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Manifest Technology Making Sense of Digital Media Technology By Douglas Dixon |
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Articles: | PC Video | Web Media | DVD & CD | Portable Media | Digital Imaging | Wireless Media | Home Media | Tech & Society | DVD & CD: | DVD & CD Articles | DVD Software Gallery | High-Def DVD Gallery | DVD Authoring Resources | DV to DVD -- End-to-End Digital Video
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But this part of the problem is being cracked, as personal computers have gotten fast enough to perform real-time DV-to-MPEG-2 conversion, or transcoding, in software. New Windows applications from MedioStream and CyberLink now can capture live from a DV camcorder through a 1394 / FireWire interface, transcode to MPEG-2 on the fly, and save the result to disk.
For those who want more control over MPEG-2 compression for DVD, tools like the Ligos LSX-MPEG Suite offer professional-quality encoding from AVI to MPEG-1 and MPEG-2, in both a stand-alone encoding tool and as a plug-in for Adobe Premiere.
All of this means that all the pieces are finally coming together to realize the dream of end-to-end digital video processing on the desktop.
So, what's the big difference between DV and DVD video anyway? After all, they're both compressed digital video, full-resolution (720 x 480) and full-rate, and even start with the same two letters. But they are significantly different formats, designed for very different purposes.
The DV compression format was designed as a capture and editing format for use in devices like camcorders. It uses a fixed data rate, which makes sense when you are writing to or reading from a video tape. DV therefore uses "intraframe" compression, in which each frame is compressed independently of each other. As a result, while DV format is great for editing since there is relatively light compression on each frame, the data size is much larger than more aggressive compression formats. The DV format uses 25 Mb (million bits) or 3.1 MB (million bytes) per second, or 187 MB per minute, 11 GB (billion bytes) per hour of material. That can fill up a disk quickly!
By comparison, the MPEG-2 compression format was designed as an efficient delivery format for pre-recorded video. It supports variable data rates, so you can tune the amount of compression, trading off quality against data size, to match the type of material and target storage medium. To compress more aggressively, MPEG-2 uses "interframe" compression, in which some of the frames are compressed independently (like DV), but most of the frames are compressed by using information from the previous and even following frames. This can provide big savings in compression size, especially when large portions of the background remain relatively unchanged from frame to frame. However, the trade-off is that the video is much less suited for editing, since it is compressed more heavily, especially the in-between frames.
As a result, MPEG-2 was a great match for the DVD format, permitting a two-hour movie to be squeezed down to fit nicely onto a DVD, along with other ancillary material. Most DVD formats now hold 4.7 GB per single-sided disc, with the video compressed using MPEG-2 at around 3.5 Mb per second. That's around 1/7 the size of DV compression, at 0.43 MB per second, 26 MB per minute, 1.5 GB per hour. Now, that's more reasonable.
Previously, converting or transcoding between the DV and MPEG-2 formats would have required three separate steps: capturing the DV video, decompressing it, and then recompressing to MPEG-2. Even worse, all that decompression and recompression would have required significant processing time and mass quantities of disk space, to store the original DV video, plus the raw uncompressed video, and then for the recompressed MPEG-2 video. But now the processing power in even desktop computers has become fast enough to perform all these operations, in real time, while capturing DV video from a 1394 / FireWire interface and writing the result to hard disk.
The proliferation of the IEEE 1394 interface (also originally called FireWire by Apple and i.Link by Sony) also has made the whole video capture process much easier. Before, with analog input, your capture board performed the analog to digital conversion, and often some form of compression, which meant the quality of the captured video was very dependent on the quality (and the cost) of the board. And taking full advantage of a high-end analog capture board also often locked you into a specific video editing application that had custom software to interface to the board.
Now, with DV camcorders, the analog to digital conversion is done in the camcorder as you shoot the video, so the data stored on the DV tape is all digital. Getting it into your PC, then is just a digital data transfer, like a file copy, over the 1394 / FireWire cable. There is actually no "capture" involved. Even better, 1394 is a generic interface, already implemented in inexpensive hardware chip sets. This mean you can install one inexpensive 1394 adapter card and expect it to work with most DV devices and DV video software applications. This technology is still new, though, so before you buy be sure to double-check the compatibility between the 1394 adapter, video editing software, and DV camcorder.
Adding a 1394 interface to your computer, desktop or laptop, is not longer a big deal. For example, ADS Technologies (www.adstech.com) sells the PYRO line of 1394 / DV capture products for both desktops and laptops. The ADS products include the PYRO Digital Video 1394 PCI card and the PYRO 1394 DV For Notebooks PC card, each for $129 (retail). These products often include basic video editing software, and can work on both PC and Macintosh platforms.
You can also use an external converter like the Dazzle Hollywood DV-Bridge (www.dazzle.com, $299) to capture analog input through a 1394 interface, and even convert from analog to DV and DV to analog without the use of a computer.
