Undersizing when using bitrate redistribution

[dvd_]

My configuration is as follows:
DVDRB 1.28.2
CCE 2.70.2.12
AVISYNTH 2.5.7.0
I stuck to the default DVDRB settings, except changing number of passes to 6.

Here is my problem: I recently encoded a movie (DVD9 -> DVD5) and ticked 'Enable Bitrate Redistribution' and 'Always use HC for Redistribution Pass', as i've seen recomended in this forum, inorder to improve video quality as much as possible.

The problem was that the final DVD5 size was 4.14GB, about 300mb short of the full DVD5 capacity.

Unfortunately I didn't keep the rebuilder.log for that encode but i do remember it finished extremely fast (about half the time it usually takes my system to encode a movie), and that in Phase II (ENCODING) there were alot of 'Extracting Video ...' as opposed to 'Creating M2V ...'.

So I decided to re-encode the movie, this time without bitrate redistribution, and the final DVD5 size came out a perfect 4.33GB.

I didn't change any setting in DVDRB, except unticking 'Enable Bitrate Redistribution' and 'Always use HC for Redistribution Pass'.

I'm attaching the rebuilder.log and REBUILDER.INI of the 2nd encode (the 4.33GB one) as a reference.
As you can see, in Phase II (ENCODING) it mainly created M2V and not extracted, as happend when bitrate redistribution was used.

So to sum it all up, my questions are:

1. what should I conclude from the above scenario, regarding the quality of the 1st and 2nd encodes?
the first is 4.14GB but with bitrate redistribution, the second is 4.33GB without bitrate redistribution. which should have better
video quality?

2. is there a way to use bitrate redistribution with this movie and still get close to a full DVD5 size?


Thanks in advance for the help

[Fishman0919]

Sounds like encoder saturation.
CCE is not able to encode some parts of the movie to the correct bitrate because it is maxing out.

Use... CCEAQM=1.

put that in rebuilder.ini under [Options]

and 3 passes will be fine


Edit: in Phase II (ENCODING) there were alot of 'Extracting Video ...' as opposed to 'Creating M2V

means that DVD-Rebuilder is taking the Original movie part and copying it to the backup.

Better quality then encoding. So the 4.14 copy would look better then the 4.33

[Sharc]

Redistribution can actually speed up the backup process. When the redistribution finds that the redistributed bitrate of a segment equals or is higher than the original bitrate it will simply extract (copy) the original segment without reencoding it. This can save time - despite the extra redistribution pass.
Without redistribution every segment is probably touched slightly in your case (ie reduced in bitrate by perhaps a few percent only) which will take more time after all.
I would assume that your first undersized run is of higher quality.

[jdobbs]

1. what should I conclude from the above scenario, regarding the quality of the 1st and 2nd encodes?
the first is 4.14GB but with bitrate redistribution, the second is 4.33GB without bitrate redistribution. which should have better video quality?The first encode, even though smaller, would result in the better quality. When you see "extracting..." it means there is no need to reencode that section. The segment stays intact -- and you can't get better than the original.

2. is there a way to use bitrate redistribution with this movie and still get close to a full DVD5 size?What you saw has little to do with bitrate redistribution. Bitrate redistribution will give you the same accuracy... it just happened in that case that some of the segments didn't require reencoding.

It is inaccurate to equate "filling the disc" with "better quality" -- in this case you are actually killing quality in order to "fill the disc". It is generally best to just let DVD-RB do its job and understand that 99% of the time it will give you the best quality you can get.

[blutach]

Of course, if you are still worried about this, you can go into the segment viewer and (only) for those segments which are to be re-encoded (i.e. not extracted), up the bitrate on them until you get an "over target size" message. In doing so, other segments might become "extractable".

Regards

[dvd_]

thanks for all the answers, i will stay then with the 4.14GB encode.

Use... CCEAQM=1.

put that in rebuilder.ini under [Options]

should i use this anytime i get an undersized encode, or add it and leave it there for good?
what are the upsides/downsides of adding this option?

thanks again

[jdobbs]

The problem with that setting (CCEAQM=1) is the CCE warns that using it might create an incompatible stream for DVD... on the other hand, I have never seen a single report that actually implied issue when using it.

