Recent Projects

Here are a few of my recent projects...

Forensic Analysis of Damaged Video Tape for Murder Trial

Occasionally, I get a call from my old friend Al (sorry, the case is pending so no full names) who I worked with some years ago at UT. Al is part of a consultancy that does forensic analysis for expert witness testimony in trials. Al calls when there is a technical issue and he would like my help on it. It usually has something to do with an audio or video recording. The latest was an interesting murder trail. Here's the scenario:

  1. Bank robber robs the bank in a small town; shoots and kills the teller.
  2. The robber then pulls the VHS surveillance video cassette from the recorder and shoots through it.
  3. The tape is sliced by the bullet into a few thousand small pieces.
  4. The video on the tape was the best evidence for convicting the bank robber of murder.

I received a picture from all showing the damaged VHS cassette and fragments of 1/2" video tape. A glance at the picture gave me some hope. VHS video is recorded using two record heads on a small drum spinning at 1800 RPM. The tape wraps approximately halfway around the drum at a skewed angle. Each head records one video field (half resolution image) as it traces a path digonally across the tape. Two adjoining tracks provide both fields of a full resolution image. This recording technique is used by several video recording formats and is known as helical scanning.

Helical ScanFor VHS, the fast spinning head lays down a track approximately 100mm long (a bit less than 4 inches) and the head to tape speed is about 5.8 meters per second. The actual forward speed of the tape is only about 33mm per second for standard video recording. Surveilance recorders move the tape much slower and skip frames of the incoming video to make it possible for one video cassette to record all day. The fast spinning head recording speed is necessary to record the high bandwidth of the video signal.

Knowing the length of the video tracks meant that if any segment of the tape was about 3-4 inches long (remember the 4 inch track is at about a 25 degree angle) could contain full frames of video. If you owned one of the old VHS home video recorders you know that they could "freeze frame."

So, I got back with Al about mounting any segment of the broken surveilence tape longer than 3 inches on a carrier tape to permit it to be positioned in a VHS player for a freeze frame. Fortunately many of the pieces were long enough. Once Al had done the necessary splicing of the segment of tape into a new tape to use as a carrier, a digital image was captured from the tape showing the robbery.

The needed images to identify the suspect were now available for use in court. It feels nice in an odd way to help bring someone to justice; especially in the case of murder. Of the cases I has supported in the past this has not always been the case. In one case both sides provided their own analysis on a 911 audio recording and the judge threw both sides analysis of the audio out of court.

Unity in the Heart of Austin Church

Founded in 2008 Downtown Unity Circle (recently renamed Unity in the Heart of Austin) was ready to move from leasing a hall on Sunday to finding a commercial space to call their own and building it out into a church with sanctuary, offices, kitchen and classroom space. This project started as a part time involvement in September 2013 as project requirements were gathered and possible sites were scouted. In late January 2014 it became a fulltime project once a site had been identified and a lease was signed. The location facing on I-35 was approximately 4500 square feet that was formerly builtout as office and file storage space for the Insurance Council of Texas.

This was my first time to do a commercial building project. I have done my personal residence some 20 years before. I really enjoyed the project and appreciate the thanks that I received from the church for my help.

Ideation - Putting together requirements and turning them into a design is a special challenge when the client is a church. While the minister and board are key stakeholders, utlimately the entire congregation has to be onboard because they will finance the project.

To achieve that a special meeting was called to get the congregations input on programs to be supported by the design, then a few concepts were drawn up and another meeting was held to get the congregation's feedback. The congregation was shown large floor plan plots that they could sketch over with whiteboard markers.

Once the floorplan was mostly defined I created video fly-through to make the project easier to understand and to help market the concept. That fly through is on the right.

Key features:

  Downtown Unity Project Fly-Through Video Sketchup Animation Created and Copyright 2014 by Charles Mitchell
Sanctuary with 120 Seats Three Childrens Classrooms Nursery with Nearby Restroom
Minister's Office Administrative Office Adult Education Classroom
Welcome Lobby ADA Compliant Kitchen ADA Compliant Restrooms
Sanctuary A/V Control Room Storage Closets Enhanced HVAC for 200+ Occupants

Architectural Drawings - We were fortunate that a local architect was willing to do our drawings for permitting and getting bids at a reduced rate. While there were a few refinements late in construction (e.g., add an outlet here please) there was only one signficant revision once the demolition of the prior office space was complete. A structural post that would be in the seating area of the sanctuary was judged to be too much of a sight line problem and the placement of the stage and storage closets were rotated 90 degrees to eliminate the problem.

