Video Capture Cards for PCs

Video data captured into computer system are organised into consecutive frames of still images. In PAL TV systems that are used in Australia and many other countries, 25 frames of still images need to be captured in one second of time, so that when these frames are played back in the same 25 frames per second speed, movement contained in the video remain smooth for human’s eyes. In a full-sized PAL video frame, there are 768X576 coloured dots or pixels arranged in 576 horizontal lines and 768 vertical columns. In full coloured mode(24-bit colour), each pixel requires 3 bytes of data to represent all possible colour information, therefore 768X576X3X25 = 33177600 bytes or 31Mega Bytes per second of data need to be captured. This is an enormous amount of data stream, and enormous space will be required for storing the captured video data: approximately 111GigaByte per hour of video. Using very fast PCs and huge amount of disk spaces, processing this un-compressed video capture is possible, and some high-end video capture cards do capture video in such an un-compressed mode. However, economy and efficiency in designing and using video capture cards call for alternative ways to capture and store video data in a less demanding fashion: reducing the video data volume before sending them to the PC for storing. Reducing data volume means compressing the data, thus a certain method need to be applied to compress the video data in such a way that significant amount of information are thrown away at the video capture stage, while satisfactory video quality can still be maintained at the video playback stage. Practice has proved that using smart compression methods, reducing video data by 5~10 times at capture stage can still achieve very high quality playback that are almost identical to human eyes as the original video. Apart from those high-end video capture cards, most video capture devices on the market use some kind of data compression mechanism, and very often than not, how they compress video decide how they are used in various application fields.

2. Host-PC Software Based Compression (top)

A series of video capture cards, normally low-end and low-video-quality capture cards, use the host-PC’s software to compress video being captured. These video capture cards normally have very simple analogue video signal to digital data conversion circuitry. These include some early model video capture cards like Intel’s Smart-Video, some current graphics display cards with analogue video input sockets, and the recent streaming video capture cards. Host PC software based video compression requires a video compression software running simultaneously with the video capture card’s capture process, this data compression software normally is called a Codec (CompressionDecompression) software, that has been installed into the PC’s operating system before the video capture process ever started. Modern PCs’ operating systems like MS Windows and Apple Macintosh’s operating systems have several built-in software Codecs(Cinepak, Indeo, Sorenson, etc), plus many other third-party Codecs available freely or as part of installing some application software. The common features of software Codec based video capture cards include low-quality video, low data volume capture, small video frame size, no simultaneous audio input facility built-in, no realtime video output ports, etc. The video files captured normally playback in slower than realtime speed, with poor colour and pixelated images, etc. The main reason for low-quality video is the low-quality analogue to digital signal conversion hardware circuitry built-into these video capture cards: increasing host-PC’s processing power here can not help enhancing the video quality. Even when software Codec used to compress incoming video signal is chosen as None, meaning that no data compression is applied onto the captured video signal, the resulting video quality is still much lower than the video quality of even the basic hardware encoding based video capture cards such as low-end M-JPEG cards. As a result, software compression based video capture cards are mainly used for creating videos for Internet transmission, e-mail, low-quality surveillance, etc, where high-quality video output to external video tapes or video disks are not required. Decent quality video editing normally can not be carried out on video files captured by software Codec based video capture cards. The final verdict is, if converting these kind of video to some form of output format to be displayed on an external TV monitor, the video quality is significantly lower than the original input video quality.

Because of the lack of on-board audio capture and play-back hardware(except for the recent Streaming Video Capture Cards), high-quality audio capture and synchronisation with video is also difficult to achieve: a sound card is required to record audio simultaneously as the video is being captured and compressed, this separate process not only introduced compatibility problem between the video and audio capture cards, but also can easily cause audio-video out-of-sync problem: audio playback lags behind the video playback, in particular when the video playback is long.

Almost without exception, host-PC software compression based video capture cards use Composite(RCA) and/or SVideo(4-pin Mini DIN) connection. Except those dedicated streaming video capture cards, audio input is usually not available on host-PC software compression based video capture cards.

As the name suggested, the Codec software used to compress the incoming video data is also used to decompress the video when video playback is carried out, that is, when playing back software Codec based video on PCs, the original video capture card does not need to be present, as long as the correct Codec software is installed on the PC. This hardware-independent playback capability makes video captured in this method useful to be passed away to other environment for either editing or playback. In recent Internet video streaming applications, all video captured use host-PC based software compression.

3. Motion-JPEG Compression Video Capture Cards (top)

Motion-JPEG is the most widely used on-board hardware compression method to capture Analogue Video Source through Composite, S-Video or Component video. “On-board” here means the video data compression is carried out on the video capture card. The name M-JPEG comes from JPEG, Joint Photographic Expert Group, a cross organization of CCITT and ISO. While JPEG deals with still images, M-JPEG deals with video as a series of consecutively arranged still images.

