avfilter/scale.c: factorize ff_scale_eval_dimensions

Adjustment of evaluated values shifted to ff_adjust_scale_dimensions
Shifted code for force_original_aspect_ratio and force_divisble_by from
vf_scale so it is now available for scale_cuda, scale_npp and
scale_vaapi as well.

doc/filters.texi

@@ -16210,6 +16210,46 @@ Supersampling
 @item lanczos
 @end table
 
+@item force_original_aspect_ratio
+Enable decreasing or increasing output video width or height if necessary to
+keep the original aspect ratio. Possible values:
+
+@table @samp
+@item disable
+Scale the video as specified and disable this feature.
+
+@item decrease
+The output video dimensions will automatically be decreased if needed.
+
+@item increase
+The output video dimensions will automatically be increased if needed.
+
+@end table
+
+One useful instance of this option is that when you know a specific device's
+maximum allowed resolution, you can use this to limit the output video to
+that, while retaining the aspect ratio. For example, device A allows
+1280x720 playback, and your video is 1920x800. Using this option (set it to
+decrease) and specifying 1280x720 to the command line makes the output
+1280x533.
+
+Please note that this is a different thing than specifying -1 for @option{w}
+or @option{h}, you still need to specify the output resolution for this option
+to work.
+
+@item force_divisible_by
+Ensures that both the output dimensions, width and height, are divisible by the
+given integer when used together with @option{force_original_aspect_ratio}. This
+works similar to using @code{-n} in the @option{w} and @option{h} options.
+
+This option respects the value set for @option{force_original_aspect_ratio},
+increasing or decreasing the resolution accordingly. The video's aspect ratio
+may be slightly modified.
+
+This option can be handy if you need to have a video fit within or exceed
+a defined resolution using @option{force_original_aspect_ratio} but also have
+encoder restrictions on width or height divisibility.
+
 @end table
 
 @section scale2ref

libavfilter/scale.c

@@ -111,8 +111,6 @@ int ff_scale_eval_dimensions(void *log_ctx,
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
     const AVPixFmtDescriptor *out_desc = av_pix_fmt_desc_get(outlink->format);
     const char *expr;
-    int w, h;
-    int factor_w, factor_h;
     int eval_w, eval_h;
     int ret;
     const char scale2ref = outlink->src->nb_inputs == 2 && outlink->src->inputs[1] == inlink;
@@ -172,10 +170,30 @@ int ff_scale_eval_dimensions(void *log_ctx,
         goto fail;
     eval_w = (int) res == 0 ? inlink->w : (int) res;
 
-    w = eval_w;
-    h = eval_h;
+    *ret_w = eval_w;
+    *ret_h = eval_h;
+
+    return 0;
+
+fail:
+    av_log(log_ctx, AV_LOG_ERROR,
+           "Error when evaluating the expression '%s'.\n"
+           "Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
+           expr, w_expr, h_expr);
+    return ret;
+}
+
+int ff_scale_adjust_dimensions(AVFilterLink *inlink,
+    int *ret_w, int *ret_h,
+    int force_original_aspect_ratio, int force_divisible_by)
+{
+    int w, h;
+    int factor_w, factor_h;
+
+    w = *ret_w;
+    h = *ret_h;
 
-    /* Check if it is requested that the result has to be divisible by a some
+    /* Check if it is requested that the result has to be divisible by some
      * factor (w or h = -n with n being the factor). */
     factor_w = 1;
     factor_h = 1;
@@ -192,22 +210,41 @@ int ff_scale_eval_dimensions(void *log_ctx,
     }
 
     /* Make sure that the result is divisible by the factor we determined
-     * earlier. If no factor was set, it is nothing will happen as the default
+     * earlier. If no factor was set, nothing will happen as the default
      * factor is 1 */
     if (w < 0)
         w = av_rescale(h, inlink->w, inlink->h * factor_w) * factor_w;
     if (h < 0)
         h = av_rescale(w, inlink->h, inlink->w * factor_h) * factor_h;
 
+    /* Note that force_original_aspect_ratio may overwrite the previous set
+     * dimensions so that it is not divisible by the set factors anymore
+     * unless force_divisible_by is defined as well */
+    if (force_original_aspect_ratio) {
+        int tmp_w = av_rescale(h, inlink->w, inlink->h);
+        int tmp_h = av_rescale(w, inlink->h, inlink->w);
+
+        if (force_original_aspect_ratio == 1) {
+             w = FFMIN(tmp_w, w);
+             h = FFMIN(tmp_h, h);
+             if (force_divisible_by > 1) {
+                 // round down
+                 w = w / force_divisible_by * force_divisible_by;
+                 h = h / force_divisible_by * force_divisible_by;
+             }
+        } else {
+             w = FFMAX(tmp_w, w);
+             h = FFMAX(tmp_h, h);
+             if (force_divisible_by > 1) {
+                 // round up
+                 w = (w + force_divisible_by - 1) / force_divisible_by * force_divisible_by;
+                 h = (h + force_divisible_by - 1) / force_divisible_by * force_divisible_by;
+             }
+        }
+    }
+
     *ret_w = w;
     *ret_h = h;
 
     return 0;
-
-fail:
-    av_log(log_ctx, AV_LOG_ERROR,
-           "Error when evaluating the expression '%s'.\n"
-           "Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
-           expr, w_expr, h_expr);
-    return ret;
 }

libavfilter/scale.h

@@ -21,8 +21,28 @@
 
 #include "avfilter.h"
 
