Half D1 bitrate help

[buttsy00]

Hi guys,

How do I calculate what bitrate to use when encoding in Half D1?

I can't see any options in videohelp's calc (https://www.videohelp.com/calc) that you can change the resolution?

Does the resolution matter in calculating the bitrate when encoding to Half D1 as opposed to Full D1?

Any help would be appreciated.
Thanks,
Grant

[ZippyP.]

In calculating the file size the only thing that matters is the running time and the bitrate.

total seconds x bits per second (average bitrate) = total bits

[daamon]

Hi buttsy00,

I think I know what you're asking:

"Coz the resolution is smaller, it requires less bitrate to get a comparable quality (not the same). So how do I know what bitrate will yield good results at 1/2 D1, just like around 5 - 6,000 average (as a min) usually yields good results for full D1"?

A rough guide is 1/2 D1, half the bitrate - the rest is trial and error and the level of your acceptance of "comparable quality".

That's based on numerous recommendations I've seen for when people are encoding at 1/2 D1. Of course, the quality of your source will be a factor...

[buttsy00]

So I should just calculate my bitrate when encoding to Half D1 the same as I would for encoding to Full D1?

What's the advantage of encoding to Half D1 though? Doesn't the bitrate affect the video quality and if I am using the same bitrate as I would for Full D1 then why not just leave it and encode at Full D1?

Or becuase the resolution is Half D1 does that make the video quality better at lower bitrates?

Sorry for all the questions but I am trying to understand how Half D1 works!

[daamon]

So I should just calculate my bitrate when encoding to Half D1 the same as I would for encoding to Full D1?

Calculate your bitrate based on the length of the footage you want to encode. If you want to get up to 4 hours on a DVD, the bitrate would be too low for full D1 to look any good. [Continued after next question...]

What's the advantage of encoding to Half D1 though?

If you for for 1/2 D1 there's less information to encode so you can use a lower bitrate, thus allowing for more footage (in terms of time) on the same size disc.

The trade off is that because you're using a lower resolution the picture won't be as sharp, it'll be softer. If you've a good source, the picture will (roughly) be like a commercial S-VHS quality.

Doesn't the bitrate affect the video quality and if I am using the same bitrate as I would for Full D1 then why not just leave it and encode at Full D1?

Yes, bitrate affects quality. So, there's a bitrate threshold below which quality at full D1 won't be good (you decide where that is). However, because 1/2 D1 is a lower resolution, there's fewer bits thus requiring a lower bitrate.

You won't get the same "direct comparison" quality for say 1/2 D1 at 4,000kbps and full D1 at 8,000kbps, but the picture in the 1/2 D1 case won't be blocky or pixelated.

Or becuase the resolution is Half D1 does that make the video quality better at lower bitrates?

Basically, yes. 1/2 D1 at 3,000kbps will be kinda S-VHS quality and a soft picture. Whereas full D1 at 3,000kbps won't be too clever.

But, 1/2 D1 at 3,000kbps will be softer, or less sharp, than full D1 at 6,000kbps because of the lower resolution.

Sorry for all the questions but I am trying to understand how Half D1 works!

No problem - (sensible) questions are good - that's how we learn. I hope that helps...

[sammie]

Second most of what Daamon said, just adding an extra couple of cents worth.

Noise is your enemy! 1/2 D1 is probably most used for video captures, especially from VHS tapes. The reason is that it's similar in resolution, so you are losing much if anything resolution wise. But! VHS capture is probably the noisiest signal you'll ever try to deal with. If it has a lot of salt and pepper, skew noise, etc....... it may take a lot of bit rate at 1/2 D1 too. Just not as much as at full size. For clean capture (DVD rips, original DV) I tend to try and keep the bit rate a bit higher than Daamon suggests, say 3200 - 3500. For ugly stuff I may go as high as 5000. For 1/2 D1 I find that TMPEGenc and CCE tend to max out their multi-pass VBRs at around 4800, i.e., it doesn't matter what average bit rate you set, the encoder is getting all it can out of things around there, so there isn't much point in going higher.

[SaSi]

The way "half-D1 works" in simple terms is as follows:

The resolution of the video frame is not the deciding factor for picture quality. The source of the picture is the quality factor. Frame size will either maintain or destroy the quality.

So, re-encoding a high quality DVD movie into half-D1 will most likely take away some of the details.
Re-encoding a VHS-LP capture to half-D1 won't because the picture source doesn't provide it in the first place.

So, you encode to half-D1 resolution material that doesn't need to have the full frame.

Typically, half the frame is half the area so it needs half the bitrate - typically. However, since the picture is scaled to 1/2, if the source material has lot's of noise- typical case otherwise you would encode to full frame - the scaling takes away some of the noise and smoothens the image. This byproduct of the scaling further reduces bitrate a little more.

So if encoding at full frame at 6000kbps makes you happy, encoding half-D1 at 3000 will also make you happy and perhaps 2800 will too.

On the other hand, we have opposite cases that justify half D1.

A high quality DVD movie that lasts 3.5 hours long! Lots of action scenes, explosions, water splashing all around - just what makes any MPEG encoder suffer!!!

If you want to fit all that on a single DVD, it will fail misserably at full frame. Encoding at half D1 will spoil some of the crispiness of the picture but at 3000kbps the whole movie will fit fine. The same movie at full frame and 3000kbps will have serious pixelation and motion artifacts in really fast scenes and high brightness (see explosions).

[buttsy00]

I appreciate the help guys!!!

Another question which rate control method should I use?