Construction - The project plans were put out for bids and three contractors replied, including the building owner's preferred contractor. The latter won the big both on competitive price and experience building out other projects in the 25+ year old building. Demolition of the old offices took just a week and in another week the floor was clean and the position of the new walls was marked on the concrete. That's when the issue with the structural support was discovered. I informed the minister and board president immediately and had a late night conversation with the architect. Together we decided to fall back to an alternative layout for the sanctuary that was in one of our early proposed layouts shown the congregation. The changes to walls was minimal, affecting less than 50 linear feet. The contractors began construction in other areas while plans were revised during the next week. By the time the contractor was ready to build the santuary walls the plans changes were complete and approved. Hence, there was no delay in the schedule.

Finish Out - The walls were up, the carpet down and the decorating committee was busy picking out furnishings when we hit our only significant delay. The building owner had not forwarded the plans to the security system company. The building management wanted to handle this and it was not part of our project, but getting a certificate of occupancy usually requires the alarm system to be in a functioning; especially in a building that does not have a sprinkler system. Fortunately, a relationship built with the city by one of the stakeholders got us temporary occupancy while the alarm system was being finished.

AV System - The church's online presence was key to its growth so the equipping of its AV system was handled in two phases. The first was ready with occupancy and consisted of a full sound system with all cables to the stage and speaker system prewired so that all that was needed in the control room was a mixer and amplifiers. I also handled the second phase as a separate project that I like to call HD on a shoestring budget. I'll cover that separately.

Occupany and Grand Opening - Temporary occupancy came in June 2015 with full certification in July. Below are pictures of the outside of the building and two interior shots.



HDTV Studio on a Shoe String

Unity in the Heart of Austin began posting video of their services in 2009 using a single camera. As the typical Internet connection got better so did the quality of the single camera video. With the new church facility the board of directors and minister wanted to significantly improve the quality of the video but had a very limited budget.

I researched and proposed a system that used three consumer grade cameras and a software based switcher that would give the church the ability to record or stream 1080p video with titles and integration of video and slides used to illustrate talks or project hymn lyrics. With the board's approval I implemented the system within the budget and met all the project requirements including the ability to operate the video recording and house sound with just two operators.

Cameras - To save money the existing Canon HF S-100 camera and fluid head tripod was reused. It was placed within the control room peering out the window into the back of the sanctuary. Fortunately, it had a relatively unobstructed view of the stage down the center aisle. The second camera, a Sony CX-290 was purchased used from Amazon.com at a significant discount. It was mounted on a ProAIM Jr. remote pan-tilt head suspended from the santuary ceiling towards the left side. The third camera was a Microsoft LifeCam 1080p, a camera usually used for video conferencing from a PC. Test showed that the camera delivered a very good quality fixed shot from the right-center of the sanctuary. This third camera was to be the 'emergency go to' camera with a view of the full stage. It would be used when either of the other cameras were changing their shots or had their shot blocked.

Camera - Both the Canon and the Sony cameras have HDMI outputs. The Canon was just a few feet from the PC running the switching software and used a mini-to-standard size connector HDMI cable. The Sony camera mounted on the pan-tilt head was about 30 feet away and an amplified 50 foot HDMI cable was used to connect it to the PC. A micro-to-standard size HDMI adapter was used at the camera to make the connection. Both the Canon and Sony cameras were LANC compatible via adapters plugged into the cameras. Both used BENQ LANC controllers to remotely control the power of/off and zoom. The Sony camera on the remote pan-tilt head had 1/8" stereo extension cable from the camera to the LANC controller. The remote camera also had power and the remote head control cable bundled together with the LANC and HDMI cables returning to the AV Control Room.

Black Magic Design Mini DeckLink Capture Cards - Two of the DeckLink cards each plugged into a single lane PCIe slot capture the 1080p video via the HDMI cables. These cards also have an SDI interface that can be used to connect to cameras via coax when the distance it to long for an amplifed HDMI cable. That becomes a requirement somewhere around 100+ feet. The presence of the SDI connectors was insurance against using a 50 foot amplified HDMI cable but the amplified cable proved to work just fine. The third Microsoft LifeCam 1080p used a 50 foot amplified USB 3.0 cable to connect to an USB 3.0 port on the back of the switcher PC.

