Audio for Podcasting: Hard Disk Recording

When digital audio first appeared, tape-based digital recorders using Digital Audio Tape (DAT) were the only viable system for recording the relatively large amount of data required by a digital audio recording system. This was because tape was less expensive to manufacture than hard drives, and tape was easy to store for later reuse. As hardware became more sophisticated, disk drives started to grow in capacity and performance, to a point where by the mid-1980's digital disk recorders started showing up in professional recording studios.

However, storage limitations and exorbitant costs meant that a 10MB drive could cost over $2000, and could hold only about a minute of audio. This worked great for MIDI and music sequencer applications like Cubase, running on the Atari ST computer (see Figure 1) but was insufficient for recording and editing high-quality voice-over narration.

Figure 1. Start of an audio revolution: Cubase 1.0 for Atari ST
[Click to enlarge]

However, as computers became more powerful, so the hard disk capacity used to store data on a computer grew. Its now common to see disk drives that store 100, 200, or even 500 gigabytes (GB) of data. Storing digital audio on hard disk makes a lot more sense and in fact now the most affordable alternative. Today you can buy a one terabyte hard disk for about $300 that gives you hundreds of hours of stereo, 16-bit recording at a 44.1K sample rate.

Advantages of Hard Disk Recording
There are a variety of reasons why hard disk recorders are more versatile and powerful than their tape-based cousins. Advantages include:

1. Instant access time. The most expensive part of most tape machines is the motors that control the motion of the tape, called the transport. Transports are often very complex mechanical devices with very precise tolerances. Since a tape machine has to physically move tape linearly across the tape heads, and shuttle the tape from beginning to end, a powerful and reliable transport is required. The better the transport, the faster you can get from one portion of the tape to another, which saves time.
   
   A hard disk drive does not have this limitation. Hard drives are now fast enough so that any data stored on a hard disk drive can be accessed in an instant of time. This means that locating any portion of a song can be done almost instantaneously since there is no tape to wind. The elimination of rewind and fast-forward locate time is a huge benefit of hard disk recording. The less time spent winding tape, the more time can be spent getting the best take recorded instead.
   
2. Flexible and powerful editing. In tape-based systems, there are two methods of editing the audio on tape: re-recording over it, or physically cutting the tape. You can record over existing material on a tape deck or record between two tape machines insert new portions of audio or move audio into a new location. The problem with editing with tape this way is that in order to perform the edit you must wipe the original material by recording over it; this is sometimes referred to as "destructive editing". In addition, since you are recording, it takes at least as long as the length of the edit to perform it, that is, inserting a one-minute audio segment will take one minute.
   
   With hard disk based recording, the data that is on the disk can be re-arranged without having to be deleted. This is often called "non-destructive editing". The audio data on disk can be also be manipulated in many different ways. The power that a disk recorder provides over tape recorders in terms of editing is substantial.
   
3. Processing the audio. In addition to editing the digital audio data stored on a hard disk (by cutting, copying and pasting), audio can be processed using software algorithms called digital signal processing or DSP. Using DSP, audio stored on hard disk can be stretched and squeezed, raised and lowered in amplitude, put on its head and turned inside out just by re-arranging the zeros and ones. Additionally, a DSP-based hard disk recorder provides one of the most substantial benefits of digital audio in the first place because audio can be manipulated and processed while remaining in the digital domain. The only practical way to perform DSP operations on digital audio is when it is stored on hard disk. Tape-based systems, with their linear recording processes makes advanced DSP features impractical to implement, regardless of tape format used.

Next time: Authoring your podcast using an audio editor.

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Moodle 1.9 Multimedia – Book Review

I've used Moodle for about four years, and in that time I've found it to be an exceptionally useful, high-functioning and user-friendly learning management system (LMS). In my view, the one deficiency in its suite of resources is that it is less than intuitive in the way it enables administrators, teachers, and learners to create, integrate, manage, and deliver images, audio, video, animations and other media types.

Enter Packt Publishing's Moodle 1.9 Multimedia by João Pedro Soares Fernandes.

I opened my copy of the text with a high expectation that it would be an informative and practical reference text. Why? Packt Publishing have been providing Moodle reference books for some time now, and their texts are usually either very good or excellent.

Now read on...

