Category Archives: Computer

Setting up a Cisco SPA122 for use with UK Telephones

This is more of a nostalgia trip / messing about thing rather than a serious use of Voice over IP (VoIP). The Cisco SPA122 ATA with Router (Analog Telephone Adapter) is a small box that allows old analog phones to be connected to a VoIP network. At the time of writing Cisco no longer manufactures these and they are currently in an end of life plan.

Cisco SPA122 ATA
Cisco SPA122 ATA with Router

I am setting this up to use two handsets that can be used to call each other through the SPA122. I don’t have a VoIP service here and don’t have need for one. Later, I will be setting up a couple of modems and using them for a dialup connection, in this part I will be going through the setup and configuration of the SPA122.
SPA122 And Two Telephones

You will need:

  • An SPA122 – I got mine from eBay, check that you are purchasing a vanilla model, rather than one that has been configured by a carrier, be wary if it has any other logos printed on it as it may be locked to that carrier.
  • A 5V power supply, this must be capable of providing at least 2A.
  • Two telephones – I got these from the Charity Shop, get ones with tone dialing (DTMF), pulse dialing will not work – I’ve also found using better quality phones made in the early 2000’s work better than cheap new ones, I ended up with BT Decor 1100 and BT Decor 1200 phones.
  • Two adapters to convert the UK phone plug to RJ11 sockets on the SPA122. Search for “RJ11 to BT Socket” on eBay or Amazon, these are cheap.
  • A wired LAN connection to your network.
  • A computer, preferably with WiFi as well as a Wired Connection, I used a Raspberry Pi 4.
RJ11 to BT Socket Connector

Default Settings

  • IP Address: 192.168.15.1 – with a computer plugged into the yellow ethernet port
  • Username: admin
  • Password: admin

Resetting the SPA122 and Gaining Access

With a network lead from your computer to the yellow ethernet port on the SPA122 open your web browser and try the address 192.168.1.15. You should now see the login screen, try the login details above.

That probably didn’t work. To reset to factory default settings use a paperclip on the rear panel reset button. With the unit powered on, use the end of a paperclip to press into the red hole marked RESET located on the bottom-left side of the back panel of the SPA122. Press and hold for at least a full 20 seconds and the Power LED will start to blink when the restore process begins, this will take around two minutes to complete. Now try logging in as admin again.

Once logged in, change the admin password to something else, if left at the default it will refuse to work.

If you are really unlucky the reset button may have been disabled in the firmware. At this stage I don’t know what to do if this has happened.

You can also configure the device by pressing the star button on your handset four times (****) but that way madness lies.

Upgrade the Firmware

At time of writing, the firmware version available from Cisco is Release 1.4.1 SR5. The update appears to be fixing a variety of security problems. You can find the current Firmware Version in Status > System Information.

Updating is straight forward. Download the file, and unzip it to extract the Payton_1.4.1_SR5_101419_1250_pfmwr.bin file, then in the SPA122 pages in your web browser go to Administration > Firmware Upgrade and follow the instructions. Everything here has been written for this version of the firmware.

Network Configuration

Even though in this case we won’t be using this as VoIP over the network, it still needs a network connection to operate.

In the Network Setup > Network Service set this to Bridge. This will allow a computer plugged into the yellow ethernet port to access / pass through to the blue Internet port which would be connected to your LAN.

Make a note of the SPA122’s WAN MAC Address, found in Status > System Settings, it may be useful for finding the box on your network when you make it available on your LAN in the next step.

Now to access the SPA122’s web pages from your LAN, go to Administration > Web Access Management and set Admin Access to Enable. Apply the changes and attach a cable from your LAN to the blue Internet port, you should now be able to login from any computer on your network. Your main router will have a list of attached devices, use the MAC address to help quickly find the designated IP address. The computer you were using to configure the ATA may need restarting to pick up an IP address from the LAN.

Although I have not tested this, with a handset attached to one of the phone ports dial * * * * and listen, if you can hear a slightly sinister automated voice saying “System Configuration Menu” then dial 1 1 0 # slowly, the key presses are read back to you, the device will then tell you its IP address 192.168.x.x.

SPA122 Ports
SPA122 Ports

Telephone Configuration

Now we are in the Voice section. At this stage listening on a handset just produces silence, or a quiet buzzing, like from a poor power supply. For setting up the ATA will need to be restarted several times. Go to Quick Setup and set the user and dial plan for each line. The dial plan describes how the call is to be handled, numbers can be blocked, routed to different ones, or in this case be routed to another port.

Line 1:
User ID: 101
Dial Plan:
(*xx|[3469]11|0|00|[2-9]xxxxxx|1xxx[2-9]xxxxxxS0|xxxxxxxxxxxx.|<018118055:101>S0<:@127.0.0.1:5061>|)

Line 2:
User ID: 100
Dial Plan:
(*xx|[3469]11|0|00|[2-9]xxxxxx|1xxx[2-9]xxxxxxS0|xxxxxxxxxxxx.|<018118055:100>S0<:@127.0.0.1:5060>|)

I have used 018118055 as the number, but you can set this to anything you like. Both phones are on the same number, but they behave separately so you can ring one from the other. If the phone has a caller ID display it will show the user ID, 100 or 101.

