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Extend the slice filter to make it issue slice height values randomly 

choosen between 8 and 32 when the supplied parameter is the string
"random".

This is useful for testing the slice support, but it is not supposed
to be used for other purposes and this interface may change in the
future, thus it is not documented.

The randomization algorithm adopted is the standard Numerical Recipes
LCG.

Originally committed as revision 22505 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Stefano Sabatini 2010-03-13 10:41:25 +00:00
parent 14268254c8
commit ec7ab610d5
1 changed files with 22 additions and 9 deletions
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31
libavfilter/vf_slicify.c
View File

@ -29,6 +29,8 @@
typedef struct {
int h; ///< output slice height
int vshift; ///< vertical chroma subsampling shift
uint32_t lcg_state; ///< LCG state used to compute random slice height
int use_random_h; ///< enable the use of random slice height values
} SliceContext;
static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
@ -36,9 +38,13 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
SliceContext *slice = ctx->priv;
slice->h = 16;
if (args)
sscanf(args, "%d", &slice->h);
if (args) {
if (!strcmp(args, "random")) {
slice->use_random_h = 1;
} else {
sscanf(args, "%d", &slice->h);
}
}
return 0;
}
@ -48,12 +54,6 @@ static int config_props(AVFilterLink *link)
slice->vshift = av_pix_fmt_descriptors[link->format].log2_chroma_h;
/* ensure that slices play nice with chroma subsampling, and enforce
* a reasonable minimum size for the slices */
slice->h = FFMAX(8, slice->h & (-1 << slice->vshift));
av_log(link->dst, AV_LOG_INFO, "h:%d\n", slice->h);
return 0;
}
@ -65,6 +65,19 @@ static AVFilterPicRef *get_video_buffer(AVFilterLink *link, int perms,
static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
{
SliceContext *slice = link->dst->priv;
if (slice->use_random_h) {
slice->lcg_state = slice->lcg_state * 1664525 + 1013904223;
slice->h = 8 + (uint64_t)slice->lcg_state * 25 / UINT32_MAX;
}
/* ensure that slices play nice with chroma subsampling, and enforce
* a reasonable minimum size for the slices */
slice->h = FFMAX(8, slice->h & (-1 << slice->vshift));
av_log(link->dst, AV_LOG_DEBUG, "h:%d\n", slice->h);
avfilter_start_frame(link->dst->outputs[0], picref);
}