[FFmpeg-devel] [PATCH 3/3] libavfilter/graphparser: Add scale_sws_opts parse support in avfilter_graph_parse2

[Andreas Rheinhardt]

Linjie Fu:
> From: Linjie Fu <linjie.justin.fu at gmail.com>
> 
> To pass the swscale options for the inserted scalers.
> 
> ffmpeg -i input.mp4 -filter_complex \
>     "scale_sws_opts=alphablend=checkerboard;format=nv12" \
>     -t 0.5 output.mp4
> 
> Update docs.
> 
> Signed-off-by: Linjie Fu <linjie.justin.fu at gmail.com>
> ---
>  doc/filters.texi          |  7 ++++---
>  libavfilter/graphparser.c | 27 +++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 790d165433..dbbb3a6940 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -204,9 +204,9 @@ 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 @ref{scale} filters where format
> -conversion is required. It is possible to specify swscale flags
> -for those automatically inserted scalers by prepending
> - at code{sws_flags=@var{flags};}
> +conversion is required. It is possible to specify swscale flags or
> +scale_sws_opts for those automatically inserted scalers by prepending
> + at code{sws_flags=@var{flags};} or @code{scale_sws_opts=@var{scale_sws_opts};}
>  to the filtergraph description.
>  
>  Here is a BNF description of the filtergraph syntax:
> @@ -219,6 +219,7 @@ Here is a BNF description of the filtergraph syntax:
>  @var{FILTER}           ::= [@var{LINKLABELS}] @var{FILTER_NAME} ["=" @var{FILTER_ARGUMENTS}] [@var{LINKLABELS}]
>  @var{FILTERCHAIN}      ::= @var{FILTER} [, at var{FILTERCHAIN}]
>  @var{FILTERGRAPH}      ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
> + at var{FILTERGRAPH}      ::= [scale_sws_opts=@var{opts};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
>  @end example
>  
>  @anchor{filtergraph escaping}
> diff --git a/libavfilter/graphparser.c b/libavfilter/graphparser.c
> index 1385c3ae71..8c63d6454e 100644
> --- a/libavfilter/graphparser.c
> +++ b/libavfilter/graphparser.c
> @@ -415,6 +415,30 @@ static int parse_sws_flags(const char **buf, AVFilterGraph *graph)
>      return 0;
>  }
>  
> +static int parse_scale_sws_opts(const char **buf, AVFilterGraph *graph)
> +{
> +    char *p = strchr(*buf, ';');
> +
> +    if (strncmp(*buf, "scale_sws_opts=", 15)) {

av_strstart()

> +        return 0;
> +    }
> +
> +    if (!p) {
> +        av_log(graph, AV_LOG_ERROR, "scale_sws_opts not terminated with ';'.\n");
> +        return AVERROR(EINVAL);
> +    }
> +
> +    *buf += 15;
> +
> +    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);

av_strndup()

> +
> +    *buf = p + 1;
> +    return 0;
> +}
> +
>  int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,
>                            AVFilterInOut **inputs,
>                            AVFilterInOut **outputs)
> @@ -429,6 +453,9 @@ int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,
>      if ((ret = parse_sws_flags(&filters, graph)) < 0)
>          goto fail;
>  
> +    if ((ret = parse_scale_sws_opts(&filters, graph)) < 0)
> +        goto fail;
> +
>      do {
>          AVFilterContext *filter;
>          filters += strspn(filters, WHITESPACES);
>