Need help to set up Variable Bitrate

[spigy]

Hey!

I am converting AVI files to MPEG2 (using Xilisoft Video Converter Ultimate) and without touching the expert options I converted the files to a quality I was satisfied with.

Here is the problem. The quality was great, but I noticed that on fast scenes (lot of movement) the quality dropped greatly.

So my first question: Is there an option to tweak this?


Now a higher bit rate would obviously solve the problem, but the files would be too big. I thought that this is where variable bit rate comes in. From what I understand VBR would convert the files using different bit rates, using more at fast scenes and less at slow scenes, therefore saving space.


The problem is I don't know how to set it up


In expert options there are a lot of options, some with a true/false option, but most with nothing at all. I'm thinking the minimum and maximum bit rate I want has to be entered here, but to where is a good question.

I turned 2-pass on, but there are other options.

Fixed Quantiser scale
Min+Max Quantiser scale
Min+Max Lagrange factor
Min+Max Macroblock quantiser scale

max difference in quantiser scale
quantiser scale blur
quantiser scale compression

these are the ones that have (VBR) next to them, so I take it they are the options for this.



Any help would be appreciated.

[edDV]

Define AVI (what format? or uncompressed?)

Define the source in more detail.

Why are you converting to MPeg2? What is the goal.

[spigy]

Right now I am converting h264 format compressed files to mpeg2.

MPEG2, because I want to edit the files and mpeg seems to work the best with my editor. I do not want uncompressed files.

I used to convert with SUPER, I set it to mpeg2 and 4800 bitrate. It was an ok quality, but at least consistent.
Now I use Xilisoft and the bitrate count is different somehow, I set it 1600 and the quality is actually better. It is easy to see on the subtitles. Now however, the fast scenes are even worse then my old method.

Although with SUPER there was an option to pick the encoder which was ffmpeg there, now I see nothing like that with this program. Don't know if that makes any difference though.

The point is that I want those fast scenes to come out looking much less pixeled, but still save space.

[edDV]

Right now I am converting h264 format compressed files to mpeg2.

MPEG2, because I want to edit the files and mpeg seems to work the best with my editor. I do not want uncompressed files.

I used to convert with SUPER, I set it to mpeg2 and 4800 bitrate. It was an ok quality, but at least consistent.
Now I use Xilisoft and the bitrate count is different somehow, I set it 1600 and the quality is actually better. It is easy to see on the subtitles. Now however, the fast scenes are even worse then my old method.

Although with SUPER there was an option to pick the encoder which was ffmpeg there, now I see nothing like that with this program. Don't know if that makes any difference though.

The point is that I want those fast scenes to come out looking much less pixeled, but still save space.

Low bit rate (I assume) h.264 was only intended for one decode for display. If variable bit rate so much so.

You are seeing the limits of compression.

However, if this is a clean Blu-Ray h.264 extraction (14-35 Mb/s), we can talk.

[spigy]

You are not seeing the point.

My problem is not the quality itself, but the loss of it in fast moving scenes. The point is that with SUPER I had worse quality, but it sustained through the entire vid. Now I have better quality (slightly bigger files), but the certain frames' drop in quality is unacceptable.

I am guessing SUPER had a different work method with bit rate. Looking at video properties that 4800 is actually just above 1200. That is why I have better quality now cause it is set to 1600. Fast scenes however look like they are 1000 or less.

I know with 2-pass and VBR, the program should be able to determine which frames need a higher bitrate and which ones don't.

I would like to set it to something like:
min BR: 1400
max BR: 2200

[edDV]

With vbr input, a programmer needs to decide if decode will be to max or average bit rate. If max the re-encode will be proportionately longer. If average, the high motion scenes get compromised.

Is there a "smart middle way"? Maybe but your results show they aren't. Motion scenes are the test of compression.

[spigy]

Did I just get a lesson in conversion philosophy?

Let me make this as simple as possible.

Does anyone know how to set up VBR in Xilisoft?

[guns1inger]

No. But I know how to use good quality tools that do the job. Xilisoft is a limited, one-click wonder toy. Don't let the Pro tag fool you into thinking otherwise.

[davexnet]

What is the resolution of the source, and what res did you set on the mpeg-2 output ?

[spigy]

What is the resolution of the source, and what res did you set on the mpeg-2 output ?

They are the same.

[davexnet]

Are you trying to create DVD compliant mpeg-2 ?