The latest releases of many video-editing tools also now support direct DV capture and editing. These include products ranging from Ulead Video Studio 5 at $90 to Adobe Premiere 6.0 at $540. Some also support output to MPEG-2 format for DVD. If you are shopping for new hardware or software look for good bundling deals. For example, Adobe is now bundling the full version of Premiere 6.0 with hardware products, not a "LE" light or limited edition version. ADS also announced the PYRO PlatinumDV with 1394 PCI host card bundled with the full version of Adobe Premiere 6.0 for $399 (MSRP). Previous PYRO DV owners also can upgrade to Premiere 6.0 for $199.
You need video editing tools if you are creating a traditional video production from a collection of clips, as a linear story using techniques like video and audio transitions and effects. But what if you want to make a quick interactive presentation out of the clips, and present it on DVD? Then you need a different kind of tool -- a DVD authoring tool to create the interactive menus and navigation paths. And you also want to work directly with MPEG-2 video format, without the processing and storage overhead of converting from the DV format.
Enter CAMpeg RT from MedioStream, Inc. (www.mediostream.com). CAMpeg RT provides a full end-to-end solution for turning DV video into DVD productions, including a 1394 FireWire adapter card, the MedioStream real-time DV-to-MPEG transcoder software, and the Sonic Solutions MyDVD authoring software.
MedioStream released CAMpeg RT in March 2001 for $249 MSRP, $199 estimated street price. It is based on the MedioStream Codec Software Development Kit (SDK), introduced in summer 2000 for OEM customers. The MedioStream SDK supports full-resolution DV and MPEG-2 compression and decompression for full-rate NTSC and PAL under Windows 98SE, 2000, or ME on Pentium III or equivalent machines, with a 1.1 GHz processor recommended. MedioStream is planning to deliver a professional version, CAMpeg Pro, later this year, which is expected to support a wider range of formats and simple editing functions.
CAMpeg RT has a very simple interface, controlled from the main window. Click the Settings button to specify the desired data rate and quality for the captured video. MedioStream describes the low quality setting as typically resulting in a bit rate of about 2 Mbits for a full size picture (720 x 480) at full 30 fps frame rate, or about 860 MB for one hour. The high quality setting results in a bit rate of about 5 Mbits for a full size picture at full frame rate, or about 2.2 GB for one hour. The actual compression rates depend on the content of your video.
To capture a sequence, first click the File button to specify the directory and name of the MPEG-2 file to be captured. Use the VCR controls to play through the video on the DV camcorder to the starting point. Unfortunately, CAMpeg RT does not provide frame step and visual scan controls, so you may find yourself using the controls on the camcorder to position the tape. Then click the Encode button to start the tape playing while CAMpeg RT captures and transcodes the video and audio, and click it again to stop. Finally, click the Review button to play back the MPEG-2 (.MPG) file in a separate window.
I tried out a preproduction version of CAMpeg RT, version 1.1.8, on a 1 GHz Windows ME machine with a 1394 adapter card already installed. It worked out of the box, interfacing to a Sony DCR-TRV11 DV camcorder and successfully capturing full-resolution full-rate DV video to disk as a MPEG file. MedioStream has designed CAMpeg RT for slower machines. It will buffer the video data to disk if needed, and also has an option to drop frames if necessary to maintain real-time performance. Be warned that, unlike other DV capture applications, CAMpeg RT requires that your Windows display be set to True Color (24- or 32-bit), and otherwise will display unhelpful error messages.
The current CAMpeg RT product also includes the Sonic Solutions MyDVD authoring tool (www.sonic.com). MyDVD is an even more user-friendly extension of the popular Sonic DVDit! application.
What is so amazing about these new video technologies is how quickly they are incorporated into consumer-level software products, as the processor speed and storage capacity of even basic desktop machines make it feasible to support them. Real-time DV transcoding to DVD format is new and cool, and yet is already subsumed as yet another feature in the latest release of CyberLink PowerVCR (www.gocyberlink.com), a PC digital video recorder application that was itself establishing a new category of applications only last year.
The latest release, CyberLink PowerVCR II Deluxe 3.0, has an impressive list of TV viewing and recording features, including multi-channel preview, instant TV replay, time-shifting playback, scheduled recording, and access to an Internet-based Electronic Programming Guide. The new version 3.0 now supports input from both analog sources like TV tuner cards and from DV devices. It can also read and convert AVI and MPEG-1 files. It even supports simple video cut & merge editing.
PowerVCR supports batch capture and transcoding from DV tape by selecting specific sections of the tape to be processed. It also can capture to multiple files, keeping each file size to around 600 KB so that they can fit on a CD disc. It can perform real-time recording directly from analog or digital sources to MPEG-1 and MPEG-2 format, including real-time transcoding from DV to MPEG-2, for output to VCD or DVD format.
The PowerVCR interface includes three floating windows: the Master Panel on the left side for access to the major product functions, the Control Panel at the bottom with play controls and settings, and the main display window in the center of the screen.
The Master Panel provides nine functions: Live / Digital Recorder (digital TV and VCR), Instant TV Replay (short-term buffering), PowerDVD (DVD or MPEG playback from a playlist), File Player (media file playback), Recording Scheduler (scheduled VCR recording), File Converter, Video Trimmer, DV Tape Transcoder (DV to MPEG File), and the "i-Power" link to Internet resources.
