High-speed vs. Real-time dubbing

Discussion in 'Blu-ray & DVD Players & Recorders' started by Rebecca, Oct 23, 2004.

  1. Rebecca

    Rebecca
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    A technical question.........

    Imagine these two situations:
    1) 4-hour show recorded into the HDD, LP mode. It is high-speed dubbed to the DVD.
    2) Same 4-hour show recorded into the HDD, but now SP mode. In order to be dubbed to DVD, it needs to be re-encoded (is that the word?), and then it is sent in real-time speed.

    Being clear that situation 2 will take more time than 1, would there be any difference in the final quality?
    I mean both will be LP at the end, but would re-encoding make quality worse than recording LP from the beginning?

    Kisses.
    Rebecca. ;)
     
  2. bobcar

    bobcar
    Active Member

    Joined:
    Oct 3, 2004
    Messages:
    708
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +21
    In theory there would be, but in practice SP is so much better than LP mode that I doubt you'd see any difference.
     
  3. sweat100

    sweat100
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I think there is a least a bit. This is because, SP is still not good enough, u see some blocks also. If you really want real time dub, i suggest u record in XP then re-dub to LP. More over doing a re-dub might increase the chances of lip sync problem.

    It is still the best to record in LP. Then high speed dub.
     
  4. tdale

    tdale
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    At the end of the day, you will get 4 hours on a DVD, so any re-encoding will have an adverse effect, as compared to doing it once woth LP.

    But I have another inteersting question, see next post on this topic
     
  5. tdale

    tdale
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I have been converting my daughters movies (Internet downloads, shhhh) to DVD. After some testing, I used LP for Pixar movies, EP for cartoon movies, and FR 180 for "movie" movies (real movies). This allowed 3 Pixar movies on a DVD, 6 hours of cartoon movies, and 2 "real" movies on a DVD.

    But I accidentally added an FR record to a dublist with the some LP records. When I realised this, I expected an error, as to high speed dub, you need to have titles that already fit to a DVD, and that all titles are recorded at the same rate. but, it worked a s high speed dub. Unfortunately I deleted the titles, Bit I am sure I checked the properties as to the record mode.

    This brings me to my key question. The manual says that FR will record to precisely fit a DVD, so my FR 180, is essentially a 3 hour mode. But I have read posts here that say that if it cant fit say 2 hour mode, it will drop back to the next mode, which is LP for example. I do recall thinking that soem titles I recorded used less megs than I expected. Its a pity I dont still have those records, as I am more up tp speed with the FR thing now, but any comments, Id like to hear.

    I notice that FR records ususally use 4100Mb, I assume this was to cater for the maximum titiles and chapters, if used. But I dubded some the other night, some cartoon movies ans shorter titles, and I had 4400Mb available as per the dubbing section. Again, can anyone offer any useful info on this? Id liek to be able to maximise the megs
     
  6. Rasczak

    Rasczak
    Distinguished Member

    Joined:
    Apr 3, 2002
    Messages:
    21,700
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Warwick
    Ratings:
    +2,578
    You should record in LP onto the HDD and then high speed dub to DVD-R. Your recording is then first generation and will not suffer unnecessary artifacts.

    Whilst re-encoding does still give very impressive results there will be a (slight) quality drop. And the drop is more significant if you go from an XP/SP original to LP/EP dub as the change of resolution tends to introduce extra artifacts.

    All that said really for archiving you should use Flexible Record (unless your films are exactly four hours in length). For example say you wanted to archive two films onto a single DVD-R. The first film is 118mins, the second 100mins. You set Flexible Record setting for 218mins (3hrs 38mins) and record each film. You edit as required and then dub the two to DVD-R completely filling the disk. Although this may seem only a marginal difference you will notice on scenes such as heavy rain, falling snow, fast action as it will allow a slightly higher data rate.
     
  7. Rasczak

    Rasczak
    Distinguished Member

    Joined:
    Apr 3, 2002
    Messages:
    21,700
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Warwick
    Ratings:
    +2,578
    tdale,

    Yes there will always be some wasted space - the amount largely depends on the Variable bitrate (including resolution changes) and also includes a margin of error. Ultimately though it's the end recording quality that matters and not the file size on the disk so I wouldn't get too stressed by all this.
     