[spigy]

No I am converting to mpeg2 because my editor program likes it. It is easy to use, no stutters and such like with most avi.

I still don't see why it's important why I am doing this though.


What I need an answer for is:

Why does program A gives a different result than program B when they are supposed to be converting at the same bitrate.

Why do "fast scenes" become so blocky when "slow scenes" are better then before?

Is VBR my answer to my problem?
If it is, then how to set it up?


I cannot be any more clearer than this.

[poisondeathray]

1) fast scenes become blocky because MPEG2 is using long GOP which codes the differences between frames. Since motion constitutes a lot of difference between frames, it needs a higher bitrate to maintain a certain level of quality

2) No, vbr isn't necessarily the answer. Using a higher bitrate will help - it will make it less lossy

3) some encoders are better than others because better algorithms, such as search vectors, frametype decisions . Some may allocate bitrate differently. For example HCEnc consistently give better results than ffmpeg's MPEG2 encoder

4) some formats offer better compression than others; for example h.264 using a good encoder can be 2x as good as MPEG2. (similar quality with half the filesize)

5) you're going to get low quality either way , the way you are approaching this. you're incurring multiple generational losses with low bitrate, using a low compression format (MPEG2). The only way to keep a decent level of quality is to compensate using a higher bitrate. A bitrate of 1400-2200 kbps is very low for MPEG2 for standard SD frame sizes like 720x480

[davexnet]

I can't evaluate your question properly, based on the bitrates you mentioned earlier, because you have yet to mention the resolution you're using. It makes all the difference in the world.
A rate of 1600 kbps might look OK at 320*240, but look like crap @ 720*480.

VBR is one answer, perhaps you're not giving a high enough average. Other solutions could be CQ mode or a high
constant bitrate.

Once you provide the resolution, we can judge it better.
"fast scenes" require more bits due to the complexity - it's pretty much as simple as that.

[spigy]

Well it is funny that I got a better overall quality from a free program like SUPER then Xilisoft.

The problem is that if I increase the bitrate so the fast scenes have good quality, the slow scenes will have unnecessary quality pumped into them.

Like 1600 kbit is more then enough for a slow scene, but I would probably need 2200 with fast scenes. Converting the whole thing at 2200 is a waste of space on my hard drive.

res is 848x480.
SUPER (set to 4800 which is around 1200) = good quality overall
Xilisoft (set to 1600) = even better quality, but fast scenes are horribly blocky.
and by good, i mean good for me, so thats not the point.

[davexnet]

If you're worried about the space and would like to contain it to a specific size, VBR is better - the size is predictable,
and the bits are allocated as necessary, based on scene complexity.

On the other hand CQ maintains a constant quality through out the whole file - it may lead to bigger files, and
the final size is difficult to predict. You get the advantage of one pass, so it's quicker.

If you like Super, that's fine. There are many fine programs to choose from, perhaps give Avidemux a try ?

[spigy]

funny thing.

I actually managed to get what I want easily. Last time I didn't have time to experiment, but now I tried something and it worked.

I de-interlaced the pictures.

Perhaps this option was turned on in SUPER and I wasn't aware.



Thx for trying guys

[guns1inger]

Deinterlacing, very low bitrates - so quality is one of the pre-requisites ?

[kashif71]

[QUOTE=spigy;1969733]Hey!

I am converting AVI files to MPEG2 (using Xilisoft Video Converter Ultimate) and without touching the expert options I converted the files to a quality I was satisfied with.

......


Hi

I think you can enable VBR in Xili by clicking "same quality = true" under video. You may enable "2 pass" under Expert which may increase size a bit and will need double the time to convert video but is supposed to increase quality. I am only experimenting myself and if you find this (or any other setting) useful please let me know as well.

[r3z0nate]

I know exactly what you are asking. There is a setting in the MKV converter under Expert for Q Scale when entering values into the field have no affect on the estimated output file and have no effect the Bitrate value. Scanning the source file and the converted file will reveal the minimum bitrate to always remain at the CBR value, unless you use same quality, which will only have it jump to the given maximum bitrate.

I've searched for the answer and cannot find it myself, but I'm not converting any more files until I find the solution. The next video I have lined up has an average of 8000kpbs but a minumum of 27 and a max of 25000kpbs. I've looked at the other solutions, but the converter does a good job on video and audio.