Bitrate doesn`t affect filesize

[The Other One]

Hello everyone,

i haven't been using tmpeg quiet a while, but when i wanted to encode a movie (vcd) a few days ago (i used the same options like i did about a hundred times before (except the bitrate of course)), i was very surprised when the size of the encoded file was like if the file had been encoded as standard-vcd (pal). I tried different templates, about 6 different tmpeg-versions and till now i couldn`t get rid of the problem. OS winXP Pro Sp1.
Any Ideas what could cause the problem?

thx

[Erik_Osterholm]

I'm having a little trouble understanding exactly what the problem is. It looks like you are trying to create a VCD, but you want to change the bitrate? That would put you outside of the VCD specifications, which requires a constant bitrate of 1500kbps. Sine it's a constant bitrate, your filesize would be determined entirely by the length of the video you're encoding, so if you were encoding similar-length movies, I wouldn't be at all surprised to find that the filesizes were similar.

If you were encoding to SVCD, DVD, or some other variable-bitrate encoding, TMPGEnc can try to target a specific filesize, which would also explain why you got similar filzesizes.

Can you elaborate what specifically the problem is? What sort of mpeg file do you want as your output? What is your input? How are you setting the bitrate (for example, are you using the built-in calculator?) And what are you using for the encoded file's bitrate?

[The Other One]

Hi Erik.

i hope my english isn't too worse, i`m trying to explain with an example:
Input is a captured uncompressed (huffyuff) tv-movie (PAL), 110 mins long. Output file shall be VCD cbr.
1) with standard-vcd-settings i have 1150 kbps video-bitrate and the file ist about 1100 MB.
2) I'm changing the video-bitrate so that the movie fits exactly on 2 700MB CD-R's (so the filesize shall be about 1600 MB). The video-bitrate i choose is 1700 kbps. but my encoded file still is 1100 MB.

No matter what bitrate i choose (900, 1150, 1300, 1700) the filesize is always 1100 MB.

[Video Dude]

The bitrate is locked in the default VCD Template.

Did you unlock all of the setings by opening the unlock template? It is named unlock.mcf in the Template\Extra folder.

Once it is unlocked you can change the VCD bitrate.

Note that this in longer a VCD, you will be making a XVCD.

[Erik_Osterholm]

Huh. Not sure, then, why it's coming out the same size...if you change the bitrate, it definately should increase the filesize. Perhaps it's a bug?

[The Other One]

@ Video Dude
Of course i unlocked first, else i couldn`t have changed the bitrate :-)
Even if i use a pre-defined template such as mvcd (just testing, my standalone doesn't like it) the filesize doesn't change.

@ Erik
That's it what is surprising me. i haven't been using tmpeg for about a year, and earlier it worked perfect. to be sure that no single bug is responsible i tried 6 or 7 different releases of tmpeg (2.5x) and the result was all the same. the bitrate is whether in- nor decreasing.
Perhaps some broken codec or something else on my system is responsible for this. my final step is to reinstall windows but that can`t be the solution.

[Video Dude]

The only thing that I can think of is that you might have it on Constant Quality (CQ). If you try encoding at 1100, then 1200, then 1300, there is a chance you might get the same file size as you described with CQ. However, if you are using CBR then the file size should be increasing. Strange problem, I have never encountered this.