why two settings for 640 x 480 and 352 x 240?

Discussion in 'DVD Video' started by Summercoolness, Jul 15, 2006.

  1. There is a question I have with the DVR and probably true for Tivo and
    Media center PCs too.

    How come we don't set the video size to 640 x 480 and then just use
    whatever bitrate to control the recording time?

    For example, use 640 x 480, but if we want to record 4 hours, use a
    lower bit rate.

    Instead, it is first "forced" into 352 x 240, and then use a lower bit
    rate. If the compression algorithm could , wouldn't it take care of
    compression automatically?

    I always wonder if Mpeg1 at 352 x 240 is quite clear with 600MB and is
    for 1 hour of video, then for Mpeg2, the size quadruple, and it is 2GB
    for an hour... so the improvement from Mpeg1 to Mpeg2 isn't so big as
    from Mpeg2 to Mpeg4? It seems that for Mpeg4, only 500MB is needed
    for 1 hour of 640 x 480 video.
    Summercoolness, Jul 15, 2006
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