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Copying Mpeg2 from HD > DVD on HD/DVD/Freeview Recorder

Discussion in 'Blu-ray & DVD Players & Recorders' started by Vic_B, Aug 24, 2005.

  1. Vic_B

    Vic_B
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    Hi all, I'm currently using a USB box connected to my PC to record Freeview. I can get exact, bit for bit copies of these recordings onto dvd either by burning the raw mpeg2's straight to dvd (which my player plays fine), or by using software such as mpeg2schnitt to chop out ads and IfoEdit to create the vob's.

    I was chatting to a friend about the upcoming integrated HD/DVD/Freeview recorders and assumed you'd be able to do the same on these, i.e. record the bitstream of the broadcast onto the HD and then archive that, bit for bit, onto the DVD. He told me that wouldn't be possible as the recorded mpeg2 would have to undergo some form of conversion/recompression to make it DVD compatible. Is that the case? If so, would it not be possible for manufacturers to include software along the lines of mpeg2schnitt to allow DVD conversion to occur without any loss of quality? Is the PC route still the only way to archive exact copies to DVD?

    Cheers,
    Victor
     
  2. Rasczak

    Rasczak
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    That is indeed the case: MPEG2 for DVB contains extra information that is not found in MPEG2 for DVD. It can also use non-standard GOP sizes.

    The process you have gone through - and likewise to those who have used PVAStrum and Project X - has not created a DVD compatible project. Whilst your DVD player - and many others - will play it fine there are loads that won't. High end players especially - such as the majority of Denon units - will not play the disc back without audio displacement including stretched audio!

    As for better picture quality? I did nearly 1000 frame by frame, scene by scene comparisons between a Sony GXD500 (which uses a 2pass all digital re-encoding process) and the raw data captured from a Topfield 5800 -the former won on every count presumably due to the Sony processing and smoothing the picture as well as converting to true DVD-Video standard. Subsequent comparison to the Panasonic DMR-ES20D yielded similar/better results.

    Having spent hours investigating this, and having spent many £1000s trying to get the best recorded picture from Freeview onto DVD, is that the Panasonic DMR-ES20D in XP mode is the best there is at present.
     
  3. GarryL

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    Hi Rasczak

    You seem to have spent a lot of time and effort on this and you clearly know an awful lot about the subject. However, I'm curious about some of this.

    My understanding is that PVAStrumento (and, although I've not used it, I believe also Project X) convert the broadcast transport stream into a program stream. This is not yet DVD-compliant - you have to author it using a program like the excellent TMPGEnc DVD Author. At this point you would, in most cases, have a DVD compatible project which you can burn.

    I write "in most cases" because there are some transport streams that PVAstrumento cannot convert or converts badly. As you mention this can because the GOPs contain too many frames, although my vague impression is that this was maybe an experimental thing done by some of the commercial channels that isn't happening anymore. PVAstrumento warns in this case.

    Would you agree that after a successful PVAstrumento run with no warnings, and a successful TMPGEnc DVD Author run, the files are then DVD compliant, or is there something I have missed?

    This doesn't *necessarily* mean the disc is not DVD compatible. It could be the fault of the player, the original broadcast, or the recorded disc could be hard to read. I tend to agree though that in some cases the conversion software is to blame and although it seems to happen the more cuts that PVAStumento has to make, I'm not entirely sure why.

    I can't argue with your subjective impression. However, it's worth mentioning that actually there is more information present in the original broadcast transport stream as preserved by the Topfield. The Panasonic and Sony will both have lost information in the extra conversions that they do. Some other possibilities to explain the subjective better quality of the lossy recording are:

    1. The machines play their own discs better than discs recorded on a PC. Maybe this doesn't apply to the comparisons you did - it depends how you did them.

    2. The extra processing emphasizes pleasing details that were quite subtle in the original. In much the same way that a radio station with a compressed dynamic range such as Radio 1 can sound better than an original recording in some environments. Or that the overly saturated pictures taken by some cameras such as Fujis can seem better than the more accurate pictures produced by say a Nikon or a Canon.

    If it really is true that it is impossible - or even just extremely difficult - to avoid a full MPEG decompression/compression cycle when saving a broadcast MPEG-2 transport stream to a fully compliant MPEG-2 DVD all I can say is I think whichever body came up with the broadcast specification has not done a very good job for consumers.

    Kind regards

    - GarryL
     

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