HalfDVD Success! (was High quality custom format XSVCD)

[Xesdeeni]

For my DVD player capable of playing 3.5Mbps CDs and also capable of playing 352x480 (I call it HalfDVD) streams from (X)SVCDs, I have been mostly successful in getting quality near that of DVD (most importantly, very minimal MPEG artifacts), with the reduced resolution, from miniDV source material (home movies). Apparently I underestimated the significance of encoding interlaced vs. progressive video.

(Thanks to KoalaBear for much guidance)

I used VirtualDub to frameserve through the following filters:
Resize (precise bilinear) -> 352x480
(Jim Casaburi's) 2D Cleaner -> interlaced, threshold 4, radius 2
Deinterlace -> blend

The miniDV source is noisier than I would have expected. It doesn't LOOK bad, but while I was experimenting I could begin to see the encoders having trouble. Hence the 2D Cleaner.

I still didn't get decent results with the Smart Deinterlacer or the Temporal Cleaner, but I'll go back and try some more later.

I then set Cinema Craft SP for CBR at 3500Kbps and in the Video... setting enabled progressive frames, linear quantizer scale, and zigzag scanning order. I didn't bother to encode audio with CCSP because I read that it had problems. A quality precedence of 25 worked well, but I suspect the ever so slight halos remaining might be helped by lower this a bit.

I tried the same settings to frameserve to TMPEG 12h, and the results were not bad, but I still got blocking, mostly vertical lines, in some skin-color gradients. I don't know whether TMPEG is more sensitive to the chroma of the 4:1:1 source, I need a different quantization matrix, or it's a genuine bug. There was also slightly more haloing in some places. I'll have to experiment some more.

Xesdeeni

[im new]

You have only made a Chao-Ji Video disc

"Chaoji VCD" (which roughly translates to 'Super VCD') is not actually a new disc format, but more like a compatibility specification for players. A Chaoji VCD player must be able to play back at least SVCD, CVD, VCD 2.0, VCD 1.1 and CD-DA discs.

Today, all of the so-called 'SVCD' players in production are actually Chaoji VCD players. Despite the mandatory CVD support, it is conceivable that the actual CVD format will be (already is?) orphaned in favor of SVCD. As far as I know, there are no features in the CVD format that would not also exist in the SVCD specification"

The only difference between CVD and SVCD is 352x480.

[VidGuy]

Why don't you just create the SVCD as an interlaced SVCD - then you don't lose resolution. They don't play as well on a computer, but they play great on a TV, which is presumably why you're doing SVCD in the first place.

[KoalaBear]

Let's parse that question into two parts:

(1) Why not create just a regular SVCD, and
(2) Why bother to deinterlace the source at all?

The answer to the first part is that SVCD is the bottom of the barrel in terms of quality potential, an astounding 20 to 50% less efficient than VCD thanks to its unique combination of high horizontal resolution (2/3 D1) and low variable bitrate.

A 352x480 MPEG coded at 3Mbps, on the other hand, is second only to DVD in terms of potential quality and about 3% more efficient than DVD at that format's average bitrate:

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Code:</font><HR ></TD></TR><TR><TD><FONT SIZE=-1><PRE>
RELATIVE EFFICIENCY OF NTSC MPEG DIGITAL VIDEO FORMATS
(1.0:1 = perfect)

nominal compression
encoding (pels per bit)
bitrate -------------------
format resolution pels/sec(1) (Kbps) min avg max
------ -------------- ----------- ------------- ----- ------ ------
DVD 720 x 480 x 30 = 10,368,000 / 6,000 VBR(3) = 1.03 1.72 5.18
CVD(2) 352 x 480 x 30 = 5,068,800 / 3,000 CBR = -- 1.68 --
VCD 352 x 240 x 30 = 2,534,400 / 1,150 CBR = -- 2.20 --
SVCD 480 x 480 x 30 = 6,912,000 / 2,036 VBR(4) = 2.79 3.39 4.32

</PRE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
(1) For all the formats listed above, an MPEG encoding bitrate equal to the number of pels per second will yield perfect reproduction of the source material as it is greater than or equal to the bitrate required to encode 30 I-frames per second.

(2) For purposes of discussion, let's call 352x480 at 3Mbps CVD (after China Video Disc, which had the same picture dimensions although the bitrate was probably lower).

(2) Assumed for convenience to be 2,000 to 10,000 Kbps, average 6,000 [(2+10)/2]

(3) Assumed for convenience to be 1,600 to 2,472 Kbps, average 2,036 [(1600+2472)/2]

Believe it or not, SVCD is a "paper tiger" specification that better serves political objectives than practical ones. China needed a bargaining chip in the form of a credible alternative to DVD, and chose this particular format because (a) it was homegrown, and (b) the specs look formidable on paper. China, like the rest of the world, will eventually settle on DVD as the format of choice but only if it is offered to Asia at a price point it can afford.

By comparison, the CVD format is directly compatible with DVD. Encode the audio at 48KHz and create an AC3 version of the soundtrack and it will be readily accepted by DVD authoring programs such as SpruceUp and QuickBuilder for distribution on CD or DVD-R. Using VBR you can yield 20 - 40 minutes per CD which is quite adequate for home video and television recording (or at the very least no more inconvenient than SCVD), so what's not to love about the format?

Now, as for the second part: interlaced video is an analog compression technology developed primarily because there was no such thing as a frame buffer in the 1930s, and if there were, the technology would have been too expensive to incorporate in a consumer device. By splitting the picture into fields the electronics of the era were able to process the incoming signal in real time, a feat which would otherwise have been impossible without a memory to accumulate, display and redisplay incoming frames at a refresh rate high enough to avoid flicker.

In the era of digital video, which is inherently progressive, interlaced pictures are a pain in the ass to deal with at best. Capture cards don't give us 60 half-frames per second, they combine both fields into a single frame which is up to us to separate if necessary. MPEG-2 contains extensions for dealing with interlaced material if there's no way to remove it, but it amounts to a waste of bandwidth because computers only deal with progressive frames and DVD players can re-generate fields for TV display on-the-fly.

<font size=-1>[ This Message was edited by: KoalaBear on 2001-07-27 23:58:49 ]</font>