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Dubbing after editing.

Discussion in 'Blu-ray & DVD Players & Recorders' started by Chris at Home, Feb 20, 2005.

  1. Chris at Home

    Chris at Home
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    I bought a Sony RDR HX-900 a few weeks ago. It certainly lives up to its expectations regarding picture quality.

    The user manual warns that when you are using the A-B erase method on a DVD+RW, the erased section may be slightly different from the points you selected. After spending a really soul destroying afternoon testing out the exact difference between the intended edit points and the actual results, I found that edit point "A" can be up to 11 frames later the selected point, and edit point "B" can be up to 10 frames earlier. Therefore, the portion removed is always slightly shorter that intended.

    When I edit the hard drive using the A-B erase method, (to remove commercials) then dub to a DVD+RW, some of the previously erased frames reappear on the DVD+RW! The secret is to cut out those extra frames each side of the portion you wish to edit before you dub.

    Now the 64 dollar question. Why do frames that were allegedly erased reappear after dubbing?
     
  2. musukebba

    musukebba
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    You cannot edit to frame accuracy with +RW (+VR) on a standalone recorder: cut-points can only be set to a certain point within a Group Of Pictures (GOP). Since this position will vary, dependent on the video content, it is indeed a frustrating experience. Frame accurate edits can be achieved for video recorded on +VR, but you need to rip it from the disc and edit on a PC.

    If you want frame accuracy on a Sony, then take the time to familiarise yourself with the editing facilities in the <minus> domain.
     
  3. Chris at Home

    Chris at Home
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    Thanks! How many frames are a "group of pictures" that you mention? Is this group a contant measure or a variable one depending on picure content? As for the 64 dollar question, (why do the allegedly erased frames reappear after dubbing from the HDD to a DVD+RW?) nobody has answered that one yet! I also noted that when the edited scenes are played back, there is a frame glitch which freezes the picture for a moment. On DVD+RW, the freeze lasts for nearly 2 seconds. On DVD-RW (VR) or HDD, the freeze duration is much shorter.

    More exciting experiments are on the way!
     
  4. musukebba

    musukebba
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    Have a brief read here first...

    It's variable depending on the manufacturer's implementation. IIRC can be as many as 15.
    The reference points for editing, usually the I-frames, are of variable frequency and position within the GOP, and as you imply are dependent on the motion content of the video.
    As a suggestion, a new I-frame is created at the cut-point and the P- and B-frames on the retained side of that I-frame still remain?
    Yes, this happens on other +RW implementations, for example, Philips. One of the many reasons I don't do on-box editing of +RW any more.

    Perhaps Rasczak could tidy up a bit here... :)
     
  5. Chris at Home

    Chris at Home
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    I think my spelling could have done with some tidying up as well! Too many late nights! I shall carry on finding things out. Only had the machine 3 weeks. Had to cram the info on all these MPEG frame terms.

    Strangely enough, my hard disk audio machine (Fostex D-108) can cut, copy, paste, etc accurate to 1 subframe (0.4 millisecond). Presumably, such a high standard would be available at "such a high price" on a DVD recorder. Wish my wife would keep away from the TV and take up bingo or knitting and maybe I could get on with my investigations!
     
  6. musukebba

    musukebba
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    Glad you are having fun.

    However you have frame-accurate editing available on your Sony at the moment - albeit in the <minus> domain.

    If you wish to continue in the quest for <plus> domain editing, then you'll only be able to do that on a PC.
     
  7. Chris at Home

    Chris at Home
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    I have since found that the dubbing I did to the DVD+RW was the high speed dubbing. If I use real time dubbing, those erased frames on the original do not appear on the copy.

    I wonder if the HDD edit is frame accurate but "masks off" a few frames that lie either side of the edit point? Somehow the masking effect is lost in the high speed dubbing process. It might be the equivalent of an overlapping tape splice.

