Resolution Vs. bitrate please explaine

[King-Of-DK]

I still have a few questions regarding this science known as video conversion. I don´t quite understand that if i have an AVI that is about 1500 kb/s in bitrate,and i convert it to SVCD 2500 kb/s or even DVD 6000->8000 kb/s the resulting mpg looks good,how can that be exactly,i mean it can´t get better than the original file right? if so how does this happen? is it like progressive scan where lines are added,bits are added? If so how does the program know where to put extra bits in so it looks better? Does increasing the resolution give better quality or is it strictly bitrate that sets the quality? I must say i have ahard time figuring these things out. I kknow the programs does all this thinking for me,but i am curious as to how this works..

[vcd4me]

I've read that a 1500bit rate vcd will look worse when converted to 2500 bit rate svcd

Are you sure the original file is 1500 in bit rate?

I have downloaded some avi and I assumed they were 1150kbps because the file name ended in cd1 or vcd1. When in fact they were actually 1600+kbps.

Hope this helps
VCD4ME

[King-Of-DK]

The bitrate varies from file to file,so you cannot asume anything,besides the file in mention is only 971 kb/s. I am quite sure what the bitrates are as i use Gspot to identify the bitrate/sound/videosystem and so forth.

My question above still stands.

[vcd4me]

Yes I know now why my dad always said

Don't assume anything because you make an
ass out of u and me.

I try not to assume anything, but sometimes I do

Good luck
VCD4ME

[King-Of-DK]

OK,i have no clue as to what you are saying!!! Never mind.

I would really like to get a real answer..

[Baldrick]

Do you mean that you get better quality after encoded? or same quality or what exactly?

[King-Of-DK]

What i meant was,when up or downsampling (increase bitrate and decrease bitrate) takes place what excactly happens?? Does information get cut away or added? If so how does this work,how does the program know where to add information and when to remove information?

I want to know if changing resolution has an effect on quality or if it is only bitrate that equals quality..I am a bit confused as to what these terms are..

Does all the formats (VCD/SVCD/DVD) have set resolutions,but not bitrates? If so,is it possible to have a VCD resolution with a bitrate of lets say 4000 kb/s??

[Baldrick]

The source video quality sets the quality. It wont help if you increase the resolution or use very high bitrates. But to keep the same quality use same resolution and highest possible bitrate.

www.dvdrhelp.com/vcd has a constant bitrate so you MUST use it or else you are making xvcd.

[King-Of-DK]

Hey Baldrick,please read above post

[vcd4me]

sorry
I wasn't trying to confuse you before with my last post. It's just an old saying

King-Of-DK

I don´t quite understand that if i have an AVI that is about 1500 kb/s in bitrate,and i convert it to SVCD 2500 kb/s o

Answer - This is impossible the quality would not get better, in fact it can't get better than the original file.

The bitrate varies from file to file,so you cannot asume anything,besides the file in mention is only 971 kb/s

That is below standard vcd bitrate what is the source file.

Does all the formats (VCD/SVCD/DVD) have set resolutions,but not bitrates?

You are getting resolution and bitrate confused
vcd= 1150 kbps... mpeg 1... 352x240 (ntsc)
xvcd = 1500-2500 kbps... mpeg 1... 352x240 (ntsc)
svcd = 1500-2500 kbps... mpeg 2... 480x480 (ntsc)
xsvcd= 1500-2500kbps... mpeg2 ...480x480 (ntsc)
dvd=3000-8000kbps... mpeg 2....720x480 (ntsc)

If so,is it possible to have a VCD resolution with a bitrate of lets say 4000 kb/s??

This would be impossible

want to know if changing resolution has an effect on quality or if it is only bitrate that equals quality..I am a bit confused as to what these
terms are

Read the newbies section there is a section for resolution.

hope this helps
VCD4ME

[King-Of-DK]

OK,now we are getting somewheree..So the resolutions are fixed in each format,right? Why would it be impossible to have a VCD with a bitrate of 4000?? If what you say is true,then when i have an AVI with a bitrate between 834 and 1225 (i actually has 4 avis with bitrates like this) One is a movie with a bitrate of 1224 kb/s according to Gspot, and i want to convert and author this to DVD-r it would be useless and a waste of time to convert it to 8000 kb/s as i do not get an increase in quality?? I use Ulead Moviefactoy,and i can set the quality as low (4000 kb/s) medium (6000 kb/s) and high (8000 kb/s) and people i have spoken to,say i should always use the highest bitrate as this gives the highest quality,but that can´t be as i can´t get any higher as my source 1224 kb/s is this right??

And last but not least:

When up or downsampling (increase bitrate and decrease bitrate) takes place what excactly happens?? Does information get cut away or added? If so how does this work,how does the program know where to add information and when to remove information?

oh,and is there a difference in resolution when using either NTSC 23,976 or 29,97?

[vcd4me]

OK,now we are getting somewheree..So the resolutions are fixed in each format,right

Well you do have some room to adjust the bitrate in xvcd, svcd xsvcd

Why would it be impossible to have a VCD with a bitrate of 4000?

vcd is the only one that has a fixed bitrate it is 1150kbpsin theory if you go higher than 1150 you are making an xvcd however xvcds can't go over 2500 according to the comparison chart

If what you say is true,then when i have an AVI with a bitrate between 834 and 1225 (i actually has 4 avis with bitrates like this)

well 834 is below vcd standard bitrate and maybe its because the person you got it from was making a one disc xvcd, and the person with 1225 was making the highest quality xvcd he could, these bitrates are all figure out using the movie length. Here is an example an 80minute movie can usually be around 1225-1250 kbps. Obviously the higher the bitrate the better the quality.

I can't make any comments on dvd-r because I don't have a dvd burner.

oh,and is there a difference in resolution when using either NTSC 23,976 or 29,97

?
23.976 is for ntsc film and 29.97 is for video . I don't think you have any film according to your post.

I'll try to help more if you need it

Signed VCD4ME

[King-Of-DK]

Actually i still need some help,because you also state that the higher bitrate the higher quality,how can this be if it can´t get better than the originals,then if the file is 1224 it would be stupid to waste time trying to convert it to 6000 kb/s because it will never exceed 1224,right??

I have today authored a DVD-R for the first time,and i had two music videos in AVI format both PAL,and one with a bitrate of 1150 and one with a bitrate of 921,and this is what the quality setting is in my program:

MPEG files
24 Bits, 720 x 576, 25 fps
(DVD-PAL)
Video data rate: Variable (Max. 8000 kbps)
LPCM Audio, 48 KHz, Stereo

What i get is an authored DVD with the first video looking very good,the second not very good (a bit blocky). Are these files in fact now more than the original bitrate,or is it excactly the same quality?

[vcd4me]

Actually i still need some help,because you also state that the higher bitrate the higher quality,how can this be if it can´t get better than the originals,then if the file is 1224 it would be stupid to waste time trying to convert it to 6000 kb/s because it will never exceed 1224,right??

That is how I have always understood, that the quality in is what you get nothing higher, sorry.

Again I know nothing about dvd-r.
I did notice you wrote variable max 8000 maybe it only encoded the first one as 1150 and the second as 921.

Now is it safe to say that the 921 is the one that looked blocky

Are these files in fact now more than the original bitrate,or is it excactly the same quality

My guess is they stayed the same

Hope this helps
VCD4ME

[furball6969]

Whatever your source is, Yoiu can encode it at whatever bitrate you want and you will see that if you use a low bitrate the compression artifacts will make the will be more prominent and even more so if the source is an already compressed clip. To avoid excessive compression artifacting when re-compressing an already compressed file you will need to use as high a bitrate as possible. This is where your own perception comes into play. If it looks good to you, do it!

