I/O connectivity

I/O Connectivity

Disclaimer - these notes should be considered as "practical suggestions", and as such no guarantee can be given as to your success in achieving desired outcomes. As with all technological issues, the basic principles of read the manuals- especially regarding power considerations and connectivity, check power and signal cable integrity, check connections and check configurations should be some of the procedures routinely undertaken before embarking on working with A/V computer I/O work. Similarly, provided links are for information purposes only and generally have Australian companies as their target. Usually there are a number of sources for products.

There are a diverse and large number of input/output devices on the market that can provide you with a connection you may not have thought possible.

Glossary

• Dongle - This is the common name given to a small plug-in device that provides connectivity. A very common "dongle" is what is also known as a USB Flash drive that connects a memory module to a standard USB port and looks like a secondary storage device.

• W - refer to the power in Watts- usually electrical input, not sound output. Contrary to what you might expect, 2 W power capability is not twice as loud. Because the human ear response is logarithmic, to get a perception of twice as loud you need to provide 10 x the power. It also helps if the sound is "mainlined" into your ear canal so you don't lose 99.9% of the sound to surrounding free air. These two facts explain why iPods need only tiny sound pressure drivers (speakers) requiring less than 20 mW and rock concerts have huge sound pressure towers and kW of power input to achieve the same perceived sound level at your ear.

• dB - refers to deciBel (1/10 Bel). The unit of loudness used to describe sound levels. Actually, it is a ratio of a signal to a standard signal. For sound, humans are reasonably comfortable with 60dB to 90 dB. Any device capable of generating more than 95dB (at the ear) is going to be on the borderline of producing deafness. As a rule of thumb, if you stand about 1 m away from someone using ear buds, and you can hear the sound- it is too loud! dB specification is very complex because of what it is referring to. There is no standard form of measurement. Generally, dB refers to the ratio of a sound intensity at one location compared to a standard intensity, however another important use is comparing sound levels from a single source at different distances. The standard distance is 1 m. It is now becoming more common to also quote sensitivity which is expressed in sound pressure (Pascals) at 1 m or 0.1 m. This is a much more meaningful specification.

• 240 VAC - the standard description for domestic power distribution. VAC stands for Volts Alternating Current. Actually, these days it is defined as 230 VAC (50 Hz) to harmonise with international specifications. 230V is 2 x 115 V which is the standard US domestic power supply.

USB and Firewire Compability?

WARNING: Firewire and USB are not hardware compatible, nor protocol compatible. Only a peripheral device that will be expensive , and specially designed can perform the conversion. Eg. A hard disk drive that has both USB ports and Firewire ports cannot use both ports at the same time. The issue is almost identical to converting analogue video to digital video.

Any device that has only USB ports is NOT plug compatible with Firewire. Any peripheral device that has both Firewire and USB ports (such as a a USB/Firewire Combo Hub) cannot be used to "convert Firewire into USB" or vice versa. At present only computers can do this job. It is highly unlikely that reasonably priced converters will come onto the market soon because Firewire is now considered to be a "niche market".

There are now on the market, adapter plugs/sockets that allow you to use cheaper USB cables for Firewire connection. The only thing they do is connect (USB to 4P Firewire) the wires. They don't provide the same power to the peripherals and could damage the peripheral device- or not work at all. You need two of these devices (one on each end of the cable) to be useful.

This issue goes even deeper. Firewire and USB operate completely differently. To be able to connect a Firewire device into a USB port would require a very expensive micro-controller based protocol converter. This is because USB relies on the CPU to drive the protocol, while Firewire ports are driven to a large extent by a dedicated micro-controller operating independently of the CPU. This is one major reason why Firewire is much more efficient at transferring large amounts of data- e.g.. to/from disk drives or devices that produce streaming video. While the basic specs(speed) may seem similar, the closer you look the more different they appear.

Portable Multimedia - Speakers

In setting up a standard size classroom for multimedia, unless you are going for 100 dB C+ and infrasound simulating earthquakes then stereo 2 x 10 W power input is adequate.

