Useful FFmpeg Commands

"FFmpeg is an extremely powerful and versatile command line tool for converting audio and video files. It is free and available for Windows, Mac and Linux machines. Whether you want to join two video files, extract the audio component from a video file, convert your video into an animated GIF, FFmpeg can do it all and even more."

How to speed up / slow down an audio stream with ffmpeg

Use the "atempo" filter:
ffmpeg -i input.mp4 -filter:a "atempo=0.5" -vn output.aac

How to change the framerate of an MP4 video without reencoding

I tried to find a solution for this question using ffmpeg, but had no luck. However the MP4Box method works like a charm.

How to concatenate multiple segments of the same video into a single file

Many video recorders (eg. GoPro cameras and many phones) split video files into 2 (or 4) GB pieces. To concatenate these pieces into a single file (without reencoding them), you can use ffmpeg's "concatenate" demuxer:
ls -1 G*0060.MP4 | sed -r "s/(.*)/file '\1'/g" > list.txt
ffmpeg -f concat -i list.txt -c copy GOPR0060.joined.MP4

TLS extension to support multiple certificates for virtualhosts

Server Name Indication (SNI) means that a compatible TLS client can send a hostname (aka. "server_name" field) in it's Client Hello message to the server indicating what virtualhost it wants to connect to and a compatible server can pick the right TLS certificate from it's configuration. This extension to the TLS standard aims to solve the SSL/TLS vs. single-IP virtualhosts problem.

Validate XML documents via a bookmarklet

I've attached a simple HTML file that contains a textarea and some JavaScript. You can paste any text into the textarea and pressing the button will invoke the browser's XML parser and test whether the text is a valid XML document.

I've also modified the JavaScript code so it can be used as a bookmarklet: Verify XML

Just drag&drop the link to your bookmarks bar, select some text on a page and click the bookmark(let) to validate it as an XML document.

Take a picture of your phone's user upon entering wrong unlock code/pattern and send it to yourself via email silently

This is a nice intro into using SL4A+Python with Tasker. And the actual task (silently take a photo of a possible thief) is useful as well.

How to execute a shell script from init.rc after boot finished

Place something like this in your init.rc:
on property:dev.bootcomplete=1
    start bootcomplete_handler

service bootcomplete_handler /system/bin/sh /system/bin/
    class late_start
    user root
    group root

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