Help With SVCD-CQ Encode (TmpgEnc)

[Enoonmai]

When trying to get a particular file size in order to fit an SVCD on x number of CDs, will I get better visual results (quality of SVCD when played) by using a higher CQ setting with lower bitrates or a lower CQ setting with higher bitrates?

[banjazzer]

What I do is set the max bitrate to 2496 and the min bitrate to 350. I then use a quality setting between 75 and 85. I don't go below 75, because I can guarantee a quality that I am happy with using this range. If you are too concerned with file size you may get a finished encode you are not happy with. If you want to guarantee files size, use the 2-pass VBR setting with the max and min I suggest, and let the project wizard choose exactly the average bitrate to fit to your required number of discs. It will take a lot longet to encode, though, because of the extra pass.

[incognito]

Two comments.

first, if you read the flame war -- err... thread -- about cq vs vbr,
there's some very good advice about using cq that goes basicly
run a test (on say 10 min of source range) with a cq and a bit rate
and check out the output to see if you're happy with it.

I've been using cq of 77, 1600-2050 max, 0 min, ntscfilm
framerate to make svcds, and I get 45-55min of video per CD.
I always leave the cq at 77 and adjust the bit rate if I need to
squeeze a little more. In my experience changing cq has a much
less predictable effect on the final size than tweaking the max bit rate.

Second, why do you need a minimum bit rate if you're
setting the cq in the 75-85 range?

[banjazzer]

Second, why do you need a minimum bit rate if you're
setting the cq in the 75-85 range?

I presume you are asking me? I have to set a minimum using CQ, so I figure I may as well set it low, so that if few bits are needed few are used!

I've just re-read it, and I suppose you are asking why not use zero minimum. The reason is, I have seen reports that certain players don't cope too well if the bitrate drops too low. However, I haven't done countless tests on this, so perhaps I should not have an opinion? 8)

[Enoonmai]

I always set the CQ at 75 to start, max to 2496, and use a bitrate calculator to guesstimate an average bitrate and use it for min. Then I pick various 10 min spots in the video and run some test encodes. If the size estimate is too big, I usually lower the min bitrate.

However, I'm finding that if the min bitrate gets too low (under 1600 or so for SVCD), I end up with "block noise" in dark scenes or in shadows and such. I assume that this is because TMPGEnc uses lower bitrates for darker scenes, even when there is a lot of detail.

Bottom line, I'm trying to lessen these "block noise" artifacts and was wondering if I should leave max and min bitrates alone and start lowering the CQ setting instead. Unfortunately, I have been "programmed" to belive that any percentage below 75 is poor, and since the CQ ranges from 1 - 100, I treat it like a percentage too.

Guess the best thing to do is just run some tests, eh?

[incognito]

banjazzer, thanks for the answer.

Enoonmai, black areas are something that it's just plain difficult for
mpeg2 to handle. Sefy swears that below 1600 or so you have to lower
the resolution to 352x480 to avoid these kinds of artifacts.

That's apparrently a legal (though seldom used) svcd resolution.
I've tried it and it plays well, but doesn't look as good on my TV--
though that could just as well be due to the relatively low bit rate.

[Sefy]

incognito, are we talking about the same Sefy ? cause I don't remember saying that, I don't even use any format besides standard VCD and sometimes my own formats, which is still VCD specifications.

[incognito]

sorry Sefy, I didn't mean to put words in your mouth!

I guess I confused your reply with Adam's when I asked
a simmilar question-- check out this thread:

http://forum.vcdhelp.com/viewtopic.php?t=79175&highlight=resolution

[Sefy]

no harm done
don't worry about it