Daniel M. Herron, MD
Asst. Prof. of Surgery
Mount Sinai School of Medicine
1 Gustave L. Levy Place #1103
New York, NY 10029
Why Digital Photography?
Digital photography provides an extremely powerful tool for the
laparoscopic surgeon. Surgery - and laparoscopic surgery in particular
- is an intensely visual specialty. The addition of photographs to the
medical record can enhance documentation, improve communications with
other doctors, facilitate teaching and enliven presentations and publications.
While conventional photography has been useful in the past, the
inconvenience, expense, and slow turnaround of film processing and editing
has impeded its widespread acceptance by surgeons. With digital imaging,
surgeons can create high-quality photographic images in the OR and view
them instantly. These images can be easily edited, copied, incorporated
into other documents, e-mailed, and archived. In short, digital imaging
is nothing less than a breakthrough that makes surgical photography a
useful, effective, and practical tool.
How is Digital Photography Different?
At first glance, a digital camera appears to be quite similar
to a conventional film camera. Indeed, many of the mechanisms inside a
digital camera are identical to those in their film-based cousins. All
digital cameras have a lens at the front to collect and focus light rays.
In most digital cameras, this is a zoom lens, allowing you to "zoom
in" on the area of interest. Like conventional cameras, less expensive
digital cameras have 2 separate lenses: a viewfinder to look through and
a second lens to capture the image. More advanced cameras are built with
"single-lens reflex" or SLR design in which a single lens serves
to both view the image and capture it.
The critical difference between digital and film cameras lies
in the mechanism used to capture light. In a conventional camera, the
image is focused upon a piece of light-sensitive film. When you've finished
shooting a roll, typically 24 or 36 exposures, your film is sent off to
your local film-processing store, where it is chemically processed with
developer, stop bath, fixer, and rinse. If you are shooting slides, the
film is fixed on a small paper or plastic mount for later projection.
If you are shooting prints, the negative is placed in an enlarger, where
a piece of photographic paper is exposed and processed through its own
developer, stop bath, fixer, and rinsing steps.
In digital photography, film is replaced by the charge-coupled
device, or CCD - a light-sensitive computer chip. First developed by Bell
Labs in 1969 for use in video phones, the CCD is a rectangular array of
light-detectors. Like the human retina, CCDs have millions of separate
detectors for red, green and blue light. Every image obtained is actually
a gridwork of millions of picture elements, or pixels, each one with its
own red, green and blue (RGB) values.
Each time you press the shutter release button on your digital
camera, you trigger a very finely-choreographed series of events. First,
the shutter mechanism is opened for a fraction of a second, letting light
pass through the lens to hit the CCD. The CCD then converts the light
intensity at each pixel into 3 numerical values: one each for red, green
and blue. Current high-quality cameras capture between 2 and 4 million
pixels. The image captured by the CCD is immediately displayed on a small
screen on the back of your camera, confirming that you have obtained an
adequate image. Finally, the image, which is nothing more than an array
of millions of RGB values, is stored on a small removable memory chip
for later retrieval.
What is a Digital Image? How is it Stored?
It is important to start by recognizing 2 important facts. First,
digital images are nothing more or less than computer files. Second, these
files can get very big!
In 2001, a typical digital camera has an image size of 2 or 3
megapixels. This means that it captures between 2 and 3 million pixels
with each picture taken. Since each pixel contains 1 byte of information
for red, green and blue light levels, this totals 3 bytes of information
per pixel. We can do the math to calculate the size of a typical image
for the camera we are using in our workshop this afternoon, the Olympus
C-2500L.
Image size: 1712 x 1368 pixels = 2,342,016 pixels
File size: 2,342,016 pixels x 3 bytes/pixel = 7,026,048 bytes
This means that each picture you take is over 7 million bytes,
or 7 megabytes (MB) in size! With a standard 32 MB memory card loaded
in your camera, you can only store 4 pictures at this setting! If you
uploaded these files onto your computer, you would fill up 1 gigabyte
of hard disk space with less than 150 pictures!
