ffmpeg | branch: master | Gyan Doshi <ffm...@gyani.pro> | Sun Nov 17 11:20:10 2019 +0530| [1c23abc88fef0a0c8486bf0ec3594f8e2d26d83f] | committer: Gyan Doshi
avutil/eval: add function to track variable use 1)Some filters allow cross-referenced expressions e.g. x=y+10. In such cases, filters evaluate expressions multiple times for successful evaluation of all expressions. If the expression for one or more variables contains a RNG, the result may vary across evaluation leading to inconsistent values across the cross-referenced expressions. 2)A related case is circular expressions e.g. x=y+10 and y=x+10 which cannot be succesfully resolved. 3)Certain filter variables may only be applicable in specific eval modes and lead to a failure of evaluation in other modes e.g. pts is only relevant for frame eval mode. At present, there is no reliable means to identify these occurrences and thus the error messages provided are broad or inaccurate. The helper function introduced - av_expr_count_vars - allows developers to identify the use and count of variables in expressions and thus tailor the error message, allow for a graceful fallback and/or decide evaluation order. > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1c23abc88fef0a0c8486bf0ec3594f8e2d26d83f --- libavutil/eval.c | 16 ++++++++++++++++ libavutil/eval.h | 10 ++++++++++ libavutil/version.h | 4 ++-- 3 files changed, 28 insertions(+), 2 deletions(-) diff --git a/libavutil/eval.c b/libavutil/eval.c index 48832979e2..62d2ae938b 100644 --- a/libavutil/eval.c +++ b/libavutil/eval.c @@ -735,6 +735,22 @@ end: return ret; } +int av_expr_count_vars(AVExpr *e, unsigned *counter, int size) +{ + int i; + + if (!e || !counter || !size) + return AVERROR(EINVAL); + + for (i = 0; e->type != e_const && i < 3 && e->param[i]; i++) + av_expr_count_vars(e->param[i], counter, size); + + if (e->type == e_const && e->a.const_index < size) + counter[e->a.const_index]++; + + return 0; +} + double av_expr_eval(AVExpr *e, const double *const_values, void *opaque) { Parser p = { 0 }; diff --git a/libavutil/eval.h b/libavutil/eval.h index dacd22b96e..9bdb10cca2 100644 --- a/libavutil/eval.h +++ b/libavutil/eval.h @@ -86,6 +86,16 @@ int av_expr_parse(AVExpr **expr, const char *s, */ double av_expr_eval(AVExpr *e, const double *const_values, void *opaque); +/** + * Track the presence of variables and their number of occurrences in a parsed expression + * + * @param counter a zero-initialized array where the count of each variable will be stored + * @param size size of array + * @return 0 on success, a negative value indicates that no expression or array was passed + * or size was zero + */ +int av_expr_count_vars(AVExpr *e, unsigned *counter, int size); + /** * Free a parsed expression previously created with av_expr_parse(). */ diff --git a/libavutil/version.h b/libavutil/version.h index 27d663baf1..af3abf7265 100644 --- a/libavutil/version.h +++ b/libavutil/version.h @@ -79,8 +79,8 @@ */ #define LIBAVUTIL_VERSION_MAJOR 56 -#define LIBAVUTIL_VERSION_MINOR 35 -#define LIBAVUTIL_VERSION_MICRO 101 +#define LIBAVUTIL_VERSION_MINOR 36 +#define LIBAVUTIL_VERSION_MICRO 100 #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \ LIBAVUTIL_VERSION_MINOR, \ _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog To unsubscribe, visit link above, or email ffmpeg-cvslog-requ...@ffmpeg.org with subject "unsubscribe".
