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Just Me
Guest
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 Posted:
Mon Feb 28, 2005 12:45 am Post subject:
Transcoding |
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Does anyone know the difference between "transcoding" a video file to be
burned on a DVD and normal "encoding" like with Divx? I've noticed that
"transcoding" is much faster but does it alter the quality of the file any
before burning on DVD?
Thanks.
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Jan Panteltje
Guest
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| Posted:
Mon Feb 28, 2005 12:57 am Post subject:
Re: Transcoding |
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On a sunny day (Sun, 27 Feb 2005 19:45:32 GMT) it happened "Just Me"
<theclient@hotmail.com> wrote in
<wrpUd.7097$873.2769@newsread3.news.pas.earthlink.net>:
| Quote: | Does anyone know the difference between "transcoding" a video file to be
burned on a DVD and normal "encoding" like with Divx? I've noticed that
"transcoding" is much faster but does it alter the quality of the file any
before burning on DVD?
|
'Transcoding' normammly refers to changing from one format into an other.
Linux 'transcode' for example can convert from many formats to many other
formats.
'Encoding' is the same thisg, starting wit ha given format.
'Encoding' will be faster if you go from a YUV-like format to DivX or mpeg,
then 'transcoding' from mpeg2 tpo DivX, as no 'decoding' process is involved.
So fro example:
mpeg2 'decoder' yuv 'encoder' DivX is a transcoding procedure.
yuv 'encoder' DivX is an encode ONLY procedure.
Encoding is faster in all cases ,as it involves only one transformaton. |
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Just Me
Guest
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| Posted:
Mon Feb 28, 2005 2:24 am Post subject:
Re: Transcoding |
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I'm using Nero Vision to burn mpeg2 files onto a blank DVD disc. It has to
"transcode" them first but I don't know why because they are already mpeg2
files and I thought all DVD videos used mpeg2 files?
Thanks for your response.
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:1109534277.a85ddac3dabbd9e4e39d533b973f2490@teranews...
| Quote: | On a sunny day (Sun, 27 Feb 2005 19:45:32 GMT) it happened "Just Me"
theclient@hotmail.com> wrote in
wrpUd.7097$873.2769@newsread3.news.pas.earthlink.net>:
Does anyone know the difference between "transcoding" a video file to be
burned on a DVD and normal "encoding" like with Divx? I've noticed that
"transcoding" is much faster but does it alter the quality of the file any
before burning on DVD?
'Transcoding' normammly refers to changing from one format into an other.
Linux 'transcode' for example can convert from many formats to many other
formats.
'Encoding' is the same thisg, starting wit ha given format.
'Encoding' will be faster if you go from a YUV-like format to DivX or
mpeg,
then 'transcoding' from mpeg2 tpo DivX, as no 'decoding' process is
involved.
So fro example:
mpeg2 'decoder' yuv 'encoder' DivX is a transcoding procedure.
yuv 'encoder' DivX is an encode ONLY procedure.
Encoding is faster in all cases ,as it involves only one transformaton.
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Jan Panteltje
Guest
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| Posted:
Mon Feb 28, 2005 3:21 am Post subject:
Re: Transcoding |
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On a sunny day (Sun, 27 Feb 2005 21:24:22 GMT) it happened "Just Me"
<theclient@hotmail.com> wrote in
<aUqUd.7096$MY6.5214@newsread1.news.pas.earthlink.net>:
| Quote: | I'm using Nero Vision to burn mpeg2 files onto a blank DVD disc. It has to
"transcode" them first but I don't know why because they are already mpeg2
files and I thought all DVD videos used mpeg2 files?
Thanks for your response.
Well, what somebody calls 'transcoding' may depend on the person of cause. |
Some programs for DVD authoring demultiplex the mpeg2 and then burn as
mpeg2 + wave audio. (The cheap ones).
Of cause it should check if it is already in a DVD format, so the audio
would have to be either mp2 or AC3 or wave.
I do not normally use windows, and have no experience with Nero Vision, but
this is what for example the DVD program that came with my burner does.