As for your question regarding where bits come from; the same place they always come from.

http://www.google.ca/search?q=mpeg+compression+theory&ie=ISO-8859-1&hl=en&meta=

[furdog]

Bitrate is not a true measure of picture quality. All it really says is how much filesize is required to hold (or stream) a given length of the video.

One reason it is expressed as a rate, is for streaming or delivery over a network (or file system) - the transport needs to be able to reliably deliver the indicated bandwith for the duration of the movie.

Divx compresses more than MPEG2. So for equivilent visual quality, the bitrate for a Divx format will be much lower than the corresponding MPEG2. This is why a Divx movie can be put on a CD. (The penalty is the processing power required to uncompress it while playing).

If your original AVI files were in Divx format, it would account for higher file sizes/bitrates in MPEG2 format for the same quality.

If you capture uncompressed AVI, you could be dealing with hundreds of Mbits/sec. If you then encode it (Divx, MPEG2) at same resolution and high quality, you are still in the single digt Mbits/sec, or less.

Comparing Bitrate for quality only really works for the same compression and resolution.

Think of still images - the file size does not really tell you anything about the image that you would see if you opened the file - the same image stored as JPG, TIF, GIF, BMP would have vastly different sizes for the same picture.

Resolution -
The quality of the algorithm used to increase or decrease the resolution will vary, and impacts the perceived quality of the image. From a absolute perpective they are all throwing some information away (decrease resolution) or adding made up information that is not real (increasing resolution). Better algorithms will make the perceived image better.

Reducing resoultion (for example cut in half) can be accomplished by throwing away every other line or pixel. Better is to take into account what the discarded pixels say about the remaining pixel (e.g. if throwing away 8 white pixels around a single black pixels, perhaps the remaining pixel should be gray in the final output, since that is what the eye would have percieved with all of the original pixels displayed.

Increasing resolution (for example doubling the resoulution) is most easily accomplished by simply duplicating the orinal pixels next to one another. This is what basic photo programs do. If you blow up the "higher resolution" image you see the blocks that are created. Better programs interpolate between the original points to try and estimate what would have been in the points in between. This smooths the enlarged image, and to the eye it appears as if there are more details. There are high end programs designed to blow fairly small images up to billboard size and still appear good.

Note that the above are correct - you cannot create information that is not there, but if need be, you can make it appear better when enlarged. The only time you would want or need to increase the resolution is if you are going to be outputting at a higher resolution than the original, and the output/display system does not do a good job scaling up. I don't know about how any of the video tools increase resolution, how good their algorithms are to the perceived quality (an interesting test of the different encoders). Also, video scaled up should theoretically compress better for the same bitrate/filesize, since the added points follow a pattern in a relationship to the points around them, by definition, which is not in true high resolution (another interesting test).

In reality, the only time I would consider trying to increase the resolution would be if it was necessary to comply with format standards (e.g. a low res movie off the internet, scaled up to put on VCD), or if I was joining clips of different resolutions and needed to pick a common one.

Otherwise, always start with the highest resolution that you think you might ever need, and reduce if necessary.

[Tbear]

The bitrate of you AVI (DivX, Xvid) has little to do with the bitrates of MPEG-1 and MPEG-2. You will have higher bitrates with MPEG-1 and 2 then with most (DivX) AVI's.

VCD CBR 1150 Kb/s 352x288/240 MPEG-1
SVCD VBR 1500-2500 Kb/s 480x576/480 MPEG-2
DVD VBR 3000-8000 Kb/s 720x576/480 MPEG-2
This are the standards for VCD, SVCD and DVD. Change any specifaction and it becomes XVCD, XSVDC and XDVD.

As you can see this use lower bitrate then does MPEG.
DivX VBR 300-1000 Kb/s 640x480 or lower
Xvid VBR 300-1000 Kb/s 640x480 or Lower


To keep the quality of the AVI's you will want to use as high a bitrate to keep the same quality. Only good way to find the right bitrate for your music videos is to do some test encoding.

[King-Of-DK]

Thank you very much everybody.