CQ, CBR or VBR? What are the advantages and disadvantages of both?

I am currently using CBR at a high bitrate and if when authored the file size is too big to fit onto a DVD-R I use DVD Shrink to shrink it to correct size.

Is that a good idea or would I be better off using VBR?

[daamon]

This link is to a rough guide.

This link is to a calculator which advises when to use CBR or VBR - it's about half way down the page, but reading the whole lot would be useful.

I've not used CQ, so can't comment.

[jimmalenko]

Sometimes the bitrate determines what frame size we should use, other times the source. It is best to choose the nearest resolution to your source, always rounding down where possible. Choose between 352 * 240/288, 352 * 480/576, or 720 * 480/576 (there may be times when you have a resolution smaller than 352 * 240 - that is OK, you'll just have to use 352 * 240). Your source's frame size is the first half of the Aspect value in the picture above from GSpot.

Given a perfect (DVD quality 720 * 480/576) source, I use the following:

If ave is < 2000kbps, I'd use 352 * 240/288 ave CBR
If ave is > 2000kbps & < 5000, I'd use 352 * 480/576 2-Pass VBR (min 1000 ave ave max 5000)
If ave is > 5000kbps & < 7500, I'd use 720 * 480/576 2-Pass VBR (min 1000 ave ave max 9000)
If ave is > 7500kbps, I'd use 720 * 480/576 ave CBR

If a resolution is "forced" because of the source, keep this in mind when perusing the above chart (ie. if your nearest resolution is 352 * 240/288, there is no point using a bitrate > 2000kbps).


EDIT:
@Daamon: update your links. I've changed the lower thresholds from 2000 to 1000 for 2-Pass VBR

I'll edit that post now

EDIT(2):
That post has now been updated

[daamon]

@Daamon: update your links. I've changed the lower thresholds from 2000 to 1000 for 2-Pass VBR

I'll edit that post now

EDIT(2):
That post has now been updated

Told ya it'd come in handy... As long as you don't change your mind again... :P

[jimmalenko]

@Daamon: update your links. I've changed the lower thresholds from 2000 to 1000 for 2-Pass VBR

I'll edit that post now

EDIT(2):
That post has now been updated

Told ya it'd come in handy... As long as you don't change your mind again... :P

I did a couple of tests and found that lowering the lower threshold a bit gives TMPGEnc a little bit more flexibility. I'm happy with these numbers as a very very rough guide

[ZippyP.]

I am currently using CBR at a high bitrate and if when authored the file size is too big to fit onto a DVD-R I use DVD Shrink to shrink it to correct size.

Is that a good idea or would I be better off using VBR?

It's always better to encode it to the correct size the first time, either with CBR or VBR.

CQ, CBR or VBR? What are the advantages and disadvantages of both?

CBR is just that, the bitrate is constant throughout. If file size is not a concern and the bitrate is high enough then it's the one to choose. Fast encoding.

VBR is best used when the bitrate isn't high enough and quality is suffering when using CBR. VBR allows a higher rate in high motion scenes and a lower rate in more static scenes. Quality is preserved and the overall bitrate (the average) is lower than an equivalent looking CBR encode. If you're using 2-pass it can take twice as long as CBR.

CQ is a type of single pass VBR, it's fast but file size is unpredictable.

When to switch from CBR to VBR depends on the source (VHS, DVD), the resolution (1/4, 1/2 or full DVD) and your tolerance level. jimmalenko gave you some good guidelines, now it's up to you to experiment and decide.

[SatStorm]

TMPGencology... My favorite subject....

Top quality for 352 x 576 = 4000kb/s CBR

Never go lower 2000kb/s with this encoder. It creates macroblocks on the static dark scenes (a stupid bug).

CQ mode works with a logic like :rise over the minimum bitrate, when is needed.
CQ_VBR is not the same: it is Find the Average (and that f**** up great some times the results)

2 Pass VBR is the best one but not for the latest TMPGenc (and PAL users in general. Don't know why this happens, but it happens! Older versions like 1.2h don't had that... A bug in the colourspace convertion? who knows!). Anyway, when you use 2 Pass VBR, never set the minimum lower 2000kb/s for a 4:3 source. Only if the source is a letterboxed 16:9 and you mask the boarders, then you can go lower...

When you can, resize always before TMPGenc. Also filter a bit, it doesn't harm...

[ZippyP.]

When you can, resize always before TMPGenc. Also filter a bit, it doesn't harm...

So do recommend Virtualdub or avisynth along with resize and noise filters? Which noise filter? TMPGEnc's noise filter is very slow, as you know.

[SatStorm]

Yes, I recommend virtualdub or avisynth along with resize and noise filters.
There are plenty noise filters to choose from. You need to get your hands dirty to see what you like and what you don't.
Filters is something you won't learn without a bit of trial and error

[FulciLives]

When you can, resize always before TMPGenc. Also filter a bit, it doesn't harm...

So do recommend Virtualdub or avisynth along with resize and noise filters? Which noise filter? TMPGEnc's noise filter is very slow, as you know.

Take a look at this here guide that I wrote:

https://www.videohelp.com/forum/viewtopic.php?t=225951

Good Luck

- John "FulciLives" Coleman

[SatStorm]

I hate you ... you Zombi! You avisynth user! You.... bt8xxx owner!

[FulciLives]

I hate you ... you Zombi! You avisynth user! You.... bt8xxx owner!

I think it's true what they say now about you SatStorm ... you are crazy

Who loves ya

- John "FulciLives" Coleman