If you are looking for a good lightweight, robust, relatively inexpensive self powered (from 240 VAC) stereo speaker pair then try the Logitech X 140. These can be found at various stores including DSE, Woolworths Big-W and Harris Technology for around $60(2009). They are very suitable for classroom use where you may have to set up and pull down each lesson.

These are 2 x 5W with active bass equalisation-providing excellent bass response in a very small solid plastic enclosure. They can be set up vertically or horizontally on a table and have independent volume control. They are permanently connected by a single cable that allows you to locate the two speakers about 2 m apart. We often place them fairly close together. They plug straight into the standard 3.5 mm stereo audio out socket of laptops (the plug is coloured light green for PC users) and the power plug into a 240 VAC power outlet.

Although not indicated as a feature, they have a very robust metal grill over the speaker cones, and a compact storage design making them very suitable for classroom use.

Audio USB

Although these are listed as particular application interfaces, they may be used with standard equipment. For example if the device has a phono connector it will be able to directly connect with other equipment with a similar connector (unless specifically stated otherwise).

HEADSET INTERFACE (private work, making PodCasts)

Glossary

LED - light emitting diode. CODEC - Coder-Decoder. A dedicated processor that converts analogue signals to digital signals or one form of digital signal to another digital signal in real-time (as it happens). Consequently codecs are either very fast software or dedicated silicon processors.

if you want to provide a USB plug-in connection for a headset (or equivalent) for a Macintosh, LINDY sell the LINDY USB Audio Adapter (42961) dongle.

• connects directly to a USB port (no drivers required)
• connects to a standard headset Audio In (3.5 mm) and standard headset Audio Out (3.5 mm) - of course these may be separately connected.
• appears as a Sound Device called 'C-Media USB headphone Set' in the Sound Pane of the System Preferences of Mac OS X. Input volume, Output volume, L-R Balance and Mute can be controlled from the control panel.
• the dongle has a Mute Button, an ON LED indicator and a active channel LED indicator.

You may also be able to purchase a similar dongle + headset package, for example form OfficeWorks.

SOUND SYSTEM INTERFACE (general Audio editing)

Glossary

Cinch, Phono - standard analogue audio connector. This is where the term "it's a cinch" came from. Should not be used for any other purpose because it is so common. These days there are a large number of types, indicated by colour coding of the barrel. There are Red(Audio), White(Audio), Black(General), Yellow(Analogue Video), RedComponent Video),GreenComponent Video), Blue(Component Video) and Orange(Digital Audio) types. Be careful of the red- it is used for both audio and video.

EDIROL made by Roland, have(had) a similar USB dongle, the UA-1X. It provides a plug-in and go approach, identifying itself as "USB Audio CODEC" in the Sound Pane of the System Preferences.

• it is a high quality analog to digital audio interface.
• provide L-R Phono (Cinch) input and L-R Phono(Cinch) outputs. Both are controlled from the Sound Pane.
• it also provides an 3.5 mm electrical/optical headphone output with a volume control on the dongle.

Behringer also sell a similar device.

Video

Converting old VHS tapes to digital

Glossary

Transcode - convert one digital/analogue signal to another digital/analogue signal. This can be done either in realtime during the copying process, or as post processing after copying from one media to another.

NLE - Non linear editing. Basically, using iMovie. In the past the capabilities were either in hardware devices costing hundreds of thousands of dollars or software costing thousands of dollars that ran on hardware costing tens of thousands of dollars.

Acquiring digital video is not a major issue any more- there are plenty of video recorders and CD-ROM, DVD sources. However, schools may still have a large number of VHS tape based video recordings and some may still be very useful.

• Firstly, remove any that are marginal or considered not worth converting. The major technical considerations are loss of colour saturation, visual noise and loss of colour balance (recorded as AM and Phase M). Sound quality normally is maintained because of the way it is recorded (as FM).