An other reason to 're-encode' the mpeg2 would be if it was not in one of
the required DVD formats (720x576, 360x576, 360x288 IIRC, or something like
that, you can look that up I am sure).
If it actually makes a DVD (your program), then it will create VOBs and IFO
files, and their backups (BUP).
These files have some more info regarding for example seeking in them.
If it is really fast, it likely just adds that timing info and makes a VOB,
and no re-encoding or demux-remux is done.
Check if it makes a DVD with wave audio from a mpeg2 with AC3 or mp2...
I hope Nero is not that bad.
May have to do with that thse programs are more expensive if they support
AC3 codec ... |
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Just Me
Guest
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| Posted:
Mon Feb 28, 2005 3:35 am Post subject:
Re: Transcoding |
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No, its not fast, it takes some time to "transcode". You might be right, it
could be changing the audio to wav format. Also, Nero Vision is the program
that came with my burner, its probably one of the "cheap" ones you were
referring to.
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:1109542932.055ec39351604a2148cb874131810fa3@teranews...
| Quote: | On a sunny day (Sun, 27 Feb 2005 21:24:22 GMT) it happened "Just Me"
theclient@hotmail.com> wrote in
aUqUd.7096$MY6.5214@newsread1.news.pas.earthlink.net>:
I'm using Nero Vision to burn mpeg2 files onto a blank DVD disc. It has
to
"transcode" them first but I don't know why because they are already mpeg2
files and I thought all DVD videos used mpeg2 files?
Thanks for your response.
Well, what somebody calls 'transcoding' may depend on the person of cause.
Some programs for DVD authoring demultiplex the mpeg2 and then burn as
mpeg2 + wave audio. (The cheap ones).
Of cause it should check if it is already in a DVD format, so the audio
would have to be either mp2 or AC3 or wave.
I do not normally use windows, and have no experience with Nero Vision,
but
this is what for example the DVD program that came with my burner does.
An other reason to 're-encode' the mpeg2 would be if it was not in one of
the required DVD formats (720x576, 360x576, 360x288 IIRC, or something
like
that, you can look that up I am sure).
If it actually makes a DVD (your program), then it will create VOBs and
IFO
files, and their backups (BUP).
These files have some more info regarding for example seeking in them.
If it is really fast, it likely just adds that timing info and makes a
VOB,
and no re-encoding or demux-remux is done.
Check if it makes a DVD with wave audio from a mpeg2 with AC3 or mp2...
I hope Nero is not that bad.
May have to do with that thse programs are more expensive if they support
AC3 codec ...
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Christian Link
Guest
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| Posted:
Mon Feb 28, 2005 4:03 pm Post subject:
Re: Transcoding |
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Hi,
On Sun, 27 Feb 2005 19:45:32 GMT, "Just Me" <theclient@hotmail.com> wrote:
| Quote: | Does anyone know the difference between "transcoding" a video file to be
burned on a DVD and normal "encoding" like with Divx? I've noticed that
"transcoding" is much faster but does it alter the quality of the file any
before burning on DVD?
|
While what the other posters said is of course correct as far as the general
term goes, the kind of "transcoding" you refer to, i. e. the "quick
recompression" within the same format that programs like DVD2One, Shrink or
Nero Recode offer, and which is really a lot faster, is a bit different:
Pedants would rather call them DCT domain transcoders (DDTs), or CDTs
(compressed domain transcoders). What they do is depack the original video
stream only down to a certain level, but not completely, and then see it
from there. Depending on the transcoder, this can mean it only requantizes
the material, or it will even do the whole DCT algorithm itself (again).
Some (and I assume: most of the current transcoders) rescan the material for
optimum bitrate distribution, too. (For more information, check out the net
for descriptions of the MPEG format; even a fairly rough one would do.)
As for altering the quality, of course it does. Quantizing alone means
losing precision and hence quality. Further, many older transcoders (in the
above sense) don't check for a better way to distribute the available
bitrate, but rather adhere to the relative bitrate spendings the original
compressor chose. Given that the material is being recompressed, it's not
necessarily true that these choices are still optimal for the new,
transcoded movie (especially not if the original material was encoded with a
constant bitrate). Last not least, the speed of transcoders is heavily
reliant on the fact they don't have to do all the time-consuming stuff like
motion compensation etc. again, but could rely on what the original encoder
had already found out. Again, this doesn't have to be the optimum choice,
either (sometimes not even for the original video, if it was a substandard
encoder).