Clearly, files this big are too unwieldy for practical use. To
reduce them to more manageable size, most cameras offer the option of
JPEG image compression to reduce file size. JPEG (pronounced "jay-peg")
stands for the Joint Photographic Experts Group, which is the name of
the committee that defined this data compression standard. JPEG compression
was designed to compress digital photo files substantially, losing only
a small amount of detail in the process. JPEG compression is particularly
useful because it is adjustable. To get the best image quality we can
choose low compression. To get the smallest possible file size, we can
choose high compression. JPEG files are easily identified on your computer
by their extension (.jpg).
How well does JPEG compression work? On the Olympus C-2500L the
high compression setting creates a 0.5 to 0.6 MB file for each 1712 x
1368 pixel image B roughly 1/12 the size of the uncompressed file! You
would need to look very closely to notice any difference in quality between
the compressed and the original image.
Where Are Digital Images Stored?
Image files are stored within your camera on removable memory
cards. They are similar to floppy disks in that they are nonvolatile,
meaning that they do not require any source of power to retain their information.
They are also erasable and rewriteable, so they can be reused indefinitely.
Memory cards are different from floppies in that they have no moving parts,
and are thus more reliable.
There are 2 different types of memory cards in widespread use:
CompactFlash and SmartMedia. Both are very small, about 1/3 the size of
a credit card. While most cameras use only one type of card, some B like
the C-2500L B can use both. SmartMedia come in sizes up to 64 MB, while
CompactFlash cards are available up to 256 MB, at a street price of just
over $2 per MB.
With a high-capacity memory card, a digital camera can store
substantially more images than a film camera. Using a 128 MB CompactFlash
card, the Olympus C-2500-L can store roughly 210 images when set to its
high-resolution, high-compression mode.
How Do I Access the Images in my Memory Card?
How do we get the image files off the memory card and into our
computer so we can view them, edit them, insert them into documents, and
e-mail them? The transfer can be accomplished in a number of different
ways. Most digital cameras come with a data cable allowing them to connect
directly to a computer. Older cameras use a serial port connection, which
is too slow to be of any practical use. Newer cameras connect through
a USB (Universal Serial Bus) port which provides much higher connection
rates, but is still a relatively slow process.
The fastest and most convenient means of accessing your card
is with a card reader adapter. These small, inexpensive devices plug into
the USB port on your desktop or the PCMCIA slot on your laptop. Your computer
treats the memory card like another disk, allowing near-instantaneous
access to your images.
Just like computer files, each image file has its own name. The
image file's original name is automatically assigned by the camera. Once
the image is transferred into your computer, you can use an image browser
program to rapidly view, sort, and organize your images. It makes it easy
to rename your photos from their original filenames (like 00001234.jpg)
to more descriptive ones (like Smith_John_cholecystectomy 10-Apr-01.jpg)
How Can These Images be Edited?
Many image editing programs are available that allow you to crop,
adjust and alter your pictures in just about any way imaginable. There
is a tremendous range of different editing programs available. At the
high end are professional-level editing programs like Adobe PhotoShop,
which we will be using in our workshop today. Simpler programs are available
that provide less functionality but cost substantially less.
One of the most common editing functions is cropping. Cropping
means cutting off the unwanted edges of a photograph. It can be accomplished
quite easily in any editing program by drawing a rectangle around the
part of the photo you want to keep and choosing the crop command.
Adjusting the brightness and contrast of your image are the next
most common editing maneuvers. Most image editors have brightness and
contrast controls similar to those on your TV. With a few simple commands
you can brighten an image that is too dark, or increase the contrast on
a washed-out image.
More sophisticated tools like the clone tool allow you to "airbrush
out" blemishes. If your assistant has inadvertently stuck his hand
into your otherwise flawless photo of a surgical specimen, the clone tool
can be used to neatly erase it. Many discardable images can be elegantly
salvaged with this technique.
What Else Can I Do With my Images?
After creating high-quality images, you will surely want to share
them with others! For example, you might want to insert a picture of a
specimen into a letter to a referring physician. This is trivially easy
in most word processors, like Microsoft Word. After clicking within the
document where you want the image to go, you select "Insert...image...from
file" and select the name of the image file. The picture will instantly
appear in your document, and can be printed out or saved.
