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Old 11th October 2019, 04:59   #41  |  Link
manolito
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Join Date: Sep 2003
Location: Berlin, Germany
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The reason for reducing the max bitrate and also the max average bitrate is that the FFmpeg MPEG2 encoder still has a lousy rate control. Overshooting the specified max bitrate is very common (even the very old and deprecated QuEnc which is also based on libavcodec had this overshooting), and this can cause errors when multiplexing and authoring the encoded stream. You can check such a high bitrate encode by authoring it with MuxMan. If MuxMan does not choke on it then you are fine, but if it does choke then you should reencode the source with a lower bitrate and/or a different quant matrix.

Other MPEG2 encoders like CCE, HCenc or ProCoder do also overshoot, but to a much lesser degree than FFmpeg. Also these encoders seem to have a better VBV buffer control than FFmpeg so you only get muxing and authoring errors very rarely.
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