macProVideo.com
Forums
  • Popykua
    Posts: 13
    Joined: Jun 2nd, 2008, 09:09
    General Digital Video fps Question
    Hi, I know that film has a frame rate of 24fps, video a plethora of others like 25fps, 30fps 23.98fps etc. I'm just wondering when it comes to digital video i.e. video stored on a computer like a quicktime movie, how does the frame rate work. I know digital video works more on a data rate, for ex: HDV 1080i runs at 3.2 MB/s but how does the frame rate in digital video work. Sometimes in quicktime I see framerates of 15fps, 8fps etc. I ask this question in perspective of a audio guy who gets a digitized version of a film to work on. So if the movie was shot on film(24fps) and the digitized video is 25fps or 23.98fps, won't there be a problem when the final audio mix is put back to film? I know there is some 'telecine' process here but I'm not sure about the whole thing. Hope this wasn't too confusing
    Reply
  • Hisham
    Posts: 70
    Joined: Nov 6th, 2006, 03:47
    Re: General Digital Video fps Question
    okay, you are mixing different things together. First there is a framerate, which is how MANY frame are within one second. Then there is the transfer rate, this is how FAST data is being transmitted/transfered. With respect to sound, sound is recorded either with video generally @48kHz with a bit depth of 12 or 16 bit. If you are designing the sound separately, for example in Soundtrack Pro, you will add sound elements within and create a mix down. Hope this clarifies a little.
    Reply
  • Popykua
    Posts: 13
    Joined: Jun 2nd, 2008, 09:09
    Re: General Digital Video fps Question
    Hi Hisham, Thanks for the reply. I just want to know how frame rate plays a role in Digitized video? I have seen a few quicktime videos with frame rates of 9fps 14fps etc. but they still look fine and playback fine. So I'm wondering if the whole system of framerates that relate to film and video, relate to digital video at all. If not how is it different from standard framerates? How is the whole data rate/transfer rate related to frame rate? is it at all?
    Reply
  • Cajypiu
    Posts: 400
    Joined: Oct 11th, 2006, 09:48
    Re: General Digital Video fps Ques...
    Hi Rishabh, digital video still has to conform to the same frame rate standards as analog, i.e. 24 for film, 25 for PAL and 30 for NTSC. There are drop frame rates as well, 23.97, 29.97 etc... but basically, if you have been handed a digital video, you will need to find out the movie's properties in order to score/ add sound effects to it properly. For example, Logic enables you to choose the video properties that you will be working on in the project settings and under synchronisation (see below) [img]http://img257.imageshack.us/img257/3381/syncprop.png[/img] The lower frame rates that you have seen are to do with compression. When you want to make the physical data size of a video smaller you are faced with only a few options: 1. Make the resolution of the file smaller (1080 would be a full size example, and this can be down sized to 720. Less pixels, less data 2. A compression algorithm can be used to approximate the picture quality with respect to colour, gradients etc. Think of digital still pictures and the difference between the formats RAW and JPEG. 3. You can reduce the number of frames the video uses to represent the footage. DV PAL is 25 frames per second. This can be downsampled to 15 (but still played back as if it were 25. The picture does not speed up or slow down, instead keyframes are played for longer which makes the image less smooth and jerky. Does that help? Cheers, j
    Reply
  • Popykua
    Posts: 13
    Joined: Jun 2nd, 2008, 09:09
    Re: General Digital Video fps Ques...
    Hi J, Thanks a lot for the reply. Actually your third point answered my question. Though I was wondering, what if i have a video who's frame rate I dont know? How can I find that out? Especially if its drop or non drop because quicktime only gives the frame rate in the properties section. not if its drop or non-drop. and if i dont choose the right frame rate, i will eventually have sync issues. Thanks again
    Reply
  • Cajypiu
    Posts: 400
    Joined: Oct 11th, 2006, 09:48
    Re: General Digital Video fps Ques...
    Hi Rishabh, no worries. Basically, the movie properties and movie inspector in Quicktime pro should give you most of what you know, including frame rates, but really, whoever is supplying you with the video should tell you what you are getting! They're the ones who made the video, so they should know what they are giving you!
    Reply
You must be logged in to post a reply
Recent Threads
Recent Posts
Feedback
Course Advisor
Don't Know Where To Start?
Ask A Course Advisor
Ask Us!
Copy the link below and paste it into an email, forum, or Facebook to share this with your friends.
Make money when you share our links
Become a macProVideo.com Affiliate!
The current affiliate rate is: 50%
Classes Start Next Week!
Live 8-week Online Certification Classes for: