Converting a file without losing quality

[bambam]

Hi
Is it possible to convert a avi file into a mpg file without having any quality lost ? If so does using the same bitrate and size in TMPGenc will do the trick ?
What would you do to have the same quality in a mpg as the original avi file ?

thanx

[jimmalenko]

Is it possible to convert a avi file into a mpg file without having any quality lost ?

Yes.

If so does using the same bitrate and size in TMPGenc will do the trick ?

Normally No.

What would you do to have the same quality in a mpg as the original avi file ?

The codecs that are used to create AVI are much better compressors than MPEG codecs. Talking low end bitrates here, this means that an AVI at a given bitrate will generally be much better quality than an MPEG at that same bitrate. I am not aware of any hard and fast rule to calculate what bitrates you should use, but I would do a few sample encodes of about 1 min duration using 2X the AVI bitrate, 3X, 4X and so on until you find the point where the quality is not diminished.

[bambam]

Ok so you think that if I have a avi file with a bitrate of 1500 kbps
and I want to convert it into a mpg
I should first try to convert it to 3000 kbps
then 4500 kbps
then 6000 kbps
?

[jimmalenko]

Ok so you think that if I have a avi file with a bitrate of 1500 kbps
and I want to convert it into a mpg
I should first try to convert it to 3000 kbps
then 4500 kbps
then 6000 kbps
?

Yes. When you do it, only encode a sample (say about 1 minute of footage) and compare each output file until you find roughly the quality that you prefer.

The appropriate bitrate depends on the frame size too. for example, you probably wouldn't notice the difference between 3000kbps, 4500kbps and 6000kbps if your source was 352 X 240.

If you provide me with some stats (screen dump preferable) for the source AVI (use GSpot or AVI Codec), I can provide some more specialised advice

[Nelson37]

I'm gonna disagree with Jimmalenko here. Any conversion involves an inherent quality loss. Whether it is VISIBLE or not is debatable.

There are too many variables to specify a bitrate, though Jimalenko's specs are as good a place to start as any.

Your file could be one of several variants of Divx, a couple of Xvids, raw and uncompressed, it also could be made by a real expert or a complete idiot. They may have used standard framesizes and framerates or some oddball variation which may cause extreme conversion problems. And then there's audio filetypes, bitrates, VBR, synch drift, etc, etc.

[jimmalenko]

VISIBLE is the key word, as is QUALITY. Both are subjective

[FOO]

The codecs that are used to create AVI are much better compressors than MPEG

I'll disagree with that one too.

You are saying that ALL codecs used with AVI are better compressors than
mpeg . That's quite a few. what do you mean "better"

[jimmalenko]

The codecs that are used to create AVI are much better compressors than MPEG

I'll disagree with that one too.

You are saying that ALL codecs used with AVI are better compressors than
mpeg . That's quite a few. what do you mean "better"

sorry, a bit too general

Given that this AVI has probably been downloaded, there's a fair chance it uses a lossy codec such as divx, xvid, etc etc. I would be fairly confident that it is not huffy or any other lossless codec. If I get a screen dump, I'll know for sure

I should clarify and say MPEG-1 or MPEG-2, although since the poster talks about putting it onto DVD, l I think this is a fair assumption anyway.

[bambam]

Ok here is an example of a file I want to convert into mpg

Video : 604 MB, 1031 Kbps, 29.970 fps, 720*480 (4:3), DX50 = DivXNetworks Divx v5, Supported

So you would recommand trying a mpg file with a bitrate of 2000 kbps ?
The problem is that when I try convert it with TMPGEnc
the bitrate value is grey in the wizard and I can't change it ? How can I change this value Right now it only offer me a default value of 1150 which is not enough ...

It seem that when choosing CBR in the step 1 of the wizard I cannot change the bitrate but if I choose VBR i can ...
The problem is that for VCD the option VBR is not there so how can i change the bitrate for a mpg1 vcd ?

[jimmalenko]

Close the wizard.

On the bottom right there is a spot to specify your video input. Browse to your AVI file and it should automatically select the same file as your audio source. Then press the Load button, and Load the DVD (NTSC).mcf file. Then press the Load button again, this time loading the Unlock.mcf file in the Extras folder. Now when you hit the Settings button, you should be able to change everything.

Do you wish to put this onto a VCD/SVCD/DVD in the end ?

Also what is the total running time of the AVI ?

[bambam]

Thanx for the reply

Ok the movies is about 90 minutes long
I want to put it on a DVD but not with a dvd quality video since my source do not have really good quality. I would like to put it on a dvd with a mpg 1 format. Is this possible ?

What is a .mcf file ?

[yoda313]

Hello,

Yes but mpeg 1 is vcd quality and not very good. Tmpgenc Dvd author will upcode the mpeg1 file for you.

Kevin

[bambam]

Since my original file does not have a good video quality (1000 kbps)
I tough I should use a lower quality video format on my dvd

So you're telling me that I should I use mpg1 format file to put about 5hrs of low quality on a DVD and play it on a dvd player ?

[yoda313]

Hello,

I guess if it's already low quality it won't matter then. That would probably be ok.

Kevin

[proxyx99]

Without getting into too much detail, 4000 avg. 6000 max would make this video fit on the DVD. If you use a wizard go with the rate that would fill the entire disc. With other words, always use the highest bitrate you can afford (in terms of final mpeg-2 size). Some Divx I've seen (not too many I admit) were of a stunning quality for the bitrate they were using. Mpeg 2 below 3.5k will further deteriorate video quality so stay above 4k avg. (up to whatever you want that is still reasonable (size issue)).

[jimmalenko]

further to proxyx99's advice, here's how I would do it:

(BTW if you actually do it, it will make more sense than just reading it )

Close the wizard.

On the bottom left there is a spot to specify your video input. Browse to your AVI file and it should automatically select the same file as your audio source. Then press the Load button, and Load the DVD (NTSC).mcf file. Then press the Load button again, this time loading the Unlock.mcf file in the Extras folder. Now when you hit the Settings button, you should be able to change everything.

Set your Rate Control Mode to 2-Pass VBR, and use min 2000, ave 4000, max 6000 as your bitrate settings. For other settings, I'd suggest you read these articles. They give a very good rundown of what each setting does and when you would use it.

[bambam]

I have always used the wizard to convert my video and the option in the wizard are still unavailable. I don't understand how to convert a video file otherwise.

Is there any way to unlock these option in the wizard ?

thanx

[jimmalenko]

You are not helping anyone (least of all yourself) if you ask a question, get an answer, and then choose not to follow it. I have told you how to do it and there are many guides on this site telling you how to as well. Start reading.

[proxyx99]

I hate to do that but jimmalenko's advice is right on the dot: read the guides. They were written to be read (not ignored) and allow for a problem to be solved on a spot without repeating stuff over and over again. No one wants to see the same subject exhumated on a daily basis without a valid reason. That would make this forum unbearable and boring.

[bambam]

Ok I will take a look at the guide
I read a few but apparently not enough
thanx for your help
I will post again if I have questions after I've done my homework )