M-JPEG is an Intra-Frame only compression method: each still image(frame) inside a video clip is only compressed using data within this frame, no consideration is taken from the previous or subsequent frames. This makes every frame to be de-compressed and displayed entirely by extracting data from its own compressed data storage, therefore is quick and accurate each time. Intra-Frame only compressed video are essential for non-linear editing process because the video editing software needs to randomly jumping forward and backward along the video files, cutting and pasting any frames at any point with accuracy and exact result if operation is performed and then cancelled then performed again. These kind of frame-accurate random accessing and editing is handled well by video editing software in association with M-JPEG video capture cards.

M-JPEG video capture cards use on-board dedicated hardware chipsets to handle video compression/de-compression, therefore the video quality is not dependent on how fast the PC is being used, although certain performance of the host PC is required to sustain the required data transfer rate. The data rate for M-JPEG capture cards vary from a few hundreds kilobytes per second to over 20 mega bytes per second, that is, at their highest data rate, M-JPEG video capture can achieve almost the same video data rate as un-compressed video capture. Contrary to the low-end software-Codec based video capture cards, M-JPEG video capture cards normally have much better quality analogue to digital video signal conversion circuitry built-in, and a special software burnt into non-volatile memory(firmware) is also constantly running on the capture card, controlling the video capture and data compression processes. Although varied among quality and prices, M-JPEG capture cards share many important common features:

(1) High-Quality video capture and playback, even basic M-JPEG video capture cards like Pinnacle’s DC10+ can achieve near the original tape’s quality when recording

captured video back to tapes.

(2) Easy Quality Control at video capture stage, including

instant adjustment for colour components, brightness, contrast, saturation, data rate, frame rate, frame size, etc.

(3) Encode/Decode video using on-board hardware,

therefore requires no separate decoding hardware when outputting video to analogue TV/VCRs. M-JPEG video capture cards can convert any video or graphics files, even DV video files into analogue video output in high quality(in contrast, many DV-only video capture cards cannot convert M-JPEG video into DV video without jittering result). Hardware video decoding plus hardware video overlay (though not all M-JPEG capture cards have hardware video overlay) combined can produce perfect full-screen live video display on PC’s. For example, Pinnacle DC30+ can display full screen full speed video through Microsoft MediaPlayer even on PentiumMMX 200 PCs with 4Mbyte video card, with a better video quality than software-based DV video play-back on PentiumIII 1GHz PCs with 64MB AGP display card.

(4) Can capture noisy video signal properly, in this aspect M-JPEG capture cards beat many DV/Analogue dual-mode capture cards like DV500/DVNowAV/DVStorm/RT2500 that convert analogue signal into DV format at the capturing stage. Typical example will be when capturing video from a poor quality old VHS tape, DV500/RT2500/DVStorm etc will capture jittering or garbled frames or complain on dropping frames, while DC30+ captures quite normal video.

(5) Clear still image capturing, in particular still images from fast-moving objects: this is superior to DV video capture cards.

(6) Widely accepted input video device, almost all video output device including DV cameras (through their analogue output sockets) can be used as input for M-JPEG capture cards, and the device types/models rarely cause any compatibility problem.

(7) Connection wires are low in price and easy to make, in particular the RCA connectors. Also the wires can sustain long distance like 5~8 meters without significant quality loss.

(8) Difficult to have accurate device control and no

universally accepted device control standard. Device Control means using PCs’ software to mechanically control the tapes movement inside camera/VCR in terms of play/stop/pause etc operations. Although several video camera and VCR manufacturers have created their own device control mechanism in their own brand of camera/VCRs, including JVC’s JLIP, Panasonic’ 5-Pin, Sony’s LANC, etc, implementing a generic interface on the PCs to control these mutually in-compatible devices is very difficult, and earlier products like Pinnacle’s Studio 200/400 failed miserably in terms of usability.

Typical M-JPEG video capture cards are PCI cards, they include DC10+, DC30+, DC50 and Reeltime from Pinnacle, DigiSuite from Matrox, Fuse and Ignitor from Aurora, etc. They all use their own proprietary software for device drivers and video capture utilities, although to some extent, some of them can work with generic video capture software from ULEAD or Microsoft.

Because of the proprietary device driver and hardware-assisted decoding, video files captured by M-JPEG capture cards are also in proprietary formats: only PCs with the same capture cards installed can read, edit and play these files. This feature makes M-JPEG videos un-suitable for archiving and transmission applications, while editing remains the main application field for M-JPEG video capture.

The differences among different M-JPEG video capture cards include captured video quality, input/output connection, audio capture capability, supported computer systems, supported operating system software and video editing software. The following table lists the differences between two typical M-JPEG video capture cards: low-end Pinnacle DC10+ and mid-range Pinnacle DC30+:

Lower end M-JPEG capture cards like DC10+ are primarily designed for entry-level users: they are easy to use, but normally cannot sustain heavy-duty usage like multi-hour video editing, while middle-ranged capture cards like DC30+ have been extensively used for editing 1~3 hour long video projects. Most low-end M-JPEG video capture cards have no audio capture/playback hardware built-in, relying on PC’s sound card to capture and play back audio, therefore might cause audio/video synchronisation problem in long video clips.