Click submit to save the changes, once restarted and logged back in, we now need to add a bit more detail, go to Voice > Line 1, and set the following:

Proxy and Registration:
Make Call Without Reg: yes
Ans Call Without Reg: yes
Audio Configuration:
Preferred Codec: G729a
Second Preferred Codec: G711u
All lines that start with FAX: set to no or none as appropriate
Modem Line: yes

The FAX settings are to do with using modems in the future. All other settings can be left at their defaults. Click submit to save the settings, this takes a few seconds, and once you have logged back in go to Voice > Line 2 and set the same settings as those you just set for Line 1.

You should now be able to make a call from one phone to the other, but the ring and dial tones will sound wrong as they are for those used in the USA.

Setting the Tones

Now we need to set the dial tones and ringer for those used in the UK, in Voice > Regional you can see there are quite a few options to be set, but here I will only be setting the ones most commonly used.

Call Progress Tones:
Dial Tone: 350@-19,440@-22;10(*/0/1+2)
Busy Tone: 400@-20;10(.375/.375/1)
Off Hook Warning Tone: 480@-10,620@-16,1400@0,2060@0,2450@0,2600@0;60(.2/0/1,.2/0/2);240(.1/.1/3+4+5+6)
Distinctive Ring/CWT Pattern Names:
Ring1 Cadence: 60(.4/.2,.4/2)
Ring2 Cadence: 60(1/2)
Ring3 Cadence: 60(.25/.25,.25/.25,.25/1.75)
Ring4 Cadence: 60(.4/.8)
Ring5 Cadence: 60(2/4)
Ring and Call Waiting Tone Spec:
Ring Waveform: Trapezoid
Ring Frequency: 25
Ring Voltage: 60
Frequency: 400@-10
Miscellaneous:
FXS Port Impedance: 370+620||310nF
FXS Port Input Gain: 0
Caller ID Method: ETSI FSK With PR (UK)

My source for UK Regional Settings is below in the Links and Sources where you can find the complete list.

My Work Here is Done

Congratulations, you can now ring one telephone from another using the old fashioned technique of pushing buttons.

Next in this series will be setting up for modems, and involves using a Raspberry Pi as a router.

Links and Sources

Setup a Network Camera with a Raspberry PI

In this post I am setting up a network available RTSP video camera on a Raspberry Pi 4 Model B with the latest Debian Buster installed, you will also want another ‘remote’ computer with VLC installed on the same network. I have used a camera module connected via a ribbon cable to the Pi’s video port. The performance is more like what you would see from a security camera rather than some fancy dedicated device. I will be making the configuration with a bash shell using SSH rather than the GUI.
A Camera for the Pi

Installation

If you haven’t already, enable the camera on the Pi with sudo raspi-config and go to Interface Options > Camera. To reduce the load on the computer I also set the Pi to boot to the Console in System Options > Boot / Auto Login and selecting Console, you should also check that at least 256MB of memory is allocated to the GPU in Performance Options > GPU Memory, when complete reboot to set the updated configuration.

Install some prerequisites, you may have some or all of these installed already:

Next add the Video For Linux (V4L) Repository, this adds the drivers for the video on the hardware side

and add the following line to your apt sources with $ sudo nano /etc/apt/sources.list

We can now install the V4L packages:

We now need to install the RTSP server from Git, this server connects to the V4L drivers above:

Configuration

To setup V4L, edit the configuration file $ sudo nano /etc/uv4l/uv4l-raspicam.conf and update the driver options and uncomment the h264 options:

Restart the service once you have saved the file:

Useful screen Resolutions; designation, ratio: width x height:

  • 1080p, 16:9: 1920 x 1080
  • 720p, 16:9: 1280 x 720
  • 720, 4:3: 1296 x 792
  • Standard Definition, 4:3: 640 x 480

I’ve chosen 720p 16:9 widescreen, this gives a good image quality without stressing the Pi 4B. The framerate is a compromise between quality and usability, its unlikely you would want to go above 25fps.

Connecting

If you don’t know it already, find the IP address of your Pi with $ ip a. Look for the address in eth0 or wlan0 depending on if you are using ethernet or wireless. In this case I will be using 192.168.2.33 in the examples.

Start the RTSP server with:

Replace user:password with a suitable username and password. I have assumed that the camera is on /dev/video0, you can test this with:

and look for a line such as Driver version: 5.10.17, if this is 0.0.0 then try a different device, /dev/video1, /dev/video2 etc.

On a successful load it will tell you the connection:

Now on your ‘remote’ computer open VLC and choose Media > Open Network Stream and place the given stream address into the network URL, you will then be asked for the username and password. For me it took less than five seconds for an image to appear, there is a fairly high latency on the image shown, the picture lags by about a second from reality.

