2] How many avi without losing quality?

jjfan19 · Joined: 20 Nov 2008 Posts: 10

how many xvid videos can i put onto the dvd without losing the quality of the source avi?

for instance i have 2 avi's (1200 and 1100 kbps), would encoding them in high quality setting be better or same as medium quality? from the vso board i see a sticky that mentions that medium quality is fine, and should be used with any project over 1hr20min?

now i tested both high and med settings.. high gives me average bitrate of 3600kbps .. whereas medium gives 2500kbps. yet when i play it back on standalone dvd player, i notice no difference really.. maybe medium looks better, does this make sense?

basically should i be going with whatever the bitrate on the avi is? i mean most avi are 700-1100kbps range.. so sounds like i can put more then 3 of them on 1 dvd without losing any quality from it at all.. true?

souper · Joined: 17 Feb 2008 Posts: 85

What was the length of your 2 movies u did with high and medium? Also read that sticky again, and read what I posted. Do it a couple time if necessary.

1st question:
2 for sure, maybe 3, depending on length, stay around 4hrs, the less the better. Maybe even 3hrs is a safe bet.

2nd question:
Well in this case high would be better because, you have higher avg bitrate 3600kbps. The higher the bitrate the better, in this case you have enough room to use high, use high...

3rd question:
That's just a recommendation and shouldn't necessarily be followed. For your case it didn't work well.

4th question:
No, High should look better in this case. Or maybe there really is no difference.

5th question:
No do not use the bitrate of the avi as guide. dont. Use the bitrate as your guide for the output, not the source. You can usually put 2 or 3 movies depending on length. Like I said stay around 4hrs if you want the best quality, while not wasting space. And more than likely you will have no noticeable quality loss.

JoeB · Joined: 02 Jul 2007 Posts: 2853 Location: Canada

jjfan19 · Joined: 20 Nov 2008 Posts: 10

ckhouston · Joined: 08 Aug 2007 Posts: 2012

I don't know if JoeB is as tired of this subject as I am, souper and I have discussed it before but he remains unconvinced apparently. I can't say much more than already said in the Sticky jjfan19 referred to, the link given there and subsequent links in it.

If bigger output is always better then why not use a program that does a constant bitrate encode, it will always give output equal to or bigger than any variable bitrate encode. But it wastes bitrate resources on scenes that don't need it and doesn't use enough on scenes that need more.

I REPEAT ONCE MORE that the so called "quality" settings in CX2D ARE NOT CHOICES OF QUALITY, THEY ARE CHOICES OF ENCODING PROFILES INSTEAD.

High is variable bitrate but the least aggressive of the settings in distributing bitrate as needed. In other words, it can be similar to a constant bitrate encode for some source files and waste bitrate where not needed and not have enough resources left for scenes that need more as JoeB stated above. Medium is more agressive in using less bitrate for simple scenes which leaves more for complex ones where it is needed. It may produce smaller output but still give equal or better results than High in some cases as jjfan19 found because it distributes bitrate better as needed. Low is even more agressive in distributing bitrate where needed.

NOTE: souper is promoting using output bitrate to decide which setting to use and yet he said in the Sticky

souper · Joined: 17 Feb 2008 Posts: 85

I understand the differences between cbr and vbr. Also all there profiles are vbr right? I also agree on the different encoding profiles. But my understanding of it is that the profiles are meant to be used for different bitrates? Low, Medium,High right. Thats why when you encode with them they only reach a certain bitrate for certain sources. Like when I encode a 20min episode with low get a 250meg file, Then you encode with High, you get a file that is a gig or more. So which is going to be better quality, high right...Since it uses a higher avg bitrate. I also believe high at 3600kb will be better than 2400kb(medium). Since its a higher avg bitrate. Also in the different encoding profiles as it goes up from low, medium to high it gets more and more like cbr, is that how its setup?

JJ · Posted: Thu Jan 15, 2009 9:05 am Post subject:

Claire · Posted: Thu Jan 15, 2009 9:35 am Post subject:

I have stickied this thread: http://forums.vso-software.fr/size-quality-what-fits-on-a-dvd-t7852.html

and I will sticky this one too to use them as a reference for any more users who maybe asking these questions.

VSO is working on a new image scaler these quality settings which are very poorly named will be put into question or change with the new options/mechanisms in version 4 (hopefully for the spring . . . but you all know how long and tedious development can be)

I am open to which threads to "sticky" or not for reference . . . . I am all ears, and am thoroughly convinced on CKhoustons explanations.

ckhouston · Joined: 08 Aug 2007 Posts: 2012

ckhouston · Joined: 08 Aug 2007 Posts: 2012

ckhouston · Joined: 08 Aug 2007 Posts: 2012

ckhouston · Joined: 08 Aug 2007 Posts: 2012

This may be a good time and place to expand on the subject of CX2D’s encoding and answer some questions that are asked over and over.

