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!!The 24p user primer!!

Last post 08-11-2009, 7:43 by Archer9. 6 replies.
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  •  05-26-2009, 13:40 310825

    Movie [~] !!The 24p user primer!!

    Over the years I have noticed a lot of posts that asked about 24p.  Sometimes there would be generic responses that 24p was bad which is just not true.  I am writing this guide in the hope that it answers some questions about the 24p process.

    1.  What really is 24p?  24p is not a magical filter you can shoot with to make your footage look better.  In many cases it will end up looking worse.  24p is the framerate at which the picture changes within a second of time.  Normal video uses 30 frames but they are split in half frames so in reality you are seeing 60 half frames per second.  24 is a much lower number then 60 and that is why 24p can look sort of jerky compared to video.

    2.  Why is 24p so jerky?  There are two reasons.  The first like I mentioned above is because the picture only updates 24 times per second instead of 60.  The second reason is that 24 doesn't divide very well into 60.  In order to fit 24 frames inside of 60 you have to alternate 2, 3, 2, 3, 2, 3 ect...  Since you do not see a even amount of frames displayed it can look a little funky.

    3.  Why do people use 24p?  Professionals use 24p because it is what they are used to using.  It offers a good framerate for story telling and is very universal.  The highest productions in the world use 24p while normal video is reserved to lower budget productions.  24p is the framrate of 35mm film and any crew coming from a 35mm film background is going to be familiar with 24p productions.

    4.  Why should I use 24p?  Well first of all you don't have to.  There is no golden rule that says you have to.  The choice is 100% yours and you are not dumb for using either format.  It is like the difference between painting with watercolors or oil based paint.  There is a rule of thumb that usually says if your production has a script and actors then you would usually use 24p.  If your production is real life without a script then use regular video.  Even then the choice is still up to you.  24p does offer certain technical advantages.

    1. Universal format for NTSC, PAL and film distribution.
    2. Higher picture quality per frame.
    3. Higher picture quality DVD productions.
    4. Footage is easy to mix in with 24p productions.
    5. Higher quality scaling and rotation.
    6. Faster render times for heavy graphics work such as compositing and rotoscoping.
    7. Some cameras allow you to shoot slow motion footage if you use 24p.

    5.  I don't plan on ever distributing on 35mm film should I still use 24p?  Well the choice is still yours.  DVD's and web based videos are two choices that work very well with 24p video.  In both cases because you have less frames of video each second that either means higher picture quality or a lower datarate for your video.  24p DVD's also look very good on a LCD or Plasma HD monitor.  Digital HD monitors are by nature progressive displays.  Even though a DVD is not HD it can still look very good if it is 24p.

    6.  Why can't I use 25p for PAL or 30p for NTSC or 50p/60p?  You can.  In fact 25p is one of the best formats to use if you can use it.  30p may look more natural and can be much easier to work with for people not used to progressive 24p shooting.  You do loose certain aspects such as universal distribution and faster render time.  50p/60p is also a great format to shoot with.  It can be easy for some people to use since it has the same look as regular video.

    7.  So how do I shoot 24p?  First of all you need a true 24p capable camera that can set the shutter at 48.  If a camera doesn't have this then it isn't a true 24p camera and there is no point even thinking about 24p production.  Sure you could convert regular video to 24p but there is no point at all.  Your footage will end up looking worse and you just wasted a lot of time and effort.  Once you have the proper camera you need to forget everything you ever knew about shooting video.

    1. You need to learn the process of correct shooting.  This means getting familiar with how slow or fast to pan the camera.  It takes a lot of practice and not even the best cinematographer in the world could do it the first time they tried.  Go outside and practice practice practice until you know without even thinking how to move your camera around to get the best shot.
    2. Make sure you shoot with a shutter at 48.  Some cameras may call this 180 degrees.
    3. Reduce your cameras electronic edge enhancement.  Film cameras do not have anything like that.  They just capture organic images.  The way persistence of motion works with 24p the softer the edges the smoother the motion will look.  If your subjects you shoot blend a bit more into the background their motion will look a little bit smoother.  This really helps.  A lot of digital 24p shooters including myself turn off the cameras edge enhancement or sharpness setting.  This will make your footage look a little soft but that's the way film looks.  The only reason why 35mm doesn't look as soft to use is because it has a much higher resolution then most video formats.  A proper HD camera such as the SONY EX1 with the detail turned off with still look very focused and detailed.
    4. Avoid zooms and blown out highlights.  These two are tell tale signs of cheap quality.
    5. There is no such thing as awesome footage directly out of a 35mm camera and the same will be true of any other 24p camera.  24p productions go through a complex color process to get the material to look the way it does.  Learn to shoot flat colors so you have more room to play with the color later on.
    6. Pick up a few books on working with 35mm film and cinematography.  If you can take a few classes.  Good 24p shooting is all about the framing of the shot, how you move the camera and so forth.  In order to properly shoot 24p you need to learn this stuff.

