Analog video recording was the preferred method of storing and archiving ophthalmic surgeries for the past 2 decades.1 An analog Charge Couple Device (CCD) (refer Appendix) camera mounted on the operating microscope grabs the video images, which are usually recorded on a videocassette recorder (VCR). The cassettes are then archived and listed in a register for future references. The analog video may be converted into digital format and stored as a digital medium using various capture cards on a computer. These videos can then be edited and compiled using either the professional video editing software like Pinnacle Pro-One or the more user friendly Ulead VideoStudio7, Ulead Systems Inc. Digital video is a binary computer file whereas the analog video contains raw signals.1 The digital video is more robust in terms of editing, archiving and distribution.2 Although the music industry completed the transition (ie, recorders and cassettes were replaced with compact discs and MPEG layer 3 compression (MP3) players (refer Appendix), the video industry is still in a transition from analog to digital technology.1 In this report we describe our experience in the transition from analog to digital video recording and archiving in our surgical setting. We believe that this is the first report in ophthalmic literature on digital video recording and archiving in ophthalmic surgery (Medline Search).
Why Digital - Why Not?
There are numerous advantages in converting into digital technology.2 Digital technology allows for grabbing the video images with hardly any generation loss (deterioration in the quality of images during copying, editing or repeated viewing of analog videos). Using a 3-chip CCD digital camera allows excellent image quality of the videos. In addition, the real-time image correction offered by the digital camera provides excellent control of exposure and white balance, especially during vitreoretinal surgical procedures. Viewing the videos is simple (using the navigation bar) and distribution of the videos is easier and less costly (by email, on compact discs). The most significant advantage is the powerful editing capability offered by the digital video editing software. Editing becomes simple and enables intergration of transitions, narration, music and text using graphic user interface (GUI).1
Analog video (Video Home System or VHS format) must be converted to digital format (MPEG) (refer Appendix) for editing and archiving as digital media. This results in loss of resolution and quality of the images which results in ′pixellation′ of the images. Additionally, such a conversion is time consuming. In the long run such techiniques may be counter-productive in a busy surgical practice. The VHS format offers a 230 lines of resolution. This can be enhanced to 400 lines if a Super Video Home System (SVHS) is used. Digital formats such as Digital Video (DV) and digital video camcorder (DVCAM) (refer Appendix) offer 530 lines of resolution. This results in higher quality video and good quality still images using the image grab feature in the software. The stills made from digital recordings are far superior in quality and are acceptable for publication purposes.2 Archiving becomes extremely easy as each video can be organized into folders on the computer and then backed up on to a Digital Versatile Disc (DVD) or compact disc (CD). These videos could further be edited and compiled easily using the appropriate video editing software.
Digital video recording
In the operating room we use the VISU-150 (Carl Zeiss) operating microscope. The operating room is used by 2 anterior segment surgeons and a vitreoretinal surgeon. The digital camera for the microscope is the Sony DXC-C33-P (PAL) Compact Color Camera, [1/3" CCD x 3, i.Link (IEEE-1394) Output and with a Camera Control Unit (CCU)]. [Figure 1]. The camera is the smallest 3 chip digital camera currently available. It is attached to the microscope using 85 mm lens and a C-mount. The camera is interfaced with a controller which is placed close to the operating room television monitor. There is also an option for a remote controller which can be placed elsewhere (eg., audiovisual room). The camera has a horizontal resolution of 850 TV lines. The image enhancement functions like white balance, color etc., can be manually adjusted and saved on to the controller or can be put in an automatic mode. These parameters can be saved in the controller as 2 files. Currently we have one setting for anterior segment procedures (file A) and another for vitreoretinal surgery (file B). The wide angle viewing system that we use for vitreoretinal surgery is the non contact Binocular Indirect Ophthalmomicroscope (BIOM III) (Occulus, GmbH, Germany). The output from the controller is connected to operating room television monitor through the S-video output. The controller is connected to the computer using an IEEE-1394 cable (DV-format) for storing and archiving (refer Appendix).
Storing and archiving the videos in the digital format
The computer for digital video capture requires an Intel chipset with a DV input (Fire wire - IEEE-1394 port). The processor recommended is a 1.8 or higher Giga Hertz (GHz) Intel Pentium 4 and Random Access Memory (RAM) of 256MB or above is ideal. Another additional advantage is that the video from a DV or DVCAM format can be transferred to any computer equipped with a fire wire IEEE-1394 port, eliminating the need for a dedicated capture card. Most computers and notebooks are currently available with the IEEE-1394 port.2
One hour of digital video (DV) requires approximately 12 Giga Byte (GB) (refer Appendix) of space. Therefore storing the videos on the hard disk alone is not feasible, unless a large capacity hard disk is used and the videos are backed up on the DVD or CD on a daily basis. This may not be an ideal situation as it becomes task intensive. The best alternative is to have an external storage media. An ideal external storage device and media should be compact, sturdy and should have reliable data storage and retrieval. Additionally it should have a high speed Universal serial bus (USB) (USB Version 2.0) or fire wire connection so that real time recording and retrieval is possible. In short it should function exactly like a portable hard disk drive.