4. DV and Firewire Video Capture Cards (top)

4.1 DV and Firewire: Relations and Differences

There are instances where any video stored on PCs are called “digital video”, even the promotional materials published by many manufacturers claim their M-JPEG or MPEG video capture cards “convert analogue video to digital”. To some extent these are not wrong because any data including video files stored on PC’s hard disk are binary data thus are in digital format (against analogue format stored on analogue video tapes etc). However, in a narrower definition, “Digital Video” refers to video originated from Digital Video Cameras: these cameras store video signal collected from their optical lens directly as binary digital data similar as data stored on PCs. There are basically two types of “Digital Video Cameras”: higher-end Digital BetaCam cameras that communicate with PCs through Serial Digital Interfaces(SDI), and the relatively lower-end “DV” cameras that usually communicate with PCs through “Firewire/iLink/IEEE1394” interfaces. In this article, we limit ourselves to discuss only the video signal created by the secondary type of DV cameras, that is, our “Digital Video”, or “DV” refers to video recorded by those cameras/VCRs in the format of MiniDV, Digital8, DVCam or DVCPro manufactured by Sony/Panasonic/JVC/Canon etc. These cameras/VCRs record video signal in a special way called DV format. DV cameras and VCRs compress video directly before storing it onto DV tapes in a digital format like computers’ data backup tapes.

Sony owns the patent of DV technology, as well as the Computer-to-Camera/VCR connection called iLink. However, iLink came from Apple Computer’s patented data communication protocol Firewire which has become an IEEE standard called IEEE1394. Although often called interchangeably by many people, DV and Firewire are actually two totally different technologies: DV is a video recording and compression technology, while Firewire (iLink/IEEE1394) is a data transmission technology. DV does not have to use Firewire(there are DV cameras that do not have Firewire built-in), and Firewire can be used without DV camera/VCR involved(such as Firewire Hard Disk, Firewire Scanner etc). The transmission of DV signal over Firewire does not use the full bandwidth of Firewire, and Firewire’s application covers much wider areas than transmitting DV signal. DV video has a bandwidth of 3.6Mbytes/sec., while the current IEEE1394a protocol has a 50Mbytes/sec. (400MBPS) maximum data rate. The upcoming IEEE1394b will boost this maximum data rate to over 100Mbytes/sec. (around 1GBPS).

Not only Firewire Video Capture cards are not limited to be used for DV capturing, they do not really compress Video Signal as other types of video capture cards do. The video signal which is digital already inside DV cameras/VCRs are merely transmitted as binary data over the Firewire cable and received by the computers as it is, just like the binary data transmitted between two computers over Ethernet network cable. The video compression process is entirely handled by DV cameras/VCRs, and is very similar to that of M-JPEG video capture cards, except the compression ratio is fixed at 5:1, and the frame size is fixed at 720X576 for PAL, and 720X480 for NTSC video. These parameters combined make the data rate for DV compression at 3.6Mbytes per second for PAL or 3.1MBytes/s for NTSC. Unlike M-JPEG video capture cards, typical Firewire cards do not have video compression hardware built-in, therefore relying on the DV camera and host PC software to compress/de-compress video. This could become an issue if video needs to be recorded back to an analogue VCR while a suitable DV camera is not available: without a suitable DV camera or DV VCR connected, most Firewire video capture cards cannot output DV video from PCs to anywhere! Here “suitable” means the DV camera or DV VCR must have DV-Input capability, i.e., DV signal has to be able to be sent into the camera or VCR --- you might be surprised to know that not all DV cameras can do this!

There are TRUE DV Video Capture Cards that not only have Firewire sockets built-in to transmit DV(or other) signals, but also have DV Hardware Encoding/Decoding chipset built-in to convert non-DV video signal to DV signal, as well as convert DV signal to non-DV video signal without relying on an external DV camera/VCR. These cards include Canopus DVRex, DVStorm, Pinnacle DV500/Pro-One, Matrox RT2000/2500, DVICO FirebirdXE, Dazzle DVNowAV etc. The differences between a Firewire-Only card and a DV Video capture card which includes Firewire ports are summarised in the following table:

From these comparisons, we might say that a DV video capture card is always a Firewire card, while a Firewire card might or might not be a DV video capture card. There are some special Firewire cards like Canopus DVRaptorRT, Pinnacle StudioDV Plus etc, that have some of the DV video capture cards’ features like outputting video to analogue TV directly, without relying on DV cameras.

When outputting DV video back to analogue TV/VCRs, if the Firewire card has no hardware encoding/decoding chipset, the video signal has to be fed into an external DV camera/VCR first, then transmitted(at the same time, no recording to the DV camera is necessary) to the analogue TV/VCR connected to the analogue output socket of that DV camera/VCR. While DV VCRs can handle this transcoding properly, quite a few DV cameras can not: they do not have DV signal input capability! Some DV cameras made a few years ago, and DV cameras sold in Europe have such a nature. For example, Sony’s VX1000 with serial number prior to a certain value all have no DV input capability. These Output Only DV cameras caused such an inconvenience for Video Editing community that a company in Germany even manufactures a device that it claims can enable many DV cameras’ DV Input. Many individuals have long known that certain DV cameras can be re-programmed to enable the DV-Input, by writing some simple commands into the DV camera’s eeprom memory chipset. Instructions and even eeprom burning tools floating around the Internet teaching people the detailed process of tinkering crippled DV cameras.

4.2 Common Features of DV Capture Cards (top)

Although having some important differences, Firewire only cards and DV video capture cards all share many common features that make them different from other types of video capture cards like M-JPEG and MPEG cards:

(1) No parameter adjustment allowed during video

capture and playback, which are really binary data transmission processes. Unlike the M-JPEG or MPEG cards, if you want to make a DV video brighter you cannot do this before and during DV video is played into your PC. This is true even when you are using those TRUE DV video capture cards like DVRex or DV500 that have DV encoding/decoding hardware built-in. There are some exceptions in this aspect: some DV capture cards like Pinnacle StudioDV use pure software mechanism to provide low-resolution video capture from DV cameras, and some recent DV-to-MPEG software tried to convert DV video from generic Firewire cards into MPEG video file in realtime. So far the real usability and success of these exceptions are not obvious. Some DV-Analogue encoding chipsets built by companies like DIVIO do allow lower resolution/smaller-frame size DV-video capture, but video capture cards taking advantages of these features are not available on the market, possibly due to no strong user demands.

(2) Audio is captured and played back together with video signal. When playing back DV video through Firewire cards, audio goes back to DV camera with video and might not go to PC’s sound card, although some capture cards like DVICO Firebird and Dazzle DVNowAV do simultaneously send audio through PCI bus to the PC’s sound card. When audio goes only through the Firewire cable, to monitor DV audio you either have to use the DV cameras’ speakers or re-wire the DV camera’s audio output to PC’s sound card audio input socket (Line-in socket). Audio capture also can choose from multiple audio channels on the DV camera/VCR. At 48-KHz sampling DV camera/VCR have two stereo channels, while at 32KHz sampling they will have four stereo channels. Which sampling rate and which audio channel was used for recording audio was decided at the camera/VCR’s recording stage, DV video capture utility software normally provides selection boxes for choosing from these audio channels.

(3)Device Control is always available for software on the PCs. All DV camera/VCRs use the function control protocol (FCP) defined by IEC 61883, Digital Interface for Consumer Electronic Audio/Video Equipment. This makes the device control from PC’s software relatively easy to implement. In addition to device control signals like Play, Record, Pause, ReWind, FastForward, FastBackward. Firewire Cards can also display the various status of the connected DV camera or VCR: the device is a camera or VCR, the tape is being played or recorded, if there is a tape and if the tape is write-protect, if the camera/VCR is PAL or NTSC standard, etc.

(5)Easy Batch-Capture.

Batch-capture means the user specify several pairs of start and stop timing points within a video tape, then ask the software to capture all the video contents between every pair of points in one go, the video between each pair of points will be captured into a separate video file(as most batch-capture software do), or into one single file(some software like DocuCap for FirebirdXE can do this).

Batch-capture is designed against Manual Capture, where the user hits Record or Capture button of the software to start capturing video at the time point where the tape is playing or paused at. Batch-capture can save disk space by capturing only the portion of video from the tape the user is interested, but it also requires the DV video tape to be properly time-coded: that is, the time-code recorded onto the video tape is continuous from zero at the start of the tape to smoothly progress to the end of the tape. In recording practice the DV camera might be used in such a way that multiple zero points of time code are recorded: this usually happens when people stop recording, rewind or forward the tape(for viewing purpose probably), then re-start recording at a point not exactly following the point where the previous recording stopped. When multiple zero points exist, batch-capture will not work properly: the captured video usually will not be from between the start/stop points you specified, or the batch operation will just fail totally. Sometimes multi-zero point time code can even cause manual capture to abruptly stop. To avoid these situation, it is a good idea for each new DV tape you perform a continuous blind recording(press Record Button while leaving the camera lid on) from the start to the end of the tape, so that a continuous time code is burnt onto the entire tape. After such a blind recording, any subsequent video recording will keep using the smoothly recorded time code therefore no trouble will be caused during video capture operation.

Speaking of Manual Capture, several DV capture cards, including DVICO FirebirdDV/XE and Matrox RT2000/2500, have a nice feature that allows them to pause the DV camera/VCR at a specific time point, then hit the Record/Capture button of the software, so that the video from the exact time code where the tape was paused at will be captured. This is against the usually awkward manual capture process, where the DV tape has to be played first, then the user has to press the Record or Capture button of the software to start capturing video.

(6) Super-Realtime Recording and Playback:

With Firewire’s 50Mbytes data transmission capability(even higher in the new IEEE1394b protocol), and only 3.6Mbytes/sec. (3.1Bytes for NTSC) required for DV video’s normal transmission speed, it is possible to capture video from and record video to DV camera/VCR at faster than real time speed: through application software, transmitting higher than 3.6 Mbytes/sec. DV data and order the DV camera/VCR to spin the tape faster than normal play or record speed will make this happen. This will be very useful to quickly dump long-hours of video from DV camera to PC or vice versa.