This being said, a compressed domain transcoder is so fast because it
"recycles" analyses the original encoder had already done, and just
"squeezes the results a bit more". This step, however, can be done pretty
quickly. That's why a transcoder can encode (well, transcode ;-) ...) a full
DVD movie in only a fraction of the time a *real* encoding would take. But,
of course, the source and destination formats must be identical. On the
other hand, the result is necessarily less fine-tuned as far as the
compression parameters themselves go (it just can't be), and it is
absolutely dependant on the original encoder's quality. The Shit in = (More)
shit out rule definitely applies here very much.
Finally, to avoid confusion, I personally suggest people to call the above
process transcoding (like you did), while decompressing the material
completely and then reencoding it (sometimes even into a different format),
should be named recoding (or encoding, if the original material was
uncompressed ;-) ...). Because you do it from scratch and have the
respective encoder do all the work itself, instead of _trans_forming your
source material more or less smoothly from one format into another.
Hope that helped a bit.
Greetings,
Chris. |
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Jan Panteltje
Guest
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| Posted:
Mon Feb 28, 2005 4:53 pm Post subject:
Re: Transcoding |
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On a sunny day (Mon, 28 Feb 2005 12:03:13 +0100) it happened Christian Link
<C.LinkSPAMBLOCK@GMX.net> wrote in
<r8t5215jgmkjnrhdgk579g33d9voq1kdvg@4ax.com>:
| Quote: | Hi,
......<snip correct suff |
| Quote: | Finally, to avoid confusion, I personally suggest people to call the above
process transcoding.
As I did say, each person has his own idea what transcoding stands for. |
Normally the proces you refer too is also known as 'recompression?'.
I have one of those programs here (Linux) and the results are just
plainly BAD. (mpeg2 to smaller size mpeg2).
In the windows version it was equally horrible.
| Quote: | (like you did), while decompressing the material
completely and then reencoding it (sometimes even into a different format),
should be named recoding (or encoding, if the original material was
uncompressed ;-) ...). Because you do it from scratch and have the
respective encoder do all the work itself, instead of _trans_forming your
source material more or less smoothly from one format into another.
|
Suggest to the Linux transcode developers an other name....
It sort of sets the standard.
| Quote: |
Hope that helped a bit.
It reminded me of the DCT program.... |
It is so much better to just install Linux and do the 'transcoding' or
'encoding' or whatever, then mux subs with submux-dvd, use dvdauthor.
And have full control over what happens.
Best is of cause a good 2 pass DivX, mine ran all night, and looks really
almost as good as the original (mpeg2).
No idea why anyone still uses MS windows...
;-)
http://panteltje.com/panteltje/dvd/
http://panteltje.com/panteltje/subtitles/ |
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Christian Link
Guest
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| Posted:
Mon Feb 28, 2005 6:32 pm Post subject:
Re: Transcoding |
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Hi, Jan,
On Mon, 28 Feb 2005 11:53:37 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com>
wrote:
| Quote: | As I did say, each person has his own idea what transcoding stands for.
|
Yup, although this doesn't get us very far in discussions, does it ;-) ? I
mean, I could legitimately call this process "Bernd" as well, but I
shouldn't wonder if nobody understood me (or misinterpreted what I was
saying).
| Quote: | Normally the proces you refer too is also known as 'recompression?'.
|
Well, I consider transcoding a very special form of recompression, which is
why you may say recompression instead of transcoding, but not vice-versa.
I'm well aware that I'm nitpicking here, but just for the sake of the
discussion ;-) .
However, let me give you an example for when confusing these terms can lead
to wrong conclusions: Obviously we do agree that the quality of DCT
transcoders (usually) isn't very good, which is why transcoders are mainly
for people who either don't care (e. g., because they're in a hurry - I can
understand that), or who are just too stupid/ignorant to deal with a real
compressor's parameters. Those are the guys who tend to use "bubblegum
machine" programs, i. e. that kind where you just invest very little - like
two or three mouse clicks - but only get an old, rotten, stinky "sweet" in
return.
