Re-encoding, much difference?

Discussion in 'Blu-ray & DVD Players & Recorders' started by tdale, Sep 18, 2004.

  1. tdale

    tdale
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    If I record a movie at XP mode on my E85, then I decide that I do now want to preserve that onto DVD, I will need to dub at normal speed using FR or SP mode. AS that will entail a re-encode from XP to FR or SP, will that end result be noticeably different than if I recorded once using FR or SP mode to DVD?
     
  2. nwgarratt

    nwgarratt
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    I do this all the time.

    With the FR mode, it will probably look bettr than using FR straight to the DVD. This is because the DVD gets filled up completely by the edited recording.

    If you record onto DVD using FR then edit, you will end up with some unused space.

    The SP mode will probably look the same.
     
  3. OARDVD

    OARDVD
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    Providing you first record in XP then personally I find that dubbing it to DVD doesn’t result in a significant loss of quality when compared with recording directly to the DVD in the equivalent mode. The reason is that XP uses full D1 resolution and has an average bitrate of 9.8Mbps, the maximum for the DVD video standard. However, as you say, there is an additional encode so YMMV. Why not try it yourself and see? Use the same source for both though.

    However, if circumstances allow, it’s often preferable to record to the HDD in FR mode then High Speed dub to DVD with no loss of quality. Basically you have to consider beforehand what your requirements are which will help you to decide between:

    Recording in FR mode to the HDD then high speed dubbing with no loss of quality to DVD-R

    OR

    Recording to HDD in full D1 resolution & a reasonably high bitrate (ie. XP/SP). You then may want to real-time dub to DVD-R in FR mode or alternatively you can split across several DVDs using High Speed mode.

    In general for the E85/95, if you want the best quality on the DVD-R then follow these rules:

    A) If you require a lot of editing, then it usually doesn’t make sense to record to the HDD in FR as you won’t be maximising the usage of space. So instead, record to HDD in XP or SP. These two modes always use full DVD resolution, D1, as long as ‘Hybrid VBR resolution’ is set to ‘fixed’. After you have edited the material then:

    1) If the running time of the edited video is less-than-or-equal-to 1hr in XP, or 2 hours in SP, then High Speed dub to DVD-R. This will preserve D1 resolution. Note that you have to have ‘DVD-R Rec for High Speed mode’ set to ‘On’ before recording on the HDD otherwise you won’t be able to High Speed dub it to DVD-R later.

    2) If the running time of the edited video is greater than 1hr in XP (or 2 hours in SP) but is less than 3 hours in total, then real-time dub to DVD-R using FR mode. This will also result in D1 resolution. However, it will undergo an additional encode process compared with A) section 1) above and the resulting video will not be quite as good but it shouldn't be bad.

    3) If the running time of the edited video is 3 hours or greater then dubbing it in real-time using FR will result in half D1 resolution at best. That is because the E85/95 can do full D1 resolution in FR mode up to around 3 hours. However, just above this it drops to half D1 resolution. Again, even if the resulting video is only just over 3 hours long it will not be quite as good as in A) section 1). If it's considerably longer than 3 hours it will look considerably worse. So alternatively, you may want to consider splitting it and then High Speed dubbing the parts to several DVDs. This will also preserve D1 resolution and produce a result equal to that in A) section 1).


    B) If you want to perform minimal or no editing then:

    1) If your recording is going to be about 3 hours or greater then record to HDD in XP or SP and follow the information in A) section 3) above.

    2) If the total recording time of the programme before edits is less than 3 hours, then record on the HDD in FR mode. Perform any required editing. Then high speed dub with no loss of quality to DVD-R. This will keep D1 resolution and maximise the usage of space on the DVD. Note that you have to have ‘DVD-R Rec for High Speed mode’ set to ‘On’ before recording on the HDD otherwise you won’t be able to High Speed dub it to DVD-R later.

    These “rules” should be taken as being very general since people have different perceptions & opinions. Also, video recorded in half D1 may not always appear significantly worse then full D1 since bitrate plays a large part as well as resolution. Indeed the relationship between bitrate & resolution as used in the encoders is complex and the downshift in picture quality going from slightly less than 3 hours to slightly over 3 hours is not as significant as might be thought. For example an average bitrate of only 5.1 may be pushing full D1 resolution to the limit whereas dropping to 4.9 may be generous for half D1.

    Note that other recorders, even older Panasonics, have different MPEG encoders and consequently have differing D1 to D2 cut-off points. Some brands of recorder don’t even do FR mode in the first place. See Rasczak's post on page 2 of this thread: http://www.avforums.com/frame.html?http://www.avforums.com/forums/showthread.php?t=150637
     
  4. tdale

    tdale
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    Thanks for that very useful info OARDVD, and the time you spent typing it.
    Much appreciated

    Tony
    New Zealand
     

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