AVI to VOB - file size difference

[NiallH]

Hi all,

I'm new to all this so this may be a stupid question to all you experts.

Can someone explain to me why, when converting an AVI into a VOB, that the VOB file size might only be a fifth the size of the AVI. I am sure this is caused by some compression tools but my AVI is only 2 GB and should fit on a DVD without compression.

Can I convert my AVI without compressing it???

Thanks in advance.

[mats.hogberg]

You can't compare AVI file size with the size of same movie encoded as DVD mpeg/VOB. But the usual experience is contrary to yours - "Why does it get so huge?" since most are working from DivX or other highly compressed AVI as source. Your AVI must be uncompressed (or nearly). DVD video is always compressed, with bit rates from ~2 to 9 kbps

/Mats

[bugster]

Avi is not a video format, it is simply a container format. It can contain video and audio using many different codecs. As Mats says, most people complain of avi (usually divx or xvid) conversion producing too large an mpeg/vob file. This is because they are going from highly compressed source to a format which has less compression. Your problem seem to be the opposite. My guess would be that your source is DV avi (from a DV camera, transferred to a PC via firewire. DV avi is ~13Gb per hour, so you must have ~10 mins of video there).
The size of any video file (of any format) is determined by 2 things only, these are running time (length) and bitrate. Mpeg-2 for DVD is typically in the 4Mb/s to 8 Mb/s range, though can go as high as 9.8Mb/s and can go much lower. DV is somwehere in the region of 25Mb/s (IIRC). That is why your mpeg is smaller than your source file. If you want to make it bigger (and the quality may improve if you do this), encode at a higher bitrate.

BTW, what encoder are you using?

[NiallH]

Spot on Bugster. It's 10 mins of video direct from DV camera via firewire. Just want to burn to DVD with best possible quality.

Had tried using Ulead Videostudio but it reduced my 2 GB to 1/2 a GB.

Would Tmpgenc do it???

[bugster]

Had tried using Ulead Videostudio but it reduced my 2 GB to 1/2 a GB.

Look at the example figures I gave for bitrates.

10 Mins of mpeg-2 being 1/2 Gb means the bitrate is around 9Mb/s. Mpeg-2 for DVD doesn't go much higher than that. In fact if it is using PCM audio, then that is about the max. If you use compressed audio (mp2 or Ac3) the video can go up to 9.8Mbps, but thta is not really much more.

Why do you want it to be bigger. Mpeg is just a more efficient compression method than DV. If there are quality issues with your result, there may be other problems and not just file size/bitrate. If the quality is fine, leave well alone.

Yes, TmpGenc can encode DV to mpeg-2, and it will allow you to use bitrates higher than those allowed for DVD, but it won't be DVD compliant and probably wouldn't play on a standalone player if you used out of spec bitrates.

[yoda313]

Hello,

won't be DVD compliant and probably wouldn't play on a standalone player if you used out of spec bitrates.

Most likely yes but some players let you play maxed out dvds. I've done movie trailers that peak above the limit but play perfectly on my old Sony dvd player.

If you want to fool around a bit take a small video clip and sample it at higher bitrates. Then burn a rewritable dvd and test it on your target dvd player. If it plays at that rate go ahead and use it. Just remember it may not work on EVERY dvd player you use

Kevin