    When I have edited sound samples on an Akai sampler and looped them to play by a MIDI keyboard, the loop can give a nasty glitch at the edit point. On DVD, it sounds like an auto mute is put on the sound output to cut out what could otherwise be a nasty "bump" which can be unpleasant on the ears and life threatening to cheap and flimsy speakers.
     
  8. musukebba

    musukebba
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    Your observations on the differential accuracy of edits between high-speed and real-time are interesting. I haven't seen that before.
     
  9. Chris at Home

    Chris at Home
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    As a matter of curiosity, if I have not made a terrible mistake, I assume both DVD plus and minus have MPEG frames of the "I", "P", and "B" type. Why does the hard drive and the DVD minus (VR) have frame accurate edits, but DVD plus does not?

    Furthermore, if I do get a DVD writer for my PC (£46 to £61, so I have heard), what software would you recommend to act as an editing station? I am not that wealthy, so I don't want to pay more for the editing kit that the DVD writer!
     
  10. musukebba

    musukebba
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    Chris,

    The general editing functions differ on your machine because of the limited implementation of +VR by Sony. There are also limitations on the accuracy of editing which are consequent on the nature of the +VR format itself, on standalone machines.

    It depends on what you want the end result to be. If you are happy with frame accurate editing and the menus that the Sony provides then you don't need to spend any more money. Just get acquainted with the <minus> domain on your recorder. You already have the ability to edit titles and archive combinations of these to DVD on the machine.

    If you want to stick with the <plus> format, or want to be more creative with menus, or are just curious about PC editing out of the limitations of ANY domain, then there are a couple of options:

    1. Combining titles from different DVDRWs without internal editing: Use DVD Shrink (freeware) to select titles from discs and combine on a new DVD (requires DVD Decrypter (freeware) for burning).

    2. Editing individual titles, with frame-accurate editing (also including ability for combining titles): Use DVD Decrypter (freeware) to extract MPEG2 content from DVD, then Womble MPEG2VCR (~£35; one month free trial) for editing out adverts etc, followed by authoring and burning to DVD using Ulead DVD Movie Factory 3 Disc Creator (one month free trial - albeit with limited audio support) full version currently on special offer of £22.

    For a guide to the latter process, which I use day-in, day-out, see here...
     
  11. Helen M

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    Hi Chris and Musukebba

    I bought a Sony HX 900 a month ago and find your posts interesting and informative. I've edited a couple of things on the HDD but found difficulty in getting the very first frame removed.

    Helen
     
  12. musukebba

    musukebba
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    Hi Helen - that's strange; normally subtractive edit points are inclusive of the particular frame they are marked on. Maybe over to you on this one, Chris?
     
  13. Chris at Home

    Chris at Home
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    Chris says:

    The user manual does not make it that clear but I discovered how to eliminate the first frame.

    Rewind to the beginning of A-B edit. What you think is the first frame is actually the start point before the first frame and you can't select that point. Likewise, what you assume to be the last frame is the end point, and you can't select that.

    What you do is start the title in A-B edit mode, pause, then use the |<< button to get to the first frame. Next, set point "A" and roll on to where you want to set point "B". Normally, you would only be able to delete a minimum of 50 frames (2 seconds) but when the first or last frames are included in an A-B edit, you may drop below the minimum of 50 for some reason. To delete the first or last frame only, do as above, but when you set point "A" press the enter button twice. This sets point "B" on the same frame, and you press the enter button again when the screen prompt appears.

    It would be a brill idea if Sony had put a frame counter on the hr/min/sec display and than you would know where the first frame was. Recently, a Kellogg's All Bran advert has been shown. It features a clapper board with the frame counter illuminated. Copy it on to a DVD and back on to the hard drive several times. It can be used for frame editing practice.

    Have fun.

    Chris.
     
  14. Chris at Home

    Chris at Home
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    I said:

    Whoops! I think the last frame does become the end point. I may have confused it with a +RW or -RW (VR) edit.
     

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