Using OpenCV

You can access the stream using Python scripts and OpenCV on your ‘remote’ computer for AI/Machine Learning. For me this is a Debian Linux box with FFmpeg as OpenCV uses this to access the stream.

You can check OpenCV is working with FFmpeg with:

and looking in the output for FFMPEG saying YES:

Links and Sources

Jetson Nano Install Notes

The Jetson Nano Developer kit – B01 is a small computer comprising of an NVIDA Maxwell GPU, Quad-Core ARM Cortex-A57 Processor and 4GB of Memory along with four USB 3 ports, Gigabit Ethernet, HDMI and Display Port output, main storage is on a MicroSD card and there is a variety of selection of expansion available via GPIO, I2C and UART. On the software side NVIDIA provide their JetPack SDK – a customised version of Ubuntu. This development kit has been produced to provide an entry point into Machine Learning, for which I will be using Python programming language. I got my board from Pimoroni

Jetson Nano
Jetson Nano
GPU 128-core Maxwell
CPU Quad-core ARM A57 @ 1.43 GHz
Memory 4 GB 64-bit LPDDR4 25.6 GB/s
Storage microSD (not included)
Video Encode 4K @ 30 | 4x 1080p @ 30 | 9x 720p @ 30 (H.264/H.265)
Video Decode 4K @ 60 | 2x 4K @ 30 | 8x 1080p @ 30 | 18x 720p @ 30 (H.264/H.265)
Camera 2x MIPI CSI-2 DPHY lanes
Connectivity Gigabit Ethernet, M.2 Key E
Display HDMI and display port
USB 4x USB 3.0, USB 2.0 Micro-B
Others GPIO, I2C, I2S, SPI, UART
Mechanical 69 mm x 45 mm, 260-pin edge connector

These notes cover my process of setting one up and links to the documentation, it not intended to repeat those install guides but to provide an install sequence and any additional commentary as needed. I’m going to assume you have a little experience of using the terminal and am familiar with using the bash command line – I’ve no idea how this would be done through the GUI.

jetson nano ports
Jetson Nano ports [source: NVIDIA]

Initial Startup

I followed the instructions for downloading and installing JetPack 4.4 on https://nvidia.com/jetsonnano-start I used a 64GB Class 10, UHS-I, U3, V30 SanDisk card. I formatted the card in a camera before using balenaEtcher to write the JetPack SDK image, this creates a partition of about 16GB on the card formatted to ext4, during installation the volume is resized to fill the card.

jetson nano connections
Jetson Nano connections [source: NVIDIA]

Despite using a good quality USB power supply with an output of 3 Amps at 5 Volts into the Micro USB port the computer would only boot long enough for the NVIDIA logo to appear on screen but after a few seconds the green power LED would go out and it would be off, the same happened when I tried a variety of USB power supplies used. I got round the problem buy using a 5 Amp power supply connected to the barrel jack J25 on the left (centre pin positive) and connecting the jumper J48 located just behind this connector.

Customising the Setup

There are a couple of thigs to do, get a network volume mounted and set the default version of python.

For the network share install samba, some network utilities and the nano text editor:

create a text file: sudo nano /etc/samaba/videoserver with the following:

And set the permissions sudo chmod 600 /etc/samba/videoserver. In this example I have a network share on my server; 192.168.1.30, called video. Create a mount point for the share: sudo mkdir /mnt/video now you need to edit fstab, sudo nano /etc/fstab and add your network connection to the end:

Reload fstab with sudo mount -a and check for any errors. Because of the way that Jetpack boots it does not appear to wait for the network so the share needs to be set to automount and this causes it to only appear in drive listings when accessed. Further reading can be found in this excellent guide to fstab: https://wiki.archlinux.org/index.php/fstab.

Jetpack 4.4 comes with two versions of Python, 2.7 and 3.6, I want it to default to 3.6 and while this is rather out of date I don’t want to go down the hole of upgrading just yet, you will also need to install pip and set pip3 as the default too.

and test its worked:

I did get an error later on, a crash was reported on the desktop when an occasional python 2 script ran. I fixed the error in /usr/sbin/l4t_payload_updater_t210 by changing the first line of the file from !#/user/bin/python to !#/user/bin/python2

Post Install Problems

A recent update occured, so I did the usual sudo apt get update && sudo apt get upgrade but one of the files gave a script error, this turned out to be with nvidia-l4t-bootloader, like so:

after some head scratching, it turns out this script is python2 only. I reverted back to the python 2.7 as the default, and tried again:

Afterwards I set the default back to python 3.6 again.

Setup the Machine Learning

There are three Machine Learning packages, OpenCV for Computer Vison, Tensorflow for machine learning models, and TensorRT – accelerated deep learning networks for image recognition.

OpenCV is already installed in Python:

Tensorflow installation can be found here: https://docs.nvidia.com/deeplearning/frameworks/install-tf-jetson-platform/ I found this to be straight forward but it did keep the computer busy for a while.

