question: VBR in TMPGenc (DVD low resolution)

[ZZ-Diego]

Hi

i use TMPGenc Plus to encode my videos to 1/4D1 (low DVD resolution) most of the time with a CBR of 1500-2000kbps.This bitrate is close to SVCD and the quality is great, much better compared to VCD. Now i read, that in VBR mode the quality can be greatly enhanced and close to DVD even though the resolution is only 1/4 of full DVD?!I´d like to burn 3 or 4 videos on one DVD....

I found out, the lowest bitrate is around 1300kbps for mpeg-2. Would it be expedient to use this as a minimum bitrate in VBR? Because conversion logs on the web show these settings:
minimum bitrate= 0kbps
maximum bitrate= 8000kbps

Will the following settings have a great influence on quality?
- motion search precision
- noise reduction (Quality mode)

1)
Also i wonder about the "Expert" > "System tab" > "Stream type" its always
locked on mpeg stream (VBR).Any ideas?

2)
I did a test with my "Very bad things" (8GB data) video.The first time it was completely ripped and encoded to DVD low resolution with a bitrate of 2500kbps.In another test i shrinked it with DVDshrink (47,2%) and also encoded it to DVD low resolution (2500kbos). Both times the output video has had 1999,091MB of size.Is that normal?


Diego

[rgathright]

Testing it out is the best way to do this. Sometimes a low quality source video (fuzzy reception from tv broadcasts for example), takes lower bitrates quite well.

The audio is another story. I always encode my audio @ 256KBPS because the encoder will tend to add the "tinny effect" to video encoded at less than this setting.

This is all from a year's of experience... others may know more.

[mastercontrol]

SVCD has a resolution of 480x480, 1/4 D1 has a resolution of 352x240, which is the same resolution as Video CD (VCD). I don't understand how you figure that 1/4 D1 video looks better than VCD, since they are the same resolution. From what I understand, MPEG2 needs a higher bitrate to achieve the same quality as MPEG1 VCD.

Now i read, that in VBR mode the quality can be greatly enhanced and close to DVD even though the resolution is only 1/4 of full DVD

VBR mode can result in a better quality picture, depending on the bitrate settings. The main advantage to VBR is that there's a more efficient use of the bitrates, so high action scenes that need more data will get it, while scenes with lower action will use less data.

Honestly though, why bother using such a low resolution for DVD when blank media is as cheap as CD media nowadays? I know here in Canada, I can get DVD media for around 50 cents a piece. To put time and effort into authoring a DVD, only to have the picture look like garbage seems like a waste of time. I could see doing Half D1, which is 352x480, and works very well for VHS sources, but 1/4 D1 will look really bad unless you're watching it on a little 13" TV.

I did a test with my "Very bad things" (8GB data) video.The first time it was completely ripped and encoded to DVD low resolution with a bitrate of 2500kbps.In another test i shrinked it with DVDshrink (47,2%) and also encoded it to DVD low resolution (2500kbos). Both times the output video has had 1999,091MB of size.Is that normal?

If you're using a CBR, that would explain it. They are the same length and set to the same bitrate, so logically that will result in the same size. If you use a VBR, you'll probably have a bit of a variance, but considering the low resolution you're using, there would be a very small difference in bitrate between the two.

[ZZ-Diego]

Hi Mastercontrol,

thanks for answering and for your ideas!

SVCD has a resolution of 480x480, 1/4 D1 has a resolution of 352x240, which is the same resolution as Video CD (VCD). I don't understand how you figure that 1/4 D1 video looks better than VCD, since they are the same resolution. From what I understand, MPEG2 needs a higher bitrate to achieve the same quality as MPEG1 VCD.

I did several tests month ago with vcd ripping software,Nero and TMPGenc and encoding with 1500kbps to dvd low resolution in TMPGenc was looking better. ...but source has to be full dvd resolution...

http://forum.digital-digest.com/showthread.php?t=47049&highlight=resolution+1%2F4

advantages of 1/4D1 - low resolution dvd i would say:
- 100% standalone dvdplayer compatibility
- full AC3 support (5.1/dts)
- better quality than vcd if source is dvd
- it needs less encoding time

disadvantage:
- dvd burner needed for authoring....

VBR mode can result in a better quality picture, depending on the bitrate settings. The main advantage to VBR is that there's a more efficient use of the bitrates, so high action scenes that need more data will get it, while scenes with lower action will use less data.

okay, thanks. But is better to set 1300kbps as minimum or set it to 0?

Honestly though, why bother using such a low resolution for DVD when blank media is as cheap as CD media nowadays? I know here in Canada, I can get DVD media for around 50 cents a piece. To put time and effort into authoring a DVD, only to have the picture look like garbage seems like a waste of time. I could see doing Half D1, which is 352x480, and works very well for VHS sources, but 1/4 D1 will look really bad unless you're watching it on a little 13" TV.

but if you encode into mpeg1 you need to reconvert and change the algorithm....To reduce mpeg-2 to a lower resolution won´t make it look ugly if you use a good encoder like TMPGenc i found out. Its really an amazing difference!

If you're using a CBR, that would explain it. They are the same length and set to the same bitrate, so logically that will result in the same size. If you use a VBR, you'll probably have a bit of a variance, but considering the low resolution you're using, there would be a very small difference in bitrate between the two.

Thats the funny part here...shrinking reduces bitrate so its different...a 8Gig film was shrinked to 4,35 and in both cases (not shrinked film) its the same mpeg-2 length.

[mastercontrol]

okay, thanks. But is better to set 1300kbps as minimum or set it to 0?

Probably won't make any visible difference, the encoder should use what it needs.

but if you encode into mpeg1 you need to reconvert and change the algorithm....To reduce mpeg-2 to a lower resolution won´t make it look ugly if you use a good encoder like TMPGenc i found out. Its really an amazing difference!

I doubt it would make much of a difference. I highly doubt that you'd see any difference in quality between 1/4 D1 MPEG-2 or MPEG-1 VCD. There's no point in trying to change your mind about the quality. If you think 1/4 D1 yields amazing picture quality, nothing I say can change your mind.

BTW, I use TMPGEnc as my MPEG encoder.

Thats the funny part here...shrinking reduces bitrate so its different...a 8Gig film was shrinked to 4,35 and in both cases (not shrinked film) its the same mpeg-2 length.

Yes, it is different, but taking the resolution down by 75%, TMPGEnc won't see much of a difference when it's encoding at such a low resolution.

[ZZ-Diego]

Hi

i did TMPGenc -mpeg 2- encoding tests on the weekend and i wouldn´t recommend VBR for low bitrates anymore if encoded less than 2000kbps. Its possible to bundle three videos (90min running time each) encoded with CBR 1500kbps and D5.1 (de-multiplexed) and re-authored on a single layer dvd which is great.The quality is superb on TV and TFT screens!

If encoded with VBR (minimum 1300kbps/maximum 8000kbps/average 1500kbps) you see fracts during TFT playback.I guess TMPGEnc doesnt accept minimum bitrates.You dont find those fracts within CBR 1300kbps encoded videos...

greets
Diego