MPG Compression

[rwm352]

Dan

My wish list item for the future is that you can implement a good
compression tool with VRD so that I can shrink my files in one
sitting and keep the audio synced. You know me, I always want too
much. While I can use DVD Shrink I like your interface better. It would be nice to lump these utilities together.

Bob

:)

[DanR]

Bob,

This is a definte item for consideration, although I can't say when. We are very much interested, as you can see by the other discussions on this forum, of providing closer integration with DVD reading, editing and burning. I think this feature would be a real plus for the "batch" or "command line" facility that Gerry has been mentioning. Take a video, optionally edit it and then burn it to DVD. If its too big, lower the bitrate so that it does. Would be very slick.

[nigelb]

Bob,
Take a video, optionally edit it and then burn it to DVD. If its too big, lower the bitrate so that it does. Would be very slick.

But please, no time consuming re-encoding. Just do the clever 'magic' that DVD Shrink & others use to change the size.

[DanR]

But please, no time consuming re-encoding. Just do the clever 'magic' that DVD Shrink & others use to change the size.Yes, that's the way I would do it.

[JER]

Bob,
Take a video, optionally edit it and then burn it to DVD. If its too big, lower the bitrate so that it does. Would be very slick.

But please, no time consuming re-encoding. Just do the clever 'magic' that DVD Shrink & others use to change the size.

DVD shrink does re-encode but uses the real time re-encoding software tehcnology developed for broadcast of films etc on digital TV. It's so fast you think it wasn't re-encoding but it is. This is another example of a feature which differing products do at different quality/performance levels. DanR should only add afeature if it can be done well enough not to use an alternative (IMHO).

[JER]

Bob,

Take a video, optionally edit it and then burn it to DVD. If its too big, lower the bitrate so that it does. Would be very slick.

Sound a lot better if the size is checked before you burn it. Many DVD authoring packages have a size line along the screen bottom which moves toward and away from the max dvd/cd size as you add /edit files. This has now been complicated by the arrival of dual layer DVD recording!

[DanR]

DVD shrink does re-encode but uses the real time re-encoding software tehcnology developed for broadcast of films etc on digital TVI disagree with you re: DVD shrink. I don't think its doing a full re-encoding but rather what's called a transcoding. It lowers the bit rates by changing the video to use different quantizer matricies. This involves undoing and redoing the VLC coding, but not the most time consuming portion which is searching for motion vectors. Could be wrong, but I can't see how shrink can get that speed if doing a full recoding.

[JER]

DVD shrink does re-encode but uses the real time re-encoding software tehcnology developed for broadcast of films etc on digital TVI disagree with you re: DVD shrink. I don't think its doing a full re-encoding but rather what's called a transcoding. It lowers the bit rates by changing the video to use different quantizer matricies. This involves undoing and redoing the VLC coding, but not the most time consuming portion which is searching for motion vectors. Could be wrong, but I can't see how shrink can get that speed if doing a full recoding.

This is a quote from DVD shrinks' info.
"DVD Shrink provides two ways of shrinking your DVD disk. These are re-author and re-encode. You can use one, or the other, or for maximum shrinkage, both combined."

I think it's symantics to start saying that a particuler method has to be employed for it to be re-encoding. It may well work the way you say but that dosn't mean it's not "re-encoding".

[JER]

I also found this non technical discription on the DVD shrink forum by their moderator:-

It dynamically determines which picture types to modify depending on the compression required, and it does this for each and every picture in the movie. It supports "partial" reduction, where only a small number of blocks in each picture are reduced, and it attempts to distribute the resulting compression uniformly among all pictures, in such a way that the error introduced by this compression does not "propagate" or amplify as playback continues.

[DanR]

How ever he does it, its very effective.

[bitter_old_man]

dvdshrink himself says this: It is "transcoding with error correction" - this is not the same as re-encoding, since as with dvd shrink the motion vectors are passed through untouched, and calculation of motion vectors is most of the work of an mpeg encoder.
You can read this at http://forum.digital-digest.com/showthread.php?s=&postid=95326&highlight=transcoding#post95326. You may have to scroll a little to see the message.

Barry

[JER]

dvdshrink himself says this: It is "transcoding with error correction" - this is not the same as re-encoding, since as with dvd shrink the motion vectors are passed through untouched, and calculation of motion vectors is most of the work of an mpeg encoder.
You can read this at http://forum.digital-digest.com/showthread.php?s=&postid=95326&highlight=transcoding#post95326. You may have to scroll a little to see the message.

Barry


Reading your link it is clear (to me) that the "It" in your quote refers to
"Instantcopy", not DVD Shrink. Yes, DVD shrink passes through the motion vectors, but it's "instantcopy" which is being described as "transcoding with error correction" - which isn't re-encoding.

[DanR]

dvdshrink himself says this: It is "transcoding with error correction" - this is not the same as re-encoding, since as with dvd shrink the motion vectors are passed through untouched, and calculation of motion vectors is most of the work of an mpeg encoder.
BarryThat's what I was saying. The fact that he's not recalculating the motion vectors means that the Shrink program can't do things like crop the image, or do cuts except at GOPs. That's not to detract from what I think is a wonderful program.

[JER]

dvdshrink himself says this: It is "transcoding with error correction" - this is not the same as re-encoding, since as with dvd shrink the motion vectors are passed through untouched, and calculation of motion vectors is most of the work of an mpeg encoder.
BarryThat's what I was saying. The fact that he's not recalculating the motion vectors means that the Shrink program can't do things like crop the image, or do cuts except at GOPs. That's not to detract from what I think is a wonderful program.

DVD shrink dosn't see itself as full blown editor but does what it it says on the box - shrink DVD's! I don't think being able to crop or cut at frames is relevent to the vast majority of users, and it certainly wouldn't be liked if implementing it meant slower rendering. This is exactly the kind of feature creep which can ruin a good product, including Videoredo!

[bitter_old_man]

More on how DVDShrink works...from dvdshrink himself.

http://forum.digital-digest.com/archive/topic/26603-1.html

Scroll down to were it says "DVD Shrink 3.0 however is a VBR transcoder."

Barry

[JER]

More on how DVDShrink works...from dvdshrink himself.

http://forum.digital-digest.com/archive/topic/26603-1.html

Scroll down to were it says "DVD Shrink 3.0 however is a VBR transcoder."

Barry

The content was enlightening but you are still talking symantics. As far as I am concerned transcoding is re-encoding without creating the full frame images. You could even have a debate as too the differences in english usage of the use of "trans" and "re", i.e "from one to another" or "to do again" in this context. Using these definitions and group theory "trans" is a group withing the group "re".


DVD shrinks site continues to say the product re-encodes, not transcodes, probably as your link shows because the exact nature of the re-encoding develops and improves and he dosn't want to ( or need to) change his website!