Using open source software can be a daunting experience, regardless of your technical or business experience, and this text's purpose is to shorten Moodle users' path to competency in designing, developing and delivering multimedia on the platform. Broadly speaking, the text covers seven Moodle-related media-based activities:

1. Evolution of Multimedia
2. Using Images
3. Sound and Music
4. Video
5. Web 2.0 and other multimedia forms
6. Multimedia and Assessments
7. Synchronous Communication and Interaction

The author assumes previous knowledge of Moodle, but not prior experience of multimedia development. Appropriately for a book about Moodle, Fernandes uses a Constructivist approach to instruction, and the content is structured so that the reader learns experientially – you learn by doing. This is a very good idea indeed: for newcomers this goes some way to providing an understanding of why multimedia in Moodle 1.9 looks and works the way it does, it acts as a pertinent reminder for experienced Moodlers, and sets the context for the content creation chapters in the book.

The book is designed in a logical and linear fashion: the author aims to guide you through the basics of content creation in each featured media type. For example, in Chapter 2: Picture This you find out about using the open source image editing called GIMP to capture and enhance images, integrate images into Moodle, create comic strips using the free-to-use Strip Generator, export PowerPoint create slideshows, and use online resources like SlideShare.

Given the assumption of little or no technical background in multimedia development, the author spends a goodly proportion of his time - in detail and very effectively - spelling out the advantages, and disadvantages of various media types, as well a processes, "how-to's" and "gotchas" of using digital media in Moodle. With nearly 12 years experience as an learning professional specializing in e-learning, I would consider that I have a pretty comprehensive knowledge of digital media tools, technologies, and services. I'm delighted to say that Moodle 1.9 Multimedia introduced me to a range of resources that I had not encountered before. This is great: any resource that enables me to deliver content to learners in a more engaging and immersive fashion is a winner with me, and this book fits comfortably into that category.

As I mentioned at the beginning of this review, I think that Moodle 1.9 Multimedia would be an invaluable companion for those new to using media on the Moodle platform. As an experienced Moodle user (and media expert), I will use the book very much as a "just enough, just in time" resource rather than as an end-to-end guide through image, sound, and video development, though I would suggest that the text would work very well if used in this fashion.

Some other positive aspects of my "user experience" of the text included the author's accessible and direct writing style, and the availability of a sample Moodle course for learners to access and "have a play with." In my view this text is a straightforward and reliable companion for those who seek to find out more about - and use - multimedia in Moodle 1.9.

Click here to navigate to Packt Publishing’s Moodle 1.9 Multimedia web page.

Click here to download a sample chapter of the text (2MB PDF).
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Podcasting for E-Learning: Benefits of Digital Audio

The first principle of digital audio is:

Digital audio is the study of discrete values.

This characteristic is very important: it allows us to manage audio information very efficiently. Using digital techniques, the capability to process information is greatly enhanced.

In a previous post, I discussed a little about the basics of digital audio. Today, I want to talk about how digital audio technology benefits podcasters. What are its advantages over an analog system of recording?

Here are a few specifics:

1. Less noise than an analog recording system.
   In an analog recording system, magnetic particles are oriented by the tape head in a manner that is analogous with the audio signal that is driving the tape head. The tape itself has billions of little magnets on it, and it is physically impossible to orient every single one correctly. These remaining magnetic particles are randomly oriented, which shows up on playback as what is called tape hiss. With a high enough sample rate and resolution, digital audio produces recordings that have significantly less noise than analog.
   
   The noise in an analog recording system is usually expressed as a "signal to noise ratio". The signal to noise ratio tells you how much more signal there is on the tape recorder outputs compared to the noise in a audio signal. For example, a digital audio system using a resolution of 16 bits will often yield a signal to noise ratio of more than -90dB (in EMG’s in-house studio the noise threshold is, for example) for decibel, a unit of measurement in the audio world. -90dB means that the noise floor is 90dB below the signal level.
   
   It would take a very high-end and expensive analog recording system to produce even a signal to noise ratio of -60db. This difference of 30dB is dramatic: the noise floor in the analog recording system will be 1000 times louder than the noise floor in a digital system. The reason for this is quite simple: a digital recording system records only the binary numbers, not analog signals which accumulate noise from the imperfect recording process. Since a digital system only records numbers (zeroes and ones, or bits, to be specific), as long as the bits can be recorded and read by the digital tape or digital disk system, then the only thing that matters is the theoretical 6dB per bit of dynamic range that is determined by the resolution of the digital recording system.
   
2. Ability to make copies without signal loss.
   Another advantage of digital audio over analog is the ability to make as many copies of the original as you want without degrading the signal quality. Every time you duplicate an analog recording, you lose audio quality and add even more noise. Remember that digital audio is just a group of digital samples, made up of zeros and ones that represent the audio.
   
