Less bitrate = better video quality? I'm freaking out!

[Chetwood]

Well guys, I'm sorry to be pushing the limits but I'm afraid it can't be helped. As prolly everyone of you already know I've been ripping some Buffy eps after I finally decided which settings suit me best. Still there are two minor problems that spoil the fun:


since I'm ripping two subtitles and 2 audio streams I have less bitrate to adjust to video

Buffy eps are a about 43 mins each so this is a lot of stuff for a single CDR
[/list=1]
Still I thought that the results were acceptable (for my little cousin I'm ripping them for, anyway). The resulting video came up with very few but still noticeable blocks/artifacts.

BUT when I encoded a new ep last night I was startled to see that it had none of the usual artifacts at all!

In a scene where the camera slowly follows a person walking from left to right of the room I did not see any blocks as I did in previous encodings of comparable scenes. I've watched this ep with a friend of mine and she was astonished too about the good quality.

So I checked the still open bitrate tab of DVD2SVCD and realized it were the same settings I'd been using all along: 2756 - 128 (audio #1) - 128 (audio #2) - 5 (sub #1) - 5 (sub #2) = 2490 which looked like this:

Between 0 and 43 use 1 CD size 800 = ?-2402
max. 2490 min. 300 min avg. 1600 max. avg 2370

But then I realized the bin-file produced by DVD2SVCD was only about 760 MB as opposed to the roughly 835 MB I usually get with these kind of settings. Then I took a look at the log files and it turned out that although both eps where encoded on 5x VBR with CCE the 'perfect' ep used less bitrate and yet managed to look better!

Below you'll get a short excerpt of both log files. If anyone can make some sense of it please let me know. But before you come up with ideas please consider this:

[list]
I've burned the 'perfect' ep to 3 different kinds of cdrs; all looked the same on my DVD standalone so it does not seem to have anything to do with a better compatibility between cdr/burner/standalone

the Buffy eps in question seem to have roughly the same amount of action scenes so the difference in quality should not result from a different number of bitrate consuming scenes. IOW it's not like comparing 'The Matrix' to 'When Harry Met Sally'.

On 2 different eps I've used the very same

- burning program (cdrwin 3.8g) at 16x
- cdr
- machine
- settings


and still I get a difference of some 60 MB and the smaller file actually looks much better. How come?

'perfect' ep:

Executing Cinema Craft Encoder.
StreamSectors: 771186864
AudioSectors: 83157368
VideoPAPO: 10657944
ScanOffsetBytes: 76770
SeqAligningBytes: 4879160
DVDBytes: 0
VideoEndHeader: 4
SubtitleSectors: 4529476
EmptySectors: 238.00
PictureSectors: 1.00
PureMPEGStream: 667886142.00
Seconds: 2564.00
CalcMPEGStream: 667886142.00
Frames: 63975
CDSize: 740.00
Cut point 730.00
Variable Settings:
Frames: 63975
Anti Noise Filter: 7
Passes: 5
Image Quality: 25
VAF file creation: On
Video Encoding Mode: Multipass VBR
Min. bitrate: 300
Max. bitrate: 2490
Avg. Bitrate: 2083
Aspect Ratio: 4:3 (No borders, encoded as 4:3)


another ep with same settings:
Executing Cinema Craft Encoder.
StreamSectors: 833934864
AudioSectors: 82794824
VideoPAPO: 11635560
ScanOffsetBytes: 76434
SeqAligningBytes: 4857805
DVDBytes: 0
VideoEndHeader: 4
SubtitleSectors: 5063996
EmptySectors: 238.00
PictureSectors: 1.00
PureMPEGStream: 729506240.67
Seconds: 2552.80
CalcMPEGStream: 729506240.67
Frames: 63695
CDSize: 800.00
Cut point 789.00
Variable Settings:
Frames: 63695
Anti Noise Filter: 7
Passes: 5
Image Quality: 25
VAF file creation: On
Video Encoding Mode: Multipass VBR
Min. bitrate: 300
Max. bitrate: 2490
Avg. Bitrate: 2286
Aspect Ratio: 4:3 (No borders, encoded as 4:3)

[UltimateDBZ]

While strange, it could just be your opinion (and eyes). Someone else might find the higher bitrate to look better. Perhaps you should post 1 frame (the same on each) of each encoded video, and specify which is which bitrate, for others to see if they agree or not... it would be interesting if, in fact, more people concluded that the lower bitrate does look better.

[Chetwood]

Originally posted by UltimateDBZ
While strange, it could just be your opinion (and eyes). Someone else might find the higher bitrate to look better.

I doubt it, cause up till now I'v ebeen watching these two eps with 3 different people on several standalone players and everyone agreed that the 'perfect' ep looked much better.


Perhaps you should post 1 frame (the same on each) of each encoded video, and specify which is which bitrate, for others to see if they agree or not... it would be interesting if, in fact, more people concluded that the lower bitrate does look better.


Right. The problem however is that I don't have two encodings of the same episode simply because whenever I encode this certain ep with the same settings I used on the other eps before I get the same good result. Still I will post the Buffy intro both from the 'perfect' and the other ep so you can compare the amount of artifacts.

But how can I extract a certain frame? Virtualdub cannot open the mpegs 'pack synchronization error'. Any other tool that can do it? Thanks.