Now, those "bubblegum" programs for today's hardware configurations (PC +
DVD burner) usually are _trans_coders. Take the ones I've mentioned in my
former post, for example. There isn't very much to configure, and they're
fast. As for the results, well, that'd be another topic, as some are quite
amazing given the amount of time you have to invest, but still worse than
doing it "like a real man" ;-) .
However, even though I didn't check those programs in a long time and thus
may have missed some newer releases, there seems to be a(t least one)
similarly simple to use program that just turns your DVD-9 into a DVD-5,
*but*: It uses an external compressor (CCE, for example; don't know if it
allows for other compressors as well, but believe so). This one clearly is
*no* transcoder (mind you: according to _my_ definition). So while it may
look like any of those "bubblegum machine" programs, it probably yields
perfect results - or at least as perfect as it gets without manual tweaking
and/or pre-filtering. Many people consider this a "transcoder", which,
however, for many of us suggests: "Quick, but ugly". A plain wrong
conclusion. It's a recoder, just like Dr. DivX is not a transcoder
(technically, you cannot transcode between MPEG-2 and MPEG-4, although
converting the motion vectors etc. _may_ be possible if you keep the
resolution - just a thought).
This is why I put such an emphasis on the difference. Other examples could
be made up, of course.
Sure, if we focus on the "trans" prefix, everything that first has to
decompress the source, i. e. everything that isn't fed plain, uncompressed
data, would be a "transcoder". You'll get to your final result through/via
another format (uncompressed video, into which the source is first decoded).
However, I doubt if many people would look at it in such a pedantic way.
| Quote: | I have one of those programs here (Linux) and the results are just
plainly BAD. (mpeg2 to smaller size mpeg2).
In the windows version it was equally horrible.
|
I don't know what particular program you refer to, but I have to say that
the results Shrink (or its "commercial brother", Nero Recode 2) produce were
quite okay. That's not to say we couldn't do better, but then again,
transcoders aren't for the quality-aware, anyway ;-) . I took some average
DVD movies (about two hours, 2,35:1 anamorphic) and what I saw in the end
was good enough to consider worth keeping (oh well, not in my case, as it
was my own source DVD, anyway ;-) ...). Sure, if you know a movie pretty
well and hence know where to look for compression artifacts, you'll surely
find them, but if you limit yourself to the plain movie and one audio track,
you usually get results good enough for viewing on an average TV. Not bad
for about 1/10th or less the time the same job would have cost you if you
did a real re-encode ,right?
(Of course, this all depends on the software as well; what I used was Shrink
/ Recode 2 ...)
| Quote: | Suggest to the Linux transcode developers an other name....
It sort of sets the standard.
|
With all due respect to the *NIX fraction, in the video area, they don't. I
have to admit, though, that given the level of computer knowledge the
average *NIX user is supposed to have (a level that in fact is embarassing
low with the average Windows user alright), one should assume they should
know better. After all, the chance that some less than qualified idiot who
never knew anything else than colorful "program construction sets" is
significantly lower under *NIX variants than in the Windows community, which
is why I tend to give *NIXers the benefit of the doubt ;-) .
.... Just not when it comes to multimedia. Not yet, that is.
| Quote: | It reminded me of the DCT program....
It is so much better to just install Linux and do the 'transcoding' or
'encoding' or whatever, then mux subs with submux-dvd, use dvdauthor.
And have full control over what happens.
|
If you want full control, I suggest you don't start with transcoding at all,
but do a *real* recompression, preferrably with light pre-filtering from
within AVISynth and/or VirtualDub. The result could then be fed to either
the DivX codec or CCE/TMPGEnc. Where you go from there, is up to you, but I
see no problem doing the following steps under Windows (e. g. via DVD-lab
pro, although I admit its subtitle support still sucks a bit).
