Is Encoding the same if done on different computers?

[zeek543]

Lets say I am encoding DV-AVI files transfered from a DVcam. I encode with 5000kbps constant bitrate mpeg-2 (dvd compliant) using TMPGenc Plus. If I encode the same exact video file on one computer and do the same on a second computer, will the movie be exactly the same? Are the resulting Mpeg-2 files produced on two completely different machines identical to each other?
I would think they would be identical because they were encoded from the same original source DVAVI and encoded with the same settings in the same encoder. However, one encoding would take longer than the other encoding because one computer is faster than the other. But that should be the only difference, right? Please let me know you're thoughts on this and if you know whether or not my thinking on this is correct that the two resulting mpeg2's would be identical to each other. Thanks.

[yoda313]

If you are using the same source and the exact same settings on the same program on both machines then yes the encoding time would be the only difference.

[edDV]

I agree they should be equal if encoded non-realtime.

Realtime encoding would force different adaptations based on CPU power.

[vhelp]

Please let me know you're thoughts on this and if you know whether or not my thinking on this is correct that the two resulting mpeg2's would be identical to each other. Thanks.

zeek543,

This would depend on a various scenarios, how each computer is setup, etc.

Computer A1
** CODEC: Panasonic dv codec
** FRAMESERVER: virtualDUB-MPEG2 v1.6.15
** FILTER: none --
** MPEG ENCODER: TMPGenc v2.502

Computer A2
** CODEC: MS DV
** FRAMESERVER: virtualDUB-MPEG2 v1.6.15
** FILTER: none --
** MPEG ENCODER: TMPGenc v2.502

Each computer can have different installation scenerios, like:
** Drivers; DirectShow; versions, etc., etc.

For instance, there are many DV codecs (decoders) that do their own
thing, hence the potential for trouble or differences, even in the
slightest.

If you are asking, will you see a difference (even in slightest)
then the answer (given the above basic example, for instance) is YES.

But just how much of a difference is only according to you and
what you perceave as difference (or whatever)

Take a look below, where this time, the CODEC are the same, but the
FRAMESERVER are different, and I threw in a FILTER as well.

Computer B1
** CODEC: Panasonic dv codec
** FRAMESERVER: AVIsyth v2.55 -- (YV12/YUY2/RGB)
** FILTER: YES -- (color space change, YUY2->YV12)
** MPEG ENCODER: TMPGenc v2.502

Computer B2
** CODEC: Panasonic dv codec
** FRAMESERVER: virtualDUB-MPEG2 v1.6.15 -- (RGB)
** FILTER: none --
** MPEG ENCODER: TMPGenc v2.502

The above scenarios were just basic examples of what can go wrong
(or, differences) in a MPEG Encoding project. Sometimes, you won't
see any differences (YMMV per person) and sometimes, you will.

Any number of things can go wrong or show differences..

A color space change, a version of a filter/plugin or frameserver or
mpeg encoder, an MPEG Encoder's encoding algorithem can change sway
from version to version or mpeg encoder tool to mpeg encoder tool, or
even the user himself, etc., etc.

-vhelp 4127

[JohnnyMalaria]

One possible difference would be if the different computers supported different levels SIMD extensions (SSE, SSE2 etc). If the various software components in the conversion chain make use of highly optimized SIMD code, you may get slightly different results from calculations of things like discrete cosine transforms (DCTs) etc. It shouldn't make a huge difference but you may get final results that aren't exact bit-for-bit copies.

This is especially true if one system has SSE and so the calculations are typically integer-based and another has SSE2/3 and software uses floating point instead.

EDIT- Oh, and if, by any chance, one computer has a programmable GPU and the software makes use of that, then there could be slight differences in calculations of DCTs etc.