   These numbers can be "copied" to another device or medium in a way that ensures that the result is the same as the original. This means that the copy is a "clone" of the original and sounds the same. This is true for the first copy or the seventy-first. Each time you copy an analog recording, you introduce between 3 and 6dB of noise, which further reduces the signal to noise ratio. Clearly, for pristine back-up want to use multiple copies of material during production, digital has the advantage.
   
3. Better audio quality for a lower cost.
   Digital audio used to be much more expensive than analog. This was because the early digital tape recorders used expensive and precise reel-to-reel mechanisms and early digital technology which was inherently more expensive. As recently as five years ago, the cheapest digital multi-track on the market was over $10,000 - analog reel-to-reel machines could be had for a fraction of that price. Now, digital technology has advanced to the point that this is no longer true.
   
   This is much in part to the advancements made in digital technology due to computers as well as cost reduction of other technologies important to digital recording like video cassette mechanisms and hard disk drives. Since digital audio technology uses similar components as the computer and multimedia industries, digital audio devices can take advantage of the lower cost of components due to their high manufacturing volumes. The result? Today's digital audio multi-tracks not only out-perform analog machines, costs less to manufacture, and is quite easily integrated into a multimedia production environment.

More...

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New E-Learning Curve’s Other Podcast episode release:

Part 7 of Transatlantic: The Flying Boats of Foynes

In Part 7: End of an Era

The War in Europe ended on May 25th, 1945. As normal life re-established itself, times also began to change for Foynes. Larger and more powerful airplanes had been built and operated successfully. A new land-based airport was established at the far side of the river. It was called Shannon International.

In this final episode of Transatlantic: The Flying Boats of Foynes, Chief Operator of Launch Operations Frank Buckley describes the end of the flying boat service in Foynes, Ireland, and the emergence of Shannon airport as the new home for transatlantic aircraft in the Post-War years.

Click here to listen to the podcast (MP3, 8.5MB).

Click here to view the transcript of this podcast (PDF, 24K).

Even though this is an e-learning blog, the observant among you will notice that the podcast isn’t about e-learning. That’s OK – the point of e-learning is to provide training professionals with a means of creating and distributing content that enables people to acquire information, knowledge, skills, and expertise on a diverse range of subjects: as e-learning practitioners, it’s our job to facilitate this process.

Some interesting Moodle audio visual plugins just released

I've been discussing podcasting in some depth recently: today I've decided to take a break from the topic, and tell you about a related subject.

Now read on...

Let's pretend for a moment that you've followed all my advice, tips, and suggestions about creating, authoring, recording and producing podcasts with alacrity. Your content needs to be stored somewhere to be distributed to your audience. In the e-learning world we use learning management systems (or LMS) to manage this task.

An LMS (or the related Learning Content Management System) is software for delivering, tracking and managing training and education resources. LMSs range from systems for managing learner records to software for distributing coursesvia the Internet, typically including features for online collaboration. LMSs can also automate record-keeping, as well as for:

• Registration of learners for classroom and online courses
• Student self-service (e.g., self-registration on instructor-led training), training workflow (e.g., user notification, manager approval, wait-list management)
• The provision of on-line learning (e.g., Web-Based Training, podcasts)
• On-line assessment
• Management of continuous professional education (CPE)
• Collaborative learning (e.g., application sharing, discussion threads)
• Training resource management (e.g., instructors, facilities, equipment)

One of the most popular, effective, and easy-to-use LMSs is Moodle. Moodle has been taking part in the Google Summer of Code, and it looks like some interesting new plugins have emerged from the project. Among them are the Nanogong and the Riffly plugins for Moodle 2.0.

The Nanogong plugin allows audio-only recording inside Moodle repositories. Captured in WAV format, files are stored in Moodle using the ImaACPCM or Speex codecs. Recorded files and the recording applet are available in all places where the repository is used to select files.

The Riffly plugin allows audio-only or audio-video recording inside Moodle repositories. Encoding in Flash FLV forma,t files can be stored on riffly.com servers or downloaded to Moodle. Recorded files and the recording Flash object is available in all places where the repository is used to select files.

Note that Moodle 2.0 is under development, and is UNSTABLE. It should NOT be used for production sites. For developers, testers and any other people who helping create the next generation of Moodle. The latest stable release of Moodle is 1.9.5. I recommend that your download, install and have a play with the platform if you haven't done so already.

Next time: Back to podcasting

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