(7)Firewire cable is a single 4-wire or 6-wire copper cable with 2 pairs of data transmission wires. In the 6-wire situation, extra 2-wire are used for DC power supply. A single Firewire cable carries all the video signal, audio signal and device control signal to/from the DV camera/VCR. Firewire cables use male connectors, leaving the DV camera/VCR and Firewire cards using the female sockets. Almost all DV cameras use female 4-pin Firewire sockets. Four-wire and six-wire combinations make it possible to produce 3 kinds of Firewire cables: 4-to-4 pin, 4-to-6 pin, and 6-to-6 pin. The length of these cable cannot be more than 4.5 metres. Although the Firewire cables are light and clean, they are not as easy to make as RCA composite video cables, and the female 4-pin sockets on DV camera/VCRs are relatively fragile so extreme care should be taken when plugging Firewire cable into and off these sockets.

(8)Multiple Firewire devices can be connected together through the same Firewire card: upto 16 devices can be daisy-chained from one single Firewire port, upto 63 Firewire devices can be connected from the same Firewire card with multiple Firewire sockets. Many Firewire hard disks and scanners have at least two Firewire ports, and many Firewire cards have 2 or 3 Firewire sockets. Since Firewire uses no ID to differentiate devices, each device plugged onto the Firewire bus will self-initiate and de-initiate when plugged in or off the bus: this provides easy hot-pluggable capability meaning no power shut-down is needed when connecting a Firewire device onto a working Firewire bus, at least in theory. But in practice, many Firewire cards do not work very well without the Firewire devices connected before the whole PC system is powered up. Frequent connecting or disconnecting DV cameras while PC is running also cause trouble on the Firewire card to recognise DV cameras properly. While multiple Firewire hard disks can be connected/daisy-chained together without too much trouble, connecting more than one DV camera/VCRs to the same Firewire card will make none of them to work properly. The reason probably lies more in the PC’s software: single PC’s video capture utility rarely deals with multiple DV cameras/VCRs connected to the same Firewire card simultaneously, therefore DV camera identification is not provided, and device control software is always assuming that the same camera/VCR is connected. This assumption makes it difficult to share several DV cameras among multiple PC users over a network.

Device drivers also play crucial role in making or breaking the Non-DV camera/VCR Firewire device connection: under MS Windows, only those Firewire cards that use Microsoft OHCI compliant IEEE1394 device drivers work well with Non-DV Camera Firewire devices like Firewire hard disks and scanners, Firewire cards using proprietary device drivers such as Pinnacle DV500, Canopus DVRaptor, currently have no support for connecting to non-DV camera/VCR Firewire devices.

(9)Smooth live video overlay on PC’s screen is difficult for Firewire cards without DV encoding/decoding hardware, since the display of DV video is very much relying on PC’s performance. Most PCs today are not powerful enough to play back DV video smoothly in large window size. Depending on the capture card’s hardware design, even some hardware DV decoding cards like Pinnacle DV500 and Matrox RT2000 cannot display large window DV video on PC smoothly. Exceptions in this aspect include Canopus DVRaptor that feeds analogue video signal from the DV camera onto PCs then overlay this video signal live on a window of the PC’s screen, resulting in very smooth realtime display of incoming DV video during the whole process of video preview, capture and output. Another exception would be the DVNow Firewire card from Dazzle, that uses hardware assisted chipset to overlay live DV video onto PC’s graphics card, much like the functions of some M-JPEG cards such as DC30+, giving a smooth and realtime video overlay even on slow PCs. Apple's Mac G4 PC also plays DV video smoothly in full screen without the help of DV decoding hardware. However, rapid performance increases in PCs, and in particular in the video display cards, and manufacturing costs make these special hardware acceleration on DV video display less favourable, with many DV capture cards manufacturers rely entirely on the host PC’s software and hardware to play back DV video.

(10) Moderate Still Image Capture

Still images captured by Firewire capture cards are of fixed size(720X576 for PAL, 720X480 for NTSC) and their image quality are as good as the DV camera can offer: good with still or low-speed moving objects, blurry or distorted with high-speed moving objects. With high-speed moving objects, DV still images are of lower quality than video frames captured from M-JPEG video capture cards. DV cameras that have separate still image storage media like Memory Stick, Flash-Compact Memory cards etc, which might store higher quality still images, normally do not allow still images stored in those media to be transferred over Firewire port to PCs.

(11) Abnormal Video Capture Stop

Un-like capturing video from Analogue video tapes, DV video capture from DV tapes relies heavily on the time-code transmitted from the DV video device. While this might be advantageous in many circumstances, it also introduced numerous problems. Typically, a manual capture from DV video tapes can suddenly stop/abort while the DV camera/VCR is still running with contents showing on their view-finder/LCD. The reason given by the capture software for such an ugly stop are usually more confusing than any help. The fact behind this abnormal stop normally lies in the time-code recording mechanism on different DV video tapes. Sometimes some DV capture card/software will stop whenever a zero time-code appears, or sometimes they stop because a tape is playing back in a DV camera different from the original recording DV camera, or sometimes just for no reason a particular DV capture card will just abort capture on one tape but not on another. In this aspect DV capture cards are poor performer compared with M-JPEG analogue capture cards. As we will see later, MPEG video capture cards will also have some similar problems.

