computer verses digital video recorder

Discussion in 'Amateur Video Production' started by Brian, Jun 12, 2013.

  1. Brian

    Brian Guest

    What I don't understand is this.
    I can record a video on the hard drive of my DVR (digital video recorder)
    in real time. I cut out bits of the recording so it I can fit 2 hours of
    the video on a DVD disc. It takes about 8 minutes to transfer the video
    from the DVR hard drive to a blank DVD-R disc loaded in the DVR. It then
    takes about 1 minute to finalize the recording so I can play the DVD video
    on any DVD player. It also has a menu added to it.
    When I try to do the same on my computer it take a long time to process. I
    can record it to the hard drive in real time so it becomes a Mpeg 2 file. I
    then can put it in a video editor and remove parts of the recording but
    when I render it into an image suitable for a DVD it takes a long time to
    complete. It also takes a while when creating a DVD from the image. The
    same long time to process happens if I want to add a menu and create a DVD
    of the recording using a video authoring program.

    Why is the DVR faster at creating the recording than what it takes to do
    with my computer?
    Does it use a special format and if it does then why can't I use this
    format on the computer?

    To fit two hours of video I'm thinking of using a variable video bit rate
    of max 6 Mbps and an average of 4 Mbps on the computer. I'm not certain if
    this is correct. The source for the video is from recordings on VHS tape.
    The recording in real time is 6 Mbps in Mpeg 2 with a 4:3 ratio.

    I could use my DVR but I'm looking at other ways of recording video as some
    files may be better left as a file and not been made a DVD video. Also as
    may DVR may wear out of break down it does not seem possible to get a
    replacement as DVR's are hard to find. Also any recording to the DVR from
    VHS always play back in 16:9 ratio even when the VHS recording is in 4:3.
     
    Brian, Jun 12, 2013
    #1
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  2. Brian

    Gavino Guest

    Your video editor is probably re-encoding the whole video rather than simply cutting
    out the unwanted bits and copying the remaining parts unchanged (which is what the DVR
    does). See if your editor supports a feature normally called 'smart rendering' to
    avoid this.

    A dedicated MPEG-2 editor might be a good idea if you do a lot of this, eg one of the
    Womble products MPEG Video Wizard or MPEG-VCR:
    http://www.womble.com/products/index.html
    http://www.womble.com/products/vcr.html
    or VideoRedo Plus:
    http://www.videoredo.com/en/index.htm

    Note however that, as the DVR uses a constant bitrate, if you want to save the edited
    output as variable bitrate (to save space) then you will inevitably have to re-encode
    everything (which is a lot slower).
    There is probably a setting on your DVR or your TV to change this.
     
    Gavino, Jun 12, 2013
    #2
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  3. Brian

    Brian Guest

    Thanks Gavino for your help. I was hoping that someone would reply to my
    problem.
    I'll take a look at the sites you've included in your post.
    I have a lot of video tapes so I'm trying to reduce the time it takes to
    save wanted parts on the tape.
    I'll try using a contact video rate to save time.
    I was hoping that I could cut out the unwanted parts using DVD Architect
    and produce a DVD with a menu but it does not look like I can do simple
    editing in this program. So I'll check out some of the program you have
    suggested.

    I could't find any setting in the DVR to show the recording in 4:3 but
    there is a screen setting on the TV the will change the picture to look
    like a 4:3 video. However all the videos including 16:9 look like a 4:3
    video so its a matter of switching the TV settings to suit the type of
    video.
     
    Brian, Jun 13, 2013
    #3
  4. Brian

    Paul Guest

    The videohelp.com site has more info as well.

    http://www.videohelp.com/tools/VideoReDo

    If you go to your search engine, and try

    site:videohelp.com smart render

    you may find other snipping tools that don't need to re-encode.

    http://forum.videohelp.com/threads/246850-Smart-Rendering-Frame-By-Frame-Editing-Software

    The video formats, have a number of frame types, arranged in
    blocks. Every once in a while, a frame will be a "reference" frame,
    and later frames are "deltas", only noting differences from the
    previous frame. When editing a video format like that, if you want
    stitchless editing, you need to edit on the borders of a block
    of frames, rather than on any random frame. If you snip at the end of
    a block, and just before the next reference, then there is no reason
    to re-encode anything. This means, you won't be able to
    edit exactly where you might want. If you pick any frame
    at random, and edit there, then that may require encoding of
    a repair (stitching some how) or complete re-encoding (i.e. if
    the software coder doesn't know how to do it any better way).

    http://en.wikipedia.org/wiki/MPEG-1#Frame.2Fpicture.2Fblock_types

    That kind of encoding technique (reference frame followed by some
    number of deltas), can also result in visual artifacts,
    as you might notice slight differences every time a reference frame
    is played. Even without editing, you might notice a pattern to
    the artifacts, that might be related to the length of the blocks.
    Bumping up the rate of reference frames, might improve video
    quality, but at the expense of data rate (or, making the video
    unplayable on certain kinds of platforms due to data rate).

    It would help if the videohelp had a way of listing all the
    smart render ones. I seem to remember they had a search engine with
    tick boxes for selection items, but I don't see that now.

    And even when a program claims to be smart about these things,
    it is up to the user to test and prove it. Some programs
    are smarter than others (i.e. some no longer live up to their
    claims).

    Paul
     
    Paul, Jun 13, 2013
    #4
  5. Brian

    Brian Guest

    Thanks Paul for the useful info.
    I don't know much about the different types of frames but it seems like a
    good time to find out more about it.
     
    Brian, Jun 14, 2013
    #5
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