• The next step is to find the very best tape VHS player you can make use of, even if you have to buy one especially for the task. If that is your only option, choose a combo VHS (player)recorder/ DVD recorder. This will allow you to have a relatively compact set up that you can leave unattended while transfer takes place.

• Plan the process- it will take a long time.

• Before recording each tape, go through an unspooling process to loosen the tape so that you don't have stuttering issues (due to stiction). Rewind the tape to the beginning, fast forward the tape to the end, and again rewind the tape to the beginning before you begin the copy process.

• Convert the material into digital format- this will take considerable time since you are playing the tape. Make sure you catalog the work as you go. Use the best copy format on the digital side (meaning the DVD will hold less material in terms of recorded time but will more faithfully record the analogue signal).

• once in digital form, recorded onto DVD, you will then need to get access for post processing. The first thing to do is transcode the result to a common file format (VIDEO_TS on a standard DVD is not easily edited) without down converting the format. Generally anything Quicktime can handle is OK, but you should aim for a standard size (generally nothing less that 800 x 600 pixels- more if possible) and highest quality of conversion. Apple have just released a new video standard, the iFrame format: 960 x 540 which is 1/4 of 1920 x 1080, a standard HD digital TV format. This would make it compact, and easily 2 x up-scalable with little noticeable loss in quality. Sanyo recently introduced two camcorders with this native format. A well respected Open Source Software transcoder is Handbrake. This will provide you with some easy to follow instructions.

• the final stage is to edit the video to make it useable- in a modern setting this usually means chopping it up into 5 to 10 minute sections- and is easily done in iMovie 8. Processing it with iMovie 8 also allows you to restore some of the colour saturation(the recorded signal loses amplitude over time due to thermal de-magnetization), reduce visual noise (arising from random re-orientation of magnetic particles), and restore colour balance (higher frequencies tend to diminish faster than low frequencies-blue fading ).

USE A USB 2.0 Dongle

AVLabs DVD Maker is a USB dongle you can get from City Software. It will convert composite PAL (Standard Video) and stereo audio from a VCR directly to MPEG4. Resolution is PAL 720 x 576 @ 25FPS. This would need sufficient HDD space- at least 2GB (but not USB connected) and at least a 1.6 GHz processor. Don't plan to use the computer for anything else while you are doing this.Set up and let run overnight would be a good approach.

Firewire realtime transcoder - more expensive but easier to use and with a better result

Canopus make a range of hardware signal converters/transcoders that work very well with analogue sources (video and audio) converting them to digital files that can be used on the Mac. They are "plugNplay" and basically connect the outputs from a VHS player/analogue TV to the Firewire port on a Mac. They can convert audio only, video only or synchronised audio video. No additional software is required to use the device.

Making Podcasts

You must plan and develop a script (usually typed text to be read, possibly with instructions) before you produce a podcast particularly if you intend to work to a specification such as "no more than 2 minutes". The podcast needs to have the same format as any story: prologue, middle(major content), and epilogue. For a 2 minute podcast you would begin, with say a basic plan of, a 10 s prologue(introduction- with perhaps theme music), 1 min 40 s middle, and 10 s epilogue(sign off- with the same theme music).

BASIC QUALITY

Making podcasts requires minimal equipment beyond an excellent computer and software like Garageband. The only other equipment you really need is:

• microphone
• quiet space - that does not have large flat, shiny surfaces

Since microphones are part of modern Macintosh laptops computers you can make Podcasts "straight out of the box". All processing (such as cutting and splicing, assembling, adding echo/ or reverberation or background music ) should be done after you capture the audio.

SEMI-PROFESSIONAL QUALITY

If you are planning on making higher quality product then it would be desirable to build a "studio". This could be as simple as setting up

• some acoustic tiles arranged like a "booth" . Acoustic tiles can be expensive, but they work well and you don't need very many. The idea is to minimise sound reflections from hard surfaces which can cause the sound to be "muddied".

