How to Increase SVCD and VCD Image Quality

What is a SVCD and what lets it down

SVCD's are Video CD's that are playable in DVD-ROM drives. The original standard use to be VCD, however VCD is based on MPEG1 and is limited to a poor bitrate of 1,150 kbit/s. This is quite low and it shows. SVCD's are MPEG2, have a larger frame size and support bitrates upto 2,520 kbit/s. Still a bit low, but considerably better than VCD's.

Unfortunately MPEG and MPEG2 image quality isn't always just related to bitrate, although if you increase the bitrate far enough, then you will indeed have a nice crisp quality image, but you will sacrifice considerable amounts of disk or CD-R space. So the better alternative is to use a bitrate that keeps the space requirements down, and somehow increase the quality of the image.

From my experience, there are 2 things which kill MPEG's image quality

01 - Compression Block Artifacts





Now we can't really do much about the Compression blocks because we're limited to 2,520 kbit/s. You can clearly see on the left image above all the compression blocks left by the codec.





As a sample test, I made another MPEG at 5000 kbit/s (almost double the bitrate), and as you can see from the above, it still doesn't equal the Div-X sample , nor does it remove all artifacts. The white edges of the star pointers are still blurry. But double the bitrate, Doubles the filesize.

02 - Poor Motion Search Precision





So the main thing we can focus on is make MPEG detect movement and motion on the frame better. See in the left image, just above the black line of the letter R, it looks like a heat haze. These artefacts are left behind when a pixel (or matrix of pixels) move across the frame and their position was not detected accurately. There are also numerous compression block artifacts still visible in the above left image, and they are part of the problem, however once Motion is detected better these can be considerably reduced. See Next image





However using Motion Search Precision uses huge amounts of CPU time and therefore can't really be used during Capturing and On-The-Fly Encoding (unless if your capture card has mpeg2 encoding in hardware and supports Motion search precision).

So the best solution, is to capture using a Lossless codec, and then post encode to MPEG using TMPGENC. For more info about 3 step capturing see some of the pages from my Main Page.


Purpose of this page.

I've made this page to hopefully demonstrate with examples, that there is a large difference between what options you choose. So if the MPEG encoder program that you use, doesn't allow for Motion Search precision, (or something equivalent), then you are probably not producing the highest possible quality SVCD files. Same applies if you are capturing in realtime (compressing direct to MPEG during capturing), then you are possibly missing out on the ability to detect motion at its maximum.


Footage Specifications

FORMAT PAL
FRAME RATE 25 fps
ASPECT RATIO 16:9
SOURCE 720 x 576 Widescreen (which playsback at 1.78:1 or 1024 x 576)
ENCODING PAL SVCD, 480 x 576, 25fps
16:9 Widescreen, which plays back at 1.78:1 or 1024 x 576


This is one of the settings screen from TMPGENC, you can see under the pulldown menu for Motion Search Precision the options listed.

If you want the maximum quality, then select Highest Quality (very slow). This unfortunately means encoding times are utterly disgusting, but the image quality improvement is worth the extra time.

By far the lowest quality, just as it suggests is the Lowest Quality (very fast) option. It is considerably faster at encoding, but the image quality is equally considerably worse.


Single Frame Comparisons

Here is a single frame from each sample file. You will clearly be able to see the image quality variation between the Motion Search Precision Settings

So the web page doesn't look to large, I have trimmed the frames to remove all unused screen portions (commonly called black bars).

MOTiON SEARCH PRECiSiON COMPARiSON
From Worst to Best
         
Below Image is for VCD.
Only 3 pictures, Lowest, Normal and Highest



If the Javascript slideshow doesn't work for you, or If you would prefer to view each image separately you can from the below links. Or right click and select "save target as"

SLiDESHOW PiCTURES
Lowest (Very Fast) Motion Search Precision
Low (Fast) Motion Search Precision
Normal Motion Search Precision
Highest (Very Slow) Motion Search Precision
Div-X (1024 x 768)
Div-X (512 x 288)
VCD Lowest
VCD Normal
VCD Highest


Sample Video Footage

If you would prefer to see first hand what those settings look like, here are 3 second samples from each setting. All of the above still frames were taken from the below footage. The footage used was from a Widescreen (like there's much else nowdays anyways) DVD Movie, so typically it has the unused screen portions top and bottom (commonly called "black bars").

DOWNLOAD DETAiLS FiLESiZE
Div-X
Div-X, 1024 x 576, Quality Based 93%.
Created as a Comparison to MPEG 2 SVCD
2,374,660 bytes
Div-X, 512 x 288, Quality Based 93%.
Created as a Comparison to MPEG 2 SVCD
1,041,618 bytes
MPEG 2 - SVCD
MPEG 2 SVCD, Lowest Quality (Very Fast) 1,208,324 bytes
MPEG 2 SVCD, Motion Estimate Search (Fast) 1,208,324 bytes
MPEG 2 SVCD, Normal 1,208,324 bytes
MPEG 2 SVCD, Highest Quality (Very Slow) 1,208,324 bytes
MPEG 1 - VCD
MPEG 1 VCD, Lowest Quality (Very Fast) 695,552 bytes
MPEG 1 VCD, Normal 695,552 bytes
MPEG 1 VCD, Highest Quality (Very Slow) 695,552 bytes


Conclusions

MOTION SEARCH PRECISION
The Highest Quality option is the only choice if your footage contains lots of fast or rapid movement (such as indycar racing), or if you simply want the sharpest mpeg2 SVCD. Normal is still pretty good, but the other two options I would seriously ignore they even exist. Normal would be the lowest setting I'd ever use.

MPEG2 versus DIV-X
Well, there's no real comparison In My Humble Opinion. Div-X even in Half resolution of 512 x 288, still looks considerably sharper than the MPEG2 files. Of course we all know that Div-X avi files are not as flexible and can't be played back in DVD-ROM drives, but I thought it would be an interesting comparison to make anyways.

ASPECT RATIO
This is something that always seems bizarre with MPEG standards. I'm sure the aspect ratio is stored in the mpeg2 header as a sort of "recommended playback method", because it can certainly be (and definitely is) ignored by most players and options. For example DVD's. Take one that is listed as PAL 16:9 Widescreen, and the footage frame size is reported as being 720 x 576. But we all know 720 x 576 is not 1.33:1. It's 1.25:1. Now when that DVD is played on my PC's DVD-ROM player, the frame size is being displayed as 1024 x 576, which is 1.78:1. Just take the MPEG2 SVCD files I created above, their framesize is 480 x 576, but they still playback here as 1024 x 576. It seems that MPEG uses Frame size Height * ratio. For example: a 720 x 576 movie will be displayed at 576 x (16 / 9) = 1024. So if you wish to ensure you view the MPEG2 files at their correct ratio, just make sure you have a player that supports MPEG2 files correctly such as WinDVD or PowerDVD. (not Windows Media Player)



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This Page was
Created on: 29th January 2oo2
Last Updated on: 19th September 2oo4

(C) Narler
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