Make Your Own DVDs And SuperVCDs
Today's CD-R Burners Can Also Do SuperVCDs
By Trevor Marshall
July 17, 2000
DVD players are everywhere, just as likely to be in your new PC as on top of your television set. Sales of DVD players are expected to outstrip sales of new video tape recorders (VTR) by the end of 2001.
But there is one glaring problem. In its rush to create a closed standard that would ensure DVD movies could not be copied, the industry has forgotten that you and I, the consumer, just might want to be able to make our own disks someday.
DVD Players Are Definitely Not DVD Recorders
Of course you can buy the Pioneer DVD Burner, an investment of $3,000 or so, and each recordable DVD-R disk will only cost you around $35! Or you can use the new DVD-RAM burners, which will make DVDs that can be played in computers, but not necessarily in the DVD player sitting atop your TV.
You see, the industry chose a wavelength for the lasers used in playing DVD movies that is different from the wavelength of the laser used in DVD-RAM drives, and different again from the laser wavelengths used for audio CDs, which is different from the lasers used in computer CD-Rs. This is why some DVD players, although they will play a mass-produced audio-CD, will not play an audio-CD that you have copied in your CD-R.
Enter The Chinese Government
In 1998, the government of China realized Western-controlled, encrypted, DVD technology would increase the cost of video media to its citizens. The VCD standard was already prolific throughout Asia, and although it has a maximum resolution of only 352 x 240 (compared to 720x480 for a NTSC DVD), tens of millions of these disks had been produced. You see, VCDs use standard audio-CD duplication technology, and are priced within the average Chinese household budget.
So, the China National Committee of Recording Standards produced the Super-VCD (SVCD) specifications in September 1998, partly to sidestep royalties on DVD technologies, and partly to lower DVD player and disk prices in China (if you are interested in reading more on the politics and technology behind SVCDs, you can read Jukka Aho's excellent overview).
Europe Approves The SVCD
Just last month, the European standards organization, the IEC, approved a standard titled "Super Video Compact Disc," essentially giving Europe's stamp of approval to the SVCD format.
Philips Electronics NV has thrown its weight behind SVCD, and is selling copies of the specification and software for creating SVCDs. But Philips is also ensuring that most of the DVD players it manufactures for sale in Europe will play the new SVCD disks. I believe it is now likely that the SVCD will become the standard for recordable consumer video, with DVD being used primarily for movie playback (and remember: you read it first at Byte.com).
The SVCD specification calls for an MPEG-2 video stream, essentially identical to that on an un-encrypted DVD, with an aspect ratio squeezed to 480x480 from an NTSC DVD's normal 720x480 (the PAL resolution is 480x576).
The recorded video width is expanded by the player's circuitry from 480 pixels to the full width of the television screen. A clever move, since TV sets that can display more than 480 horizontal pixels are few and far between. Also, the storage space saved in the video file by using the smaller frame size becomes critical when you are trying to fit one hour of video onto a standard CD-R.
Like DVD, SVCD supports a 16:9 anamorphic widescreen aspect ratio. It can also support subtitling, and to enhance Karaoke lyrics the sub-titles can be highlighted with different colors. Up to four separate channels of subtitles can be displayed.
An SVCD video can be indexed into multiple chapters, with multi-level hierarchical menus. It can even be organized as a slide-show of still images. SVCD supports HTML-style hyperlinks to index to locations within a disk.
Finally, the SVCD has the capability to carry four audio channels, compressed with MPEG Layer 2.
A typical running time of an SVCD disk is 35 to 45 minutes, although it can be extended to over an hour by careful attention to the efficiency of your MPEG encoding.
Which DVD Decks Already Play SVCDs?
I cut an SVCD and took it down to the local Circuit City and Best Buy Superstores. Even though not one of the DVD players said anything about SVCD in their user manuals, half of the machines at Circuit City and a few at Best Buy happily accepted and played my disk. After all, the manufacturers of DVD players now have had over a year to make the choice. Do they sell a DVD player that will only play DVDs or will they also prepare support for SVCD? Clearly, they have no choice if they want to sell to the Asian countries, where SVCD is already emerging as a commercial vehicle. Now that the IEC has chosen to bless the SVCD, manufacturers have accelerated the production of players supporting it, in most cases without telling the consumer.
