Real-Time, VBR Encoding System Provides Exceptional Quality Video and Audio

Amber encodes analog footage in real-time using Main Profile at Main Level MPEG-2, also called MP@ML. While other MPEG-2 systems use I-frame or IP-frame only, MP@ML provides true IBP frame format.

Amber has an easy-to-understand user interface that provides complete control of the MPEG-2 compression process, along with preview before and during encoding. With Composite and S-video inputs, Amber is scalable up to Full-D1 resolution with NTSC and PAL format support. Amber’s high-quality MPEG-2 video output streams can also be used with DVD authoring and satellite distribution systems.

Amber is a great addition to Canopus’ DV non-linear editing solutions, DVRex-M1 and DVRaptor. The Amber kit allows Canopus editors to maintain data in DV format – the original acquisition format – during the editing process. To achieve the best output quality, it is important to minimize the number of times users convert their source material to another format in the editing process. Each unnecessary digital-to-analog, analog-to-digital step, or transcoding between compression formats, decreases quality. Since MPEG-2 is currently regarded as the best format for video archiving and distribution, the appropriate solution to achieve maximum quality output is to edit in native DV format and save the final master in MPEG-2.

AMBER Key Features Single PCI board MPEG-2 D1, Half-D1 and MPEG1 real-time encoding Encodes I,P,B frames (MP@ML) I-frame-only option Bitrate 1-15Mb/s user adjustable (CBR/VBR) PAL (720x576)/NTSC(720x480), CCIR-601 S and composite video input and output Video parameter controls Single image capture Prefiltering 4:2:2 to 4:2:0 Windows 98 ad NT4.0 compatible MPEG Layer I and II audio encoder Simultaneous high quality VGA video overlay and analog video output Video and audio locked in sync during capture	Format	Bus mastering PCI card 175mm(w)x107mm(l) PCI half-size
	Operating system	Windows 98 and NT4.0
	Video format	PAL (720x576)/NTSC(720x480), CCIR-601
	Video input and output	S (miniDIN) and composite(RCA) 4.2.2. sampling
	Capture resolutions	NTSC 720x480, 352x480, 352x240 PAL 720x576, 352x576, 352x288 (CBR/VBR)
	Video compression	MPEG2 (ISO/IEC 13818-2) Main Profile@ Main Level (I,B,P/MP@ML) I-frame only support MPEG1 (ISO/IEC 11172-2)
	Filtering	2D
	Audio input	Stereo (RCA)
	Audio output	Stereo (mini jack)
	Audio sampling rates	32kHz, 44.1kHz and 48kHz (all 16 bit)
	Audio compression	ISO/IEC 11172-3 layer I/II (software compression)
	Audio bit rate	64,96,112,128,160,192,224,256,320,384 kb/s
	Multiplex	ISO/IEC 13818-2 MPEG2 program stream ISO/IEC 11172-2 MPEG1 program stream ISO/IEC 11172-2 MPEG1 transport stream
	IRQ requirements	Uses one IRQ
	Memory address	Uses 512 byte configured by PCI
	Power consumption	+5V 1.5A, +12V 160mA, -12V 100mA
	Minimum requirements	1 free PCI slot (PCI 2.1 compliant) P166 or better 64MB RAM (or more) 1024x768x16bpp
	VGA overlay	DirectDraw compatible, real-time preview
	Format	CCIR 601 to suqare pixel conversion

Q: How many minutes of video can I store on n GB?

A: This is a question without a real answer.  The amount of video you can store as MPEG-2 really depends on what audio and video bitrate you are encoding at, and whether you are using Constant Bitrate (CBR) or Variable Bitrate (VBR) for the video.

Amber DVD in stock! $2999

What is the Best Compression Format
for Non-linear Video Editing?

By Hiro Yamada, President and CEO of Canopus Corporation

April 1999

Regardless of the compression format chosen for nonlinear video editing, the desired end product is usually a high quality master tape that can be duplicated for distribution or aired for broadcast with minimal loss in quality. The better the source material and the cleaner the editing chain, the better the end result will be. This has driven the highest end systems to handle video in a completely uncompressed format. Due to the lower cost of the equipment, most videographers use MotionJPEG- or DV-based systems for video editing. New MPEG-2-based editing systems are just coming on the market, so which format is really best for non-linear video editing?

For the last 7 years, MotionJPEG has been the compression format of choice for capturing and editing analog video. The lower data-rates, good image quality and lower cost editing equipment resulted in MotionJPEG’s wide acceptance. However, the lack of good data-rate regulation limited MotionJPEG to the PC environment, where an individual video frame could be any size, and prevented it from becoming a viable encoding standard for tape-based camcorders.