I tried out the new CyberLink PowerVCR II version 3.0, which was released in mid-March 2001 for Windows 98SE, 2000, and ME. The DV Tape Transcoder tool successfully interfaced to the Sony DV camcorder and displayed the video from the tape. The tool works by making a batch list of clips to record, by moving through the tape and setting in and out points. The controls to play and step through the tape and specify in and out points were somewhat clumsy, only playing or scanning in short spurts and scanning very slowly for the start point.
CyberLink claims that PowerVCR can record 320 x 240 resolution video in real-time on a Pentium II 350, record 720 x 480 resolution on a Pentium III 650, transcode full DV to MPEG-1 on a PIII 600, and transcode DV to MPEG-2 on a PIII 900. It provides a large set of built-in profiles for MPEG-1, MPEG-2, Video CD (VCD), DVD, and DV-compatible recording, for NTSC and PAL, ranging from 3 to 5 Mbits per second data rate and from 320 x 240 to 720 x 480 resolution.
PowerVCR successfully recorded 320 x 240 video out of the box on the test system, but full-resolution video was jittery. The built-in PowerDVD player provides a nice tool for playing and comparing different recorded files.
PowerVCR 3.0 is available from the CyberLink web site by the time you read this article. The previous version, PowerVCR II Deluxe, was $129. The Deluxe version of 3.0 includes the CyberLink PowerDVD 3.0 DVD player application ($129). It is also available in a Pro version without PowerDVD ($90), and a Standard Edition without DV camcorder support ($50). A free trial version of PowerVCR and the other CyberLink products are available on the web site. The trial versions typically expire after a month or so, and are limited in the length of video and audio material they can process.
Direct DV to MPEG-2 is a powerful solution for getting clips to DVD quickly and easily. But if you are editing the clips first, you will want to capture and edit them in a less compressed format like DV, and then transcode them to MPEG-2 as a final step before creating the DVD. DVD authoring tools like Sonic MyDVD support this approach with built-in support for transcoding imported video files in a variety of formats.
As you get deeper into working with MPEG-2 video and DVD, however, you will find yourself wanting more control over the data rate and quality of the compressed video. A separate compression tool like the Ligos LSX-MPEG Encoder can provide more flexibility in compressing video to take advantage of the MPEG-2 format, including variable bitrate compression to use more data on the more complex frames and rate control to more precisely limit the data rate of the compressed file.
The Ligos LSX-MPEG Suite 2.0 includes three components, the LSX-MPEG Encoder 3.5 for MPEG-1 and MPEG-2 digital video transcoding, the LSX-MPEG Player 3.0, a DirectShow filter that allows you to play MPEG-1 and MPEG-2 files in Windows media players, and LSX-MPEG for Adobe Premiere, a plug-in that enables you to output MPEG-1 or MPEG-2 streams directly from Premiere.
You start working with the Encoder by specifying the input AVI file and output file name. You then set the basic compression parameters, using one of the 18 predefined profiles for MPEG-1 and MPEG-2 at different resolutions and data rates, or define and save your own profiles.
The Encoder also provides fourteen sets of advanced parameter settings, ranging from low-level compression features to options to work with interlaced video, crop the edges off captured frames, and resize the frames. It also offers several performance parameters, to trade off processing speed and visual quality, and to take advantage of parallel processors.
Even better, if you are working with more than a few video files, the Encoder has a batch processing mode, in which you can specify a list of files and a compression profile, and then start the Encoder working away on them.
The LSX-MPEG Suite 2.0 is available as a download product from the Ligos web site for $399.95, and the individual components are available separately: the Encoder for $179.95, the Player for $29.95, and the Premiere plug-in for $179.95. Ligos also offers time-limited trial downloads of the products.
For DVD production, the LSX-MPEG Encoder also supports the Video CD (VCD) and Super Video CD (SVCD) formats, for playback on DVD players that support SVCD playback.
DV to DVD is the dream of digital video on PCs, capture, editing, and production with all-digital processing. And these tools are starting to realize the promise. MedioStream CAMpeg RT offers an end-to-end solution with all the components, from DV adapter to software transcoder to Sonic MyDVD authoring. With real-time DV to MPEG-2 transcoding, you can go from video clips on tape to an interactive DVD production in minutes.
Meanwhile, CyberLink PowerVCR II 3.0 shows how real-time transcoding can be part of a larger system, and also provides nice tools for playing and performing simple edits on MPEG-2 files. And the Ligos LSX-MPEG Suite provides more flexible tools for high-quality MPEG-2 encoding, exporting from Premiere, and viewing files using standard windows players.
MedioStream - CAMpeg RT
www.mediostream.com
CyberLink - PowerVCR II Deluxe 3.0
www.gocyberlink.com
Ligos - LSX-MPEG Suite 2.0, LSX-MPEG Encoder 3.5
www.ligos.com
Sonic Solutions MyDVD
www.sonic.com
ADS Technologies - PYRO Digital Video 1394 Interfaces
www.adstech.com
Dazzle - Hollywood DV-Bridge
www.dazzle.com
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