4.3 Capture DV Video into Non-DV Formats (top)

Some Firewire Video Capture Cards have special software to capture DV video directly into Non-DV formats. The video file format conversion can be handled either by the on-board hardware, or by software running on the host PC. Typical examples include Z-Fire from Omni Technology(Realtime MPEG1 encoding),

DC2000 from Pinnacle(Realtime MPEG2 capture), Osprey500 from ViewCast (Realtime Windows Media Technology Video Encoding), Pinnacle Studio DV(Realtime proprietary video format), etc. As overall performance on PC increases, more effort will be spent on utilising the low-priced pure Firewire cards to realtime encode DV video into different formats from PC based software.

4.4 Connection Type to Host PC

While DV Video Capture Cards with hardware encoding/decoding capabilities are always PCI devices, pure Firewire cards(no DV hardware encoder) have many PCMCIA models for Laptop PCs connections, as well as numerous PCI devices. Other connection types have not been seen on the market.

4.5 Software for Firewire/DV Video Capture Cards (top)

Most of the pure Firewire cards have no firmware running on board, and utilise PCs’ operating system support for device drivers: this is true for IBM compatible PCs using Microsoft Windows as well as Apple Computer’s Macintosh PCs, which have had Firewire built-in as standard interface. MS Windows 98 SE, Millennium, 2000 and XP editions all have built-in device drivers for Firewire devices conforming to OHCI format. Standard application software development interface is also supplied in both Windows and Macintosh operating systems, making customised application software development possible by third party software developers without relying on proprietary hardware interfaces. Good examples would be software to realtime encode incoming DV video into RealVideo/MS .wmv formats, thus negating the necessity to have dedicated Streaming video capture cards. Apple’s software development support is called Firewire API, while Microsoft’s support is built into its latest Windows SDK to allow any DirectDraw application software to call some standard interface functions to control and communicate with the Firewire devices connected to OHCI-compliant Firewire cards.

Contrary to Firewire socket only cards, True DV Video Capture Cards with hardware encoding/decoding capabilities have much less common support from the operating systems. Apart from their on-board proprietary firmware, these video capture cards’ device drivers and/or video capture/playback utilities are supplied as proprietary software from the cards’ manufacturers. DVICO’s FirebirdDV/XE and Matrox’s RT2000/2500 might be an exception because they use Microsoft’s built-in device driver for its TI Firewire chipset(therefore they can connect to Firewire hard disks etc).

Another important software for DV/Firewire video capture cards is the DV Codec, the software used to encode and decode DV format video files on the PC. Microsoft Windows supplies some DV Codecs that are used by many OHCI compliant Firewire cards, but many medium to high end DV video capture cards use their own proprietary DV Codec software. DV Codec plays crucial role in the quality of the DV video outputting back to external TV monitor or cameras, they also decide how good a non-DV video file can be converted to a DV format video file. For example, the Windows’ built-in DV codecs can hardly convert any non-DV video file into a perfect DV video file to be played back to external DV camera smoothly, while some proprietary DV software Codec like Digital Origin’s Codec can accomplish this task relatively well.

4.6 Compatibility with DV Camera/VCRs (top)

Being a device conforming to a standard serial communication protocol, Firewire and DV video capture cards have a compatibility issue to solve: not all DV/Firewire video capture cards work with all DV Camera/VCRs, and every DV capture card has some problems working with some DV cameras. Problems can range from system crash to no device control or no video display at all. Contacting either capture card manufacturer or camera manufacturer normally result in wasted time and effort. Each well-known Firewire/DV capture card manufacturer has some DV Camera Compatibility Listing on their Web site or Product packaging boxes, but the fast emerging camera models and different availability of cameras in different countries make these listing difficult to follow: if my DV camera is not on this Firewire card’s compatibility list, is it compatible or not compatible? The answer is unknown until your camera is tried on that particular Firewire card installed in your PC.

Firewire devices connected to Firewire cards communicate with PC's Firewire device driver software all the times, including at system boot up stage, this is especially true with Microsoft Windows built-in Firewire device driver. While this tight integration with the operating system makes connecting Firewire devices easy, it is also easy to cause hanging and crashing of the operating system software when there is a problem with the Firewire device. Typical problem will be connecting DV camera/VCR to an incompatible Firewire card, or simply connecting a faulty DV camera to a healthy Firewire card: PC can crash and hang at booting up or malfunction. In one instance three brand new Panasonic DS15 miniDV cameras caused 5 to 6 PCs with different Firewire cards to either hang or crash or not recognize the cameras. In another instance one Sony TRV17 miniDV camera caused 5 to 6 DV/Firewire cards to malfunction. This problem is normally more serious with Firewire cards using Microsoft Windows built-in Firewire device driver.