Encoding is a matter of compression and how much scenery can be compressed depends on the scenery itself. Look at the plots above. Notice the bitrate for some scenes (simple scenery) is low while that for others (complex scenery) is much higher. Simple scenes can be compressed a lot, complex scenes cannot, they require more data (bitrate) to describe them as accurately as simple scenes.

Complex scenes have a lot of detail like many sharply defined contrasting edges, many areas with varying visual properties like color or brightness, etc., and/or motion including camera pans and zooms. Simple scenes are the opposite. They include dark scenes, most closeups and even action scenes where the background is blurred due to camera pans.

Just How Much Video Can I Really Put on a DVD Without Losing Quality?

The thread title has not been fully answered yet, mostly because there is no simple answer. Some people will tell you to never put more than 3, possibly 4, hours on a DVD5 disc. Yet I have seen some users perfectly happy with 8, and in one case 11, hours on a DVD5.

Much depends on what quality level is acceptable to you personally, the TV you have, how far you sit from it, and very much on the type of scenery in your video (a long project with a high proportion of simple scenery can produce better quality than a much shorter one with lots of complex scenery - it is simply a matter of compression).

Here are some suggestions that may help if you are intent on trying to get as much as possible on a single DVD:

First try using the suggestions above to choose the best “quality” level to use. Note that those suggestions are based on using the standard Full D1 output resolution. (Edit Note: A better discussion is given below in the post labeled How to Determine the Best “Quality” Setting to Use - SUMMARY)

Then, if you see objectionable block type pixilation, which you can expect for about 5 or 6 hours of average video scenery content, try converting to one of the lower permissible output resolutions that are available for DVD Resolution on the DVD Specification tab in Settings.

Lower resolutions can prevent macroblock pixilation because more bitrate can be used per pixel since there are fewer pixels. About twice as much bitrate per pixel can be used for Half D1 and 4 times as much for SIF (sometimes called Quarter D1).

“Quality” level choices should be adjusted accordingly. For example, a 5 hour production at Half D1 is similar to a 2 ½ hour video at Full D1, so Medium would be appropriate. But Low would probably be best for a 6 hour project at Half D1. In other words, for example, if you reduce the resolution by ½, multiply the times given above for switching “quality” settings by a factor of 2, if you reduce resolution by ¼, multiply them by 4. (again, a better discussion is in the post below labeled How to Determine the Best “Quality” Setting to Use - SUMMARY)

There is a tradeoff of course. Half D1 will produce jaggies on near vertical edges that may be objectionable. SIF will produce them on both near vertical and near horizontal edges.

Why is the Converted Size Bigger, Smaller or not the Same as the Original Source?

The answer depends mostly on three factors.

Bitrate per pixel has to be maintained in order to preserve as much quality as possible (quality is always reduced by almost every process done to a video), so low resolution sources converted to a higher one one for the DVD will have a bigger converted size. Conversely, high resolution sources converted to a lower one permitted for DVDs will produce smaller output.

The second factor is efficiency of compression. DVDs must be encoded in the MPEG-2 format which does not compress as efficiently as formats used in most source files. The converted size will tend to be bigger because of that.

The third factor has to do with differences in compression algorithms between encoding of the source and that used by CX2D. One may assign more bitrate to describe a certain characteristic in scenery. This is common, not only in video, but in compression of any type of content including graphic images, text or binary files.

Wouldn’t Increasing Bitrate so Output Size is Bigger be Better?

The short answer is no for the encoding presently used in CX2D.

There are some programs that allow some control of output size by offering choices of average bitrate either directly or indirectly. Choosing anything but the optimum results in smaller output that is inferior to the optimum of course. So one can easily get the idea that bigger output is better, and it is for those programs.

But CX2D always gives the optimum size that it can for a given “quality” setting. It allows instantaneous bitrate to go as low as needed and as high as DVD standards permit, and also keeps average bitrate low enough so the DVD capacity is not exceeded. And it does what any encoder is expected to do for maximum quality, it keeps the average quantization factor as low as possible for each setting (a simple discussion of quantization is given in the post near the bottom of http://forums.vso-software.fr/bad-algorithm-for-deciding-target-average-bit-rate-t4378.html ).

Some people may still argue that bigger output size would be better. That would be true of course if CX2D used encoding designed to do so, in other words, if it used a different quantization table that somehow produced bigger and better output.

But forcing output to be bigger than the encoder is designed for just adds useless padded data that contributes nothing to quality as has been said many times in this forum.

