Standard quality/size for MPEG (*.mpg) videos?

[Ashman01]

Hi.
First of all, my apologies if this is a stupid question. I did try to look for an answer in the forums but had no luck.

I've started working with videos a few days ago, I've always worked only with audio so it's like new for me.

I have many videos that I've recorded with my digital camera, and in my opinion their size is too large. If I compare them with other videos I have (downloaded music videos for example), they have the same good quality but a much smaller size.
So I decided it's time to convert them. I looked for some info in ViDEOHelp.com and downloaded Avidemux.

What I do not know is which is the standard relation between quality and the size of the video. I have seen videos converted and they kept the same exact quality but the file size was much smaller.


I believe a good number is something like 10 MB for every minute of video that is 640x480 @25 fps, is that right?

Suggestions?


Thanks a lot in advance.
Greetings!

[Baldrick]

For mpeg2 is that a bit too low if you have lots of motions for example but if you instead use xvid or h264 it should be enough. And if you don't need an exact output file size try use constant quality/quantizer mode in the codec settings and the bitrate/file size will adjust to your source, lots of motion and details will have higher bitrate.

[Ashman01]

Hey thanks A LOT for your answer.
I'm really sorry I did not reply before (I was out of town and didn't have Internet access where I was staying).

So I tried to do that, and also read the help in the Avidemux home page.
But I still have issues selecting some options, and depending on what I select it is asking me for the average bitrate or size of the file, which I understood I should not select according to what you told me.

Maybe I didn't find help topics for that because I don't know exactly the name of the action I want to perform. How is this called? I am just trying to re-encode the videos, is that correct?
They are still too big even if I change the options in my digicam (for example, a 1' 30'' video takes a 168 MB file, I believe it's too much).

Do you know any thread/forum where I can find hepl for this?

Thanks a lot and I'm sorry for my dumb questions... I see what newbies ask about things that I am knowledgeable about and I know it's silly sometimes.

Greetings!

[PuzZLeR]

Different codecs/formats have different compression metrics.

MPEG-2, what's used in DvD, compresses well, but would fail miserably with most source at 10MB per minute (the "Blockness Monster").

DivX/Xvid should produce something a bit blocky, but watchable, at that size. It's also playable on many DvD players with the DivX logo. You may have to reduce the resolution to something like 480x360 to have less blockiness though.

x264, which is a free implementation of the H.264 standard, will do better than all at that size. For most sources, you should get a decent picture at 640x480. But, again, it won't be perfect for most movies - on a big screen TV you will notice blur/smear artifacts from the deblockers it uses. But then again, it's the best for low, low bitrates.

Now if you want better quality, you need to raise the bitrate. The more you raise it, the less of a compression advantage MPEG-2, DivX, Xvid and x264 will have over each other. At a high enough bitrate you may as well stick with MPEG-2.

10MB per minute translates to roughly 1200kbps if you use a bitrate calculator. You are in DivX/Xvid/x264 domain with this for "decent" video.

A good size IMO for good quality is about 25MB-35MB per minute. MPEG-2, with a good encoder like HC, CCE or TMPGEnc will compete nicely here.

168MB per minute and a half is overkill for any of the mentioned codecs at that resolution.