ViMix HD Software - Initially I contacted other churches to see what they used as a video switcher. I quickly found the cost of even the simplest Sony or Panasonic HD switcher I found at another church was $3,500. Many had video switchers costing much more. Any of those would have busted the budget. I looked at Black Magic Design's own switcher, a rack mounted device that required a PC to control it. Then I found Vmix, a software switcher product from a Australian company. I was skeptical at first but I was delighted when I downloaded a trial version to my home desktop PC. I ordered one of the Black Magic Mini DeckLink Cards to try it out with the church's existing camera. The software worked really well so I took a bit of a risk to go with it and a PC built out to ViMix's specs. It has turned out to be a great decision.

The Switcher PC - VMix recommended an Intel Core i7 processor and demos the software in online videos using a notebook PC with Core i7. Since a desktop has a better thermal envelop and the processor can run much faster I went with a Core i5-4690S. This is a quad core Haswell-generation processor with clock speed up to 3.9 GHz. About 25% faster than the processor used in the VMix demo. Again, this processor has an advantage over the one VMix used for demonstration videos. The Haswell-generation processor is a newer design with 5 - 15% greater performance per clock than the older Core products. In short, the system works great with the Core i5-4690S and the processor utilitization is about 50% during shoots. VMix also recommends NVIDIA graphics cards and I equipped the PC with one of the latest budget models. There is no need to buy a more expensive version since the video encoder built into the card is what VMix uses. In the future VMix might use the computer power of the GPU.

Here's a block diagram of the full design and a costed bill of materials.

Costed Bill of Materials:

  • $315 - Vmix HD Software ($349 AUD)
  • $157 - Opened Box Sony HDR CX-290/Li
  • $475 - PROAIM Jr. Remote Pan-Tilt Head
  • $  27 - Vivitar LANC Controller with Sony A/V R Adapter
  • $  25 - Sony VMCAVM1 A/V R to Multi Terminal Adapter Cable
  • $  56 - Microsoft LifeCam Studio 1080p (Cam 3 for fixed wide shot)
  • $  50 - Rosewell MicroATX Tower with 450W Power Supply
  • $  69 - Asus H81M-PLUS Motherboard
  • $215 - Intel Core i5-4690S (Haswell 4-core 3.2GHz Base, 3.9GHz Boost)
  • $147 - BlackMagic Design DeckLink Mini Recorder Capture Card (Camera 1)
  • $147 - BlackMagic Design DeckLink Mini Recorder Capture Card (Camera 2)
  • $  80 - Two Kingston HyperX 4GB DDR3-1600 DIMMS (8GB Total)
  • $  87 - Samsung 120GB EVO-series SATA III SSD
  • $  58 - Western Digital Blue 7200RPM 1TB SATA 6Gb/s HDD
  • $110 - Gigabyte GTX750 GDDR5-1GB 2xDVI-D/I 2xHDMI Graphics Card
  • $130 - Asus VS228H-P 22-Inch Full HD LED-Lit LCD Monitor
  • $  15 - Amazon.com Basics Keyboard and Mouse
  • $250 - Lots of Cables (VGA, HDMI, Audio, Etc.) and Hardware
  • $  10 - Pyle PLGI35T 3.5mm Stereo Audio Ground Loop Isolator

Total of about $2423

You can watch one of the videos produced by this system on the church's YouTube channel by clicking here. Videos starting with "In the Beginning: A Metaphysical Exploration of John" from September 7, 2014 use the new system. Videos are posted on YouTube in reverse order so newer videos are on top.

The video is surprisingly good considering the shoe string price tag. Probably the single improvement that would make the greatest improvement in the video quality would be to replace the Sony CX-290 camera with a camera with less video noise. Used Canon G20 cameras in perfect working order can be purchased for as little as $500 and would greatly improve the remote camera video quality.

If your church or other organization is interested in learning more about this type of inexpensive solution for broadcasting on YouTube go to the Contact page and send me a message. I would be delighted to share more information.



I Love Projects

And I like writing about them. So as time passes I'll write some more.