Inserting your digital images into a PowerPoint presentation
is done in a nearly identical fashion. PowerPoint then allows you to draw
the viewer's attention to a specific part of your photograph by adding
circles, arrows, or labels. If you have access to a video projector, you
can very quickly put together a "slide show" in this manner,
with none of the inconvenience or slow turnaround time of conventional
35 mm transparencies.
How do I Make High-quality Prints of my Images?
With the proliferation of low-cost inkjet printers these days,
it is no more difficult (and only slightly more expensive) to print out
a high-quality color photograph than a black-and-white document. Newer
4- and 6-color inkjets costing between $200 and $500 can create pictures
that are quite near photographic quality. Additionally, they can be used
to print high-quality text documents with imbedded pictures. Dye-sublimation
printers, while more expensive to buy ($1000) and operate ($2/page) than
inkjets, will create prints truly indistinguishable from photographs.
It is important to know that the ink used by most inkjet printers
is not very long-lasting, and will fade over the years. If you need to
have permanent photos, i.e. for medicolegal purposes, you will need to
use a dye-sub printer, or an inkjet that takes archival-quality inks.
Additionally, the quality of the paper used for printing directly
affects the quality of the image. Regular copier paper will produce adequate,
but not publication-quality images. If a photo really needs to look perfect,
invest in some high-grade glossy printer paper (between $0.50 and $1.00
per sheet).
Can I Archive My Digital Images?
You will probably want to keep your digital images around for
a few years. The easiest way to keep them archived is to leave them on
the hard drive of your computer. This works fine until a) you fill up
the hard drive, or b) you get a new computer. If you want to store your
digital images for longer than 2 or 3 years, you will need a long-term
storage medium.
Floppy disks are cheap and widely available but - with room for
only 2 0.5 MB files - are clearly not the answer. Zip disks are essentially
high-capacity floppy disks and can store 100 MB, roughly 50-200 images
(depending on compression). However, it is critical to remember that floppies
and Zip disks are all magnetic media! The information on any magnetic
disk is not permanent, and will start to degrade noticeably in about 10
years time!
To store your images for the longest possible time, you will
need to use a CD-burner. A CD gives you roughly 600 MB of storage - enough
for 1200 or more images! Plus, if you use archival-quality CDs, your data
will be stable for 100 years or more - greater than the statute of limitations
in most states!
How Can I Learn More in a (Relatively) Painless Manner
Any of the books in the glossary will provide you with an in-depth
introduction to digital photography and digital photo editing. Of course,
the best way to learn more is to take the SAGES Workshop in Digital Still
Photography this afternoon. The workshop is designed to provide an afternoon-long
hands-on education in digital cameras, scanners and image editing.
Glossary
Card Reader Adapter A device which plugs into your computer.
You can insert your memory card
into a slot on the adapter, and your computer will read the image
files on the
card as if it were an additional hard disk.
CCD Abbreviation for "charge-coupled device." This
is the light sensitive "digital
film" which converts light into electric charges, which
in turn are converted into numerical arrays of RGB values, or image files.
Clone Tool One of the powerful functions of an Image Editor program,
the clone tool
allows you to select one portion of your image to use as "paint"
to airbrush
over another undesired portion of the image.
CompactFlash One of the 2 major types of removable memory cards.
These come in sizes up
to 256 megabytes. See SmartMedia.
Cropping One of the most commonly-performed image editing maneuvers,
cropping
can be performed using an Image Editor like Adobe PhotoShop.
Dye Sublimation (Also called "dye-sub") A type of color
printer that provides photo-quality
glossy prints. It works by heating a film coated in thermally-activated
dyes.
Requires special paper, costing $1-2 per page.
Gigabyte One gigabyte is a thousand megabytes, or roughly billion bytes of information.
Current hard disk drives are able to store 10 to 40 gigabytes on average.
Image Browser A program which allows you to easily view, save, and copy your image files.
Image Editor A program which allows you to modify your images with functions like
cropping, brightness and contrast adjustment, softening, sharpening, and many
other modifications. Adobe PhotoShop is the most commonly-used
image editor.
Inkjet A widely-available, low-cost type of color printer that works by spraying very
fine dots of ink onto the paper. Can print on plain, high-quality, or glossy paper.