• a "studio quality" microphone. There are now semi-professional microphones that have USB connectors such as Samson GoMic Portable USB Condenser Microphone, with all of the analogue-to-digital conversion and powering of the microphone element done in a processor in the microphone. They are very suitable for this kind of application. Generally Macintosh computers will automatically recognise these as an alternative audio-in device so you can "patch" it using the sound preference pane or a dedicated application.

All processing (such as cutting and splicing, assembling, adding echo/ or reverberation or background music ) should be done after you capture the audio.

Podcasting is now recognised as a form of media generation and as such major manufacturers of A/V peripherals now package what you need to make audio podcasts usually for a very good price. There are generally two types: USB based system, Firewire based system. The Firewire system is usually of a higher quality than the USB system and with a correspondingly higher price.

For most podcasting, you can start with the basics: a microphone feeding the microphone input to a laptop computer and using the controls offered by Core Audio and Audacity. You only need to get hold of a relatively inexpensive microphone, Audacity (for free) and you're in business.

Moving up a notch, you will want to obtain a small mixing desk that provides at least LEVEL control and COMPRESSION control. A good quality dynamic microphone or condenser microphone is useful at this stage. A complete package would cost in the order of $200 to $300. It would also be worthwhile at this stage looking at how to use Garageband and iMove to add to the post narration composition.

There are several enhancements possible after this: either go down the path of using USB technology or Firewire technology. Assuming you want to make the upgrade easy, and so that you can use the equipment with a number of different computers, USB would be OK. Bear in mind that it is limited to managing a stereo pair (input and output) per USB port. The main limitations appear too be the CODEC chips used, operating at Rev 1.1 (12 MHz) rather than Rev. 2.0 (480 MHz). However this is not a major limitation if an appropriate setup is used.

A second consideration is the way in which the interface/mixer is powered. Less expensive models or models that provide more than 6 channels use external power. While this may be useful in terms of a power, it has drawbacks (1) you need to carry an external power brick (2) it is one more cable to worry about.

Interfaces/ mixers do not record the signal, only capture it, process it while it is analogue and convert it to digital form. The attached computer, or Digital Audio Workstation(DAW) does the digital processing including saving.

Several companies have reduced these issues to USB powered mixer/interfaces. One of the more ergonomic range is the Audiogram 3/ Audiogram 6 range from Yamaha that also comes with Cubase AI recording software. These are USB powered AND provide one TRS/XLR combo port with Phantom +48 V power on channel 1-essential for good quality condenser microphones. The Audiogram 3 additionally provides stereo in/ stereo out and headphone monitoring paths, hence 3 signal paths. It does not provide COMPRESSION. Mixer based compression, that dynamically limits the signal range while recording is almost essential because raw narration can be very plosive, and the level can vary considerable over a short period of time.

The Audiogram 6 has been well designed and expands on the Audiogram 3 capabilities with 3 more signal paths,(a second microphone and second stereo in), as well as adding COMPRESSION to the microphone path and GAIN control of the two microphones and 2 stereo line level paths. They can be purchased from music stores. In response to issues regarding latency, signal dropouts and compatibility with SL 10.6.+, Yamaha have released Audiogram3, Audiogram 6 Driver for Mac -10.4.11 to 10.6.+ that may be used instead of the generic Core Audio Drivers. When these are installed the device reports itself as "Yamaha USB 2 in/ 0 out" and Yamaha USB 0 in/ 2 out" to Core Audio rather than the generic "Audio Codec" and will do D-A(signal out) at 32 kHz, 44.1 kHz or 48 kHz. Interestingly it does A-D(signal in) at 8, 11.025, 16, 22.05, 32, 44.1 kHz and 48 kHz. If at all possible set both to 48 kHz, you can always down convert later. The lower rates are assumed to be for capturing low quality speech to produce very small files.

