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djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

deandob

    // Live video stream management for HTML5 video. Uses FFMPEG to connect to H.264 camera stream, 
    // Camera stream is remuxed to a MP4 stream for HTML5 video compatibility and segments are recorded for later playback
var liveStream = function (req, resp) {                                            // handle each client request by instantiating a new FFMPEG instance
    // For live streaming, create a fragmented MP4 file with empty moov (no seeking possible).

    var reqUrl = url.parse(req.url, true)
    var cameraName = typeof reqUrl.pathname === "string" ? reqUrl.pathname.substring(1) : undefined;
    if (cameraName) {
        try {
            cameraName = decodeURIComponent(cameraName);

akras14

Git Cheat Sheet

Commands

Getting Started

git init

or

zserge

#include <array>
#include <cmath>
#include <fstream>
#include <iostream>
#include <vector>

struct Vec {
  float x, y, z;
  Vec(float vx, float vy, float vz) : x(vx), y(vy), z(vz) {}
  Vec operator+(Vec vec) { return {x + vec.x, y + vec.y, z + vec.z}; }

wdullaer

# Ask for the user password
# Script only works if sudo caches the password for a few minutes
sudo true

# Install kernel extra's to enable docker aufs support
# sudo apt-get -y install linux-image-extra-$(uname -r)

# Add Docker PPA and install latest version
# sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 36A1D7869245C8950F966E92D8576A8BA88D21E9
# sudo sh -c "echo deb https://get.docker.io/ubuntu docker main > /etc/apt/sources.list.d/docker.list"

chrismdp

# You don't need Fog in Ruby or some other library to upload to S3 -- shell works perfectly fine
# This is how I upload my new Sol Trader builds (http://soltrader.net)
# Based on a modified script from here: http://tmont.com/blargh/2014/1/uploading-to-s3-in-bash

S3KEY="my aws key"
S3SECRET="my aws secret" # pass these in

function putS3
{
  path=$1

ibc

/Google\ Chrome\ Canary --enable-logging --v=1  --vmodule=*/webrtc/*=2,*/libjingle/*=2,*=-2 --enable-logging=stderr

// Easier:

/Google\ Chrome\ Canary --enable-logging --v=1  --vmodule=*/webrtc/*=2,*=-2 --enable-logging=stderr

eevee

HEY: I've turned this into a blog post, which is a little more in depth.

🚨 https://eev.ee/blog/2016/06/04/converting-a-git-repo-from-tabs-to-spaces/ 🚨

---

Death to tabs, long live spaces

Do this

pabloko

update: https://framagit.org/tytan652/ffmpeg-ndi-patch use this patch. this gist is outdated

ffmpeg 4.4 with NDI

This patch adds libndi_newtek to last ffmpeg version, and fix timecode related issues that produces wrong PTS/DTS timestamps that seems to happen with newer NDI SDKs.

changes

• Updated libndi methods by newer versions (v2/v3)