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*Frame* Rate vs. *Refresh* Rate

Discussion in 'Electronic Basics' started by Radium, Jul 6, 2007.

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  1. Radium

    Radium Guest

    Hi:

    What is the difference between "frame rate" and "refresh rate"?

    Is it best for the frame rate to have a frequency the same as the
    power supply [60 Hz in USA/Canada, 50 Hz in Europe/Asia]? Is this true
    even if the video is digital and played through a digital plasma
    screen?

    In digital video, how is the sample rate mathematically related to the
    frame rate?

    In digital video, how is the sample rate mathematically related to the
    refresh rate?


    Thanks,

    Radium
     
  2. I am not aware that they are related in any way.

    The highest frame rate of any DSLRs that I am aware of is 10 frames per
    second on high-end Canon SRLs. According to Ct (which in turn cited sources
    in Canon corporation) this frame rate is artificially lowered because at
    many venues a higher fps rate is considered filming and the fees are
    significantly higher than for photography.

    On the other hand the only refresh rate that comes to my mind would be the
    time until a flash can fire again.
    Huuu? Where do you find a DSLR with a frame rate of 60 fps? That's nuts.
    Huuuu? What does digital video have to do with SLR cameras?

    jue
     
  3. Guest


    That's really interesting... because I have a Canon Powershot A530,
    and the manual (which is for both the A530 and A540) mentions that the
    A540 can shoot 640x480, 30fps, and 320x240, 30fps.

    My A530 can only shoot at 20 fps at 320x240 (or 10 fps at 640x480).
    Using Nero's VCD Burning Tools, I was able to create a Video CD that
    would play on my DVD player... video was a bit jerky, though.

    Makes me wonder whether I should just get an A540 (smaller), or
    actually buy a digital camcorder next time...

     
  4. Alan

    Alan Guest

    One is how fast information frames come, one is how fast the screen is
    refreshed.

    Not really. It helps in reducing the visibility of hum bars if all three
    are the same, but power supplies are way better now, so that is of little
    import.

    Yes, it is unimportant even if the video is digital and shown on plasma.

    By an integer multiple.
    What makes you think it is?

    Alan
     
  5. Well, but how many professional photographers are out there using a
    Powershot for their work?

    jue
     
  6. That confused me too but look at where the question has been
    crossposted and its obvious the OP is erm... clutching at straws for
    an answer.

    Doc
     
  7. contrex

    contrex Guest

    What baffles me is how does he type wearing a straitjacket?
     
  8. Flasherly

    Flasherly Guest

    Twice. 24 to 48 for high motion film or field rates using two stops at
    each frame. As applied interlacing, and apart from detail,
    deinterlaced line rates are accountable for a multiple again twice
    over to equal perceived smoothness.
    Depends on the digital video card capabilities and whether or not it's
    limited to the vertical sync of the monitor. A monitor maximum sync
    at 60Hz isn't going to help a card capable of rendering 100 frames a
    second, so it's a parity function while within specification limits of
    the hardware.
     
  9. Crayon in mouth. It's common practice. Apparently.

    Doc
     
  10. I see that you guys already know Radium :)
     
  11. Alan Browne

    Alan Browne Guest

    Whatever the answer I wish you had not x-posted this to a photogrpahy group.
     
  12. Stephen

    Stephen Guest

    In digital video, how is the sample rate mathematically related to the
    For PAL television the field rate is 50 Hz and the frame rate is 25 Hz. For
    NTSC television the field rate is 59.94 Hz and the frame rate is 29.97 Hz
    (or more accurately 60 times 1000/1001 and 30 times 1000/1001 respectively).

    Both PAL and NTSC use 2 to 1 interlace which means that each field contains
    only alternate horizontal scan lines. So in "625 line" PAL with 576
    horizontal active lines per frame, each field refresh contains only 288
    lines. In "525 line" NTSC with 480 horizontal active lines per frame, each
    field refresh contains only 240 lines.

