@@ -76,6 +76,12 @@ In a complete filterchain all the unlabelled filter input and output

 pads must be connected. A filtergraph is considered valid if all the

 filter input and output pads of all the filterchains are connected.

+Libavfilter will automatically insert scale filters where format

+conversion is required. It is possible to specify swscale flags

+for those automatically inserted scalers by prepending

+@code{sws_flags=@var{flags};}

+to the filtergraph description.

+

 Follows a BNF description for the filtergraph syntax:

 @example

 @var{NAME}             ::= sequence of alphanumeric characters and '_'

@@ -84,7 +90,7 @@ Follows a BNF description for the filtergraph syntax:

 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)

 @var{FILTER}           ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]

 @var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]

-@var{FILTERGRAPH}      ::= @var{FILTERCHAIN} [;@var{FILTERGRAPH}]

+@var{FILTERGRAPH}      ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]

 @end example

 @c man end FILTERGRAPH DESCRIPTION

@@ -349,6 +349,30 @@ static int parse_outputs(const char **buf, AVFilterInOut **curr_inputs,

 #else

 #define log_ctx NULL

 #endif

+

+static int parse_sws_flags(const char **buf, AVFilterGraph *graph)

+{

+    char *p = strchr(*buf, ';');

+

+    if (strncmp(*buf, "sws_flags=", 10))

+        return 0;

+

+    if (!p) {

+        av_log(log_ctx, AV_LOG_ERROR, "sws_flags not terminated with ';'.\n");

+        return AVERROR(EINVAL);

+    }

+

+    *buf += 4;  // keep the 'flags=' part

+

+    av_freep(&graph->scale_sws_opts);

+    if (!(graph->scale_sws_opts = av_mallocz(p - *buf + 1)))

+        return AVERROR(ENOMEM);

+    av_strlcpy(graph->scale_sws_opts, *buf, p - *buf + 1);

+

+    *buf = p + 1;

+    return 0;

+}

+

 int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,

                           AVFilterInOut **inputs,

                           AVFilterInOut **outputs)

@@ -358,6 +382,11 @@ int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,

     AVFilterInOut *curr_inputs = NULL, *open_inputs = NULL, *open_outputs = NULL;

+    filters += strspn(filters, WHITESPACES);

+

+    if ((ret = parse_sws_flags(&filters, graph)) < 0)

+        goto fail;

+

     do {

         AVFilterContext *filter;

         filters += strspn(filters, WHITESPACES);