[dvd_]

i apologize in advance for the newbie question, but i didn't really understand what CCEAQM=1 supposed to do.
from reading in the forum i understand that it enables an adaptive encoding approach when the encoder maxes out.
does it enhance the video quality? or just help "fill the gap" when its an undersize encode?

[jdobbs]

A little of both. It lowers quantization factors (which usually improves quality) in order to allow CCE to add additional bitrate when it comes in low. But (here's the problem), in most cases it only gets used after CCE has already determined that it has reached it's point of near-perfection. In other words -- it essentially "pads" the bitrate to filll space. Another problem is that even if it decides to do this -- it then has to deal with limitations of the maximum bitrate set for encoding (and in DVD the maximum is fixed based on the standard and the disc spin rate).

[Sharc]

The problem with that setting (CCEAQM=1) is the CCE warns that using it might create an incompatible stream for DVD... on the other hand, I have never seen a single report that actually implied issue when using it.
In fact I have seen many commercial DVDs changing the matrices dynamically on a per GOP basis (same as CCEAQM=1 does), so CCE's warning is probably history I presume.

[dvd_]

Thanks for all your replies.

I read a bit more and as I understand, I have 3 options:
1. set CCEAQM=1
2. raise TargetSectors (currently using default)
3. go to segment viewer and raise the bitrate for those segments that were encoded

Which option would you recomend if my only goal is to use the unused 250mb to improve the bitrate of the encoded segments?

[jdobbs]

This isn't the case in your example, but just for clarity to others -- if the issue were caused by saturation, neither of the second two options will probably have an impact.

[dvd_]

You mean that in my case its probably a saturation issue and CCEAQM=1 is the solution?

[jdobbs]

No, exactly the opposite. In your case the resulting calculated bitrate would have made the new segment bigger than the original -- and therefore the original was kept intact. Saturation can only occur when you reencode.

[dvd_]

ok, i re-encoded with CCEAQM=1 but the output size stayed the same: 4.14GB.

what is the recomended solution from these 2 options:
1. raise TargetSectors (currently using default)
2. after prepare stage, go to preview window and raise the bitrate for those segments that are to be encoded,
so the output size will be close to 4.37GB (currently it sais 4.18GB after prepare stage)

thanks

[jdobbs]

I wouldn't recommend either. But if you really want to do something -- go with option 2.

The only other thing you might do would be to select "Force Reencoding" -- but that isn't recommended because even though the disc would be filled -- the result would not have the same quality as the 4.14GB that you currently have. You only want to reencode when you have to (to make the output smaller).

[dvd_]

thanks jdobbs, and regarding option 1: can you please elaborate on what it actually does,
and how it affects video quality (if at all)?
i've read few posts in this forum that indicate that raising the default TargetSectors value
can help with the undersize issue.

[jdobbs]

It sets the target size (in sectors) for the output. DVD-RB uses that value in all it's calculations (bitrate, etc.) in order to match the specified size. The default value will give an output of approximately 4.32GB. It is intended to give users an option to make it a little larger in the event they want to push sizes all the way to the edge of the disc (but that isn't recommended).

Since in most cases undersizing is the result of encoder saturation, this value wouldn't have typically have any effect. If the encoder is already saturated at a lower bitrate -- it would still be saturated when the bitrate is increased.

[dvd_]

the movie has 32 segments.
with the original bitrate redistribution (which resulted in the 4.14GB output) 23 were extracted and 9 were reencoded.
i raised the bitrate by 10% for each of the 9 segments and i got 4.3GB final size, so that fixed the undersize issue.

from reading in the forum i came across this thread: http://forum.doom9.org/showthread.php?t=127377
which seems to describe a problem similar to the one in this thread.
just wanted to make a note of it: maybe raising the birate of the segments which are to be encoded
can be automated in dvd-rb instead of doing it manually.

and just to make it clear, after prepare stage - the preview window sais: output 4.18GB (which actually resulted in 4.14GB).
so maybe in such cases that the output is predicted as undersized, more bitrate can be distributed among the reencoded segments.