Encode dv to mpeg2 or mpeg4?

[mijalis]

Question is simple:
Which one is better in terms of quality, mpeg2 or mpeg4 (xvid, divx)
Eg suppose you have 1 hour of home video (dv).
In (double pass) mpeg2 (dvd quality) it will be ~4.5GB, appr. compression ratio: 14/4.5 = 3/1
In (double pass) divx/xvid ~700MB. , appr. compression ratio: 14/0.7 = 20/1
Will quality be the same?
Or one could ask:
What should the compression ratio (or bitrate) for xvid/divx in order to surpass the mpeg2 quality?

Any resources will be appreciated...

Thanks.

[jimmalenko]

Not an exact science. DivX/XviD can achieve better compression (and therefore a smaller filesize) for the same quality. So it could be said (as the roughest of rough guides) that all things being equal, a DivX/XviD encode can be significantly smaller in terms of filesize while retaining the same quality. As for the "magic" number, I don't believe that anyone has done any in-depth testing or comparison in order to deduce this, but I could be wrong.

Why don't you conduct these tests yourself ? Do an encode in MPEG-2 that uses a bitrate that fills up the disc. Next, do a couple of MPEG-4 encodes, using bitrates such as 1000, 2000, & 3000 and compare them so you can make up your own mind.

[mijalis]

Not an exact science. DivX/XviD can achieve better compression (and therefore a smaller filesize) for the same quality. So it could be said (as the roughest of rough guides) that all things being equal, a DivX/XviD encode can be significantly smaller in terms of filesize while retaining the same quality. As for the "magic" number, I don't believe that anyone has done any in-depth testing or comparison in order to deduce this, but I could be wrong.

Why don't you conduct these tests yourself ? Do an encode in MPEG-2 that uses a bitrate that fills up the disc. Next, do a couple of MPEG-4 encodes, using bitrates such as 1000, 2000, & 3000 and compare them so you can make up your own mind.

I have already done several tests, but my conclusion is very subjective...I would like to see professional tests..any links?
I've heard somewhere that sat broadcasting will use mpeg4 in the future... is that true?

[jimmalenko]

I have already done several tests, but my conclusion is very subjective...I would like to see professional tests..any links?
I've heard somewhere that sat broadcasting will use mpeg4 in the future... is that true?

Sorry, don't know anything about any of that. Regardless of who does the tests, any results are still going to be subjective dependent on your eyesight, playback device, etc etc (all the uauals).

IMO there's too much grey and not enough balck & white in your question

To answer your other questions:

In (double pass) mpeg2 (dvd quality) it will be ~4.5GB, appr. compression ratio: 14/4.5 = 3/1
In (double pass) divx/xvid ~700MB. , appr. compression ratio: 14/0.7 = 20/1
Will quality be the same?

My testing would indicate that it takes roughly 3-4x the bitrate (and therefore the output size) in order to reach an equivalent quality. So I would say a "typical" 4400MB 2-Pass VBR MPEG-2 would require an 1100MB 2-Pass VBR XviD to be comparable.

[junkmalle]

In my experience, MPEG2 requires from 2 to 4 times the bitrate to match MPEG4, depending on the source material.

I rarely use 2-pass anymore. I use single pass quantization (constant quality) mode. Results are as good as two pass (at the same file size) but it only requires one pass. The only problem is you don't know exactly how big the file will be until your done. I'm not creating files to burn onto CD-R (where a ~700 MB file size becomes important) so I don't really care how big my AVI files are.

[mijalis]

The point is how can you judge quality... in an objective manner...
Probably there is no way of doing that, but I am just asking just in case...

[bugster]

Question is simple:

No it is not

Which one is better in terms of quality, mpeg2 or mpeg4 (xvid, divx)

You could just as easily ask if xvid is better than divx, forgetting mpeg-2

Eg suppose you have 1 hour of home video (dv).
In (double pass) mpeg2 (dvd quality) it will be ~4.5GB, appr. compression ratio: 14/4.5 = 3/1
In (double pass) divx/xvid ~700MB. , appr. compression ratio: 14/0.7 = 20/1

You are asking the wrong question. Yes, mpeg-4 offers more compression than mpeg-2. Does it offer better quality? Well, if you specify a particular mpeg-2 encoder, a particular setup of that mpeg-2 encoder and a specific source file, then specify a particular mpeg-4 codec (xvid x.xxx or divx 3.xx, 4.xx, 5.xx) with a particular setup and in these cases a particular front end control app (vdub. drDivx etc) then a meaningful comparison may be possible.

I think what I am trying to say is that mpeg-2 and mpeg-4 are different beasts, designed for different purposes and a direct comparison is not only nearly impossible, but unfair.

You don't say what your destination playback device is, and this can have a large bearing on choice too (iterlaced TV vs progressive PC monitor).

Will quality be the same?
Or one could ask:
What should the compression ratio (or bitrate) for xvid/divx in order to surpass the mpeg2 quality?

Any resources will be appreciated...

Thanks.

Too many variables.........