[Xvid-devel] bug in thread count calculation

[Michael Militzer]

Hi Lukasz,

thanks for pointing this out! I've checked in a patch based on what you
suggested.

Regards,
Michael


Quoting Lukasz Marek <lukasz.m.luki2 at gmail.com>:

> Hello,
>
> During some tests of ffmpeg encoders (it uses libxvidcore) I noticed there
> is not allocated memory in use.
> Bad line is encoder.c:466
>
> bug is in following code
>
> #ifndef HAVE_PTHREAD
>                 int t = MAX(1, create->num_threads);
> #else
>                 int t = MIN(create->num_threads, (int)
> (pEnc->mbParam.mb_height>>1)); /* at least two rows per thread */
> #endif
>
> For height <=16 pEnc->mbParam.mb_height is 1. (it is calculated earlier as
> (height +15) /16) so it produces t = 0.
> It is later used in
>
> pEnc->smpData = xvid_malloc(t*sizeof(SMPData), CACHE_LINE);
>
> Im not sure what is correct fix, but one of follows may help
>
> #ifndef HAVE_PTHREAD
>                 int t = MAX(1, create->num_threads);
> #else
>                 int t = MIN(create->num_threads, (int)
> (pEnc->mbParam.mb_height>>1)); /* at least two rows per thread */
>                 t = MAX(1, t);
> #endif
>
> or
>
> #ifndef HAVE_PTHREAD
>                 int t = MAX(1, create->num_threads);
> #else
>                 int t = MIN(create->num_threads, (int)
> (pEnc->mbParam.height>>1)); /* at least two rows per thread */
> #endif
>
> or
>
> #ifndef HAVE_PTHREAD
>                 int t = MAX(1, create->num_threads);
> #else
>                 int t = MIN(create->num_threads, (int)
> (pEnc->mbParam.mb_height>>1)); /* at least two rows per thread */
> #endif
>                 if (!t)
>                     goto xvid_err_nosmp;
>
> Regards,
> Lukasz Marek
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>