The storage device we use is the Iomega® REV[TM] drive [Figure 2] which uses a revolutionary new technology called Removable Rigid Disk (RRD). The Iomega® REV[TM] drive combines high speed, reliability and ease of use of hard disk technology with the advantages of portability and expandability of tape and optical media. It backs up data at a speed (25MB/sec) that is 8 times faster than traditional tape drives and retrieve files in seconds, versus minutes (compared to linear access with tape drives). It appears as a standard drive letter to both the user and on the operating system and therefore easily supports the drag-and-drop method of files or folders. Organizing data on the drive (eg., renaming a file or storing the video files done on a particular day in single folder) is done exactly the same way as on a hard disk. The disk in the drive is smaller than a floppy disc and holds 35GB or 90GB (compressed) data. This is almost equivalent to 3 hours of high quality digital video data. The data from the REV drive is burned onto a DVD and once archived the data is deleted from the REV disc. With its high speed, capacity, and removable media, the Iomega REV drive is an ideal solution for desktop and server-level backup as well as high-capacity, portable storage applications. Other storage devices like a portable harddisk drive or a high capacity desktop harddisk drive are also viable options. We have also tried capturing DV on to MiniDV cassette using the Digital Camcorder (Sony Corporation) without appreciable loss in quality.2 Though it is cheaper than most of the storage devices and media that are available, the transfer of files to the computer was time consuming; one of the major drawbacks of all tape drive storage devices.
In our surgical setup, on every surgical day, a new folder is created on the REV disc through the Ulead capture program and each surgery is organized into individual subfolders with the patient identification number by the operating room nurses who are trained in using the computer and the REV drive. The surgeries are captured and stored in these folders. All surgeries are recorded and at the end of the week the desired surgical videos are trimmed using the video extract option in the Ulead Video studio software and archived onto a DVD in the DV format. The DVD is labeled and a register is maintained with the DVD number and the surgical procedures with the respective dates. The data on the REV drive is then erased and the disc is ready for capturing new videos.
Video editing is done as and when required. Videos are selected from the corresponding DVD and edited using the Ulead VideoStudio. Text, transitions and effects can be added after the videos are edited. Finally the videos are complied and saved as either DV format or MPEG 2 format for large screen presentations purposes. For publications, the selected frame can be grabbed by freezing the screen and saved as high quality TIF or JPEG images. These images are of a quality much superior to that of images grabbed from analog video (Figures 3 and 4). For advanced users or for professional video editing, a high end software like the Adobe® Premier® is recommended.
The cost of the Sony Digital 3-CCD camera DXC C-33 P is Rs. 3,35,000. The cost of the REV drive along with the computer (with a DVD writer) is Rs. 70,000. The REV drive comes with 5 discs. The Ulead VideoStudio 7 comes bundled along with the REV drive and the computer. Thus the total cost of going fully digital is only Rs. 4,25,000. It is approximately 25% costlier than the analog set up.
Digital video recording is here to stay. The memory hungry DV files require large amounts of storage space for archival. Currently available hard disks offer monstorous storage space upto 2 terabytes (TB). These costly hardwares are primarily intended as storage devices for digital video archival. Blu-ray technology or the Blu-ray Disc (BD) was primarily developed to store the High Definition Videos (HDV) and High Definition Television (HDTV). A single-layer Blu-ray Disc can hold 25GB, which can be used to record over 2 hours of HDTV or more than 13 hours of standard-definition TV. There are also dual-layer versions of the discs that can hold 50GB.3 Holographic storage is also poised to become a compelling choice for next-generation storage needs. With this technology it is possible to have a CD sized storage medium offering upto 200 to 300 GB of storage space.4(refer Appendix)
This short review highlights the advantages in shifting to a totally digital recording and archiving system for documenting ophthalmic surgeries. The transition from analog to digital video recording and archiving was smooth in our surgical setup. We found that the quality of the videos were exceptionally good especially when documenting vitreoretinal surgical procedures. Change from analog to digital has helped to us have a systematic archiving system along with excellent quality videos and stills of surgical procedures. Though the initial investment is relatively high, we believe that this is an important investment for an ophthalmic surgeon who is interested in academic presentations and innovations.
Acronyms and Definitions
CCD = Charge coupled device. Semiconductor device made of a matrix of individual photosensitive elements, called picture elements or pixels. Each pixel in the image is converted into an electical charge the intensity of which is related to a color in the color spectrum.
MP3 = The name of the file extension and also the name of the type of file for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (more specifically, the redundant and irrelevant parts of a sound signal. Those signals the human ear doesn′t hear anyway).