JPEG An abbreviation for Joint Photographic Experts Group, the committee that
designed the most commonly used image compression standard in use today.
A JPEG (pronounced "jay-peg") file is a compressed image file. It works
particularly well for photographic-type images.
Megabyte One megabyte is a thousand kilobytes, or roughly a million bytes of
information. Often abbreviated to "MB" or "meg." An image file might be
0.5 - 8 MB in size.
Memory Card A removable storage card on which your digital photos are stored. These are
removed from your camera and inserted into the card reader on your
computer.
PCMCIA This is the name of the card slot on your laptop computer. You can insert an
adapter into this slot that will allow your laptop to access your camera's
memory card directly. (It stands for Personal Computer Memory Card
International Association).
Pixel Image files are rectangular arrays of millions of picture elements, or pixels. The
greater the number of pixels in the image, the higher the resolution, and the
sharper the picture.
RGB Each pixel in a color image has a red, green, and blue value. A black pixel would
have RGB values of 0,0,0. A white pixel would have values of 255, 255, 255.
RGB refers to any color image stored with this type of system.
Serial Port A port on older digital cameras that permits the transfer of data to your
computer one bit at a time. This type of port is too slow to be of any practical
use. It has been largely supplanted by the USB port. If your computer uses this
type of data connection, you will want to use a card reader adapter, which
greatly speeds up the transfer of images to your computer.
SLR Abbreviation for "single lens reflex," a type of camera design in which one lens works as viewfinder (to look through) and camera lens (to focus light on the film or CCD). Typically found in more expensive, professional-level cameras.
SmartMedia One of the 2 major types of removable memory cards. These come in sizes up
to 64 megabytes. See CompactFlash.
USB Abbreviation for Universal Serial Bus. Faster than the serial port, the USB port
is a plug in the back of your computer that supports transfer of digital images
from your camera to your computer over a USB cable. Many other devices,
such as printers or card reader adapters, can also plug in through the USB port.
Bibliography
- Curtin D (1999) A short course in digital photography.
Shortcourses.com Marblehead.
- Greenberg S (1999) The complete idiot=s guide
to digital photography. Que Indianapolis.
- Johnson D (1998) Digital photography: Answers!
Certified tech support. McGraw-Hill New York.
- King JA (2000) Digital photography for dummies.
A reference for the rest of us. IDG Books Foster City.
- Sadun E (2000) Digital photography! I didn't
know you could do thatY Sybex Alameda.
8. Digital Video for Minimally
Invasive Surgeons
Steven D. Schwaitzberg, MD
Department of Surgery - New England Medical Center
Boston, MA
Surgeons who perform video controlled surgery are ideally suited to record, edit and produce tapes, CD's, DVD's or web based versions of their surgeries. All of us who work in this arena have a VHS tape or two sitting on a desk somewhere with a great case, ie 10 minutes of surgical artistry buried in two-hours of magnetic media. In the past, these tapes would have to be edited in a linear fashion on an analogue editing system that were usually located in professional studios or educational media centers. These systems have been the workhorses of the video editing world for many years but are now rapidly being replaced by digital or nonlinear systems that are now affordable for almost anyone to buy.
Video formats
The basic language of video, digital or analogue is the tape and file format. Below are the most common tape and file formats. Analogue formats use waves to represent audio and video signals. Digital formats use binary information (1's and 0's) to represent the audio and video information
Analogue Tape
VHS This is a composite (combining light and color in a single signal) format. Each subsequent generation (copy) degrades significantly making this format a poor choice for editing. Rather this is the most common format of the end user essentially ubiquitous in the United States.
S-VHS This format uses tape that is the same size and shape as VHS. The light and color signals are separated. Video editing with this format is useful since degradation is minimal from generation to generation. This format is often called Y/C. VHS tapes will play in S-VHS players but not vice versa.
Beta-SP is a high-resolution component format used by professional videographers worldwide. The light and color signals are separated as above but the color components are further separated to assure accurate reproduction across generations. Until recently this was the long-standing gold standard of video production.
