-
OT. How do I work out video dimentions for web streaming?
This is a little off topic. I’m posting here because you guys know about video sizes.
I’m trying to create FLV files from PAL 16:9 footage and can’t seem to understand the dimentions.
PAL is 720×576. If I make an FLV and set the dimentions to what I think is half of that at 360×288, the aspect looks wrong. You would think it would be right wouldn’t you?
448×240 looks right and for the life of me I can’t understand why. This isn’t making any sence.
Firstly for general web viewing are half the dimensions as I’m trying to achieve above a good standard web size or should I be going smaller/larger?
-Frankie
-
6 Replies
-
It’s an odd size because you’re rendering to square pixels but you’re starting with non-square pixels.
Douglas Spotted Eagle
VASSTCertified Sony Vegas Trainer
Aerial Camera/Instructor -
> 448×240 looks right and for the life of me I can’t understand why. This isn’t making any sence.
Just to expand a bit on what Douglas said, there is something called Pixel Aspect Ratio (PAR) that must be added to the equation for it to make sense. The web uses a PAR of 1.0. This means that each pixel of the video represents one pixel on the screen. We call this “square pixels”. PAL Widescreen uses a PAR of 1.4568. This means that each pixel of video represents 1.4568 pixels on the screen. We call this “non-square” pixels.
To answer your original question “How do I work out video dimentions for web streaming?” you must multiply the horizontal dimension of the video by the PAR. For PAL Widescreen that would be 720 * 1.4568 or ~1049 making PAL Widescreen 1049×576 at PAR 1.0. If you want your web video to be half resolution you should use 524×288.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
…I work with flash 8 encoder and with NTSC AVI widescreen files (720 x 480)to make FLV files and I HAVE to encode to 873 x 480… (1.2121, which is the PAR for widescreen x 720 equals 873)… this is my new base numbers if I want smaller screens…
I think this applies for PAL so your new base screen (at least for flash encoder) to get correct aspect ratio on your FLV file will be 873 x 576 ….
works for me… hope it helps…
good luck
Enrique Orozco R.
iDEA DigitalVideoStudio -
> I think this applies for PAL so your new base screen (at least for flash encoder) to get correct aspect ratio on your FLV file will be 873 x 576 ….
No, unfortunately it does not apply for PAL. 🙁 PAL Widescreen uses a different pixel aspect ratio than NTSC (1.4568 vs 1.2121).
~jr
http://www.johnrofrano.com
http://www.vasst.com -
[John Rofrano] “To answer your original question “How do I work out video dimentions for web streaming?” you must multiply the horizontal dimension of the video by the PAR. For PAL Widescreen that would be 720 * 1.4568 or ~1049 making PAL Widescreen 1049×576 at PAR 1.0. If you want your web video to be half resolution you should use 524×288.”
Ok I understand now – Also thanks for your help everyone.
Firstly what do you mean by ‘~1049’ above?
Also
Lets say I wanted a custom size what do I do then? Lets assume I want to fit within an approximate area of a web page how would i work that one out?
I’m assuming I would have to start with a custom horizontal size, so lets say that’s 450 or something like that, how would I work out the verticle size?
–Frankie
-
> Firstly what do you mean by ‘~1049’ above?
‘~’ means approximately. 720 * 1.4568 = 1048.896. Since it’s impossible to have .896 of a pixel I rounded up to 1049.
> Lets say I wanted a custom size what do I do then? Lets assume I want to fit within an approximate area of a web page how would i work that one out?
You can render to any dimension you want but if it’s not a multiple of the original video size the video will be stretched. You might want to ensure that the space you leave on the web page maintains the aspect of the video.
> I’m assuming I would have to start with a custom horizontal size, so lets say that’s 450 or something like that, how would I work out the verticle size?
Once you have established the dimensions of your video in square pixels, the rest is just straight math:
Your original video is 1049×576 so if you want the width to be 450 you would divide that by the original width of 1049 to get the percentage of reduction and multiply the vertical dimension by that.
In other words:
(new width / old width) * old height = new height
or
(450 / 1049) * 576 = (0.4289) * 576 = 247.0464
So your new dimensions are 450×247 (see… it pays to stay awake in math class) 😉
~jr
http://www.johnrofrano.com
http://www.vasst.com
Reply to this Discussion! Login or Sign Up