3 Replies Latest reply on May 2, 2009 8:09 AM by Paul_LS

    what affects file size/quality


      I have several questions, I'll try to stay organized..


      I was told by my streaming video host to reduce my flash video files to 15 frames per second because it wasn't noticable and it would cut the file size in half. But when I do this, the file size is the same.  When I'm editing the export to flash profile, it seems the bitrate setting is all that will change the file size, not frame width/height or frames per second.   It seems to me that by cutting the number of frames in the video in half, the file size should, as they suggest, also cut in half.  Is premiere using less compression on the remaining frames to give it a better quality since the profile bitrate still let's the video go to the same preset bitrate?  I'm trying to figure out what I can do to give me good quality but keep file sizes small.  I encode my videos to 640x480 because I like to have my videos big, but my new service will only stream at 320x240, but the player does have a full screen option and they did suggest that I could keep encoding to 640x480 and that would still help the full screen performance. I hope I'm getting my thoughts across clearly enough..thanks

        • 1. Re: what affects file size/quality
          Paul_LS Level 4

          Your file size is being governed by the bit rate that you have set, reducing the frame rate will not reduce the file size. Reducing the number of frames per second means the recording can contain less information and therefore will be smaller, however because the file size is governed by the bit rate the encoder will use more bits per frame.

          So, you could try reducing the frame rate and bit rate. I would try different settings until you are happy with the quality. Also note that reducing the frame rate will make fast on-screen motion less smooth.

          • 2. Re: what affects file size/quality
            unc417 Level 1

            That all makes sense. But in my head, something else must be happening when I lower the frame/sec.  I'm envisioning this to be a kind of balancing act, I reduced one thing, it must be raising something else to keep the actual bitrate the same. Or am I just way out of the ballpark here?


            Do you have a preference of what you use?  Right now I'm using the flash8 400k profile, but I changed the size to 640x480.  Does that lower the quality any by doubling the frame size?


            What's the difference in the flash8 and flash7 profiles?


            As I said before, the default size for my videos is now 320x240 but I still want it to look decent when enlarged to full screen.

            • 3. Re: what affects file size/quality
              Paul_LS Level 4

              You are correct, and as I mentioned, as the frame rate is reduced and as you are getting the same file size PE7 is using more bits per frame so the quality will be increased. Likewise with frame size, if you maintain the bitrate constant and increase the frame size the quality will reduce.


              I cant really help you with the flash options as I do not use it I am afraid.