Digital Tape
MiniDV This is the consumer digital format. The resolution quality is very close to Beta SP and the audio is a little better. Generation losses are minimal due to digital nature of the information. Digital information is bi-directionally transmitted via IEEE 1394 (Firewire, I-link) connection. Most Mini DV camcorders/recorders also have analogue outputs as well for S-VHS/VHS recording
Digital Computer Files
Video Formats
Windows video (.AVI) This stands for audio-video interleave. Video imported into PC's is often in this format. Although there is a generic Windows AVI format, most computer video capture boards use their own proprietary compression-decompression (CODEC) schemes. Thus an AVI file captured on one proprietary system may not play on another.
QuickTime (.MOV) This format was created by Apple and can play on Macs, PC's and Unix based systems. Streaming versions of this format are now available.
MPEG 1 & 2 (.MPG) MPEG is a set of international standards for audio and video compression. MPEG-1 provides excellent audio and video quality at 1x and 2x CD-ROM data rates. It is used for a wide range of applications. They may be embedded in several other formats, including Quick Time. In order to achieve this level of quality, MPEG requires fairly powerful playback hardware. Nearly all computers sold today have sufficient CPU power for basic playback, and many high-quality video cards now include MPEG playback acceleration. MPEG-2 provides broadcast quality digitally encoded audio and video. It offers outstanding image quality and resolution (somewhat better than laserdisc). MPEG-2 is the primary video standard for DVD-Video. Playback of MPEG-2 video generally requires special hardware, which is built into all DVD-Video players, and most (but not all) DVD-ROM kits. Some of the fastest CPUs may be able to play MPEG-2 without specialized hardware, but this is currently rare. MPEG-2 was based on MPEG1, but optimized for higher data rates. This allows for excellent quality at DVD rates (300-1000KBps), but tends to produce results inferior to MPEG-1 at lower rates (See www.terran.com/CodecCentral/Codecs/MPEG1.html)
MPEG-4 (.MPG, .VTC) is the internationally recognized ISO/IEC standard developed by the Moving Picture Experts Group (MPEG) for the encoding and decoding of digital multimedia and its transmission over networks. Unlike proprietary technologies, MPEG-4 promotes interoperability between vendors and defines a baseline standard for streaming a full range of digital multimedia across all types of networks. (see www.e-vue.com)
Real (.RM) These clips are encoded by the real video CODEC and a variety of audio CODECS. Computers that have the Real Media player on them. (certain versions are free and can be downloaded from www.real.com) are able to play them as they are streamed from an internet source. Real Sytem has replaced both Real Audio and Real Video.
Windows media (.ASF) This is the Microsoft streaming format and requires the latest version of the Windows Media player to decode. Encoding is performed using the Microsoft media encoder 7.
Audio formats
Microsoft (.wav) These files are generally created in audio recording programs. The quality and file size is proportional to the sampling frequency of the sound being recorded.
MP3 (.MP3) MPEG Layer 3 (commonly known as MP3) is a very popular standard for delivery of music on the Internet. It produces very high quality audio, most commonly around 16kBytes (128kbits) per second. These data rates don't support modem streaming, so MP3 files are generally downloaded for later playback.
In the beginning, there was.............. source material
Ultimately, we would like to work with digitized video clips (files) of the interesting surgeries, arranging them on a computer in some order, adding titles, graphics and a few effects here and there. We can get to that point in a variety of ways depending on budget, available equipment, technical prowess, and the need (perhaps obsession) to achieve perfection.
This is a key component of the digital video process, but preparation is essential. Full screen video captured from the OR occupies at least 2GB for every 9 minutes. Thus if you are going to work in this media, you can never have enough hard drive space! For practical purposes a digital video computer needs at least 40 GB these days and 100GB would not be unreasonable. All of these computers have at least IEEE 1394 input capabilities and many have analogue to digital conversion boards to input standard tape. Fortunately the cost of storage space is plummeting even for drives fast enough to capture the video information without losing bits and pieces.
If you want to edit video clips of operating room material, specifically laparoscopy, in your computer there are a few basic ways to get the information in.
Option 1) Capture the information digitally on the computer in real-time
This option requires a video camera box with a digital output leading to a digital input into the computer and hard drive. Since few laparoscopy setups have digital output at this time and the storage requirement for even an hour of surgery is enormous (14GB), this is not practical for too many operators.