A simple sound synchronisation technique to help in post production

Besides podcasting, these small mixer/interfaces are useful for easy synchronising audio from a camcorder to an external microphone. One technique is:

• Record the stereo "ambience" L-R tracks using the camcorder, but instead of monitoring through headphones connected to the camcorder, pass the line level R signal out to the mixer onto the R channel. Do not mix the L-R signal first because you want access to just the R signal in two different ways.
• Connect a studio style microphone to the mixer on the L channel.
• While the camcorder is recording, it will record the L-R ambient tracks. The DAW will record through the mixer the L ambient track and the higher quality R track from the external microphone. You can monitor the process using the headphones output on the mixer/interface or through the DAW.
• When the recording is done you will have 3 distinct tracks (2 x L-R).
• Load the audio from the camcorder in to the DAW, and carefully align identical points on the the R camcorder track with the R mixer track. You then have all 3 distinct tracks perfectly aligned, and editing can begin. This process precisely removes any latency that may exist in the system and makes it easy to synchronise speech with video.
• Before starting editing, create an additional stereo track (L-R) for background music.

USB

4 PORT HUBS

It is very useful to purchase a multi-port USB hub. But be careful in what you connect to it. There are a number of gotchas.

• A USB 2.0 hub will run at the speed of the lowest connected device - so don't connect a(extra) keyboard or mouse, that runs at 12 MHz (USB 1.1) in with a USB Flash Drive (USB 2.0) that runs at 480 MHz. This is one reason why Flash drives sometimes seem to work slowly on some machines, compared to others.

• Always run the hub from an external power supply so that you can connect high current draw devices without overloading the device. You will not harm it but will just refuse to operate (properly). A few years ago we had a terrible time with people overloading hubs. The issue was intermittent and seemed unpredictable, until we Iooked at what was being done. At times people were intermittently inserting several USB devices into a hub at a time- that was line powered(max 500 mA current draw for all functions-ie equally distributed about 100 mA per USB socket) and was in the days when USB Flash Drives consumed much more than they do today. This caused the hub to exceed the maximum allowed current draw causing it to reset and renegotiate the link, or even go into a power-down mode to self protect. Not good when you have other flash drives connected or streaming audio/video or hard drives connected. Today, the same issues could arise with other types of devices- such as hard disk drives, and USB powered devices- such as speakers.

• Be wary of connecting external 2.5" portable hard drives that claim to connect directly to USB ports without external power. These operate at close to the rated maximum current draw. (500 mA). Connecting two or more of these requires externally supplied power, and are best connected to a dedicated channel into the computer.
• Don't be tempted to construct a RAID from these(as if you would try!). They might just possibly work, but that is all! USB was not designed for RAID.

REAL-TIME VIDEO STREAMING

USB was not designed for video streaming. It does not handle isochronous links very well and unless the video is highly compressed, well buffered, packaged into relatively small packets and feeding a direct USB connection into a computer- in which case it can establish and maintain an isochronous link. Never use a hub. You should consider using Firewire instead. On the other hand, these days, the recording and buffering of free-to-air digital TV programme material is done using hard disk drives or dedicated hardware.

FireWire

Glossary

FW400, FW800 - the clock speed of the Firewire transceiver (FW400 = 400 MHz, FW800 = 800 MHz). Unless you connect a cable with 9P on both ends, the link will be auto-negotiated at the FW400 speed)

4P,6P,9P - the number of pins in the connector. Currently there are 3 types: 4P (FW400 without power support), 6P (FW400 with power support), 9P (FW800 with power support).

One of the decisions made recently by Apple was to "bring back" Firewire to their mid range of MacBook Pro range, after considerable user backlash. However they provided only one FW800 Port. Many FW products use FW400 so you need to buy a FW800 to FW400 connecting device. The link will automatically be established at 400 MHz. Despite the proliferation of USB devices, FW400/800 is the only readily available peripheral protocol that properly handles isochronous links. These are highly desirable for video work and high speed data transfers to and from external disk drives- particularly for HD video streaming.

There are at least two options:

• purchase a converter cable with a FW400 6P connector on one end and a FW800 9P connector on the other end

• purchase a connector dongle that is a FW800 9P plug connected to a FW400 6P socket. LINDY sell a device that also very usefully allows 300* rotation in two axes.