[willster2k]

One way is to use TMPGenc

Load the file as the video source, click setting ->Advanced -> double click Source, Select a start and end frame (for just one use the same value), click OK, make sure that Source is checked, click OK.
Go to file, Output To File -> Sequence BMP/PPM/TGA/JPG file.
Choose a save location, type (don't use JPG ! it will use Lossy compression and introduce artifacts !!!), put the extension in the filename ie file.bmp for a BMP file and click save. You will get the frame or frames saved as a picture.

Undoubtidly there are probably a hundred different ways, but this is one way I know how to do it with a variety of video files that you can type/select in the particular frame(s) you want.

WinDVD can also capture frames to BMP but it would be a hit and miss affair.

[Chetwood]

Sorry guys, been busy the lasat weeks so here we go. I've used power DVD 4 to make some screenshot of the Buffy opening screen (correct name for this?) and the difference in quality is quite obvious. But the files are bitmaps and 1.3 MB huge. So which format can I use to upload 2 of them here? I guess, a jpg would introduce some artifacts that would spoil the whole procedure of illustrating the quality?

[UltimateDBZ]

No it wouldn't, just use a jpeg without any compression, it will still be a ton smaller, but won't introduce artifacts.

[Chetwood]

Darn, the 2 jpg images are 160 KB each! And if I resize them the process might destroy the obvious difference between the two encodes. Anyone got a website I could up them and link to?

[UltimateDBZ]

Just get a free account off of http://www.netfirms.com real quick, and upload them with your favorite FTP software, and then post the links here.

[Chetwood]

Thanks for the cool link, Ultimate!

Alright, so here come the two pictues. Please bear in mind that the better one actually comes from the encode with lesser bitrate that resulted in a 80 MB smaller mpg file.

IMO there can only be 2 explanations for this:


compared to other Buffy eps this one really has lots of low action scenes so there's not as much to encode

the CCE setting 'image quality priority' of 25 was too high


I'm not at all sure about this but I think I had used a lower setting before and only when I've read it in the CCE FAQ that 25 was the default setting that I'd changed it. Can this setting be looked up in the DVD2SVCD logfile?

Anyway, in case you have any suggestions please let me know. Thanks.

perfect ep
http://chetwood.netfirms.com/img/buffy_perfect.jpg

standard ep
http://chetwood.netfirms.com/img/buffy_standard.jpg

[UltimateDBZ]

Wow, that is a very noticeable difference! I for one think this deserves further explanation and/or research.. such could prove helpful in the future.

[Jaspa]

how can this be!!!!
are you sure, that the bette rpicture, has the less bitrate!!!

there is no explanation, for this

strange i must say,

[Chetwood]

Originally posted by UltimateDBZ
Wow, that is a very noticeable difference! I for one think this deserves further explanation and/or research.. such could prove helpful in the future.

Right, but where to start? Does anybody know about this CCE setting 'image quality priority' setting and could this be one of the factors? And if not, what else could it be.

I mean, I've got the proof here: the perfect ep is about 80 MB smaller than a standard ep. But it's a bit too large to upload to anyone ;)

[UltimateDBZ]

Perhaps it is the image quality priority, I can't be sure as I don't know exactly how it works. Perhaps someone that does? Anyone?

[jledhead]

but don't you have image quality priority set to the same thing in both rips (25)???

I think the standard looks better just from the jpgs, seems a little more clear.

the avg bitrate is higher on the standard though, do you use the max and min bitrate and avg or do you use the ranges based on cd size.

[Trahald]

im not saying this is the answer.. but better or lesser compressability between episodes can happen. only common thing is the opening. might be less noise, less motion in the perfect one (hard to tell by just looking at the origional) if you still had the origional captures, you can do a (quality) quantizer 2 based
one-pass with xvid or divx encode on both.. my guess is the 'perfect' one will come out smaller (meaning its so compressible quantizer 2 (best) can be acheived with less bitrate

[Chetwood]

Originally posted by jledhead
but don't you have image quality priority set to the same thing in both rips (25)???


Yep, you're right. I wasn't sure about this anymore but now I've simply taken a look at the logs I've posted (duh!). Point is, this was the only setting I've been messing with in all my encodes but obviously not on these two encodes so I guess we can just leave it at that.

the avg bitrate is higher on the standard though, do you use the max and min bitrate and avg or do you use the ranges based on cd size.

Maybe I'm messing things up but I actually use both methods! First I set it based on CD size

Between 0 and 43 use 1 CD size 800 = ?-2402
max. 2490 min. 300 min avg. 1600 max. avg 2370

and then I go down and enter the bitrate I've calculated myself:

2756 (max video) - 128 (audio #1) - 128 (audio #2) - 5 (sub #1) - 5 (sub #2) = 2490

So I use 2490 as max and (as required by CCE) 120 less for max avg bitrate = 2370 as well as a min avg of 1600.

It looks like this:

http://chetwood.netfirms.com/img/bitrate_tab.gif

So, basically what you are saying is that I should use only one of those settings and leave alone the other? So what if I use both settings as I've done all the time. Which is used by DVD2SVCD?

[ux-3]

Very interesting...
I do work with TNG and I have a few suggestions too...

Check the DVD! It could well be that the quality of the original is different. It's true for Star Trek TNG.

Did you use build 109? If so, did you recover an encode?

Is the result reproducible, i.e. will you get the poor or good quality again?

Are you muffing cce errors?

Have you tried to repeat enocding the two episodes crossed over?

The scripts for the frameserver might help too...