Let me give an illustration.

CX2D used an encoding scheme that did allow some control of output size for a brief time during development of version 2. It used the Medium encoding profile and allowed the user to pick both minimum and maximum bitrates to be used. Lowering the max below DVD standard max would usually give smaller output, increasing the minimum would usually produce bigger output.

I did a test with one of those versions using the same 20 minute source as used for the plots above but with a min bitrate of 4 GB/sec. That increased bitrates considerably for the simple scenes shown in the 20 min Medium plot and did produce much bigger output. But, guess what, close examination of magnified captures of individual frames revealed that quality was actually slightly less for those simple scenes even though much more bitrate was assigned to them.

The quantization factors were the same for both conversions so that result was not unexpected. Once a program has produced the lowest average quantization it is capable of (the best average quality it is capable of in other words), there is no logical way of forcing bigger output that I know of, it will just pad with useless data that can even lower quality.

Conclusions

Use the “quality” recommendations given above and adapt them as discussed for converted resolutions different than Full D1. Those switch times should also be multiplied by 8100/4300 = 1.88 to get appropriate times for a DVD9.

Trust CX2D to give you the best it can.

CX2D can give excellent quality output IMO and that of many that have posted here if appropriate settings are used, even though it uses a single pass conversion. IMO, VSO will have a difficult job coming up with a 2 pass encode that will actually produce better quality, and it will naturally be slower.

Claire · Posted: Wed Feb 18, 2009 1:20 pm Post subject:

Thank you again for another excellent post.

Claire · Posted: Wed Feb 18, 2009 3:50 pm Post subject:

for clarification, when you say

ckhouston · Joined: 08 Aug 2007 Posts: 2012

Yes, that is the best simple rule of thumb I can give. (Edit Note: A better discussion is given below in the post labeled How to Determine the Best “Quality” Setting to Use - SUMMARY)

I personally rarely use High anymore, I use Medium for everything up to 160 minutes and Low for projects longer than that. Medium gives results for me that are almost indistinguishable from High even for short high quality sources, and it actually improves lower quality sources that are typical of short videos IMO by filtering out some of their bad characteristics. I might use High though if I had a short very high quality source like one ripped from a high quality commercial DVD.

There are always exceptions to rules of thumb though. The optimum time to change settings for a particular video depends a lot on the type of scenery in it. My recommendations are based on videos typical of adventure movies that have about equal proportions of simple and complex scenes. Optimum shift times for videos that have more simple than complex scenes will be longer. Those with more complex than simple scenes will have optimum shift times that are lower, although there are very few videos that I found that fit this scenario.

So I also suggested (for those that want to go to some extra trouble to get better shift times for a specific video) that a more accurate method is to try a conversion with one setting and, if the conversion fills the DVD (meaning 95% or more disc occupancy), switch to a lower setting.

However, I found from extensive analysis of more than 100 tests that very little quality is lost, if any, if one makes the shift too early but much can be lost if the shift is too late. So I personally do not go to that extra trouble, I rely on the simple rule of thumb instead.

I realize that many that read this are naturally skeptical. These recommendations must seem radical in view of the names and descriptions presently given to the so called "quality" settings.

So I want to point out that I ran many tests using several different source types. But I did not rely on personal opinion of the quality of playback of the conversions because our minds are powerful filters. Most people will believe a conversion at High "quality" has to be better than one at Medium and that is what they will see, even if the one at Medium is actually better. So I took a more objective approach. A comparison of bitrates and quantization factors usually indicated the best conversion. But the best determination of quality came from comparing zoomed frame captures (not screen captures from a software player) at several types of points.

goarweam · Joined: 22 Feb 2009 Posts: 10 Location: Philippines

I'm new to this stuff, and I don't really understand the conversion advisor.

I have episodes of a tv series and they are DVDRipped, XVID codec:
AVI videos, 350MB size and 44min. each.

Target size was DVD5 4.4MB

When I added 2 files, the conversion advisor light was green (excellent)
After adding another two, the light became yellow
and after another 2 it became red.

What I don't understand is that the target size is 4.4GB, but my input file is only 350MB for each video, so 6 of them wouldn't even get pass 50% of the target size so why does the conversion advisor say that the quality would become lower?

It should expand the files, not compress them right? I mean 6 files x 350MB is 2.1GB, so to make it fit in the target size of 4.4GB, it should expand the files, not compress them. So the quality should not be lower.

This is what baffles me about this conversion advisor. I think I also forgot something, but I'lljust post it later if I remember it.

JoeB · Joined: 02 Jul 2007 Posts: 2853 Location: Canada

goarweam · Joined: 22 Feb 2009 Posts: 10 Location: Philippines

thank you to JoEb!

