Re-encodes ALWAYS= WORSE quality?

[jedi]

well i have the bourne identity screener from tcf, and its a standard VCD. if i was to re-encode it with tmpeg in order to turn up the bitrate, it'll look alot worse than the original? or will it still look good? i want to make it an XVCD, because there are alot of fast scenes in the movie so i want to turn up the rate a bit. i usually do a CQ of 90, max 2350, and minimum 1150.

[LanceSteel]

The quality can't get any better than that of the original. Upping the bitrate from 1150 to 2115 (2350*0.90) will not make the movie look any better (in fact you are just wasting bitrate.) You should just leave it at the bitrate it is at.

Now since you are upping the bitrate, the quality should not decrease. It should stay the same. If you go below 1150 then you will see a degradation in quality.

[jedi]

will a higher bitrate help on high pace action scenes? like less blocky or something like that? so there's no way to decrease picture quality, unless u decrease the bitrate, rite?

[banjazzer]

Re-encoding may not make it look much worse - in fact you may not notice a difference. It cannot make it better as has been pointed out. What you could do is make it much smaller - perhaps to fit on one disk, by using max-bitrate=1150 and min-bitrate=300. Large parts of an mpeg-1 often don't require the full 1150 kbps.

will a higher bitrate help on high pace action scenes? like less blocky or something like that?

They would if you were re-encoding from the original source, but throwing more bits at a blocky scene will not remove the blocks!

[Poplar]

The painful truth is, anything you do will bring about quality loss. If there are cases in which you seemed to "improve" quality, it's most likely because your original source can't be more crappier........

[CogoSWSDS]

In a word, yes, any time you re-encode something with a lossy compression algorithm (such as MPEG-1/MPEG-2) you are going to suffer some quality loss. In my quest to burn my first VCD I had an OK quality MPEG right after an encode (with the exception of the sound followed the video by about 0.5sec) and silly me I erased the AVI file I had created it from. I didn't want to recapture the video from the original source so I decided I'd load up VirtualDub, demux and re-mux, then re-encode with TMPGEnc. Bad idea. The quality of the MPEG after that was horrible. Very pixely and blocky. So I recaptured from the original video source (again and again I might add until I figured out why the sound was out of sync with the audio) and reencoded using TMPGEnc and everything looked lots better.

My motto now is "Encode once and only once. Work with uncompressed if you can during editing (I hear HuffyUV is pretty good too) then encode at the end."

Motto #2 is "Avoid coasters - while creating a VCD, use CD-RW's then when you finally get it the way you want it, copy the CD-RW onto CD-R."

CogoSWSDS

[vhelp]

jedi,

The short true w/ those blocks is, no.
You cannot help reduce those blocks by raising the bitrate, because those
blocks are already there. I mean, the video has blocks. Each frame in
those fast scens (you were talking about) have blocks in them - permanent.
So, by raising the bitrate, you are not reducing blocks, becuase the info
is just not their. The blocks replaced the good info in those fast scenes.
The information is not in the video any longer.

So, re-encoding to 10,000 bitrate will not reduce them - no matter how
high'er you go.

Sorry.
-vhelp

[jedi]

ok thanks for all the helpful info guys. but have u guys by any chance seen the tcf screener for this movie? if u have, what do u guys think? decent quality? oh yeah, what do ppl increase the bitrate for? what are the benefits of having a high bitrate?

[DJRumpy]

The screener vcd for this is decent quality for a VCD, which isn't saying much. It looks like an old VCR tape, but it is viewable.

People re-encode, usually only when they have the original source (DVD, or AVI, or high quality DIVX/xVID rip). The original sources for these, if they are good quality, could have a max bitrate equal to what you would find on a DVD (9MB +). They then re-encode these for SVCD, Divx, etc, using lower bitrates, to make the file smaller so it will fit on lesser media like CDR's, and DVD-R/+R. Your copy of this screener has been squashed to about the limit of viewability (is that a word?).

You've heard the tearm, Garbage In - Garbage Out?
Every time you encode in MPEG1 or MPEG2, you dump garbage into the mix. You lose image quality, and in the case of this movie, you've lost the original bitrate, which is what gives you the blocks in high motion areas.

It is true, that you could re-encode it, using a filter to 'smooth' out the blocks, but the end result would just be more blurry for it, and not worth your time.

[fantomlord]

ok thanks for all the helpful info guys. but have u guys by any chance seen the tcf screener for this movie? if u have, what do u guys think? decent quality? oh yeah, what do ppl increase the bitrate for? what are the benefits of having a high bitrate?

higher bitrate=better quality (at least in general)
that is to say, starting from the same source and making 2 encodes at different bitrates, the one with the higher bitrate will be better quality, assuming all other variables remain unchanged.
as far as why people use higher bitrate...if you have a good quality source (i.e. DVD rip), with high bitrate SVCD's (and XVCD's) you can achieve very good results.