Transcoding vs Encoding

[pcexpress-guy]

ok, I follow... so what about dvdshrink, with compression turn-off, wouldn't that do the same things as TDA, in terms of non-encoding?

[jimmalenko]

ok, I follow... so what about dvdshrink, with compression turn-off, wouldn't that do the same things as TDA, in terms of non-encoding?

I would say No...but...

TDA takes a MPEG stream and modifies the headers as well as writing information files about the DVD and creating DVD structure. I would argue that DVDSHrink is a VOB stream editor when used without compression. All it does is remove unwanted streams if you require it. The DVD structure is already created - it is simply modifying the stream content.

So i guess yes, in terms of strictly being a non-encoder ?

[pcexpress-guy]

I am curious how do we know how any of these programs interact with the mpeg decoder/encoder (or is it transcoder)?

doesn't matter, but how do we know exactly what these programs do?

How would you say dvdlab fits into these catagories?

[jimmalenko]

doesn't matter, but how do we know exactly what these programs do?

This is the most sensible thing I've ever seen you post in your 140-odd posts so far, and there have been some pearlers.

You're right, it doesn't matter. It works.

[pcexpress-guy]

well... the reason I ask is sometimes, some author programs can pull up VOB/DVD folders, sometimes these programs can not. TDA does this to me a lot, when I try to open a new DVD folder. A BLANK add dvd screen shows up sometime, but there is working dvd content in there. So what i found to be a good practical solution is use DVDshrink, import the thing in, and then backup to another folder, using no compression. I then bring it to TDA if I need to. (I find TDA more efficent to use for editing, but that may just me.) So then this issue of transcoding and encoding came up, some people said one, some said the other... so I was just wondering in this context, if I lost anything by approaching this problem, this way. (if there is any video lost, i can't tell) Another way to fix some of these DVD folders, is to use ifoedit, strip streams or create new IFO option within it. Of course I could just demux the thing and do it that way too. It seems like from a time standpoint, the options are about the same.. i could be on crack though, not sure.


is this a pearlers? Btw, is a 'pearler' a rock band groupie?

[jimmalenko]

a pearler = a doozie = an unbelievable post

[pcexpress-guy]

man you should have told me you were from the oz, us usa guys get confused too easy.

btw, which post is a pearler?

you're not refering to the time I put all my electronic gear in the microwave? I am still paying for that research. The hard way.

8)

[jimmalenko]

man you should have told me you were from the oz, us usa guys get confused too easy

Sorry, I didn't realise. I should have dumbed it down a little bit.

btw, which post is a pearler?

you're not refering to the time I put all my electronic gear in the microwave? I am still paying for that research. The hard way.

That would just about do it.

[pcexpress-guy]

yea, man dumb this down for us folks in the usa.

dumb is as dumb does

[lordsmurf]

Here's a wll-written paper by HP:
http://www.hpl.hp.com/personal/Susie_Wee/PAPERS/hpidc97/hpidc97.html

[Sefy]

Dear lord, this is even more confusing now!

Transcoding differs from the encoding and decoding processes in that both the input and output of the transcoder are MPEG video streams

If I were to do an SVCD from a DVD, which both use MPEG2 compression, exactly what would be the difference then ? it's still encoding them 8)

Or I could also say, even if I do DVD to VCD, they are both MPEG Video Streams, so is that encoding or transcoding ? I think someone invented a new word just cause he didn't want people to think transcoding reduces the quality like encoding, but the end result is the same, they both reduce quality of the movie :P

[mats.hogberg]

My view of the process is this:
Encoding: Source video is decoded frame by frame, and this decompressed frame is then re-encoded using some (same or different) compression method like DivX, mpg1, mpg2 & cetera.
Transcoding: The frames in the source aren't decompressed, but alteration is made in the compressed data in the source file. I'm not saying that it is so, but the speed difference between the two ways of making (let's say a mpg2) video file smaller makes me believe that's the way it works.
Maybe mr. DVDShrink or me ReJig can shed some light on this?

/Mats

[jimmalenko]

Transcoding differs from the encoding and decoding processes in that both the input and output of the transcoder are MPEG video streams

Where did this come from ?

[Sefy]

That came from lordsmurf link of HP's well writen article 8)

[adam]

Sefy converting from SVCD to DVD cannot be done without decompressing the frames first. Its mpeg->uncompressed->mpeg. So its encoding.

If you instead used a transcoder which operated in the compressed domain there would be no decompression. You would go directly from mpeg to mpeg. It does this by simply requantizing co-efficients. Its much less efficient except at very small compression amounts.

[jimmalenko]

What he said.

[pcexpress-guy]

what is "requantizing co-efficients?"

[Sefy]

@adam, I see, that makes more sense now!

[FOO]

what is "requantizing co-efficients?"

Take a number , say 6 bits , which can represent 64 different values ,
and chop off the lowest bit to make 5 bits which can only represent 32
values. Like "rounding" to the nearest whatever
If taken to the extreme , this results in a "paint by numbers" look.

[AdobeNoob]

Wow. For some reason google thinks that this thread (from 2004!!) leads to a good answer to the general question of 'what the heck is the difference between transcoding and encoding'. Must have some good SEO going down here on videohelp.com, 'cause after reading the responses to this thread I was left wondering :)

This sums it up nicely:

http://answers.yahoo.com/question/index?qid=20090407193727AA95hi9

In a nutshell:

Transcoding is moving from one lossy format to another lossy format while encoding is moving from a lossless format to a lossy format.

Provided you know the difference between a lossy and lossless format, this answers the question concisely. Although it is in keeping with my own experience and hence I accept it, I make no assertion that it is true.

[poisondeathray]

Wow. For some reason google thinks that this thread (from 2004!!) leads to a good answer to the general question of 'what the heck is the difference between transcoding and encoding'. Must have some good SEO going down here on videohelp.com, 'cause after reading the responses to this thread I was left wondering

This sums it up nicely:

http://answers.yahoo.com/question/index?qid=20090407193727AA95hi9

In a nutshell:

Transcoding is moving from one lossy format to another lossy format while encoding is moving from a lossless format to a lossy format.

Provided you know the difference between a lossy and lossless format, this answers the question concisely. Although it is in keeping with my own experience and hence I accept it, I make no assertion that it is true.

That's not correct.

You can encode to a lossless format to a lossless format for example . e.g. wav to flac for audio. or lagarith to huffyuv for video.

You can encode from a lossy format to another lossy format as well. e.g. mpeg2 DVD to xvid

Transcoding , in the strictest sense , was explained above for video : it's requantizion of DCT coefficients with lower precision. It's a lot faster than encoding. However, these days people seem to use "transcoding" and "encoding" interchangably

[AlanHK]

"Yahoo answers" is just what some random guy with a Yahoo account says. Even Wikipedia is more reliable.