    8.  Cool.  So I shot some 24p material.  How do I work with it in Liquid?  There are three basic ways a digital camera will shoot 24p material.  Keep in mind that 24p on most digital cameras is actually 23.976/  Liquid reads this as 23.98.

    1. Native raw 24p - You just need to import it into a 24p project and you are ready to go.
    2. Soft telecined 60i - The 24p is recorded as regular 60i video but certain flags are placed in the video track so certain NLE's know how to read the video as 24p.  Liquid cannot do this so a 3rd party program is needed for this process.
    3. Hard telecined 60i - The 24p is recorded to tape as 60i with no flags.  The video to a deck, TV or NLE is basically a regular video.  You can bring this into Liquid in a normal 60i sequence and edit as 60i.  This isn't as good as true 24p editing but it can work well for cuts only projects if you cut in the right areas.  You can also use a 3rd party program to figure out how to convert this type of footage to native 24p footage.

    9.  I edited my native 24p project now what?  Now you can export to your desired format.  For the web you can go ahead and export your favorite web format using 24p presets or settings.  A 24p DVD a a bit harder from Liquid.  Liquid doesn't have true native 24p DVD support so you will have to export your video and use a 3rd party program for proper encoding and authoring of a true 24p DVD.  A true 24p DVD is different then just encoding 24p and 60i and making a DVD.  A true 24p DVD will have soft telecined flags so a progressive scan DVD player will know how to play the material as native 24p frames.  On a regular TV the material will play as 60i.


    More to come

  •  05-26-2009, 19:48 310894 in reply to 310825

    Re: !!The 24p user primer!!

    Part 2:


    10.  What sort of cameras can I use for 24p production?  There are a good number of cameras you can use.

    1. Panasonic or Canon DV cameras that support 24p shooting.  For example the Panasonic DVX100 or the Canon XL2.  These cameras do need a 3rd party program to convert the 60i recorded to tape into native 24p.  Liquid doesn't have any pulldown support for DV cameras.
    2. JVC HDV cameras.  These shoot native 24p which works very well in Liquid.
    3. Canon pro series HDV cameras.  These cameras also record in a special 24p format that works very well with Liquid.
    4. SONY HDV cameras such as the V1.  These cameras do not use any flags so to Liquid the footage will look like 60i.  You will need a 3rd party program to convert the footage to native 24p.
    5. SONY EX XDCAM based cameras.  These cameras shoot in native 24p that works very well in Liquid.  The cameras shoot in a mp4 file format that needs to be converted into a MXf file with the free Sony Clip Browser.
    6. Any HD-SDI based camera that can feed into Liquid Chrome Xe.  With Chrome Xe any camera or deck that can playback native 24p can feed it into the system and capture as 24p.

    11.  How can I view my 24p project on my TV?  For proper live output you will need Liquid Chrome Xe.  This will output your 24p project as you edit to your HDTV or SDTV.  If you do not have Chrome Xe you can use a second computer monitor to view full screen video.  This works very well for progressive video and in many cases will be just as good as a SDI output.

    12.  I noticed rendered effects can look a bit jerky.  Is this normal?  Yes actually it is.  In the real world moving objects always have a certain amount of blur called motion blur.  The faster they move the more motion blur they have.  The key to great 24p graphics is to either move things very slow or use motion blur.  Of course Liquid cannot really do motion blur on animated graphics.  This is currently one of the downsides to 24p editing in Liquid.  Although to be fair most NLE's don't use motion blur on animated graphics.  For the best quality 24p graphics you should use a program such as After Effects.  60i animation works in Liquid because there are 60 moments in time instead of 24.  This means the gap between each frame is much smaller and harder to notice.  Most high end 24p productions don't have a lot of animation anyway unless it is for a specific purpose and it is usually done in 3rd party software.  You can limit yourself to subtle movements or still graphics and you will be fine.

    13.  Are there any tricks to be able to use the Pro BOB for 24p editing?  Well there are two options although they are sort of workarounds.

    1. You can convert your native 24p video into 30p by doing a time shift.  This means each frame is a solid frame but the audio is sped up.  You can edit this way and during your final output the video can be shifted back to 24p.  This can be a funky way to edit but it can sometimes work well for short productions such as music videos.
    2. You can also create a blank 60i sequence in Liquid.  When you want to view your 24p sequence through the BOB you can drop the 24p sequence into the 60i sequence and you will be able to output the video.  Liquid will do a dummy pulldown process where it duplicates every fourth frame so it will not look perfect but can work well in a pinch.