My Own DVD/SVCD Player
I have to admit that until I started researching these columns I had been uneasy about DVD technology, and had not bought a DVD player for my TV (I had a DVD drive in my computer, of course). It didn't take too much research to find out I needed a Raite AVphile 715 multi-standard player from Frys Electronics, since I wanted a player that would handle both PAL and NTSC videos. After I downloaded the ROM firmware conversion kit, unzipped the new ROM image, and burned it onto a CD ROM ... Presto! I had converted my Raite into a PAL/NTSC DVD/Audio-CD/MP3-CD/VCD/SVCD player -- for around $240! But your mileage may vary.
What Other Tools Do You Need?
The DVD/SVCD player is only a small part of the cost of getting into digital video. In May, I reported about a new technology that was revolutionizing the transmission of Movies on the Internet, based on Microsoft's MPEG-4 codec. Since Microsoft included the MPEG-4 software in Windows, the MPEG-4 codec is freely available (although nobody is really sure how compliant it is with the actual MPEG standard).
DVDs and SVCDs, however, use MPEG-2 compression technology. Just like DVDs themselves, the industry has tightly controlled MPEG-2 technology. You can buy low-cost systems, but they will not give you video quality anywhere near what you are expecting. The best MPEG-2 software costs upward of $2,500. All the shareware encoders, with the exception of Tsunami MPEG , do not make the grade.
Encoding MPEG-2 video for DVD is somewhat simpler than encoding for SVCD, as the data rate is much higher, and the compression technology is not so critical.
I tested the Ligos LSX-MPEG encoder ($299) and the Heuris MPEG Power Professional 2.0 ($1,500 to $2,500). In May, I had encoded a video clip using the Divx (MPEG-4) encoder at 600 kilobits-per-second (Kbps).
At this data rate, two hours of video fits onto a standard 700 meg CD-R. I found that even these two "top-of-the-line" MPEG-2 encoders had trouble producing acceptable video at such low data rates. To fit 40 minutes onto an SVCD you must use a data rate around 2,100 Kbps, and to fit an hour onto the SVCD you have to use data rates around 1,100 Kbps. It seemed that the video encoded with Divx was crisper than an MPEG-2 file encoded at three times the data rate. Of course, you do need at 600-MHz PIII to decode the Divx in real time, and it will not play in your set-top box.
I have posted a 15-meg ZIP file containing the same Divx sample video clip, but produced at 1165 Kbps with the LSX-MPEG standalone encoder. There is another containing the output of the Heuris encoder. An invaluable tool for comparison of MPEG-2 encoder quality is Teco's Bitrate Viewer and Figure 1 shows the analysis of the output from the Heuris encoder at SVCD data rates.
The quantization level is in green, and the instantaneous data rate is in yellow. You can see the Heuris package produced quite compact VBR code with a low, average quantization level. Figure 2 shows the data screen for the output from the LSX encoder. Even though the LSX codec produced a higher level of quantization artifacts, the video was acceptable (and it is a lot less expensive; download the clips and see for yourself). One difference between the videos is due to the quantization efficiency of the Heuris encoder. Look at the face of the child on the right (the knife seller) in the last 10 seconds of the video. You can see that the facial features are blurred by the LSX, but are still visible in the Heuris output. But again, is it worth the difference in the package cost?
Both the clips are in SVCD format, ready for burning onto an SVCD of your own using the NERO Burning ROM software. You can also view them using most software PC DVD players, or by using Ligos' $29 MPEG-2 plug-in for the Windows Media Player.
There was little quality difference between the Ligos and Heuris packages, and both were way ahead of the Panasonic MPEG-1 encoder and the bbMPEG encoder. The closest freeware runner-up was the Tsunami MPEG encoder. At DVD data rates (5,000-9,000 Kbps) there was less difference between the top-three contenders.
Why Are All The Tools Based On Windows?
Heuris actually sells a Macintosh version of its encoder, but there is still very little MPEG software available for Linux, with the exception of some MPEG-1 authoring software, and a new Divx (MPEG-4) player. A Beta Divx for BeOS was recently released. Microsoft has been working closely with the MPEG standards committee, and this has given Windows a head start in the race.
It is certainly possible to produce DVD-quality video on a PC without having to buy a $20,000 studio-production system. But there is A LOT MORE to authoring DVDs and SVCDs than I have been able to cover in one column. In my next column, I will describe how the software tool chain fits together, and examine the entire DVD and SVCD creation process in more detail.