+/**
+ * Parse and evaluate string expressions for width and height. Upon success,
+ * ff_scale_adjust_dimensions must be called with evaluated width and height
+ * to obtain actual target dimensions.
+ *
+ * Returns 0 upon success, negative value if one of the expressions could
+ * not be parsed or if NaN was the result of their evaluation.
+ */
 int ff_scale_eval_dimensions(void *ctx,
     const char *w_expr, const char *h_expr,
     AVFilterLink *inlink, AVFilterLink *outlink,
     int *ret_w, int *ret_h);
+
+/**
+ * Transform evaluated width and height obtained from ff_scale_eval_dimensions
+ * into actual target width and height for scaling. Adjustment can occur if one
+ * or both of the evaluated values are of the form '-n' or if
+ * force_original_aspect_ratio is set.
+ *
+ * Returns 0.
+ */
+int ff_scale_adjust_dimensions(AVFilterLink *inlink,
+    int *ret_w, int *ret_h,
+    int force_original_aspect_ratio, int force_divisible_by);
 #endif

libavfilter/vf_scale.c

@@ -237,31 +237,9 @@ static int config_props(AVFilterLink *outlink)
                                         &w, &h)) < 0)
         goto fail;
 
-    /* Note that force_original_aspect_ratio may overwrite the previous set
-     * dimensions so that it is not divisible by the set factors anymore
-     * unless force_divisible_by is defined as well */
-    if (scale->force_original_aspect_ratio) {
-        int tmp_w = av_rescale(h, inlink->w, inlink->h);
-        int tmp_h = av_rescale(w, inlink->h, inlink->w);
-
-        if (scale->force_original_aspect_ratio == 1) {
-             w = FFMIN(tmp_w, w);
-             h = FFMIN(tmp_h, h);
-             if (scale->force_divisible_by > 1) {
-                 // round down
-                 w = w / scale->force_divisible_by * scale->force_divisible_by;
-                 h = h / scale->force_divisible_by * scale->force_divisible_by;
-             }
-        } else {
-             w = FFMAX(tmp_w, w);
-             h = FFMAX(tmp_h, h);
-             if (scale->force_divisible_by > 1) {
-                 // round up
-                 w = (w + scale->force_divisible_by - 1) / scale->force_divisible_by * scale->force_divisible_by;
-                 h = (h + scale->force_divisible_by - 1) / scale->force_divisible_by * scale->force_divisible_by;
-             }
-        }
-    }
+    ff_scale_adjust_dimensions(inlink, &w, &h,
+                               scale->force_original_aspect_ratio,
+                               scale->force_divisible_by);
 
     if (w > INT_MAX || h > INT_MAX ||
         (h * inlink->w) > INT_MAX  ||

libavfilter/vf_scale_cuda.c

@@ -82,6 +82,9 @@ typedef struct CUDAScaleContext {
     char *w_expr;               ///< width  expression string
     char *h_expr;               ///< height expression string
 
+    int force_original_aspect_ratio;
+    int force_divisible_by;
+
     CUcontext   cu_ctx;
     CUmodule    cu_module;
     CUfunction  cu_func_uchar;
@@ -305,6 +308,9 @@ static av_cold int cudascale_config_props(AVFilterLink *outlink)
                                         &w, &h)) < 0)
         goto fail;
 
+    ff_scale_adjust_dimensions(inlink, &w, &h,
+                               s->force_original_aspect_ratio, s->force_divisible_by);
+
     if (((int64_t)h * inlink->w) > INT_MAX  ||
         ((int64_t)w * inlink->h) > INT_MAX)
         av_log(ctx, AV_LOG_ERROR, "Rescaled value for width or height is too big.\n");
@@ -536,6 +542,11 @@ fail:
 static const AVOption options[] = {
     { "w",      "Output video width",  OFFSET(w_expr),     AV_OPT_TYPE_STRING, { .str = "iw"   }, .flags = FLAGS },
     { "h",      "Output video height", OFFSET(h_expr),     AV_OPT_TYPE_STRING, { .str = "ih"   }, .flags = FLAGS },
+    { "force_original_aspect_ratio", "decrease or increase w/h if necessary to keep the original AR", OFFSET(force_original_aspect_ratio), AV_OPT_TYPE_INT, { .i64 = 0}, 0, 2, FLAGS, "force_oar" },
+    { "disable",  NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 0 }, 0, 0, FLAGS, "force_oar" },
+    { "decrease", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 1 }, 0, 0, FLAGS, "force_oar" },
+    { "increase", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 2 }, 0, 0, FLAGS, "force_oar" },
+    { "force_divisible_by", "enforce that the output resolution is divisible by a defined integer when force_original_aspect_ratio is used", OFFSET(force_divisible_by), AV_OPT_TYPE_INT, { .i64 = 1}, 1, 256, FLAGS },
     { NULL },
 };
 