Option2) Record the procedure digitally on tape and transfer the information via IEEE 1394 protocol (firewire) into the computer. This is a very practical solution and straightforward to implement. Firewire boards (or PCMIA cards for laptops) are relatively inexpensive in the $200-$500 range and easy to install. Many newer computers have them as standard inputs. Digital recording decks (Mini DV, DVC Pro, DVCCAM) are commercially available with standard video analogue inputs at prices starting at less than $1000. Once recorded, selected segments can be imported via an IEEE 1394 cable and stored on the hard drive as .AVI, .MPG or .MOV files.
Option 3) Record the procedure on VHS/S-VHS tape and digitize it later. Since nearly every laparoscopic surgeon can record procedures on VHS or SVHS tape, this is a convenient starting point. This method requires you to install an analogue video capture board into a computer (or buy one so equipped). This A to D (analogue to digital) device converts the signal as it is being played out of the VCR into a digital file on the hard drive. Most boards can work in reverse and play out video files from the computer as an analogue signal that can be recorded on a VCR. Capture board quality varies from terrible to excellent and to a certain degree is a function of the dollars invested. If your goal is to create full screen videotape as a final product, plan on spending at least $700-900 (prices are falling all the time) to import standard tapes into your computer. The basic problem with less expensive devices is that you get what you pay for, ie these boards don't capture all of the information being played by the VCR. Severe compression occurs and the material captured is suitable for partial screen computer playback only. Don't scrimp! A variant of this technique has recently become available. Just released are transcoding boxes that have multiple inputs and outputs. Analogue output (VHS or S-VHS) from a VCR is played into this device, which converts this signal (transcodes) into DV format. This is transferred out in real-time via an IEEE 1394 output that can be fed into the computer as in option 2 above.
Option 4) Capture digitally to removable media. Laparoscopic capture systems are being built now that will capture video clips digitally in a fashion similar to still pictures ie onto a recordable removable media. This will allow the surgeon to selectively record clips onto a removable media such as a CD (650 MB) or DVD (4.5GB) and take them to the digital editing station later. This approach will have a terrific convenience factor but will require capital operating room purchase.
Digital Editing
Now that the raw operative footage has been imported into computer, the fun begins! If you have ever edited on an analogue system and needed to make one little change in the middle requiring you to discard everything after the imperfection, then you have experience the pain of working on a linear system, ie the editing starts at the beginning of the final product and works sequentially to the end. The beauty of digital editing is the freedom to arrange and re-arrange the clips in any order, speed them up or slow them down, play them forwards or backwards, and superimpose titles, pictures or other clips onto them. You can start building your video from any point in the movie you please. Transitions between clips are simple to create and a large variety of software is available for the novice, enthusiast or professional. The most commonly used software for this process is Adobe Premiere. (www.Adobe.com) This software in some form is often bundled on a variety of turnkey computer video editing systems (e.g. Sony Vaio) available today.(Legitimate academic users can purchase advanced versions at a greatly reduced price.) You are free to make changes anywhere on the time line as often as you like, thus the process is non-linear. What's the catch? The process of setting and arranging the clips onto a storyboard is reasonably quick and painless, but after that is done the movie must be rendered. The time this takes depends on how fast the computer processor, hard drive and RAM are. Often complex projects must run for hours or even overnight. Last minute work can be tough or even impossible. Professional video houses invest in multiple computers to distribute the work and special boards to speed up the rendering process to as close to real-time as possible. At this stage of technology a surgeon can make relatively complex video productions with a modest investment as long as he/she can tolerate the long rendering times.
OK, you have made your masterpiece.... Now what?
With the time line completed, the next step depends on what you intend to do with the project. Since rendering a long project can take a few hours some forethought is optimal. If VHS or S-VHS tape is the ultimate end product then the movie has to be rendered into the format that will allow you to get the movie out of the computer. In most cases this will be the .AVI format and in some cases MPGE2 or Quicktime (.MOV). Once rendered the file can be passed out of the computer usually by the pathway it came in, ie via the IEEE1394 port into a digital recorder, camcorder, or transcoding box and then onto VHS tape using the analogue outputs from one of these devices. Remember unlike copying VHS tapes and losing quality in each subsequent generation, digital transferring is essentially lossless.
