SansGrip
21st July 2004, 20:10
DVD-RB now keeps the original frame structure intact through all three phases
I interpret this, and the fact that DVD-RB generates a D2V file with every frame set to "TFF no RFF", to mean that upon rebuilding DVD-RB sets the field flags in the new video stream to be consistent with those in the old video stream.
Is that correct?
That's a pretty clever way of handling it, and means the new video will never be "worse" (wrt interlace artifacts etc.) than the original. However, I see two drawbacks to this approach, both stemming from the fact that Avisynth and the encoder aren't seeing the frames as they're "meant" to be seen:
1) Filters (except deinterlacers and some/all resizers) should be run on progressive material. While a lot of DVDs are encoded and authored properly so that no corrective procedures are necessary, this is often not the case. Some titles really do benefit from some preprocessing, whether it be a smart IVTC (telecide/decimate) because of a sloppy application of telecine or editing done after telecine has been applied, or have a great deal of noise which will eat up precious bitrate when re-encoding. Such corrective measures are currently impossible, or suboptimal.
2) The encoder is, for a lot of titles which have been "hard telecined" (had pulldown applied prior to being encoded as "interlaced"), not seeing the original material. It's actually seeing a telecined version of it. This means the encoder is working with decidedly suboptimal material which adversely affects overall compressibility.
For example, I'm currently re-encoding The Shield Season 1 Volume 1 (R1), containing four episodes of a 4:3 TV show. It was mastered a little sloppily and is decidedly "hybrid" -- the D2V from DVD2AVI shows many long stretches of 2s throughout the usual 0 1 2 3 telecined material, and also a large number of oddities like 0 1 2 2 3 2 0 1 2 ...). Normally I would use Decomb to correct this kind of thing and feed the filters and encoder genuinely progressive material. I can't do this with DVD-RB at the moment, and (particularly with this title) the original mastering errors are clearly visible as artifacts when played on my HDTV (just as they are when I play the source disc, of course).
I propose one way to enable this kind of "cosmetic surgery" to be used with DVD-RB:
Default to "forced TFF, no RFF," but provide another mode which generates "vanilla" D2Vs containing the actual field flags for each frame. You would still only need to produce one D2V file for the entire stream.
Advanced users could then use the available Avisynth tools to correct badly mastered originals, and feed the encoder as close to the original, progressive source as we can get.
DVD-RB could then, in the rebuild phase, set the field flags to indicate a pulldown over the entire stream.
Of course, this provides enormous potential to mess things up (which is why DVD-RB should of course default to the current mode), but that comes with the territory when doing things like selective IVTC in Avisynth.
DVD-RB is an awesome tool, and I bow to the author wrt the remuxing portion alone. But just because DVD-RB has an outstanding "one-click" mode doesn't mean it can't provide more control to advanced users who aren't satisfied with simply duplicating the mastering errors of the original, but want to produce a backup that's even better than the source.
P.S. I just initiated a transfer from my bank account to PayPal and shall be donating as soon as it goes through (usually 5-6 days because it's coming from Canada). I wish I was able to donate what I think the author really deserves, but if I do that the kids won't be eating for a month or so ;).
I interpret this, and the fact that DVD-RB generates a D2V file with every frame set to "TFF no RFF", to mean that upon rebuilding DVD-RB sets the field flags in the new video stream to be consistent with those in the old video stream.
Is that correct?
That's a pretty clever way of handling it, and means the new video will never be "worse" (wrt interlace artifacts etc.) than the original. However, I see two drawbacks to this approach, both stemming from the fact that Avisynth and the encoder aren't seeing the frames as they're "meant" to be seen:
1) Filters (except deinterlacers and some/all resizers) should be run on progressive material. While a lot of DVDs are encoded and authored properly so that no corrective procedures are necessary, this is often not the case. Some titles really do benefit from some preprocessing, whether it be a smart IVTC (telecide/decimate) because of a sloppy application of telecine or editing done after telecine has been applied, or have a great deal of noise which will eat up precious bitrate when re-encoding. Such corrective measures are currently impossible, or suboptimal.
2) The encoder is, for a lot of titles which have been "hard telecined" (had pulldown applied prior to being encoded as "interlaced"), not seeing the original material. It's actually seeing a telecined version of it. This means the encoder is working with decidedly suboptimal material which adversely affects overall compressibility.
For example, I'm currently re-encoding The Shield Season 1 Volume 1 (R1), containing four episodes of a 4:3 TV show. It was mastered a little sloppily and is decidedly "hybrid" -- the D2V from DVD2AVI shows many long stretches of 2s throughout the usual 0 1 2 3 telecined material, and also a large number of oddities like 0 1 2 2 3 2 0 1 2 ...). Normally I would use Decomb to correct this kind of thing and feed the filters and encoder genuinely progressive material. I can't do this with DVD-RB at the moment, and (particularly with this title) the original mastering errors are clearly visible as artifacts when played on my HDTV (just as they are when I play the source disc, of course).
I propose one way to enable this kind of "cosmetic surgery" to be used with DVD-RB:
Default to "forced TFF, no RFF," but provide another mode which generates "vanilla" D2Vs containing the actual field flags for each frame. You would still only need to produce one D2V file for the entire stream.
Advanced users could then use the available Avisynth tools to correct badly mastered originals, and feed the encoder as close to the original, progressive source as we can get.
DVD-RB could then, in the rebuild phase, set the field flags to indicate a pulldown over the entire stream.
Of course, this provides enormous potential to mess things up (which is why DVD-RB should of course default to the current mode), but that comes with the territory when doing things like selective IVTC in Avisynth.
DVD-RB is an awesome tool, and I bow to the author wrt the remuxing portion alone. But just because DVD-RB has an outstanding "one-click" mode doesn't mean it can't provide more control to advanced users who aren't satisfied with simply duplicating the mastering errors of the original, but want to produce a backup that's even better than the source.
P.S. I just initiated a transfer from my bank account to PayPal and shall be donating as soon as it goes through (usually 5-6 days because it's coming from Canada). I wish I was able to donate what I think the author really deserves, but if I do that the kids won't be eating for a month or so ;).