There are some non-DV type video devices that also have Firewire interface built-in, such as stand-alone DVD-Recorders, Sony MicroMV MPEG camcorders, etc. These devices normally cannot interface with Firewire video capture cards properly, regardless what their manufacturers claim. Most of the times even their bundled software do not work on PCs, let alone the vast number of third party software and numerous brand of Firewire cards.

4.7 Video Output from DV Capture Cards (top)

It will be ideal if edited DV video can be output to external DV or analogue camera/TV all the time without any extra effort, plus smooth display on the PC’s screen simultaneously. In practice different DV video capture cards implement different video output mechanism: the best is like the implementation of DVStorom and DVNowAV cards: edited video goes out to all possible output devices simultaneously: external DV camera, analogue TV, and on PC screen display. The vast majority of Firewire port only cards output DV video to DV camera only, analogue TV/VCR can only receive video signal through a DV camera’s analogue output connector. Some of the Firewire capture cards need manual switch between outputting video to DV or analogue output ports(such as Pinnacle DV500), others need manual switch between displaying video on PC’s screen or on external DV camera(DVICO Firebird, Pinnacle DV200). Some Firewire Port only cards can independently output video to analogue port without going through a DV camera(Canopus DVRaptorRT, Pinnacle StudioDV Plus).

During and after video editing process, it would be most convenient to display the video on DV camera or analogue TV right from the spot where video is being edited(timeline or story board), but not all of the Firewire/DV video capture cards, or not all of the video editing software can do this: Firewire cards running under ULEAD VideoStudio or MediaStudio need to switch to some output mode and load in a video file before video output can be started, while the Pinnacle Studio DV and StudioDV Plus need to goto a MakeMovie process to play DV video back to DV cameras. The recently released Canopus DVRaptorRT can only output video to analogue monitor from the timeline of its video editing software(Adobe Premiere 6). Not only having these confusing and in-efficient varieties of video output methods, DV video output often is not instant: between user pressing output button and the actual video signal reaches the external DV camera, there is a time delay, that is, after PC’s software has started playing the DV video clip, it is after awhile that the playing video signal shows up on the external DV camera: this often leads to missing the first few seconds of video to be recorded onto the DV camera. To avoid this, many editing software like Adobe Premiere have a dedicated Output to Tape or Print to Tape mode, where a specific time code on the DV camera/VCR can be specified to be the starting point of recording, then the software will pause the camera slightly before the recording point before starting the video play on PC and sending a Record command to the DV camera, for the purpose of recording the entire video clip on the PC precisely at the recording point of the DV camera.

4.8 Realtime Effects Video Editing (top)

During the video editing process, outputting titles, transitions, filters etc, that are applied on video clips immediately in realtime speed to external monitor is one of the most desirable features for video editors. With the appearance of relatively low-priced(below $3000) realtime effects video editing cards like Pinnacle DV500/Pro-One, Matrox RT2000/RT2500, Canopus DVRaptor RT and DVStorm, some of the effects and transitions can be applied without going through the so-called “rendering” process: the software compilation of the effects/titles into the original video clips. The simplest example of realtime effects is superimposing a title over a video: after arranging the title somewhere on the video and clicking the Play button, on the monitoring TV screen, the title shows up instantly in front of the video playing underneath in realtime speed. Here “on the TV” and “playing in realtime speed” have to be emphasised: although long before these realtime effects video capture cards, some video editing software already allow instant preview of applied effects on PC’s screen, but the effects do not output to external video device such as TV or camera. Yet another type of video editing cards and software, such as those low-end OCHI-compliant Firewire capture cards running under Adobe Premiere 6 using MS device driver and MS DV Codec, can instantly preview any effects on the external TV or camera, by manually drag video play indicator over the video and transition slowly with Alt Key pressed simultaneously, but the video’s play speed is not realtime(not 25 frames per second for PAL). Only video capture cards that display effects instantly on an external TV or camera in realtime speed can be counted realtime effects video capture card. Some of the features of these entry-level realtime-effects video capture cards can be listed as follows:

(1) Almost all of them capture video in DV format, even when the actual input video is from analogue source such as S-Video or Composite video: the captured video files are still in DV format because the analogue video signal is instantly converted into DV video by the video capture card.

(2) Video files that can be used for realtime effects have to be captured by the same video capture card, and they have to be in exactly the same format(if the same video capture card offers different video capture format).

(3) Realtime effects can certainly be output to analogue socket such as S-Video and Composite video socket, but only Canopus DVStorm and DVRex can output realtime effects to DV video camera/VCR through Firewire, the other cards(Pinnacle DV500/Pro-One, Matrox RT2000/RT2500, Canopus DVRaptorRT) have to render every effects when the video output is through DV cameras or DV VCRs.

(4) All realtime effects are video capture card dependent: only those effects that are supplied or modified by the video capture card manufacturers can be output in realtime, otherwise any effects/transitions/filters/titles will have to be rendered. The types and numbers of realtime effects offered by each video capture cards vary, and there is no such a video capture card that offers all realtime effects that all other capture cards can offer: there is always some realtime effects offered by one capture card that others do not offer. Third-party application development toolkits do not exist, so no third-party realtime effect is possible.

