Looking for an opinion on encoding compromises??

[droopy]

Just looking for an opinion on following assumption.

What is the better compromise for DVD encoding. Lower resolution at a certain bitrate, or higher resolution with the same bitrate?

My logic tells me that it is better to have a lower resolution at a certain bitrate as to prevent blocks during encoding as much as is possible. This though leaves you in the hands of your DVD player regarding the quality of resizing.

In my case I'm thinking it to be better to encode using a resolution of 352*576 with a certain bitrate then to take the option of using 704*576 with the same bitrate?????

Am I right and is this making sense or did I have to much to drink this evening and am making absolutely no sense at all??

Thanks for any insights.

Best regards, Leon

[zeb7]

Theirs are a lot of Variables , which is why my post is long as i have tried to cover the Variable
Happy reading.

Years ago i did lots of tests about same time the SD "Xcard" was in beta)
I needed a archive format that would be easily playable in the future (hardware&software independent)
Mpeg4 and WMV where not ,and are sill not establish to have a secure future.
SD only seem interested in getting DVD-Rip's with AC3 working (what home camera can do AC3 ?)
Which left DVD compliant Mpeg2 as the only option.
I then set about testing all the mpeg2 encoders i could find.

Quote;
" My logic tells me that it is better to have a lower resolution at a certain bitrate as to prevent blocks during encoding as much as is possible."

Yes i found this to be mostly true in testing , But their is a point (gray area) that you reach
that makes the decision to resize the 352*576 difficult.
You should review all the factors that go into making the Mpeg2 file.

1.Soure of video :
2.Motion in the video :
3.Frame size (with the trade between blurred frame or blocky frame)
4.Bitrate
5.Encoder
6.Display size/type
7.Youre Psychovisual system (eyes/brain)

Source of video :
If the Source video is very old (like 10 year old Recording done in LP mode) then you can safely use 352*576
but you must capture in 704*576 and bilinear resize to 352*576 for best quality.
you may know VHS has a active resolution somewhere between 200*576 too 350*576
this is the detail that the VHS player can reproduce above a given error ratio (Signal to noise ratio)
So logic would follow that 352*576 mpeg2 would be enough to reproduce VHS on a DVD, its not as easy as
that because the VHS is producing a picture with a gradual reduction in detail past 352 lines and at
the same time increasing in noise in its fine detail , an effect the human eye has grown accustom to.
the bottom line is the 352*576 dvd can look like the original VHS copy with the sharpness turned down.
Not saying 352*576 is a bad idea ( i use it myself ) just don't expect it to look the same as a good VHS tape.

Frame size :
720*576 ,704*576 ,352*576 using 352*576 will help ,at least statistically because the 352 pixels need to
be stretched back to 704*576 on playback any blocks in the frame can look worse ,because the blocks are 2* bigger
And by the same effect a 704*576 at the same bitrate will have more blocks but they are smaller so can sometimes
be more pleasing to the viewer, because it looks more like the random noise were used to seeing with analog.

Generally if you need to use a low bitrate and the video has lots of motion use 352*576

Bitrate :
This depends on so many different factors , motion,frame size,clip lenth,size of media (DVD)
If you want to squeeze a specific amount of video on to a DVD then 2pass VBR is recommended
If you're archiving lots of videos clips to a DVD you may find Constant Quality better.
Youre question is difficult ,because if you're certain bitrate is very low say 1000kbs
352*576 will always look better , but at 2000kbs 704*576 will look better if the video has very little motion.

Encoder ;
The encoder is more important as you lower the bitrate, as it needs to be more efficient
Download all the demos , encode a short clip in each at a little lower bitrate to increase the amount of
blocks in the video for the viewing test.

Top 5 "Lowbitrate" encoding programs (in 2002/3 - Last time a checked)
ProCoder (but the demo didn't work then,with the Matrox MJPG codec ?? i had to use Huffy)
LSX (this is found in MSP / and maybe other Ulead products) (i use this)
MainConcept (Good encoder but the CQ VBR was bad at the time i tested its first release)
TMPGEnc (Great program ) (i use this)
CCE (this product is designed for speed no VBR)

Display :
When viewing on the PC monitor its going the show all the encoding problems very well.
If you're final display is a TV/DVD player you must run the test on that setup , TVs are less sensitive
to color changes and tend to have better detail in darker areas of the screen.
Plus people sit away from the TV.

(eyes/brain) :
When you lower the bitrate down to the point where it just possible to see visual distortion
in the frame , your dealing with human perception , The basis of a good encoder is its ability
to hide its lowbitrate/errors from you're eyes ,so if the encoder estimates you attention
to be on the moving object or the high contrast areas it would give more bits to that area.
leaving low detail or darker area's with less bits.
Different encoders attack these problems with different results and encoding times.

Ok i've gone information overkill probably cause i've not posted here in a long time
sorry if you wanted a quick `n` simply reply

Also had a drink myself so i apologize if i missed something,

Regards zeb,

[droopy]

Hi Zeb7,

Thanks for the very elaborate answer. I was already starting to think that I'd asked a question which was to difficult to be answered by forum members, or extremely stupid.

Anyhoe, I've also not posted or even looked at the forum for a long long time as I was happy with the way I was going about it all and its results.

Many of the things you wrote make sense and I've therefore decided to make a test episode both with 704*576 and 352*576.

Bitrate I intended to use wasn't to low, about 2000-2500kbps using TMPGenc 2pass VBR. (Me favorite ever since I've started with video a couple of years ago) The only important thing to me was to get about 10, about 1/2 hour, episodes of the series I wanted to record on 1 DVD with a fancy menu and stuff in something resembling good VHS qualityon TV.

That's also where the question comes from as I thought that the encoding details would be better in 352*576 as you then have the bitrate used available to encode details for half the amount of video data. Source is a recent VHS recording, about 1 to 2 days old at most.

Thanks again for the insight.

Best regards, Leon