In 1996, Sony and Panasonic introduced the first DV camcorders and changed the world of the video professional and prosumer forever. For the first time, digital quality video recording was available at the then "affordable" price of $2500 to $4500 (now as low as $799 with Digital8). The DV format data size was smaller than MotionJPEG and it captured video directly to tape with all analog to digital conversion performed by high quality circuitry in the camera. In addition, the DV camcorders introduced a completely digital interface called IEEE-1394, also referred to as iLINK or Firewire, to transfer the pure digital video and audio data directly to the PC in perfect lip-sync. Further improvements in camera optics and CCDs have produced a quantum leap in quality from standard analog S-Video/Hi8 sources.

The net result is that pure digital acquisition, editing and distribution is now possible at a very affordable price. The DV standard has eliminated the analog-to-digital and digital-to-analog conversions previously required with MotionJPEG and lowered the data rate of the video stream down to 3.7MB/second versus the nearly 7MB/second for similar quality with MotionJPEG. Because every analog-to-digital and digital-to-analog conversion reduces quality, the DV format retains the highest possible quality by keeping video in the digital domain throughout the acquisition process. The lower data rate means you do not have to spend as much money to configure a DV editing system because you can use lower cost components such as IDE RAID drives versus SCSI. Going forward, as video professionals add DV cameras to their analog cameras, it makes more sense to edit both the analog and DV content together in the DV format. This keeps the digital content pure and reduces the size of the compressed analog video in your system.

Recently, with the increasing acceptance of the DVD movie format and Direct Digital TV to the home, the MPEG-2 compression format has been considered as a possible video editing format. This seems logical because it offers superior quality compared to current VHS videotapes, broadcast TV and even Laserdisks. A significant obstacle to MPEG-2 is that, unlike DV where the data rate and image quality are consistent across all implementations, MPEG-2 image quality can vary significantly by the encoding system used and the processing power put behind it. The DVD movie you watch is the result of an intensive, multi-pass MPEG-2 encoding process to maximize quality at a specific data rate. Do not expect to see this level of quality on a low-cost, single-pass MPEG-2 editing solution.

Another obstacle to MPEG-2 editing involves the application of IBP frames in the video stream and the large amount of data lost in order to achieve the low data rate. An I-frame is a full video frame containing the same information that a MotionJPEG frame would contain. In fact it is nearly identical in format and algorithm to the MotionJPEG frame. P- and B-frames contain mostly frame differences and need to refer to the nearest I-frames to be reconstructed. P-frames reference the nearest previous I-frame while the B-frame refers to both the nearest previous and future I-frames to be reconstructed. Using all three frame types, MPEG-2 compression can be very high while maintaining exceptional image quality. Until recently, MPEG-2 editing systems edited in I-frame only, in effect, making them almost identical to editing in MotionJPEG with the same higher data rates and the above mentioned analog-to-digital conversion issues inherent in the MotionJPEG standard.

Newly introduced MPEG-2 editing systems use Main Profile at Main Level (MP@ML, IBP) or Simple Profile at Main Level (SP@ML, IP). The highest quality at the lowest bandwidth is MP@ML. The next step down is SP@ML. SP@ML, using I- and P-frames only, requires higher bandwidth and adds unnecessary loss. Since the P-frame is not a full image, the MPEG-2 decoder and editing software must reconstruct a full image from the last I-frame and the changed portion represented in the P-frame. A typical B- or P-frame contains only about 5% of the data found in an I-frame. The reconstructed frame seldom reproduces the same quality as a full I-frame. It is like looking at a photographic print. The photo image itself is very high quality, but making a copy, or editing the photograph should not be done from the picture itself. You must go back to the negative to achieve the highest quality. In the case of MPEG-2 IBP editing, the negative does not exist, it was never captured that way.

When all is said and done, the basic principles of video acquisition and editing have not changed. To achieve the best output quality, it is important to minimize the number of times you convert your source material to another format in your editing process. Each unnecessary digital-to-analog, analog-to-digital step, or transcoding between compression formats, decreases quality. In addition, the compression scheme must keep enough data available during the editing process to maintain image integrity.

The best option for the highest quality output is to maintain data in the original acquisition format – if the source is digital, keep it in digital format throughout the editing process – and keep it in the same digital format throughout the process.

With DV cameras becoming more and more affordable and the DV format offering low data rates while maintaining high image quality, the editing format becomes clear. Edit in DV. And since MPEG-2 is currently the best format for video archiving and distribution, the best solution is to edit in native DV format, and save the final master in MPEG-2.

Hiro Yamada is President and CEO of Canopus Corporation. Based in San Jose, California, Canopus designs and manufactures award-winning graphics and video editing products for the PC.

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