DVI as far as a signal is far superior than an SDI signal both in the way it is transmitted as well as the amount of GBs transferred, TMDS (Transition Minimized Differential Signaling) used to transfer DVI is impervious to hum and electromagnetic interference and replicates the original digital signal perfectly and without differential from the source. SDI is a scrambled signal sent to a decoder that uses 10 1s and 1 0s to unscramble the interface line by line in a frame, DVI constantly reproduces the entire frame instead of scans it, it sends unencrypted, un-packeted data using TDMS which also allows for much high transfer rates.Originally Posted by jasonrudolph
SDI depends on 4 different and expensive protocols to reach digital 1080p signals, while DVI-D only uses 2, DVI and DVI dual link to reach 4K signals. Here are some comparisons:
SD-SDI = 270 Mbit/s, 360 Mbit/s, 143 Mbit/s, and 177 Mbit/s Max resolution = 480i, 576i
DVI-D= Is pixel sensitive and transmits the luminance and 24 bits of color per pixel up to 6.15 miles with resolutions of up to 2112x1214 pixels at a stunning rate of 161mhz.
HD-SDI transmits the exact same way as SD-SDI except that it uses 20 0z and 20 1s and can achieve resolutions of uo to 1920x1080 I=Interlaced
Dual link -DVI shatters that barrier at a very low cost transmitting 3840 × 2400 (4k) at 70mhz.Max.
The standards for the extremely expensive equipment that is used to transmit a Dual Link SDI signals needs 2 SDI cables and maxes out at 1080P, with Dual link SDI CRC (error correction) is required as well as packet timing synchronization, this is why the gear to make it happen is so much more expensive than DVI, it has lot more to process and decode as well as time each packet that comes in. DVI doesn't send packets, it send one frame continuously and seamlessly.
The only competition for the clarity of video signal to DVI currently is HDMI which allows for copy protection and encryption.
This year at CES all video standards will have been voided out by a completely new standard called UDI, United display interface, combining the features of both DVI dual link and HDMI, still using TDMS instead of serial data packetization that SDI uses. The big difference is that you will be able to send Rights managed content through it at 36bits per pixel and an alarming 4 times the amount of transfer rate (16gbs compared to 4gbs HDMI and DVI use), it also has clock sync included so i expect this to be the best possible standard for computer based media servers.
Regarding Cabling, Copper DVI cable is just as robust as SDI cabling, I agree that it is not as easily found yet but as with all new standards it takes time for everyone to get on the same page. FiberST is very strong and practical for multiple installations, it was made rugged and furthermore it is very thin as well as totally impervious and unaffected by electromagnetic interference as SDI and RGB-HV is.
When you are using a computer as your video source and Catalyst, you don't need a scaler. This is one of the biggest areas of confusion between Video operators and Catalyst operators, the video operators want to scale everything to fit the raster when it's much better for the Catalyst operator to scale and fit the display to the Raster as he/she needs it. I've had scaling wars between me and the video operator. The biggest advantage is that I have a globally updating palette should the raster start drifting as it usually does so I can update the scale and position of my image within the raster as I need it and without the use of external scalers. The other thing I hate about ImagePros and scalers is that the video techs tend to try to squeeze the entire raster into whatever sized area so that any NTSC or PAL standard ccir 601 data can be played through it without any problems. I HATE it when my content that I build to fit certain resolutions is squeezed into an unrecognizable vertically or horizontally thin area. I plan on certain resolutions and I use many different ones to fit certain screens instead of just one or two. Some people may find this to be complex, trying to fit 18 submixes per cue into each screen, it can be done in 2 seconds with a flick of the wrist if you number all of your comps in the same order every-time and they relate to the screens. You just need to use Fan start when you grab all you video source layers in sequence or ina group and fan them into place. It's that simple. People have made it harder and that is why some video operators I know squeeze everything into an area that any standard 720x486 piece can be played in. This has always bugged me.
To some things up, standard are always changing, DVI, in my humble opinion is both a superior signal for clarity than SDI and is less susceptible to hum.
UDI should be what the real future thinkers are thinking about.
Since SDI has been as video standard for so long, it's always difficult to sway standards, look at Catalyst for example,Profile and EVS are still the standards in large productions but Catalyst has so many more features at a much lower price.
I see the industry divided, there are protocols and equipment that are both technologically and visually superior most importantly a fraction of the cost and there are the current standards that are less superior and cost a fortune still so everyone can pay off their gear. I tend to want to go with the technologically superior and higher clarity products that are cheaper than the one's that are less superior and exponentially more expensive.
Time will tell where things are headed. All ImagePro HDs already have DVI ports on them and have had for years. They recognize that DVI is a hugely growing standard.
To sum things up, I recently did a job in NY and they used some mpeg video server that used nothing but DVI-D and Thinklogical extenders. The screen was the clearest and most color accurate projection I have seen in years. Furthermore they used a scrim in front of the screen and made a 3d logo all with DVI-D and it looked like it was literally popping out at you. It was so clear, everyone was impressed. There was no banding, it looked very clear, there wasn't any digital artifacting - it was 3 blended projectors blended within the software and it looked way better than anything I've seen. That one experience really made me think "Why are we downconverting to analogue and then upconverting to SDI when we already have DVI-D available to us straight out of the mac, then I started looking at prices of DVI equipment and knew right then that it was both a much cleaner signal and much more affordable way to go direct to both projectors and element labs/barco LED processors that only take DVI-D.
Everything is headed digital anyway. It's hard to even find an analogue monitor these days.
This isn't directed to you, Jason, I don't mean to be argumentative ust informative, but anyone on the ImagePro bandwagon needs to protect their interest, after all they paid a fortune for each one and need to get them paid off before technology passes them up, guess what guys, it already has. So when I hear, SDI and Image pros are better than DVI, I just shake my head in disbelief that someone actually believes that.
All catalyst owners can upgrade their systems to DVI output including cabling and extenders for the cost of an imagepro Rental. If you don't wish to use fiber, you can use copper DVI cable up to 300 meters 600ft with no problem.
Christian Choi
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