However, with regard to this newsgroup's topic, I think we're getting
carried away a little ;-) .
| Quote: | Best is of cause a good 2 pass DivX, mine ran all night, and looks really
almost as good as the original (mpeg2).
|
Fully agreed. Although I never really did "serious" movie backups via DivX
without pre-filtering, I just made some quick recodes without any filters at
all, i. e. just used a small AVISynth script for importing/cropping/scaling
the output, and fed that directly to the codec. I was amazed how good these
movies looked even if you just calculated 1/2 or 1/3 DVD-5 for one. Sure,
they were widescreen, and the "anamorphicity" had to go, so I saved a bit of
vertical resolution. Still, the results in general - i. e. some definitely
bitchy scenes notwithstanding - looked nice on a monitor, so I believe
they'd look even nicer if you carried them over to my external player
connected to the TV. Okay, there are some blocks here and there (especially
with the 1.5 GB versions), but compared to what a transcoder would have done
with that little space, they were great.
| Quote: | No idea why anyone still uses MS windows...
;-)
|
Because those who are semi-professionally into video would miss AVISynth and
VirtualDub (not to mention CCE), the professionals would miss Premiere et
al., and those who don't belong into either of these groups, wouldn't know
where to find Minesweeper and Solitaire (or Outlook, for that matter).
Simple as that :-) .
(Um, in case AVISynth and/or VirtualDub have long been ported, slap me now -
I deserved it ;-) ...)
Greetings,
Chris. |
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Jan Panteltje
Guest
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| Posted:
Mon Feb 28, 2005 7:13 pm Post subject:
Re: Transcoding |
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On a sunny day (Mon, 28 Feb 2005 14:32:50 +0100) it happened Christian Link
<C.LinkSPAMBLOCK@GMX.net> wrote in
<fv46219c3d9adnkc2bn6qits7hrem6mpp6@4ax.com>:
| Quote: | No idea why anyone still uses MS windows...
;-)
Because those who are semi-professionally into video would miss AVISynth and
VirtualDub (not to mention CCE), the professionals would miss Premiere et
al., and those who don't belong into either of these groups, wouldn't know
where to find Minesweeper and Solitaire (or Outlook, for that matter).
Simple as that :-) .
(Um, in case AVISynth and/or VirtualDub have long been ported, slap me now -
I deserved it ;-) ...)
|
Ah, yaaa, professionsal video.. you are teasing Unix people.
Vdub is nice, it runs (with some menu problems) in Linux wine windows
emulator.
I have to point out then when I started using transcode (the program) in
Linux to make DivX (4) with divx.com libdivxencore (4), the quality
I got from that even stunned the whiz kids here that were really into that,
to the point of me receiving emails of 'How did you do that?'
Same for the subtitle rendering with subtitler (I wrote it, I peeked at
vdub source, but wen ta different path, added some control, it can do chroma
key, slicing, rotation, movie in movie, subtitles of cause, animation (to
some extend) ).
Only subtitle software available for the 'normal' people was SubstationAlpha.
In windows.
So I wrote xste subtitle editor for linux.
Actually, except for the codecs, I have written the whole scala now.
The xvid people work on the codecs though... some on OGG too.
Some mpeg2 editor should be written that does the frame thing.
I have not been able to convince myself I need it, as transcode with subtitler
can do pretty good 'editing' and special effects, but is slow (because
of the re-encoding).
Somebody did send me that DCT shrink program IIRC, cannot remember the name
of it, maybe even erased it, was bad.
So, there is of cause more stuff in Linux, cinelerra for example.
http://heroinewarrior.com/cinelerra.php3
But I am no user of it... (now compile problems, missing headers..).
Then of cause you must have heard about Sun and Unix and rendering....
MS windows for me will stay that pay for every mouseclick kids stuff.
Yep.
And with DRM coming you will have to pay every time you watch, a communist
idea to disallow private property (of music), by the Pol Pot of computing,
a Bil Gates.
I will have to hang on to this DRM free box, it may be valuable in the
future.
Once they F*ck up the hardware, use the old PC from the attick, do not throw
it out.
If you know your stuff.
Ok, my view on transcoding .... |
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