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Thread: dimension for high quality FLV

  1. #1
    Join Date
    Jul 2006

    dimension for high quality FLV

    I convert H264 HDV 1080i video ( I use Canon HV30camcorder) to FLV using adobe flash CS3.
    I set dimention 1280(height) 720(width) with high quality setting
    File size is 155 MB. I think this is not too big, but when I play the video on my mac computer, it is jumpy, not smooth.
    Should I setup dimention 640(height) 360(width) for smooth playback??
    But size is the same with the both video.......
    Last edited by yunakokimama; 11-23-2010 at 07:13 PM.

  2. #2
    Senior Member
    Join Date
    Sep 2010
    Not sure what you mean by "jumpy, not smooth". Do you mean that it stops playing, downloads a little more, then plays for awhile, then stops, downloads some more, etc.
    If that's the case, it's happening because the bitrate of the video is higher than your Internet connection speed allows the data to be downloaded.
    That is, for the video to play un-interupted, you need a faster Internet connection...OR lower the bitrate of the video. Currently you have a combined video/audio bitrate of 1628kbps. That is VERY HIGH for an Internet video.
    I have a 6Mb connection and I had a very hard time downloading the video... very stop and go. not pleasant at all.
    Changing the display dimensions has nothing to do with the bitrate. Depending on you video editing program, you may have the option to set a particular bitrate. For Internet video, once you get over about 1000kbps, there will be problems on less than super fast Internet connections.
    Quality of the video is tied to the bitrate and the display size of the video. So as you increase or decrease the display dimensions of a video, you can increase or decrease the bitrate to maintain the same quality.
    1280 X 720 has 4 times the number of pixels as 640 X 360 does. So as an approximation, the larger area would need 4 times the bitrate of the smaller display. or in other words, by reducing the display size to the smaller size, you could reduce the bitrate to about 1/4 of that needed for the larger display.
    So I'd suggest using a little smaller display but mainly reducing the bitrate of the video.
    Best wishes,
    Video Man

  3. #3
    Join Date
    Nov 2010
    well, by jumpy i think he means a jittery video here and there. I experienced it recently, Video man, Wherein my video jittered at times. I think it was because of the bit rate i have chosen. My video is of size 1000*517, please advice me as to what bitrate should i ideally use for the best possible output and what software i should usew. I presently use Adobe flash media encoder CS4.

    thanks in advance.

  4. #4
    Senior Member
    Join Date
    Sep 2010
    When it comes to bitrate, you really need to start with the normal Internet connection speed of your viewers and then from there, you can determine what the optimum dimensions will be.
    If you start with fixed dimensions.. then if you need a higher bitrate to produce the best quality, you may well exceed the download connection speed of your viewers. If that happens, you have to decide if your viewers would rather suffer through multiple start/stop as the video buffers or if a little less quality would be better.
    That being said, let's create sort of an approximate formula for bitrate per dimension.
    To start, lets say that a 320 x 240 video will display a good quality video at a bitrate of 350kbps.
    So 320 times 240 = 76,800 px
    1000 x 517 = 517,000 px or 517,000/76,800 times the area = 6.7 times the display area.
    So to "paint" that area would require about 6.7 times the amount of "paint". In our case, it's "data", not paint. But it would still require approximately 6.7 times the amount of data that the smaller video would, to produce the same quality.
    So 350kbps x 6.7 = 2.345Mbps. So for your video with dimensions of 1000 x 517 to have the same quality as the 320 x 240 video, you would need a bitrate of 2.345Mbps.
    This is a VERY HIGH bitrate and most viewers would have problems downloading videos with bitrates higher than 1000kbps.
    Keep in mind that this formula is just an approximation... but the math is real.
    So starting with set dimensions is a problem because you can't do anything to increase your viewers Internet connection speed.
    To improve quality at any given bitrate, reduce the display size.
    Best wishes,
    Video Man

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