4.9 Video Quality Issues for DV Capture Cards (top)

Even in Firewire/DV video capture, occasionally corrupted frames --- video with noise or totally non-related contents or coloured-image turned into black and white etc--- can be seen in the captured video, this is especially true when the input video footage has high-level noise, such as video recorded into DV camera from analogue video sources. Corrupted video frames could be due to bad data transmission result between DV camera and the Firewire/DV capture card, which might not always be picked up by the error correction procedure of the Firewire communication protocol, or could be a bad data file creation process that stored corruted binary data. Another symptom is that when using DV video tapes recorded in one DV camera/VCR, then play back in a different DV camera/VCR, corrupted or jittering video frames will appear in the captured DV video files. Contrary to the widely distributed media claims that all DV capture produce exactly the same quality as the original video tapes, almost all DV/Firewire capture cards on the market can capture corruted video frames at some stage, these include the mid-range products from Pinnacle/Matrox/Canopus/Dazzle/DVICO and all other low-end Firewire-only capture cards from numerous manufacturers.

There has been a common (mis-)understanding that DV video captured from different Firewire cards all have the same quality, provided no frame is dropped during capture and playback. However, this understanding does not take into account the fact that, different format of DV video files inside PC, have to be decoded differently by different DV decoding software(Codec) during the video output process. More over, when these DV video clips are being edited, they will be encoded differently by those different DV encoding software or hardware(Codec). These different decoding and encoding processes will make even perfectly(remember they are not always perfect!) captured DV video files to output different quality video. Different hardware design and data file storage methods also result in different quality DV video captured & output by different Firewire cards.

In practice many low-end Firewire cards using Microsoft Windows’ built-in software Codec(ADS Pyro, Pinnacle StudioDV etc) often output DV video with occasional jittering, while several proprietary software DV codec based Firewire cards (DVICO Firebird, Canopus DVRaptor etc) can output their video perfectly smooth, although both kind of cards have no hardware DV Codec chipset built-in.

Most DV video capture is for editing. Editing involves changing the content of the video by adding titles, graphics, filters, transitions and special effects. These modified portion of the video has to be seamlessly incorporated into the raw DV video captured: every frame of the modified video has to be re-built pixel-by-pixel mixing the changed content with the original raw video, in the format strictly conforming to the requirement of the DV video capture card. This complicated video re-creation can be handled either by software or hardware: by software will invoke software DV encoder associated with the video editing software and DV video capture card, by hardware will invoke some on-board DV encoder built onto DV video capture card. Since the quality and efficiency of DV encoders vary, the result of edited DV video sent back to DV cameras can not always keep the high quality as the captured DV video. This is especially true when converting Non DV video format into DV format video. Using low-end Firewire port only capture cards, converting non-DV format video into DV video will almost always show jerky and jittering video on the DV camera’s screen. Another easy example is adding swift transitions like short period page turns or band-wipes into captured DV video. Quite often low-end Firewire cards will generate jittering around the added transitions during DV playback. Pure Firewire socket cards(no DV hardware encoder built-in) need software encoding for edited video contents, normally the software DV encoding is realised during the video rendering or exporting process from within the video editing software: the results depend on the Compression Method(Codec) selected, the Firewire card and the device driver for the Firewire card. Using the same editing software Adobe Premiere 6.0 for Canopus DVRaptor and ADS Pyro, both are Firewire Socket Only cards, with complicated transitions/titles rendered, generally DVRaptor produces better quality output video than Pyro: the play back video around the added transition area are cleaner, smoother, and with no obvious artificial jittering. This clearly indicates the differences of software compression methods and device drivers used by the two cards: DVRaptor has its own proprietary codec and device driver, while Pyro uses generic DV codec and Firewire device driver provided by MS Windows. Interestingly, these quality-lowering problems can even happen on DV video generated by some hardware-based DV Codec: capture cards like Pinnacle’s DV 500 can occasionally generate jittering video output around transitions area when displaying video to DV camera.

Regardless software or hardware Codec involved, lower-quality DV video output due to encoding/decoding defects should be differentiated from problems due to poor PC system performance: the latter problems can cause much more severe symptoms like frame skipping, video play stopping and total video blackout etc. Some DV capture cards like Matrox RT2000 have warning messages displayed when PC system performance can not meet the requirement of DV video playback.

Being a video digitising device, DV cameras themselves can introduce un-wanted result, such as mosaic blocky frames that can be seen from tape playback when the shooting camera was swirled quickly from one scene to another totally different scene.

4.10 Capture Analogue Video into Firewire Card (top)

With the proliferation of the low-cost Firewire Only cards, how to capture analogue video into these cards have prompted the appearance of Analogue-to-DV conversion devices. These external boxes convert incoming composite, S-Video or Component analogue video signal plus audio signal into combined DV signal and send the DV signal out through a Firewire socket, making an appearance to the Firewire card that a DV camera or DV VCR is sending signal to it. After video has been captured into PC’s hard disk, a reversed process can convert the processed video back to analogue TV/VCR connected to the analogue