libavfilter/vf_scale_npp.c

@@ -98,6 +98,9 @@ typedef struct NPPScaleContext {
     char *h_expr;               ///< height expression string
     char *format_str;
 
+    int force_original_aspect_ratio;
+    int force_divisible_by;
+
     int interp_algo;
 } NPPScaleContext;
 
@@ -347,6 +350,9 @@ static int nppscale_config_props(AVFilterLink *outlink)
                                         &w, &h)) < 0)
         goto fail;
 
+    ff_scale_adjust_dimensions(inlink, &w, &h,
+                               s->force_original_aspect_ratio, s->force_divisible_by);
+
     if (((int64_t)h * inlink->w) > INT_MAX  ||
         ((int64_t)w * inlink->h) > INT_MAX)
         av_log(ctx, AV_LOG_ERROR, "Rescaled value for width or height is too big.\n");
@@ -552,6 +558,11 @@ static const AVOption options[] = {
         { "cubic2p_b05c03",     "2-parameter cubic (B=1/2, C=3/10)", 0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_CUBIC2P_B05C03     }, 0, 0, FLAGS, "interp_algo" },
         { "super",              "supersampling",                     0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_SUPER              }, 0, 0, FLAGS, "interp_algo" },
         { "lanczos",            "Lanczos",                           0, AV_OPT_TYPE_CONST, { .i64 = NPPI_INTER_LANCZOS            }, 0, 0, FLAGS, "interp_algo" },
+    { "force_original_aspect_ratio", "decrease or increase w/h if necessary to keep the original AR", OFFSET(force_original_aspect_ratio), AV_OPT_TYPE_INT, { .i64 = 0}, 0, 2, FLAGS, "force_oar" },
+    { "disable",  NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 0 }, 0, 0, FLAGS, "force_oar" },
+    { "decrease", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 1 }, 0, 0, FLAGS, "force_oar" },
+    { "increase", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 2 }, 0, 0, FLAGS, "force_oar" },
+    { "force_divisible_by", "enforce that the output resolution is divisible by a defined integer when force_original_aspect_ratio is used", OFFSET(force_divisible_by), AV_OPT_TYPE_INT, { .i64 = 1}, 1, 256, FLAGS },
     { NULL },
 };
 

libavfilter/vf_scale_vaapi.c

@@ -40,6 +40,9 @@ typedef struct ScaleVAAPIContext {
     char *w_expr;      // width expression string
     char *h_expr;      // height expression string
 
+    int force_original_aspect_ratio;
+    int force_divisible_by;
+
     char *colour_primaries_string;
     char *colour_transfer_string;
     char *colour_matrix_string;
@@ -81,6 +84,9 @@ static int scale_vaapi_config_output(AVFilterLink *outlink)
                                         &vpp_ctx->output_width, &vpp_ctx->output_height)) < 0)
         return err;
 
+    ff_scale_adjust_dimensions(inlink, &vpp_ctx->output_width, &vpp_ctx->output_height,
+                               ctx->force_original_aspect_ratio, ctx->force_divisible_by);
+
     err = ff_vaapi_vpp_config_output(outlink);
     if (err < 0)
         return err;
@@ -247,6 +253,11 @@ static const AVOption scale_vaapi_options[] = {
     { "out_chroma_location", "Output chroma sample location",
       OFFSET(chroma_location_string),  AV_OPT_TYPE_STRING,
       { .str = NULL }, .flags = FLAGS },
+    { "force_original_aspect_ratio", "decrease or increase w/h if necessary to keep the original AR", OFFSET(force_original_aspect_ratio), AV_OPT_TYPE_INT, { .i64 = 0}, 0, 2, FLAGS, "force_oar" },
+    { "disable",  NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 0 }, 0, 0, FLAGS, "force_oar" },
+    { "decrease", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 1 }, 0, 0, FLAGS, "force_oar" },
+    { "increase", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 2 }, 0, 0, FLAGS, "force_oar" },
+    { "force_divisible_by", "enforce that the output resolution is divisible by a defined integer when force_original_aspect_ratio is used", OFFSET(force_divisible_by), AV_OPT_TYPE_INT, { .i64 = 1}, 1, 256, FLAGS },
 
     { NULL },
 };