flt.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt dbl mov_dbl.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt u8p mov_u8p.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt s16p mov_s16p.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt s32p mov_s32p.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt fltp mov_fltp.mp4
	ffmpeg -i MVI_2595.MOV -sample_fmt dblp mov_dblp.mp4

	#!/usr/bin/env python
	# Implementation of algorithm from http://stackoverflow.com/a/22640362/6029703
	import numpy as np
	import pylab

	def thresholding_algo(y, lag, threshold, influence):
	signals = np.zeros(len(y))
	filteredY = np.array(y)
	avgFilter = [0]*len(y)
	stdFilter = [0]*len(y)

	# Copyright Louis Dionne 2013-2017
	# Distributed under the Boost Software License, Version 1.0.
	# (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)

	language: c++
	sudo: false

	# Do not build branches of the form "pr/*". By prefixing pull requests coming
	# from branches inside the repository with pr/, this avoids building both the
	# branch push _and_ the pull request.

	/*
	Settings (the ones below are examples: choose what is best for your data)
	set lag to 5; # lag 5 for the smoothing functions
	set threshold to 3.5; # 3.5 standard deviations for signal
	set influence to 0.5; # between 0 and 1, where 1 is normal influence, 0.5 is half
	*/

	// ZScore on 16bit WAV samples
	func ZScore(samples []int16, lag int, threshold float64, influence float64) (signals []int16) {
	//lag := 20

	# Lets say we want to add a library and an executable, both with the same name.
	# In this example, it is resman

	add_library(resman ${src_cpps} ${src_hpps} )
	target_link_libraries(resman ${Boost_LIBRARIES} ${LIBYAML} ${LIBFMT})
	#
	# Add resman executable
	#
	# We call the executable resman-bin
	add_executable(resman-bin main.cpp )