AVI to MPG - does this sound reasonable?

[Pro-cras-tination]

I'm converting AVI's to MPG's using the bitrate of the original AVI file, not using the VCD standard bitrate. I sometimes have to decompress the AVI to get the sound to work properly and this makes me wonder if I'm doing the right thing because the decompression usually doubles the size of the AVI to over 1GB.

Would an MPG need to be larger than the AVI to be the same quality? Am I losing information by using the same bitrate as the original AVI? (usually 750-850)

I've given up on making standard VCD's due to the huge files. I'm in the process of converting MST3K episodes from AVI to MPG and am able to fit 5 1-1/2hr episodes onto a DVD (for a standalone player).

The original AVI's are about 700mb each so the quality isn't the best to start with, I just don't want to make it any worse. The biggest problem seems to be blockiness, the frames look fine if they're still but they get kind of chunky during playback. I'm using the highest quality "motion search precision" in TMPGenc but it doesn't seem to help for some of them.

Any suggestions would be much appreciated.

Thanks,

M

[Treebeard]

Well the reason for the blockiness your seeing is as you stated above.

same bitrate as the original AVI? (usually 750-850)

That is waaay below the VCD standard which will have bad quality results. if you really want to keep that low of a bitrate then the results arent going to improve much no matter what u do.

[Pro-cras-tination]

So would the original AVI file need to be at VCD bitrates to be worth making it into a true VCD-sized MPG?

Using the same bitrate as the original makes an MPG that is about the same size. Why does an MPG get so large if you increase the bitrate to VCD specs?

Thanks again,

M

[Duminas]

From what I've seen, no. (to the bitrate question -- filesizes have always been slightly bigger for the MPEG1 or MPEG2 than the AVI depending on the original compression; for me, anyways). And I assume the reason for the filesize being like this is the bitrate and compression on MPEG1 and 2 being absolutely horrid.

I took videos (AVI) that are about 600-700 on the bitrate, and encoded them as VCD CBR 1150kbps... very little blockiness except in the extremely high action scences, but that's just because 1150kbps is not enough to keep up. (I use SVCD with the headertrick now, just because MPEG1 has kinda fallen short, especially with the stuff I encode (read: SEED))

That's just my experience though... it really depends on the program you use, as well.. I'd reccomend TMPGEnc, but you may already be using it, so... ^^

[Laddydaddy]

In order for your mpg files to be similar in quality to your avi file you will have to up the bit rate somewhat. In fact, I would encode the file as an svcd or DVD. Most avi files are either uncompressed, or compressed using MPG4 compression techniques. I've never made an avi film myself, but from what I've seen MPG4 much more efficient than mpg1 (vcd) or mpg2 (svcd, DVD ) encoding. This is why so many people are looking forward to standalone DVD players that can play Divx (mpg4 compression) files. Using this kind of compression you will be able to fit even a 3 or 4 hour film on one DVD5 disc.

[shin_zer]

The best way to get a good quality is:

Use XVCD or XSVCD, this is increasing the resolution (352x480 for NTSC gives good results) and a very high bitrate. And good motion precision... but with standard coded below 1000 Kbits Divx, there IS already a quality loss so blockyness will appear no mather you encode 10000 Kbits. I recomend at least 1800 in CBR to good speed results and good output. Some people arround here like to use VBR. A little slower and bigger files but it may get some results.

I'm just a newbie so corrections and flames are welcomed.

[ZippyP.]

Some people arround here like to use VBR. A little slower and bigger files but it may get some results.

Here's your first correction:

VBR does not necessarily give bigger files, if using 2-pass then the size depends on the average bitrate selected. In fact, most people use 2-pass VBR in order to get better quality while reducing the size of the file. VBR applies higher bitrates where they are needed while saving bits from less demanding scenes, it's more efficient. If file size is not an issue then just use a high bitrate CBR, the results will be similar.

A 352x480 encode with 200 min, 2500 max and 1800 average would give the same file size as your 1800 CBR encode, but the results would be superior.

2-pass can take almost twice the time, that's why I do my encoding overnight.

[matneaves]

read this

it explains what to do

http://homepage.ntlworld.com/matthew.neaves1/VCDorSVCDencoding.doc

[steptoe]

DON'T encode using the source bitrate, especially if its a DivX, as their bitrate is totally different to the bitrate settingsfor MPEG1/2

Thats why your output is total crap

Read the guide on converting DivX to DVD/VCD/SVCD, you'll find what you need in there, or at least point you in the right direction

[shin_zer]

Correction accepted. I learned something today

If you are using DVD. Give the file a lot of bitrate... I don't know what is the limit but use the maximum. Size is not the matter.

Remember, some downloaded divx files have crappy compresion so ussually they are blocky or jerky (I once saw a "Private Ryan" with 300 Kbits and it SUCKED). Remember the compression is lossy, so there is no recovery...


CYA

[Pro-cras-tination]

Thanks for the help everyone.

I don't see much of an increase in quality when I increase the MPG bitrate above the bitrate of the original AVI. There's still some blockiness in fast moving scenes but the overal quality is decent enough (especially for episodes with better source VHS tapes).

I think I'll stick with the direct bitrate method I've been using so I can maximize the number of episodes per DVD. There's no way I'm storing 200 cd's/dvd's of one TV series.

Boy, I'd pay good money for a full (official) DVD release of these things. If they can put "Sanford and Son" on DVD, why not Mystery Science Theater 3k?

Thanks again,

M