If computer presentation is your is goal, then a slightly different strategy can be employed depending on the type of software you own. The timeline must still be rendered, but different output choices can be made directly. Many editing programs can render to MPEG1, MPEG2, or Quicktime as well as AVI. This usually takes a few hours as well since an entire movie will have to be transcoded and compressed. Often this process converts 2GB of AVI material into 30-100MB of .MPG or .MOV files. If your goal is to play these on CD's or DVD's then the files can be burned onto the media of choice after the movie is rendered from the timeline. If the output options are limited or if greater control of features like data-rate is necessary, then rendering your movie to an .AVI files and using transcoding software ( e.g. Media Cleaner 5) is the method of choice. These transcoding programs offer great control of these process and offer a wide variety of file output options to meet almost any need including DVD, CD, kiosks, streaming media.
If the goal is to use this movie clip in a Powerpoint presentation, then creating a MPEG version of the movie is sufficient. This file can be imported onto the slide in the same fashion as still pictures using the "insert" function" A dialog box will ask you if you want your clip to play spontaneously as the slide is viewed or only play only when you click on it. Although in theory QuickTime files could be imported in the same fashion, some versions of Powerpoint have trouble playing them.
Streaming Video
Downloading still photographs from the Internet is a straightforward process that takes from seconds to a few minutes even on a standard modem 56K connection. On the other hand, attempting to download a 5-minute video clip even on a fast Internet connection might require an extraordinary amount of time to complete. That's where streaming comes in. Using where appropriate either a Real Systems, Quicktime, or Widows Media player, special compressed files are sent from a video server to your computer. The key concept is that after accumulating a few seconds of the video to get started, you can watch the audio and or video "stream" as it is passing by your computer. You don't actually acquire the file as in downloading still pictures. This saves tremendous amounts of time and storage space. All of these players are available for free from their respective websites or come bundled with software packages. Perhaps the next phase of streaming video will be the diffusion of the MPEG-4 standard, a new photo/video compression algorithm that aims to make video streaming over the Internet a reality. Not only will MPEG-4 videos and photos have smaller file sizes than comparably sized QuickTime videos and JPEG images, but this algorithm crunches still pictures and video so small that soon it's going to be possible to stream MPEG-4 video and still images onto small handheld wireless devices such as cell phones and Internet-enabled PDAs. MPEG-4 can do video layers and multidimensional objects and that makes it extremely powerful for low bandwidth users. What this means for surgeons is that low bandwidth users may watch the video stream of an operation only, while high bandwidth users may see the video from several angles and receives text information, literature references, Internet links (you guessed it - for the products used) at the same time. You can expect to see this type of multilayered broadcasting work its way into the traditional television and cable markets.
Summary
While this syllabus portion only scratches the surface of digital video, the best way to learn about this is to dive in and try it out. The cost of these technologies continues to fall placing digital video with in reach of most physicians.
Glossary
Analogue These formats represent the audio and video information as waveforms. Significant
quality loss occurs as each generation is copied
Compression The process by which audio or video files are reduced in size usually by removing
reoccurring or less important information. The methods of doing this vary greatly
and the scheme for doing so is called the CODEC (compression-decompression).
In order to play the video file on a given computer, the CODEC of the video must
be recognizable to that computer.
Data rate The amount of video information processed for each second of playback of the file.
Digital The process of coding audio and video in a binary format ( 1's and 0's).
Firewire Name given by Apple Computers to the IEEE 1394 input/output protocol This bi-
directional connection between the computer and enabled devices also allow for
device control by the computer. Also known as I-Link on Sony PC's.
Linear The process by which the movie made on tape decks can only be made from the
beginning working sequentially to the end of the production.
Nonlinear The process by which the movie can be made on a computer by starting from any
point in the production and working until the time line is filled.
Render The process by which each frame of a movie is created at a speed less than the 30
frames/sec that denotes "real-time". The actual time required is a function of the
complexity of any one frame and the speed of the computer.
Transcode The process of converting from one file format to another (eg .AVI to MPEG-1)
Video server A computer who purpose is to distribute multimedia material via the Internet, intra
nets, or local area network (LAN).
