MPEG-2 - MPEG-2... any quality loss?

[Jeomite]

I have a theorical question.
If I encode a MPEG-2 file in TMPGEnc and output the MPEG-2 with the exact same setting I used to encode the original MPEG-2 file, will the output be truly the same file, 1:1 duplicate?

i.e.
Input File: MPEG-2, 2500kbit, 480x480
Output File: MPEG-2, 2500kbit, 480x480
'exact same settings'

[Elchknie]

no.

-Elchknie

[Kdiddy]

may I ask what would be the point of this exercise?

[Peter]

interesting, why don't you try it out!

[PolarBear]

A somewhat interesting academic question that could easily be confirmed by a test. The answer is no, btw.

I have been making a practical use of something like this. I get sick of how limited Premiere plugins are so I usually export to AVI before final encode. I've tried the avisynth plugins but they just aren't ready for prime time. So now instead of generating a 10+ GB file, I encode to a high bitrate MPEG2(5+Mb) from Premiere(using LSX or sometimes CCE when it doesn't lock up :/ ). Then use dvd2avi and vfapi, load into virtualdub, filter away, then frame serve into encoder(usually tmpgenc).

In that case, I'm essentially encoding from MPEG2 to MPEG2(or 1 depending on application). I only have a relatively small MPEG2 to start with, but with great quality and its presence doesn't stop me from other video projects. The quality of MPEG2 to MPEG2 is great if the original is very high bitrate(no artificts at full screen).

Matt

[Peter]

@PolarBear: you first encode to a higher bitrate.

Jeomite wanted to know what happened when encoding a MPEG-2 in TMPG to MPEG-2 with the same bitrate. I assume he meant CBR TMPGenc has to achieve 0 compression!

[Tommy]

I say that yes you might have some quality loss. If you had noise reduction on the first time and kept it on the second time, it would make a difference.

[Jeomite]

The whole point was that I wanted to encode a current MPEG-2 file to a new MPEG-2, but adding a Noise Reduction Filter.

Assuming no quality is loss when pure MPEG-2 -> MPEG-2 encoding. I can take advantage of the Noise Reduction Filter, without losing any 'quality'.

[Yeshi]

hmm, theoritaclly there will be, but it is so minimal that it is almost unnoticable.

[Kdiddy]

hope you got time on your hands..using TMPG's noise reduction adds SIGNIFICANT time to encoding.

[Yeshi]

Yeh its bloody hopeless. its a terrible filter, all it seems to do is smudge the picture to get rid of noise, the only thing it is evently remotely close to useful for is extremely low detail cartoons.

[hitechjunkie]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-10-09 01:33:01, Yeshi wrote:
the only thing it is evently remotely close to useful for is extremely low detail cartoons.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

exactly! i've taken some moderately-to-heavily artifacted 10-20 minute cartoon mpeg clips, and re-encoded them using TMPGEnc's noise filter set at 100, and produced MUCH nicer looking mpegs.

p.s. the resulting mpeg turns out smaller, as well, without the "noise"...

<font size=-1>[ This Message was edited by: hitechjunkie on 2001-10-09 06:09:48 ]</font>