    When viewed on a large scale the sample rate for the picture as a whole is
    the same as the field rate which is the same as the refresh rate, i.e. 50 Hz
    (PAL) or just under 60 Hz (NTSC). Movement is generally perceived on a large
    scale so it is seen as though it were sampled at 50 or 60 Hz.

    Fine vertical detail (i.e. detail which goes vertically across the
    horizontal scan lines) is only sampled once per frame, on alternate field
    refreshes, so this has a sample rate of only 25 or 30 Hz, and can flicker
    violently if there is too much difference in intensity between adjacent
    horizontal lines.

    Large LCD and Plasma screens use "de-interlacing" to avoid this, but this
    has drawbacks because it has to either display one field for twice it's
    original sample period (i.e. display a 1/50th second exposure for 1/25th
    second) or start doing clever things like only doing this for fine details,
    or guessing where the patterns of the image should be in the missing lines
    of each field by examining the picture details from adjacent fields and
    lines. Most large screens use the "clever" approach, but none of this
    processing can be done perfectly and it tends to introduce lag, smearing or
    exaggerate mpeg artefacts by freezing them on the screen for twice the
    length of time they would be displayed by a CRT display which is not
    de-interlaced.

    Modern large screens also have to resample the whole picture from 576 lines
    to the 768 lines of the display which inevitably reduces the resolution to
    about half of 768. This is why standard definition looks poor on an "HD
    ready" screen but looks virtually the same as 768 line HD when displayed on
    a CRT at 576 lines from an RGB Scart.

    Modern HD ready screens also use heavy edge sharpening to try and offset
    their lower-than-SD resolution when displaying standard definition, but this
    also exaggerates mpeg artefacts (erroneous detail information), which is
    another reason why these artefacts are objectionable and intrusive on HD
    ready screens, when they are barely noticeable on a CRT.

    It is an unfortunate fact that, since most TV we actually watch is still SD
    but most TV's on sale now are "HD ready" with poor SD performance, it is no
    longer possible to buy a new TV which is capable of displaying the majority
    of TV broadcasts properly. For most broadcasts we can only get proper
    pictures on "legacy" CRT TV's which have a limited lifespan and cannot be
    replaced.
     
  13. Nice to see such a clear explanation. If only the programme makers understood
    it so well.
    It's unfortunate that nobody is ever likely to see such clear HD pictures with
    such a smooth rendition of movement as the ones that were being shown at trade
    shows like IBC more than twenty years ago. The interlaced signals were derived
    from Plumbicon tube cameras, subject to control by vision engineers, and
    displayed on cathode ray tubes with no digital processing in between. For a
    while I thought it a normal symptom of the approach of old age that caused me
    to be cynical about the notion that "progress" always represents an
    improvement, but since then its even closer approach has disabused me of this.
    It seems a waste of money to keep buying ever newer, ever more elaborate and
    allegedly innovative domestic television equipment while the quality of the
    material available to show on it proceeds on its present downward spiral.

    Rod.
     
  14. Flasherly

    Flasherly Guest

    There's that feature incorporated into my brand, in their newest $2500
    offering, four or five times a magnitude I alloted, as chipset
    enhancements marketed by a name something along 'The Director's
    Chair'. Besides an entropy factor in layered encoding, which
    spuriously generate artifacts that do, generally, detract from the
    source material, the onus is then shifted into chipset algorithms, as
    best fit to be weighed to derive positive potential in marketing
    enhanced perception as an object apart from, otherwise, artifices.
    Software layering is similar to that end, and makes a nice testbed
    when dispensing with the tuner and layering a digitally enhanced
    signal directly through the computer and into the display unit.
    Although rudimentary, apart from encoding options available, there's
    nonetheless benefits. I first used software test-pattern programming
    to attempt to adjust for optimal edge sharpness, very different, being
    limited in a few set and discrete steps, from a range given to "dial
    in" sharpness from an analogue or legacy CRT. What's interesting,
    beneficial, is one of the software players, GOOM (from the ranks of
    freeware distribution), which also offers sharpness, noise, and
    smoothness filters. I've effectively then two layerings from
    sharpness, having initially adjusted the set, as well as software
    smoothness, and added noise. Noise is a textural effect, either as an
    artifice induced by color, if not b&w, which adds a sense of fine
    "grain" to substances, overall, which can be additionally set for a
    degree of greater or less magnitude, as can all three layers.
    Sharpness is foremost to my usage beneficial, although depending on
    the source material, animation for instance, the other two settings
    may be worthwhile considerations. Given refinement, I should hope on-
    the-spur filter decoding will continue to develop with more to offer.
     