TensorRT can be found at: https://github.com/dusty-nv/jetson-inference/blob/master/docs/building-repo-2.md I used the instructions in the Quick Reference section and installed the default models without any errors, I have not yet had the opportunity to test it.

Further Reading

Copying and Resizing a Raspberry Pi SD Card

The Micro SD Card I use in a Raspberry PI ran out of space so here is how I copied the contents of the 15GB drive to a new 64GB card and resized the partition. I used a separate computer running Debian and as the machine does not have a monitor or keyboard attached this will be being completed through the bash command line using SSH.

1. Making a copy of the SD Card.

Insert the old card into your computer, if the computer attempts to mount the drive then unmount it. We need to find which mount point has been used, do this with the lsblk command:

The device sde matches our SD card. So we will use that. The dd command is used to create the ISO image, I am creating the file in my home directory:

once complete, check that the records match:

Swap the SD cards and check the mount point again:

Now copy the iso image to the new card:

this can take a while, the write speed is rather slow:

and lsblk shows us the new partitions:

2. Resizing the partition

The copied partition is now the same size as the original. If you have space remaining, the new card can be put back in the Pi and use the raspi-config utility, and using the Expand Filesystem option in the Advanced Settings section. However if the drive is completely full you won’t be able to login as there won’t be enough space available for the temporary files created at login, to get round this you can use parted to resize, start with:

if you get the following message:

then quit from parted, if you are using a full size SD Card, check the Write Protect tab on the side of the card and try again, otherwise try:

If problem persists try formatting the new card in a camera, as these have a simple file system, and write the ISO image again.

We need to resize the larger partition /dev/sde2 with the ext4 file system, the smaller is used to boot the Pi and can be ignored. In parted, list the partitions with the print command:

Using resizepart set the new size, I set this to larger than the 15GB but smaller than the unallocated space, this to save me having to accurately work out the remaining space manually:

Now update the boundaries to grow and resize the partition into the freshly allocated space:

Now boot the Pi with the new card, login and use the raspi-config utility then in Advanced Options choose Expand Filesystem and follow the onscreen instructions. Once rebooted you should now be set to fill up your new card.

Links and Sources

Extracting GPS data from the GoPro 7

While extracting the telemetry data from the GoPro is reasonably well documented I have found some gaps for getting the extracting utilities installed and when extracting and combining data from multiple files. These notes are for a Debian/Ubuntu installation in a BASH Shell.

Installing the gopro-utils

As I couldn’t find any straightforward instructions for installation, I’ll be going through everything I needed to do to get it working, you may have some of these packages installed already.

Now to get the gopro-utils and install them, I’m placing the source files into my Downloads directory, as well as the GPS data extractor we’ll be adding the other telemetry tools too, this is all a bit long winded.

Extracting the Data

You will need to find which stream in the video recording the data has been saved to, to find this use ffprobe to examine the recording and look for the stream that contains GoPro MET, for example:

You can see that what we are wanting is on stream 3, as far as I can tell this stays the same every time, I don’t know if it is different for other GoPro models.

This bash script extracts the GPS data in GPX format from all the GoPro GX recordings in the directory, other options have been commented out, if you are using Garmin VIRB edit there is also an option for use with that. The script creates two files, one that contains the raw data and another with the desired GPS data, the GPS output file has the same name as the recording, but in lowercase with a .gpx extension.

Merging GPX files

As the GoPro splits recordings into 4GB blocks, when extracting you will get a single GPX file for each recording. Many pages found by Google say that to create a single track from these all you need to do is append the files into one big file. This is wrong, what you end up with is a single file with many short tracks, when what you are after is one long track covering the entire journey. This bash script uses gpsbabel to create single merged file from the extracted GPX data, it creates a file called “gpsoutput.gpx”.

The next stage will be to write a script that combines all these and completes the job in one easy process.

Links and Sources

Using Inkscape for CNC designs

Inkscape is a free vector graphics editor for all major platforms, generally it is aimed at art and design users but it does have an option for generating G-Code for use in your favourite CNC software. While Inkscape doesn’t have many of the functions of proper CAD/CAM software it is an relatively easy place to start for creating basic designs, I have been using it to make boxes out of 3.5mm plywood.

These notes are based around my cheap CNC machine sold as an CNC3018 by a variety of Chinese manufacturers on Amazon and eBay, the included controller is a Woodpecker CNC board (Ardunio clone) I have upgraded to GRBL v1.1 and I am using version 0.92.4 (April 2019) of Inkscape with the included Gcodetools.

CNC Wood Cutting

This post focuses on setting up Inkscape for the CNC machine and producing the g-code from your drawing, it is not intended to be an Inkscape tutorial.

Document Setup

With a new drawing set your Document Size, this should be the same as your CNC bed, in my case this is 300 x 180mm. From the Inkscape menu go to File > Properties and in the Page Tab set the Display Units (millimeters in my case), the Orientation to Landscape and Page Size width: 300 and height: 180. In the Grids Tab set the Grid Units to mm and the Spacing X and Spacing Y to 1.0. Back on your main page, turn the page grid on with: View > Page Grid.

