Some conversion questions

[Viper187]

I have some random MOVs I was considering converting to MPEG or DivX, and I was wondering how others determine what MPEG settings to use. Like how do you decide the bitrate, etc? I don't want to lose anymore quality than I have to, but I don't want to be excessive about it either. Is there something that can tell me what the bitrate of the MOVs is or does it matter? Gspot doesn't say.

I also have a couple huge AVIs that were encoded by Virtualdub a long time ago. They should be DivX, but nothing will open them. Gspot doesn't even think they're video, so I'm sort of out of ideas. I'm actually not even sure I still have them. I was just thinking of them and thought I'd see if anyone had any ideas. I use the K-lite mega codec pack, etc so I know I have most of the major codecs installed.

[jimmalenko]

Since the OP is looong-gone I'm answering this for the benefit of anyone who happens to find this thread via a search or forum browse. My comments are mainly aimed towards conversion to VCD/DVD, but I will digress towards the end.

The "correct' bitrate to use relies on a number of factors. Firstly, you need to decide if you're a "use all of the disc at the expense of a little quality" type or a "quality is everything and I'll use as many discs as it takes" type. Once you've got that dilemma sorted, then you can proceed.

You need to choose a frame-size that suits your source. My experience tells me that resizing up in small amounts is OK, but don't expect miracles when resizing too much - for example, resizing a 320 x 240 clip to 720 x 480 will most decidedly look worse than the original file, whereas, you could probably get away with resizing a 512 x 384 clip to 720 x 480 (provided the source is decent quality) and you may not notice any difference. YMMV though.

In the back of your mind you also need to know rough bitrates - for this a bitrate calculator comes in very handy. I prefer this one. Once you have a rough idea of the bitrate required to fit to one disc, and you have a rough idea of the frame size you'd like to use, then you can start making decisions.

Through all this you've got to consider your source - if you've got a 320 x 240 DivX/XviD/WMV file, then I strongly doubt you'll get any better results using anything other than 352 x 240. In addition to this, there's probably no point in using a bitrate over 1500-2000kbps for this frame size.

We then go into an overkill scenario - say you've chosen to use Half D1 (352 x 480), and your bitrate calc says you can use 7500kbps to fit one disc, there's probably no real need to have the bitrate that high as a CBR 5000kbps will more than likely look exactly the same.

There's many, many variables, and no real "one size fits all" formula for determining these things.

As for converting to DivX or MPEG solely for PC or settop-capable player playback, the CQ modes offer a nice compromise between speed, quality and filesize. A CQ of 2 or 3 is generally considered to be the best compromise, but I'd suggest you do your own experiments as everyone is different.

... and there's no reason why you can't use CQ mode for conversions to VCD/DVD, except that your end filesize is pretty much unknown. I prefer to either use 2-Pass VBR or drop my frame size if I'm "cutting-edge" with fitting my material onto one disc, but again, that's all individual preference.