bitrate question before conversion ..

[greendesert]

I have one Good Fellas movie vob file of a typical 0.99 GB length. When I check the file thru
PVAStrumento, it shows :

VIDEO #1
Resolution 720 x 480
Aspect ratio is 4:3
Frame rate 29.97 fps
Nominal bitrate 7500000 bps
First PTS: 00:00:00.250

AC3 AUDIO #1
Format: 3/2
Sampled at 48.0 kHz.
First PTS: 00:00:00.233

AC3 AUDIO #2
Format: 2/0 / Dolby Surround
Sampled at 48.0 kHz.
First PTS: 00:00:00.233

AVIcodec shows:

Video : 2.74 GB, 7500 Kbps, 29.970 fps, 720*480 (4:3), MPG2 = MPEG 2 (SVCD/DVD), Supported
Audio : 144 MB, 384 Kbps, 48000 Hz, 5 channels, 0x2000 = AC3 DVM [0x80], Supported

So, I see the video is at 7500 kbps and audio at 384 kbps while the file length is 0.99 GB. So, why does AVIcodec show the video file 2.74 GB.

And when I load this file in Tmpgenc DVD source creator, the bitrate setting page shows that at 7999 kbps video and 384 kbps audio, the file size would be 3206 mb. I just dont understand that at 7500 kbps video the file actually is only 0.99 GB but TDSC shows at 7999 kbps video the output would be more than 3 GB ??

any insight into this, thanks !

[adam]

Nominal bitrate is just set by a flag in the stream. You can set it to anything you want regardless of what the actual bitrate of the file is, and for whatever reason it is often set much higher than what you've actually got.

To measure actual bitrates try bitrate viewer. It sometimes gets thrown off but its usually close.

Ultimately its not that big a deal. If you need to re-encode this then just use a bitrate calculator and then you can encode exactly to whatever target size you want.

[manono]

Hi-

That 7500 is meant to be the max bitrate, not the average. It may or it may not be correct. As adam says, it's just a number. I'm inclined to think that in this case, though, it's correct. Usually they say 9800.

Bitrate Viewer, for NTSC anyway, gives figures that are too high, about 18% too high, by my reckoning. The most accurate average video bitrate is given by the latest DGIndex. Open the vob, set Options->Playback Speed->Maximum, run File->Preview, and wait a few minutes. It's a little bit slow, but it'll get there.

[greendesert]

Hey

I downloaded the Bitrate Viewer and when installed, it has just this one program Scancalc 1.0. What does it do ? Are you talking about this program ??

[manono]

If you follow the link to the site, you can download BV.exe. When installed and open, It says BitRate Viewer at the top. I've never heard of ScanCalc 1.0.