Inkscape Document Properties

By default Inkscape scales the stroke/line width when you resize a shape, to prevent this click the the fourth box from the right in the top icon bar “when scaling objects, scale the stroke width by the same proportion”

Turn Line Scaling off to prevent the line width changing when resizing

You can save this as a template, such as: CNC3018.svg or as the document default with: default.svg by saving the file to your templates directory:
On Linux and OS X: ~/.config/inkscape/templates/
On Windows: C:\Users\<username>\AppData\Roaming\inkscape\templates

The lines you draw will need to be the same width as the bit you are using in the CNC machine. Draw a rectangle, Right mouse click on the rectangle and select Fill and Stroke…. In the Fill Tab click the X – no paint box and on the Stroke Style tab set the width to that of the bit you are using – 1.5mm, subsequent rectangles will be in the same style, other shapes will need to be setup this way too. The colour of your lines should be black, there is some functionality for different colours to represent different depths but I have not yet worked out how to do this.

Setting the line width

Layout Tips for G-Code Routing

Remember to check the dimensions of the cuts, with an outside cut such as the width and height of a box side you need to measure for the inside of your rectangle, for holes in your box measure to the outside edge, Inkscape sets distances to the outside edge.

For positioning holes for switches and the like, I add thin lines 0.1mm thick as guides and make use of the width/height settings as well as the Object > Align and Distribute options. A pair of digital vernier calipers are a great aid to discovering the required sizes. Remember to delete these before G-Code encoding.

Using guidelines for accurate layout

When generating the G-Code each shape will be seen as an individual object, so lets say you want to have two sides of your box cut from a single sheet of plywood, this would be two rectangles abutting each other with a side to be cut overlapping. As it takes four passes to cut each shape 1mm at a time, this means it’ll take six passes down the centre. To fix this select both rectangles and then Path > Combine followed by Path > Difference to make a single object.

Outputting to G-Code

Now that you have completed your drawing, save your work then convert your objects to paths by selecting all objects then Path > Object to Path. You may also want to place your drawing near the bottom left of the document, as this is where the CNC router starts. Now using Gcodetools there are three things you need to do to produce the G-Code file. None of the Gcodetools windows close automatically when apply is clicked, you will need to do that yourself. From the Inkscape menu:

1. Extensions > Gcodetools > Tools Libary…
Select Tools Type: cylinder and click apply In the overlarge green box that appears you will need to set the tool diameter and feed speed.

Gcodetools Tools Library

This can be a bit fiddly as the text can become detached from the box and the settings lost, what seems to work most reliably for me is to change to Text Objects (F8) click on the numbers you want to change and once done go back to Select and Transform (F1). Resize the box afterwards to check that it is still working – if the green box moves but the text does not then Ctrl-Z a few times and try again.

Gcodetools Tools Library – Green background is detached from the text – this won’t work.
setting default used description
Diameter 10 1.5 tool bit diameter in mm
Feed 400 300 speed while cutting through the material in mm/second
Penetration angle 90 90
Penetration feed 100 100 Plunge speed in the material in mm/second
Depth Step 1 1 Depth of cut on each pass in mm

2. Extensions > Gcodetools > Orientation Points
This tells the g-code where to start, normally bottom-left on the CNC Set the following:
– Orientation type: 2-points mode
– Z Surface: 0mm – this is the top of your surface
– Z Depth: -3.4mm – this is the thickness of material to cut, a negative number

With the Orientation Points added.

3. Extensions > Gcodetools > Path to Gcode
This creates the G-code file, in the Preferences Tab set the following:
– File: output filename 
– Directory: output directory
– Z safe height: 5mm – height above the work surface when moving between cuts
The filename once set doesn’t change, an incremental number is appended to the output filename. Click the Path to Gcode Tab before clicking apply (this appears to be a bug).

Your image will be updated to show the g-code routing, give this a visual check to ensure that all objects have been coded and that it looks right, the path to be taken should be in colour and contain arrows showing the direction of the router.

If there are too many arrows or if a line has arrows pointing in different directions then there may be an object underneath, check on your original artwork, in the image with the three circles below you see that A has not been converted to a path with Path > Object to Path, B has a duplicate object underneath and C is correct.

Gcode check; A and B have problems, C is correct.

The generated G-Code does not appear to include the Spindle Motor Start command – So remember to start the spindle manually in your CNC software before running the G-Code – its interesting how easily these bits break with a sideways load. Remember if you are cutting trough rather than engraving, don’t forget to put a layer to sacrifice between whatever you are making and the CNC’s bed, I use 5mm MDF/Fibreboard.

Links and Sources

FFMPEG for Video Conversion

FFmpeg is a command line program to manipulate, convert, record and stream video and audio, it is available for Mac, Linux and Windows. Here is a handy list of commands for reference, these have been tested with version 3.1.12 in a Debian Linux environment. I expect this list to grow over time as needs arise.