    14.  What codecs in Liquid work well for 24p?  You pretty much have 3 options.

    1. Uncompressed AVI.  This format is as good as it gets in terms of quality.  You can't get any better 8 bit format.  The files are huge however.
    2. mpeg2.  This is the normal HDV setting in Liquid.  This codec doesn't care what framerate you use.
    3. One of my special Liquid mpeg2 codecs.  This offer a few extra presets that work well for high quality rendering and export.

    15.  How can I use a Blackmagic Decklink product for 24p production with Liquid?  There are two ways to best use these products with Liquid.

    1. capture as mjpeg.  The video will be captured as 60i if you use component or HDMI.  HD-SDI gives you the option of capturing as native 24p if you footage and deck support it.  If you capture as 60i you will need a 3rd party program to remove the pulldown to convert to a new 24p mjpeg AVI file.  Liquid will work with the Blackmagic flavor of mjpeg files but you have to install the card and drivers first and then install Liquid.
    2. Capture as uncompressed.  The same rules apply as above except the quality will be a bit better.  Liquid doesn't work with the uncompressed Blackmagic file formats so your converted format will have to be either mjpeg or mpeg2.  If possible try to convert to a I frame only mpeg2 format that matches one of my codec presets.
  •  05-27-2009, 12:02 311103 in reply to 310825

    Re: !!The 24p user primer!!

    Great post, thanks!!!
  •  07-15-2009, 5:50 322685 in reply to 311103

    Re: !!The 24p user primer!!

    Thanks again



  •  07-31-2009, 10:18 326549 in reply to 322685

    Re: !!The 24p user primer!!

    Is there a single consumer videocam that captures in real 24p?  Don't they all employ 60i, which gets telecined to crypto 24p, probably with some motion corruption?  If I upload a 60i or 30p video to Vimeo or YT, does it get converted to 24p by some similar means?

    Do Hollywood productions based on digital cameras use 24p at any step at all, prior to final rendering to celluloid?  Is any broadcast or cable HDTV in 24p?  Even when one sees a broadcast or cable transmission of a film, no matter what the playback protocol of the file or disc, might what gets transmitted or what one sees actually be 30p or 60i?  Might the only real way to see authentic 24p be to put an old 35mm reel on a projector and flip it on?  Or isn't even 24p film presented in post 1950s projectors in a manner that, using analogue triple-shutter tools, mimics 60i?

    Can the 60p video shot by the Sanyo, Panasonic, or Kodak devices, which I understand is a digital interpolation of 30p that yields a "subjective" 60p, be conveyed to any edit file output or disc image that retains the 60p smoothness?  Could the 60p effect be created in the NLE with ordinary 30p or even 60i video? 

  •  07-31-2009, 12:40 326586 in reply to 326549

    Re: !!The 24p user primer!!

    Yes the new Canon HV40 records to native 24F which is Canon's form of 24p.  It is exactly 24p but they like to call it 24F which is a by product name from their Canon Pro series cameras that used 24F.  In those pro cameras they had to call it 24F and not 24p because the chips were not native progressive.  On the HV40 however the video is native progressive.  The next step up that I know of is the JVC HM100 which is their new small HD camera that uses the same recording formats as the SONY EX1 camera.

    Yes it is true that most HD broadcast is 24p sitting inside of a 60i broadcast.  That doesn't mean much though unless you really wanted a perfect progressive frame.

    Keep in mind that Blu-ray can also be native 24p.  It sends true 24p to your HDTV which is then played as 24p inside of 60 progressive frames.  You can also have a native 24p DVD which in effect can do the same thing if you have a progressive scan DVD player.

    24p playback is a bummer is NTSC based countries but it is something most of us are used to.  I would love to have a more even format such as 30p but that can cause a lot of problems.  If film were to change to 30p what are PAL based countries going to do?  It wouldn't make any sense at all for Europe to shoot their movies at 30p when their TV system if 50i/p.  I know there are ways to convert the framerates but they are far from perfect  and that would leave one large group of movie watchers left with inferior quality just to make movies easier to shoot for those who are not cinematographers.

    I can tell you from first hand experience that when we shoot with HDCAM or RED we are shooting raw native 24p with no funny business.  In fact we stream live events in HD at a native 24p over the internet.  All digital cinema is in fact shot at native 24p solid frames, edited as 24p, polished in 24p and output as 24p.  It never enters 60i until the movie is broadcast on TV.  Most digital cinema producers will never touch a single 60i in their life except for their own home movies.

  •  08-11-2009, 7:43 328996 in reply to 326586

    Re: !!The 24p user primer!!

    This is great info. Some of these things I have wondered about for some time now. Thanks for posting.

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