  8. tdale

    tdale
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Tks Rasczak for your quick reply. Can you comment on the third paragraph of my post?

    Cheers from NZ
     
  9. Rebecca

    Rebecca
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I think I get your point.
    In the Toshiba, e.g., I should record both with the 2.4 rate (which is 3h 41min), and then high-speed dub then. In order to do this, I need to know the length in advance, which is no problem for archiving, but it may be a problem when recording something from TV. If the lenght was miscalculated, then re-encoding is the solution to put everything in a single DVD. Am I right?

    In the Toshiba, which rates are the limits of the different qualities? I thought that since the bit rate could be changed linearly, the quaility worsening would also be linear, but it seems there are some breaking points where the quality drops a lot.

    Kisses.
    Rebecca. ;)
     
  10. Rasczak

    Rasczak
    Distinguished Member

    Joined:
    Apr 3, 2002
    Messages:
    21,700
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Warwick
    Ratings:
    +2,578
    tdale,

    The Philips and Thompson models do this - no others! The Panasonic (or Toshiba/Pioneer etc) will adapt the bitrate precisely to fit the disk. As already stated the end recording may be a couple of hundred MBs less than you were expecting but that is just taking into account the possibility of high action scenes. It does not revert to LP mode hence the reason you see owners banging on about where the resolution drop happens to the precise minute!
     
  11. Rasczak

    Rasczak
    Distinguished Member

    Joined:
    Apr 3, 2002
    Messages:
    21,700
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Warwick
    Ratings:
    +2,578
    Rebecca,

    Yes this is correct. As You say you need to know the length of the programme your archiving. Generally you will have a reasonable idea of how long it will be - US TV series episodes are normally about 42-45mins for example - so in many situations you can use a suitable bitrate. However if you have no idea then use the highest quality setting and then re-encode.

    Do note though that if you ultimately want to archive at low resolution then you may find you get better results by using the highest bitrate setting under the resolution drop and then re-encoding.

    The 2hrs 20min (per DVD) mark is where the Toshiba drops from high resolution to low resolution.
     
  12. sweat100

    sweat100
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I noticed this problem and recently i did some trial test on the Panny recorder. I came put with a formula.
    For XP recording is around 1.12 to 1.13MB/s
    SP recording is around 0.56 to 0.57MB/s

    When you use DVD-R, the recorder recognise it as 4409mb, for DVD-RAM is 4383mb(i think).

    So after quite a number of test, i found out that for XP you can record up to 1hr and 5min and SP 2hr and 10min.

    In other words, if you use FR and varies from 1 hr to 2 hr. Every minute you increase entites you to 1/12 min of extra time.

    So, if you have a show say 1hr Xmin, where X is arbituary dependent on time of the show.

    1hr *min (to be set in recorder) + 5 min + X/12min = 1hr X min (show time)

    By substituting the appropriate X values. You can find the vaule of * to be set in the recorder FR mode. I tried this for a few times and it gives me 4300+mb.

    I only tired this is the range of 1 hr to 2 hr FR modes. I believe this formula is linear. If someone can confirm it is linear, then it will work for FR 1hr--->6hr.
     
  13. OARDVD

    OARDVD
    Standard Member

    Joined:
    Jul 6, 2003
    Messages:
    241
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    16
    Location:
    Deepest Hertfordshire
    Ratings:
    +0

    I've often wondered why Panasonic’s FR algorithm doesn’t increase the bit rate towards the latter part of a recording? There must come a point near the end when, even if all subsequent scenes have high action, there would be still be enough remaining disc space to encode at a higher bit rate. This would ensure that the remaining few hundred MB are used.

    I suppose a possible obstacle to the above approach would be setting the Hybrid VBR setting to ‘fixed’. If the machine was recording at half resolution and with a bit rate that was already at the ceiling (for that resolution), then it would be prevented from increasing the bit rate further because it would have to jump to full resolution (which it’s prevented from doing so by the setting).
     

Share This Page

Loading...