• Rescale a 4K video to 1080p

• Convert to H.264 (AVC) codec for use on uploading to YouTube, Vimeo, etc:

Using this codec reduces the time it takes for the video to be available after upload, however YouTube converts the file again to the VP9 codec and unless you have a popular channel, 100 subscribers or more, then this can take a few days or weeks and in the meantime your video can appear quite poor and blocky even when watching at 1080p, especially when there is a lot of movement like in a car dash-cam video. You can use FFmpeg to encode to VP9 webm format with this bash script:

This script is based on the encoding method shown in the WebM Wiki on my computer it is very slow and takes a quite a few hours to encode just nine minutes of video and the eventual results are so poor you’ll be wondering why you bothered.

• Convert to MP4 for use in Vegas Studio:

If you have a particularly old/odd video and get lots of pts has no value errors, then try this:

The -fflags +genpts option adds a Presentation Timestamp (PTS) to the frames, this must be before the -i as shown to work. Source.

• Set the video playback speed, this method adjusts the Presentation Timestamp (PTS) on each frame which may not work with older software. To slow down video divide the PTS by your required speed, this example slows the action by two times setpts=PTS/2.0. You can also reduce the number of dropped frames by increasing the frame-rate -r 50, in this case I went from 25fps to 50fps, but depending in the chosen speed frames may still be dropped.

Speed up your video by multiplying the PTS, in this case two times faster: setpts=PTS*2.0

• Convert file or extract audio from file into an MP3, the output is set to 128K constant bitrate

• Concatenate Video Files
This combines two video files, when using formats such as MP4 or MKV you will need to create intermediate files, otherwise only the first file will be included in the output:

• The opus not found error
When converting a file and you see an error like Could not find tag for codec opus in stream #1… you will need to state the output format

Links and Sources

Extracting MP3 audio from video files

Here is a small Bash script that converts any supported ffmpeg video format; such as .MKV, .MP4 or .MOV and extracts the audio to an .MP3 file, It will also split that MP3 file into chunks and put them in a convenient directory. You will need to install ffmpeg and mp3splt for your particular platform.

Example Usage:

This uses ffmpeg to convert “big fat file.mkv” to “big fat file.mp3” and then uses mp3splt to create a directory “big fat file” containing the files 01 – big fat file.mp3, 02 – big fat file.mp3, etc. The MP3 files will be encoded at 128k Constant Bit Rate and each file will be around 50 minutes in length. To install in Debian/Ubuntu use: sudo apt-get install ffmpeg mp3splt

mp3splt can find the audio in a quiet region near where the split is desired rather than midway through a word, this should make for much cleaner playback across tracks.

Alternative Method

This script gives the same results but uses ffmpeg to split the large MP3 file and then adds track numbering metadata using id3v2. To install in Debian/Ubuntu use: sudo apt-get install ffmpeg id3v2

Creating an Audiobook

Taking this further, I was thinking that it would be nice to have these converted into the M4B Audiobook format for use on my elderly iPod. The script below assumes that you have processed the files as above and have added metadata tags using a tool like mp3tag (yes I know this is for Windows).

To complete this we need to: Combine the multiple MP3 files into one big file, or read the original big file then convert that to M4B format at 96K bit and add chapter marks every ten minutes. For this I have used ffmpeg v3.2.12 and libmp4v2 (for the mp4chaps utility), to install in Debian/Ubuntu use: sudo apt-get install libmp4v2-dev mp4v2-utils ffmpeg

This script works best from a single MP3 file rather than from those that have been re-combined back into a single file, recombining the files caused ffmpeg to exclaim “invalid packet size” and “invalid data” errors. It is able to tell the difference between a directory and a single MP3 and processes the file accordingly, don’t forget to add metadata tags and cover art before you run the script.

When encoding to the M4B using a re-combined file I saw a few of these errors from ffmpeg:

These appear to be caused by the mp3splt program from when the original MP3 file was being split into 50 minute chunks, but I can’t hear any effect on the output.

Lots of information about the file can be gotten using mediainfo, to install in Debian/Ubuntu use: sudo apt-get install mediainfo, example use:

Links and References

Bluetooth Low Energy (BLE) on the Raspberry Pi

Bluetooth Low Energy – BLE – Bluetooth 4.0 is an industry-standard wireless protocol built for the Internet of Things – IoT, it is designed to provide connectivity for devices operating from low capacity power sources such as coin cell batteries.

Raspberry Pi2 with ASUS USB-BT400 Bluetooth 4.0 Dongle

In this introduction to BLE I’ll be configuring a Raspberry Pi2 computer to talk to a smart watch. We will be installing the latest version of BlueZ from source, enabling BLE support. This is not a tutorial on decoding the data from the watch I am just using it as an example, although I may write about decoding it in a future posting.

I am using a ASUS USB-BT400 Bluetooth 4.0 Dongle on a Raspberry Pi2 but this will work on any computer with a Debian based distribution. Your dongle must be BLE/Bluetooth 4.0 capable otherwise this won’t work. I am using an ID107HR activity tracker with pedometer and heart rate monitor, randomly chosen from the list of cheap ones available on Amazon. While using the Pi to talk to the the watch make sure Bluetooth on the phone is off as it can only connect to one device at a time.