DVCAM = Digital video camcorder
USB = Universal serial bus. A serial connection technology that is almost universally available in current PCs. Version 1.x allowed for 12Mbps (Megabits per second) transfer rates, and this was boosted to 480Mbps for USB 2.0. USB 2.0 competes with FireWire for transmission speed.
VHS / SVHS = Video home system/Super video home system. VHS uses a vertical resolution of 260 lines and the SVHS uses 360 lines.
Firewire/IEEE 1394(Institute of Electrical and Electronics Engineers)/ i.LINKTM (i.LINK stands for IEEE-1394-1995 standards and their revisions.) A very fast external bus standard that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b). Products supporting the 1394 standard go under different names, depending on the company. Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link (Sony corporation) and Lynx, to describe their 1394 products. IEEE 1394 is an ideal interface between a computer and a video/audio device because of its ability to transfer a real-time data stream at low cost and high reliability and ease of use.
DV (Digital Video) is the standard for consumer digital video. DV complies with the same IEEE1394 interface standard. The Sony DXC-C33/C33P is equipped with a DV output terminal so that images can be recorded into an i Link interface-equipped VTR with no quality deterioration. It has a resolution of 850 lines.
MPEG1 is a digital video format with a resolution of 352 X 288 pixels. This is a low end universal standard video compression codec. A codec (short for coder-decoder or compression decompression) is a mathematical algorithm by which large raw video files are compressed to smaller files with some quality loss.
MPEG2 enables high resolution of upto 720 X 576 pixels with an excellent overall quality. This is similar to DVD quality. A computer equipped with a DVD can usually run MPEG 2 videos. Otherwise DVD softwares or Windows Media Player version 10, which have the MPEG 2 codecs can play MPEG 2 videos.
MPEG3 is also known as MP3. This is currently the accepted format for compressing and playing audio files. This is not used in video compression.
MPEG 4/Div X Has a superior quality when compared to the MPEG 1. However the basic resolution remains at 640 X 480 pixels. This is commonly the format of video recording in digital still cameras with flash memory cards.
Pixellation - An effect which occurs when an image of low resolution is enlarged so that the individual pixel are obvious to the eye.
NTSC/PAL - National Television Standard Committee/Phase Alternating Line. Different countries use different types of broadcast TV system, most of which are to varying extents incompatible with each other. The NTSC is responsible for setting television and video standards in the United States. 525 is the number of lines in the NTSC television standard. In Europe and the rest of the world, the dominant television standards are PAL and SECAM. PAL has 625 horizontal lines and 25 frames per second and is the television standard for broadcast in India. SECAM stands for Systeme Electronique Couleur Avec Memoire, and was adopted in 1961. It has 625 lines and 25 frames per second.
Computer related terminology
Bit = Short for binary digit, the smallest unit of information on a Computer or any data storage device..
Bytes = A byte is commonly used as a unit of storage measurement in computers, regardless of the type of data being stored. A byte is composed of 8 bits.
KB = Kilobytes - 1000 bytes (103Bytes)
MB = Megabytes - Million Bytes (106Bytes)
GB = Giga Bytes - Billion Bytes (109 Bytes). Most commercially available harddisk for Small Office Home Office (SOHO) use ranges from 40 GB to 400 GB.
TB = Tera Bytes - Trillion Bytes (10 12Bytes) Tera in greek means monstor. A typical video library will have a collection of videos approximately 5 to 8 terabytes in size.
Blu-Ray Disc (BD) = Blu-ray, also known as Blu-ray Disc (BD) is the name of a next-generation optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of the world's leading consumer electronics, personal computer and media manufacturers. The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data.
Holographic data storage = Holography breaks through the density limits of conventional storage by going beyond recording only on the surface, to recording through the full depth of the medium. In order to increase storage capabilities, scientists are now working on a new optical storage method, called holographic memory, that will go beneath the surface and use the volume of the recording medium for storage, instead of only the surface area. Unlike other technologies that record one data bit at a time, holography allows a million bits of data to be written and read in parallel with a single flash of light. Thus the HVD's transfer rate is up to 1 gigabyte (GB) per second - that's 40 times faster than DVD. The Storage media (Holographic Versatile Disc or HDV disc) is similar to a CD or DVD but is expected to have 200 to 300 GB of space as compared to 700 MB on a CD and 4.7 GB on a Single layer DVD.
www.Ulead.com Ulead Systems Inc.
www.pinnaclesys.com Pinnacle Systems
www.iomega.com Iomega Corporation
www.adobe.com Adobe Corporation
www.sony.com Sony Corporation
www.blu-ray.com Information on Blu-ray technology
1. Miron H, Blumenthal EZ. Bridging analog and digital video in the surgical setting J Cataract Refract Surg. 2003;29:1874–1877
2. Prasad S. Digital video in a surgical setting J Cataract Refract Surg. 2004;30:2302–2303
4. Ashley J, Bernal MP, Burr GW, et al Holographic Storage. http://www.research.ibm.com/journal/rd/443/ashley.html