buffersrc: accept key=value arguments.

The current flat arguments syntax is not easily extensible
due to sws_param possibly containing commas.
This is also consistent with abuffersrc.

doc/filters.texi

@@ -3162,33 +3162,26 @@ Buffer video frames, and make them available to the filter chain.
 This source is mainly intended for a programmatic use, in particular
 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
 
-It accepts the following parameters:
-@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}:@var{sample_aspect_ratio_num}:@var{sample_aspect_ratio.den}:@var{scale_params}
-
-All the parameters but @var{scale_params} need to be explicitly
-defined.
-
-Follows the list of the accepted parameters.
+It accepts a list of options in the form of @var{key}=@var{value} pairs
+separated by ":". A descroption of the accepted options follows.
 
 @table @option
 
-@item width, height
-Specify the width and height of the buffered video frames.
+@item video_size
+Specify the size (width and height) of the buffered video frames.
 
-@item pix_fmt_string
+@item pix_fmt
 A string representing the pixel format of the buffered video frames.
 It may be a number corresponding to a pixel format, or a pixel format
 name.
 
-@item timebase_num, timebase_den
-Specify numerator and denomitor of the timebase assumed by the
-timestamps of the buffered frames.
+@item time_base
+Specify the timebase assumed by the timestamps of the buffered frames.
 
-@item sample_aspect_ratio.num, sample_aspect_ratio.den
-Specify numerator and denominator of the sample aspect ratio assumed
-by the video frames.
+@item pixel_aspect
+Specify the sample aspect ratio assumed by the video frames.
 
-@item scale_params
+@item sws_param
 Specify the optional parameters to be used for the scale filter which
 is automatically inserted when an input change is detected in the
 input size or format.
@@ -3196,7 +3189,7 @@ input size or format.
 
 For example:
 @example
-buffer=320:240:yuv410p:1:24:1:1
+buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
 @end example
 
 will instruct the source to accept video frames with size 320x240 and
@@ -3206,9 +3199,14 @@ Since the pixel format with name "yuv410p" corresponds to the number 6
 (check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
 this example corresponds to:
 @example
-buffer=320:240:6:1:24:1:1
+buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
 @end example
 
+Alternatively, the options can be specified as a flat string, but this
+syntax is deprecated:
+
+@var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}]
+
 @section cellauto
 
 Create a pattern generated by an elementary cellular automaton.

libavfilter/buffersrc.c

@@ -45,10 +45,10 @@ typedef struct {
     unsigned          nb_failed_requests;
 
     /* video only */
-    int               h, w;
+    int               w, h;
     enum PixelFormat  pix_fmt;
     AVRational        pixel_aspect;
-    char              sws_param[256];
+    char              *sws_param;
 
     /* audio only */
     int sample_rate;
@@ -216,35 +216,81 @@ unsigned av_buffersrc_get_nb_failed_requests(AVFilterContext *buffer_src)
     return ((BufferSourceContext *)buffer_src->priv)->nb_failed_requests;
 }
 
+#define OFFSET(x) offsetof(BufferSourceContext, x)
+#define V AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption video_options[] = {
+    { "time_base",      NULL, OFFSET(time_base),           AV_OPT_TYPE_RATIONAL,   { 0 }, 0, INT_MAX, V },
+    { "video_size",     NULL, OFFSET(w),                   AV_OPT_TYPE_IMAGE_SIZE,           .flags = V },
+    { "pix_fmt",        NULL, OFFSET(pix_fmt),             AV_OPT_TYPE_PIXEL_FMT,            .flags = V },
+    { "pixel_aspect",   NULL, OFFSET(pixel_aspect),        AV_OPT_TYPE_RATIONAL,   { 0 }, 0, INT_MAX, V },
+    { "sws_param",      NULL, OFFSET(sws_param),           AV_OPT_TYPE_STRING,               .flags = V },
+    { NULL },
+};
+#undef V
+
+static const AVClass vbuffer_class = {
+    .class_name = "vbuffer source",
+    .item_name  = av_default_item_name,
+    .option     = video_options,
+    .version    = LIBAVUTIL_VERSION_INT,
+    .category   = AV_CLASS_CATEGORY_FILTER,
+};
+
 static av_cold int init_video(AVFilterContext *ctx, const char *args, void *opaque)
 {
     BufferSourceContext *c = ctx->priv;
-    char pix_fmt_str[128];
+    char pix_fmt_str[128], sws_param[256] = "", *colon, *equal;
     int ret, n = 0;
-    *c->sws_param = 0;
 
-    if (!args ||
-        (n = sscanf(args, "%d:%d:%127[^:]:%d:%d:%d:%d:%255c", &c->w, &c->h, pix_fmt_str,
+    c->class = &vbuffer_class;
+
+    if (!args) {
+        av_log(ctx, AV_LOG_ERROR, "Arguments required\n");
+        return AVERROR(EINVAL);
+    }
+    colon = strchr(args, ':');
+    equal = strchr(args, '=');
+    if (equal && (!colon || equal < colon)) {
+        av_opt_set_defaults(c);
+        ret = av_set_options_string(c, args, "=", ":");
+        if (ret < 0) {
+            av_log(ctx, AV_LOG_ERROR, "Error parsing options string: %s.\n", args);
+            goto fail;
+        }
+    } else {
+    if ((n = sscanf(args, "%d:%d:%127[^:]:%d:%d:%d:%d:%255c", &c->w, &c->h, pix_fmt_str,
                     &c->time_base.num, &c->time_base.den,
-                    &c->pixel_aspect.num, &c->pixel_aspect.den, c->sws_param)) < 7) {
+                    &c->pixel_aspect.num, &c->pixel_aspect.den, sws_param)) < 7) {
         av_log(ctx, AV_LOG_ERROR, "Expected at least 7 arguments, but only %d found in '%s'\n", n, args);
-        return AVERROR(EINVAL);
+        ret = AVERROR(EINVAL);
+        goto fail;
     }
 
     if ((ret = ff_parse_pixel_format(&c->pix_fmt, pix_fmt_str, ctx)) < 0)
-        return ret;
+        goto fail;
+    c->sws_param = av_strdup(sws_param);
+    if (!c->sws_param) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+    }
 
-    if (!(c->fifo = av_fifo_alloc(sizeof(AVFilterBufferRef*))))
-        return AVERROR(ENOMEM);
+    if (!(c->fifo = av_fifo_alloc(sizeof(AVFilterBufferRef*)))) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
 
     av_log(ctx, AV_LOG_INFO, "w:%d h:%d pixfmt:%s tb:%d/%d sar:%d/%d sws_param:%s\n",
            c->w, c->h, av_pix_fmt_descriptors[c->pix_fmt].name,
            c->time_base.num, c->time_base.den,
-           c->pixel_aspect.num, c->pixel_aspect.den, c->sws_param);
+           c->pixel_aspect.num, c->pixel_aspect.den, (char *)av_x_if_null(c->sws_param, ""));
     return 0;
+
+fail:
+    av_opt_free(c);
+    return ret;
 }
 
-#define OFFSET(x) offsetof(BufferSourceContext, x)
 #define A AV_OPT_FLAG_AUDIO_PARAM
 static const AVOption audio_options[] = {
     { "time_base",      NULL, OFFSET(time_base),           AV_OPT_TYPE_RATIONAL, { 0 }, 0, INT_MAX, A },
@@ -318,6 +364,7 @@ static av_cold void uninit(AVFilterContext *ctx)
     }
     av_fifo_free(s->fifo);
     s->fifo = NULL;
+    av_freep(&s->sws_param);
 }
 
 static int query_formats(AVFilterContext *ctx)