The current distribution of Raspbian – jessie on the Raspberry Pi comes with version 5.23 of the BlueZ Bluetooth stack that’s rather old, dating from September 2014 which lacks many of the features we will be needing. The current version 5.44 of the BlueZ has many changes in the package with many familiar components such as hcitool and gatttool being depreciated, so I will be ignoring those and using the available commands, bluetoothctl, on the terminal.

Installing BlueZ

With Raspbian – jessie installed we will need to update the Pi make sure some packages are installed and then installing the latest version of BlueZ. But first, remove the installed version 5.23 of BlueZ:

Next, perform the traditional housekeeping updates then install the build tools and USB libraries. Those parts that are installed already will be automatically skipped.

Now, download the source code, at time of writing the current stable release is version 5.44, check the BlueZ site for the latest version.

Inside the BlueZ directory, configure, make (this takes a while), and install. The experimental option adds BLE support and enabling the library allows for python use later on:

Configuring and Starting BlueZ

At this stage we will need to check that the installation worked and that we can see your bluetooth dongle. With your bluetooth dongle in a USB port you should see it on your list of USB devices, here you see mine as device ID: 0b05:17cb ASUSTek Computer, Inc.:

You will also need to enable the experimental services, edit the file /lib/systemd/system/bluetooth.service and in the [Service] section change the ExecStart line to end with –experimental:

Start the bluetooth service, and while we are at it enable it to load on boot:

Once started, check the status of the bluetooth daemon with:

Should you need to, the service can be stopped and prevented from loading on boot with:

Finally, you may want to enable auto-power on for the device, to do so create this bluetooth config file:

and add these two lines:

You should restart the Pi at this point and check that the daemon has loaded properly with sudo systemctl status bluetooth

Testing BlueZ

Start the bluetooth controller, you should see your dongles MAC address and alias:

for first time use, try scanning to find your watch, if it doesn’t appear it is out of range, its battery is flat, or your dongle does not support BLE, here you can see it as ID107 HR:

bluetoothctl remembers your devices, so when you next use the program the watch appears on the list at the start. The controller has a number of options, these can be seen with help command. You can use show to view the status of your dongle:

The list of UUID’s show the services supported by the Dongle. Now we can power the dongle on, set the agent – this manages the connection, and then connect to the watch on which the bluetooth symbol will appear. Once connected there will be a pause then you will see a list of attributes supported by the watch, it is advertising the services available:

and now that we have connected we can ask for some info:

These UUID’s are used to describe the sevices available on the device, some are pre-defined and can be found in the a href=”https://www.bluetooth.com/specifications/gatt/characteristics” target=”_blank” rel=”noopener noreferrer”>GATT schema, others are vendor specific and unless they publicly release these, decoding can become rather difficult. There are four types of attribute:

  • Services – collections of characteristics and relationships to other services that encapsulate the behavior of part of a device
  • Characteristics – attribute types that contain a single logical value
  • Descriptors – defined attributes that describe a characteristic value
  • Declarations – defined GATT profile attribute types

Each attribute is identified by a 128 bit ID, for example, one of the characteristics from the list above: 00002902-0000-1000-8000-00805f9b34fb, the first eight bits are used as an unique identifier: 00002902 and are shown as UUID’s: 0x2902. Data is contained in services, each service has a number of characteristics that may contain further descriptions depending on the requirement of the characteristic. You can see how the data is mapped out in this chart:

Service Containers

A spreadsheet with the watch data reformatted and tastefully coloured to illustrates this. Observe the Service URL column, it looks a lot like a directory structure:

Here we see two services /service0008 and /service000c looking further into the second service: /service000c we see that it has four characteristics, and to of those have descriptors. We can interrogate the characteristics and descriptors to glean further information by selecting the attribute and reading, like so:

Which is all very nice, but not particularly helpful as the manufacturer has chosen to use custom, proprietary, UUID’s for the watch. We don’t know the instructions to send to have the watch realease its data.

Those Scripting BlueZ

Inevitably, you’ll be wanting to automate connections. This becomes easy with the automation scripting language expect. Install, then make a script file:

In this example the script forgets the watch, finds the watch, connects to the watch, gets some info and then disconnects:

in the script, send sends a command, don’t forget to add the carriage return – \r and expect is used to wait for a response within the timeout period, here it is set to 10 seconds. expect -re is using regex when looking for a reply, otherwise it uses a literal string. So much more can be done with expect and there are many tutorials, such as this one written by FluidBank.

More Bluetooth Data

For analysing bluetooth data a couple of very useful tools are available, Wireshark and Android data logging. I will go through the installation but not look at the data in any detail, this posting is getting a bit long. This Section is in two parts, installing Wireshark and Android Debug Bridge.