  15. Ray Fischer

    Ray Fischer Guest

    In a year and a half it will be moot as there will be no more of the
    same old TV broadcasts. They will all be replaced with digital
    signals, and probably of better quality.
     

  16. I hope you don't write any technical documents.

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  17. Here's an interim solution if you have one of them new fangled HD TVs-
    may not be possible on all, but on my 4 year old Sony 60" what I do for
    NTSC broadcasts is to split screen, and size the lo rez broadcast down
    to where it's sharpest. It's about equal to the rez. I'd get on a non HD
    tv. The other screen can be tuned into something slow, such as baseball
    or golf, or Planet Earth.
     
  18. Piggy

    Piggy Guest

    Don't be wicked!....he knows his stuff.
     

  19. He still doesn't know how to make a readable post. That was just a
    mess. No paragraphs, and no white space to seperate the ideas.

    The whole idea of technical writing to to quickly and cleanly allow
    someone to read and understand what you've written.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  20. Flasherly

    Flasherly Guest

    So do you. Well, least what I've come up with so far. :;

    freeware - codecs
    ACE Mega CodecS Pack 6.03 - Professional
    Edition Media Player FilterS, Media Players (MM Classic)
    and other UtilitieS. Also I added Authoring
    ToolS for video watching, audio and video
    processing. In Add-On Pack you can found
    Authoring ToolS for content creation.

    and/or

    freeware- movie player
    GOM Player includes many codecs (XviD, DivX,
    FLV1, AC3, OGG, MP4, H263 and more) so you
    won't need to install separate codecs for
    most videos. For those videos that require a
    separate codec, GOM Player will find one and
    direct you to a place where you can download
    open source version of the codec. That way,
    you won't get stuck with unnecessary codecs
    on your system. Play Broken AVI Files
    (Patented) AVI files can't be played if the
    index is broken, or the file isn't completely
    downloaded. This is because index is located
    at the end of the file. GOM Player's patented
    technology enables users to view files with
    broken index or that are still being
    downloaded. Powerful Subtitle Support GOM
    Player supports SMI, SRT, RT, SUB(with IDX)
    files for subtitle. You can specify margin,
    location, size, resolution, font and others.
    You can also enable shadow, view ASF files
    with subtitle, karaoke subtitle mode. You can
    even synchronize subtitle and video if
    there's any mismatch. Convenient Playlist GOM
    Player supports playlist formats such as M3U,
    PLS, ASX. You can include different media
    types on a playlist. Also, it also lets you
    edit playlists for different media types.
    It's easy to create and edit your own
    multimedia playlist with GOM Player. Support
    Different Media Types Along with different
    media format such as AVI, MPG, MPEG and DAT,
    GOM Player also supports streaming Windows
    media format (WMV, ASF, ASX). You can also
    watch DVD-quality videos with 5.1 channel
    audio output. Screen Capture Screen capture
    allows you to take a screenshot of your video
    directly from GOM Player. Using the Burst
    Capture feature, you can take continuous
    screenshots upto 999 shots. Advanced Features
    There are other endless number of advanced
    features. Customize brightness, contrast and
    saturation. Sharpen and add noise to your
    video. Try audio equalizer. Repeat a section
    of your video with our A-B Repeat feature.
    Fast forward/rewind a few seconds using
    left/right keys. There are even more for you
    to discover!

    (...keyboard macro reassignment/additions, which aren't mentioned)
     
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