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/bc_handler.sh
    class late_start
    user root
    group root
    disabled
    oneshot

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