Sniffing with the Shark
Wireshark is a network and bluetooth packet sniffer, it shows you network and bluetooth traffic occurring on your Pi. Here is a quick installation method for a reasonably new version of Wireshark (v2.2.4) from the backports, answer yes to the question “Should non-superusers be able to capture packets?”:

and if you get a message about permissions, reconfigure the package and answer yes:

Start Wireshark and double click your bluetooth device on the list, in my case bluetooth0. There is not much to see as Wireshark will only see traffic between the watch and the Pi:

Wireshark Data Capture

Android Debug Bridge – ADB
For Anroid 4.2.2 and above, activate developer mode on the phone, go to Settings, tap About Phone and at the bottom of the list tap Build Number three times. Back in the main settings page Developer Options has appeared, tap developer and turn USB debugging On. With the phone plugged into a USB port a little Android head should appear in the information bar at the top-left of the screen. To begin we will need to install some udev rules written by Nicolas Bernaerts:

Install the android tools, confirm that you have at least version 1.0.31, and start ADB

At this point on the phone an allow USB debugging dialog will appear, give permission and always trust to authorise it. ADB will now show the device as a device:

If the device list is empty, with everything plugged in good and proper and the phone setup in developer mode, start your diagnosis by checking udev; open another terminal window and view logging with udevadm monitor –environment and reload with sudo udevadm control –reload I’m not entirely sure what I did to get it from ‘not working’ to ‘working’. If all else fails elevate yourself to root.

Data Capture
With ADB now setup we can capture the Bluetooth data being exchanged. With bluetooth off, in the Developer Settings find Enable Bluetooth HCI snoop log and turn it On. In the smartwatch app synchronise with your watch, once complete turn Bluetooth off manually – this is to minimise the amount of captured data. Don’t forget to turn logging off on the phone when done. To find where the log file has been stored and copy the file from the phone to the Pi use:

We can now use Wireshark to read the log file…

Wireshark reading the Android Bluetooth Log

This wasn’t quite the posting I originally had in mind, I wanted to decode the data from the watch for my own use, making something more useful, impressive graphs and charts, than that provided by the Android App VeryFit 2.0 but as the manufacturer has chosen to use proprietary GATT codes it makes the job that much harder. It may be much simpler to just buy an expensive FitBit and download the data from them. But with writing this I now know a few things that were previously unknown, and I hope that this has provided some light to your BlueZ (a pun!, right at the end!).

Links and Sources

Fixing the Arduino incoming network connections error on the mac

On the Apple Mac if you use the Teensy micro-controller with the Arduino IDE you may have come across a persistent firewall error message when starting the IDE, I have seen this error for quite a while over a range of system and software upgrades. I have applied this fix to:

  • OS X 10.10 Yosemite and above / macOS 10.12 Sierra
  • Arduino IDE 1.6.13 – all versions, at least 1.5 and above.
  • Teensydunio 1.33 – and older versions

The Arduino IDE is installed in the default applications folder, as is the Teensyduino. Some knowledge of using the terminal is required.

Symptoms

On your Apple Mac, you installed the Teensyduino software for the Teensy and now when you start the Arduino IDE this error message appears:

Do you want the application “Arduino.app” to accept incoming network connections?
Clicking Deny may limit the application’s behaviour. This setting can be changed in the Firewall pane of Security & Privacy preferences.

Incoming Network Connections Error

Cause

When the Arduino IDE is installed it includes a certificate to assure the system that everything is correct, the Teensyduino installation makes changes to the IDE configuration and this causes a mismatch and the signature in the certificate does not match the installation.

You can verify the failed certificate in the terminal with the spctl command:

Without the Teensyduino software installed, the certificate shows correctly:

Another check is to use codesign

Fix

To fix this, first we need to create a self-signed certificate. In finder Keychain Access can be found in Applications > Utilities > Keychain Access

Keychain Access certificates

From the menu choose: Keychain Access > Certificate Assistant > Create a Certificate… and set the following:

  • Name: anything useful, without spaces. You will be using this name later to apply the certificate – I used ‘arduino’
  • Identity Type: Self Signed Root
  • Certificate Type: Code Signing
  • Check the box “Let me override defaults”, this is important
Certificate Creation

click continue, and continue again past the security warning, then over the next few pages:

  • Serial Number: 1 – The serial and certificate name combination must be unique
  • Validity Period: 3650 – this will give you ten years
  • Email, name, etc: anything you like, or leave blank
  • Key pair info: set to RSA, 2048 bits
  • On the next four screens, from “Key usage extension” to “Subject Alternate Name Extension” accept the defaults
  • Location: login keychain.

Once created and back in the list, choose your certificate and from the menu go to File > Get Info (Cmd-i). In the Trust section at the top change: When using this certificate to Always Trust.

Trusted Certificate

Now that the certificate has been created, you need to apply it to the application, in terminal use the codesign command, this takes a few moments:

You’ll be asked to verify this, click ‘always allow’. To verify that your certificate has worked, check with codesign, using spctl will not work as this is a self-signed certificate.

Now, when you start the IDE on first run it will give you the allow/deny message again, click Allow and on subsequent use it will open as expected.

Links and Sources