I'm sorry I just posted right away without even browsing through the entire thread. Guess I'll just copy the thread and print it, I don't want to read it straight in the monitor because of my eyes.

Anway here's what I forgot:
1. Is the burn system in the program advisable or can we burn the converted file using other programs other than ConvertXtoDVD?

2. Is it possible to turn off the monitor while converting and burning? I mean, it can save energy right? But would it ruin the burning process and come up with a devastating result?

hansK · Posted: Mon Feb 23, 2009 10:59 am Post subject:

Hi goarweam,

point 1
Yes, many users use the included burning software.
If you want to use other software to burn, uncheck [ ] Burn result to DVD

point 2
yes, no prblem on result.

Regards,
hansK
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ckhouston · Joined: 08 Aug 2007 Posts: 2012

How to Determine the Best “Quality” Setting to Use - SUMMARY

For projects converted to a DVD-5 (4300 MB) Target size at Full D1 DVD resolution, the best simple rule of thumb I can give for videos with typical scenery is:

1. Use the High setting for projects less than 80 minutes long.
2. Use the Medium setting for those between 80 and 160 minutes long.
3. Use the Low setting for those over 160 minutes long.

where the project length is the Total time shown in the CX2D status bar as source files are added to the project. (The status bar is at the bottom of the main CX2D window.)

In order to properly use this rule of thumb, you have to understand the justification for it. It is really intended to keep from filling the DVD (meaning 95% or more occupancy in the log), because quality deteriorates rapidly once it does due to increased compression.

Converted results for High and Medium are usually almost indistinguishable from each other even when neither fills the disc. Medium surpasses High when High does fill the disc. There is a little more difference between Medium and Low, but most people will never notice it, especially for less than perfect quality source files. Low is definetly better than Medium though when Medium fills the disc.

These change times of 80 and 160 min have to be modified for conversions done to other Target sizes and/or at other DVD resolutions.

#################
Edit Note: The correction factors given below for Half D1 And SIF resolutions appear to be too big. I am investigating this as time allows and will post new values if necessary.
#################

The correction for different target sizes is simple, it reflects the fact that more data can be put on bigger targets and less on smaller ones. So the new change times become

80 x (TS/4300) and 160 x (TS/4300)

where TS is the Target size in MB that you specify on the Encoding tab in Settings.

The correction for other DVD resolutions reflects the fact that longer projects are possible if fewer pixels have to be described during conversion. The correction should be the ratio of the number of pixels in Full D1 divided by those in lower resolution choices (Broadcast D1, Half D1 and SIF). But we will use the following approximate resolution correction factors (RCF):

RCF = 1 for Full D1 and Broadcast D1
RCF = 2 for Half D1
RCF = 4 for SIF

This correction is also simple if all Titlesets in your project are converted at the same DVD resolution. Suppose the target size is 4100 MB and all titlesets will be converted to Half D1, the time to change from High to Medium would become

80 x (4100/4300) x 2 = 153 min

But, if all Titlesets are not converted at the same DVD resolution, a weighted correction factor must be used. This can happen if you select Automatic for DVD resolution in settings or if you manually change the Resolution of a titleset under the Video section in the CX2D tree view.

SUMMARY

The weighted resolution correction factor then becomes (for titlesets 1, 2, 3, ....)

WRCF = (D1 x RCF1 + D2 x RCF2 + ....) / (D1 + D2 + ....)

where D is titleset duration in minutes and RCF is the appropriate correction factor for the titleset resolution chosen from the list above. (Note that (D1 + D2 + ....) = Total time given in the status bar after converting to minutes.)

The titleset Resolution can be found under the Video section in the tree view and the titleset Duration is found under the Source File(s) info section. If a titleset has merged video files (more than 1), the duration for the titleset is the sum of durations of all the merged video files.

So the modified time for changing from High to Medium becomes

80 x (TS/4300) x WRCF

and that for changing from Medium to Low is

160 x (TS/4300) x WRCF

AN EXAMPLE

Suppose your project's target size is DVD-5 (4300 MB) and you have one titleset 30 min long to be converted at Half D1 resolution and a second titleset with two merged video files totaling 90 min duration (of video) to be converted at Full D1. The weighted resolution correction factor is

WRCF = (30 x 2 + 90 x 1) / (30 + 90) = 1.25

So the appropriate time to change from High to Medium would be

80 x (4300/4300) x 1.25 = 100 min

and for changing from Medium to Low would be

160 x (4300/4300) x 1.25 = 200 min

So you should use the Medium setting since your total project length of 120 min falls between 100 and 200 min.