bitrate not improving "visible" quality?

[sunmanking]

Hello,

I was wondering, is there any bitrate above which
image quality does not improve substantially? I mean,
maybe from 2800 to 4000 kbs there is no real "visible"
difference. What do you guys think?

e.g. I can burn an xvcd at say 2800 kbs, and that
is really ok. Now, let's suppose I could burn it even
at a much higher bitrate, 4000 kbs and that both the
cd-r burner and dvd player could play them, without
any problem. Let's also take for granted that the
image quality at 2800 is really nice, I mean, I cannot
say any blocking taking place, everything looks really
good. Then we could assume that 2800 is the desired
bitrate. Anything above would be sort of a waste of
encoding time.

In my case, an xvcd at 2013 kbs looks superb. I
don't know if a higher bitrate could improve what so
far looks great.

What do you think?

Thanks,

Sunmanking

[furball6969]

At VCD resolution I could see 2Mbit being pretty much saturated, as maximum DVD bitrates are around 8 - 9 Mbit/sec. Taking into account that there are four times as many pixels in a DVD than there is in a VCD - 2 - 2.5 Mbit for a VCD sounds about right.

[Anonymous65]

Remember that your capture card and source material will also set the upper limit for your video quality. As mentioned above, for mpeg video the quality normally maxes out at:

352x240 mpeg-1 ~ 2Mb/sec
352x480 mpeg-2 ~ 4Mb/sec
720x480 mpeg-2 ~ 8Mb/sec

Only very noisy video can improve a bit with a higher bit rate.

[sunmanking]

Hello furball6969 and skittelsen,

Thank you for your replies.

Could you please explain the maths behind e.g.

352x240 mpeg-1 ~ 2Mb/sec

I posted this message because some people claim that
their dvd players can play xvcd at 5000 kbit/s which
astounded me as way too high a bitrate.

I say so because, I'm using PAL, so that is 352*288, and I'd like
to know what the maximum would (at least, in theoretical terms).

TMPGEnc's latest release 2.510 finally lets you make
*TRUE* xvcd, I have checked it myself and now it does work.
I've used:
2013 kbs video bitrate
128 kbs audio bitrate
------
2141 kbs video+audio

BTW 1 Mbit = 1000 kbits ? If so, I'm using 2.14 Mb/sec
Or just as in bytes, 1Mbit = 1024 Kbits? I had never had
to think about this conversion before...

The last xvcd I've made is:

2759 video+128 audio=2887=2.87 Mb/sec

And I have to watch it again to check whether the dvd player
can play it smoothly or there are some times (sure very
few) when the dvd player can't cope with all the data. I'll
post my views on it too, just in case some people are
interested in this issue too.

Looking forward to your replies

Sunmanking

[Nelson37]

RE the XVCD at 5000, REMEMBER THE "X"!!! They more than likely, (although without specification there is ABSOLUTELY NO WAY TO KNOW) used a higher than normal resolution. I can't imagine any other reason to use such a high bitrate.

What is a "TRUE" XVCD as opposed to anything else? Non-standard equals non-standard, period.

[Anonymous65]

1000 kilo bits = 1 mega bits. It's just easier to write 4mb/sec instead of 4000Kb/sec. The value of the bit rate is identical.

1 byte = 8 bits

When speaking of *file size*, 1 Mbytes (1.024 Mbytes) = 1024 Kbytes.

mb/sec = megabits per second
MB/sec = megabytes per second

kilo = 1000
mega = 100000

[Heavensent]

its all about birate + resolution.
if you can go upto 5000kb xvcd without having problems in your dvd - go ahead.
but you will see the big change ONLY if you use higher resolution.

i tried to rip a dvd once, it was some live show, so it had much action
and effects.
i tried to make a svcd out of it, even if i went to 8000 kb - which is more
like an xsvcd, it whould still look bad.
i had to choose a higher resolution for it and i gave it 6000 kb.
looks wonderfull.
in your case i dont think xvcd with higher bitrate then 2000 whould look better UNLESS you choose higher resolution.
and while you are at it - just use svcd, it looks better on most cases.

[sunmanking]

Hi,

Thanks for the info on kb, mb and so on. I already knew
most of them, but I appreciate anyway.
I need this one badly 1000 kilo bits = 1 mega bits

Now, yes, it's all about resolution and bitrate, but since
It's a VHS rip I'm not going to to use a resolution higher
than 352*288 (pal). I've tried svcd and xsvcd and I can
assure you there is no visual difference. And I do pay
attention to the tiny little details... If I were ripping a DVD
I surely would use DVD.

BTW, I've already had a second look at the 2759+128 kbs
xvcd and I can tell you the results keep on being excellent,
brilliant, superb! I'm that glad I'm using xvcd! I thought
it would be better if I sticked to standard VCD but after
many MANY trial and error tests, I stick to xvcd when
ripping VHS. Definitely. I'm just sorry I made a *vcd* out
of New Year's concert from Wien directly ripped from the
aerial...

And yes, I couldn't tell there's difference between my
first xvcd at 2013 and this one at 2759. So you guys
were so right! Congratulations to you all and thanks
for your advice.

BTW, if you could let me know the formulae for:

352*240 --> approx. 2-3 Mb/s

I'd appreciate...

Thanks again,

Sunmanking

[Anonymous65]

There is no formula for finding out at what bit rate the quality is more or less maxed out. It is all based on visual observation.

For VHS video tape, there is little gain in quality by going over 352x480. If you only do 352x240, you are missing almost one half of the vertical resolution, and the video will look a bit softer. So, eighter do a 352x480 or 480x480 (X)SVCD. 352x240 will not reproduce all the details of a VHS video tape.