warning, clipping 1 dct coefficients to -127..127 ??

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warning, clipping 1 dct coefficients to -127..127 ??

Joel Ben M
Hi everyone,

I'm encoding a video (following output_example.c), and for every frame I get
the message [msmpeg4v2 @ 68B292E0]warning, clipping 1 dct coefficients to
-127..127

What is it? how can I get rid of it?

thanks so much for _any_ idea,
Joel
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Re: warning, clipping 1 dct coefficients to -127..127 ??

Rich Felker
On Wed, Jan 09, 2008 at 12:02:34AM -0500, Joel Ben M wrote:
> Hi everyone,
>
> I'm encoding a video (following output_example.c), and for every frame I get
> the message [msmpeg4v2 @ 68B292E0]warning, clipping 1 dct coefficients to
> -127..127
>
> What is it? how can I get rid of it?
>
> thanks so much for _any_ idea,

It happens if the qscale is too low, especially 1 but also sometimes
with q=2. Better codecs like true mpeg4 have ways to deal with the
overflows (e.g. adaptive quantization raising the q for individual
macroblocks) but for msmpeg4 (aka divx3) you either need to accept the
overflows and the glitches that come with them or else use qmin=3.

Rich
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