TMPGEnc 2-pass VBR: bug found !! (maybe...)

[Giuliano]

Considering the different results from what expected from BitrateCalc and what TMPGenc produced I've done the following experiments:

encoded 60'' of a PAL 25 fps filmd (1500 frames), at different average 2-pass VBR rates (1950, 1777), the same audio bitrate (224) and giving different DC bit space (8 and 10 - i thought this could be the reason of the 20% difference..) .

The results were asthonising:
in any experiment the size was 20.444 Kb !!

Just to remind, I would have expected 15.923 Kb for 1.950Kbs average, and 14.653 Kb for 1777 Kbps.
Both far away from the right result and unreasonably identical !!

Interesting, isn't it ??

Giuliano

[MITSUI_1]

What stream type were you using?

[Truman]

which TMPG version?
which 2pass mode?

[Giuliano]

which TMPG version?

TMPG 2.53.35.130

which 2pass mode?

??
In the video tab, rate conrol mode field, I've got only one 2-pass VBR.

In its settings button, the max pass offers just 2-pass(old type) and anything else.

By the way: the test is so extremely (only 1500 PAL frame) simple and so easy (the size expected for a minute is very easy to calculate given a known average VBR rate) that I invite you to performe the same test, checking the results.
It takes only 4/5 minutes !!

If it is, it is a very bad error.

Giuliano

[Giuliano]

What stream type were you using?

I frameserved it with DVD2AVI.

Or you intended something else.. ?

giuliano

[MITSUI_1]

No, I mean the last tab -- the one that lets you put a comment in if you want to. Did you set it to:

MPEG1 VCD

MPEG1 VCD (non standard)

MPEG1 Program Stream

MPEG2 Program Stream

or

MPEG2 SUPER VCD

[Truman]

I can not confirm this.
I encoded 60'' of a PAL 25 fps film (1500 frames), at different average 2-pass VBR rates (1950, 1777),min0, max 2520, the same audio bitrate (224), SVCD PAL.

average bitrate: 1777kbps, expected filesize: 14657KB, real filesize 14898 KB
average bitrate: 1950kbps, expected filesize: 15924KB, real filesize: 16182KB
The difference is toleratable due to the inaccuracy of the MPEG encoder.

[Giuliano]

No, I mean the last tab -- the one that lets you put a comment in if you want to. Did you set it to:
....
or
MPEG2 SUPER VCD

MPEG2 SUPER VCD (VBR)


Giuliano

[Giuliano]

I can not confirm this.
I encoded 60'' of a PAL 25 fps film (1500 frames), at different average 2-pass VBR rates (1950, 1777),min0, max 2520, the same audio bitrate (224), SVCD PAL.

The only difference I see is the minimun rate, that I putted 300 and allowed the mimimum to be padded with blank in case.
Shoudln't anyway influence the final result, beeing the averege the target to reach anyway...

average bitrate: 1777kbps, expected filesize: 14657KB, real filesize 14898 KB
average bitrate: 1950kbps, expected filesize: 15924KB, real filesize: 16182KB
The difference is toleratable due to the inaccuracy of the MPEG encoder.

It's very strange.
Do we have the same version of the program ??

If they are the same, could you kindly e-mail me a trivial template of your work, so to be sure that there are not silly errors around midifying the results?

Thanks in advance.
Giuliano

[Truman]

I just loaded the SVCD PAL template from the TMPG\template subdirectory, changed CBR to 2pass VBR and set the bitrates.
I used v.2.53.35.130, that's why I asked.

[Giuliano]

I just loaded the SVCD PAL template from the TMPG\template subdirectory, changed CBR to 2pass VBR and set the bitrates.

Trying..... =:-0 ... with the template the fise size is _Correct_.
I cannot figure out the reason. Beein in tread, I checked it again and again......

"Truman, dear Truman..." :-)) .....can you try it also in the manual way ??

I used v.2.53.35.130, that's why I asked.

Interesting..... with _this_ version, i found in all SVCD template an audio bitrate of 128 (???!!!)
Did you modify it by hand to 224 (as I did) ?

Giuliano

[Baldrick]

Interesting..... with _this_ version, i found in all SVCD template an audio bitrate of 128 (???!!!)
Did you modify it by hand to 224 (as I did) ?

are you sure you are using this version?
http://www.tmpgenc.net/files/TMPGEnc-2.53.35.130.zip

because all those svcd templates using 224 kbit/s as audio bitrate.