[FFmpeg-devel] libavfilter/vf_scale: Ensure scaled video is divisible by n

Submitted by Lars Kiesow on Aug. 12, 2019, 1:58 p.m.

Details

Message ID 20190812135814.14976-1-lkiesow@uos.de
State Accepted
Commit 74d4bc0fa0e0f63b89ce020893c61e6703f3f282
Headers show

Commit Message

Lars Kiesow Aug. 12, 2019, 1:58 p.m.
This patch adds a new option to the scale filter which ensures that the
output resolution is divisible by the given integer when used together
with `force_original_aspect_ratio`. This works similar to using `-n` in
the `w` and `h` options.

This option respects the value set for `force_original_aspect_ratio`,
increasing or decreasing the resolution accordingly.

The use case for this is to set a fixed target resolution using `w` and
`h`, to use the `force_original_aspect_ratio` option to make sure that
the video always fits in the defined bounding box regardless of aspect
ratio, but to also make sure that the calculated output resolution is
divisible by n so in can be encoded with certain encoders/options if
that is required.

Signed-off-by: Lars Kiesow <lkiesow@uos.de>
---
 doc/filters.texi       | 12 ++++++++++++
 libavfilter/vf_scale.c | 15 ++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

Comments

Michael Niedermayer Aug. 13, 2019, 9:42 a.m.
On Mon, Aug 12, 2019 at 03:58:14PM +0200, Lars Kiesow wrote:
> This patch adds a new option to the scale filter which ensures that the
> output resolution is divisible by the given integer when used together
> with `force_original_aspect_ratio`. This works similar to using `-n` in
> the `w` and `h` options.
> 
> This option respects the value set for `force_original_aspect_ratio`,
> increasing or decreasing the resolution accordingly.
> 
> The use case for this is to set a fixed target resolution using `w` and
> `h`, to use the `force_original_aspect_ratio` option to make sure that
> the video always fits in the defined bounding box regardless of aspect
> ratio, but to also make sure that the calculated output resolution is
> divisible by n so in can be encoded with certain encoders/options if
> that is required.
> 
> Signed-off-by: Lars Kiesow <lkiesow@uos.de>
> ---
>  doc/filters.texi       | 12 ++++++++++++
>  libavfilter/vf_scale.c | 15 ++++++++++++++-
>  2 files changed, 26 insertions(+), 1 deletion(-)

will apply

thx

[...]
Lars Kiesow Aug. 14, 2019, 8:39 a.m.
Hi Michael,

> will apply

Thanks.

Patch hide | download patch | download mbox

diff --git a/doc/filters.texi b/doc/filters.texi
index e081cdc7bc..01262d845e 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -15369,6 +15369,18 @@  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 the output resolution is divisible by the
+given integer when used together with @option{force_original_aspect_ratio}. This
+works similar to using -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. This may slightly modify
+the video's aspect ration.
+
+This can be handy, for example, if you want to have a video fit within a defined
+resolution using the @option{force_original_aspect_ratio} option but have
+encoder restrictions when it comes to width or height.
+
 @end table
 
 The values of the @option{w} and @option{h} options are expressions
diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
index 7aebf56ad8..bf340b8e7b 100644
--- a/libavfilter/vf_scale.c
+++ b/libavfilter/vf_scale.c
@@ -86,6 +86,7 @@  typedef struct ScaleContext {
     int in_v_chr_pos;
 
     int force_original_aspect_ratio;
+    int force_divisible_by;
 
     int nb_slices;
 
@@ -237,7 +238,8 @@  static int config_props(AVFilterLink *outlink)
         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. */
+     * 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);
@@ -245,9 +247,19 @@  static int config_props(AVFilterLink *outlink)
         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;
+             }
         }
     }
 
@@ -600,6 +612,7 @@  static const AVOption scale_options[] = {
     { "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 },
     { "param0", "Scaler param 0",             OFFSET(param[0]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, FLAGS },
     { "param1", "Scaler param 1",             OFFSET(param[1]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, FLAGS },
     { "nb_slices", "set the number of slices (debug purpose only)", OFFSET(nb_slices), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },