On 08/09/2015 07:35 PM, Luca Barbato wrote:
On 09/08/15 23:16, Justin Ruggles wrote:
On 08/07/2015 06:13 PM, Luca Barbato wrote:
Give priority to pixel formats closer to the input.
---

I kept it as simple as possible on purpose.

   libavfilter/avfiltergraph.c | 97
+++++++++++++++++++++++++++++++++++++++++++++
   1 file changed, 97 insertions(+)

diff --git a/libavfilter/avfiltergraph.c b/libavfilter/avfiltergraph.c
index 0fc385c..91a9d71 100644
--- a/libavfilter/avfiltergraph.c
+++ b/libavfilter/avfiltergraph.c
@@ -31,6 +31,7 @@
   #include "libavutil/internal.h"
   #include "libavutil/log.h"
   #include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"

   #include "avfilter.h"
   #include "formats.h"
@@ -742,6 +743,100 @@ static int pick_formats(AVFilterGraph *graph)
       return 0;
   }

+#define same_flag(d1, d2, flag) \
+    !(!!(d1->flags & flag) ^ !!(d2->flags & flag))
+
+static int find_best_pix_fmt_match(AVFilterLink *outlink,
+                                   const AVPixFmtDescriptor *in_desc,
+                                   int in_format)
+{
+    int j;
+    int best_idx = -1, best_score = INT_MIN;
+
+    for (j = 0; j < outlink->in_formats->nb_formats; j++) {
+        int format                     =
outlink->in_formats->formats[j];
+        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
+
+        int score;
+
+        int same_alpha = same_flag(desc, in_desc,
AV_PIX_FMT_FLAG_ALPHA);
+        int same_rgb   = same_flag(desc, in_desc, AV_PIX_FMT_FLAG_RGB);
+        int bpc        = desc->comp[0].depth_minus1;
+        int in_bpc     = in_desc->comp[0].depth_minus1;
+
+        if (bpc < in_bpc)
+            score = bpc - in_bpc;
+        else
+            score = 0;
+
+        score += -10 * abs(desc->nb_components -
+                           in_desc->nb_components);
+
+        if (same_alpha && same_rgb) {
+            score += 2;
+        } else if (desc->flags & AV_PIX_FMT_FLAG_ALPHA) {
+            if (same_alpha)
+                score += 1;
+        } else {
+            if (same_rgb)
+                score += 1;
+        }
+
+        if (score > best_score) {
+            best_score = score;
+            best_idx   = j;
+        }
+    }
+
+    return best_idx;
+}
+
+static void swap_pix_fmts_on_filter(AVFilterContext *filter)
+{
+    AVFilterLink *link = NULL;
+    const AVPixFmtDescriptor *desc;
+    int format;
+    int i;
+
+    for (i = 0; i < filter->nb_inputs; i++) {
+        link = filter->inputs[i];
+
+        if (link->type == AVMEDIA_TYPE_VIDEO &&
+            link->out_formats->nb_formats == 1)
+            break;
+    }
+    if (i == filter->nb_inputs)
+        return;
+
+    format = link->out_formats->formats[0];
+    desc   = av_pix_fmt_desc_get(format);
+
+    for (i = 0; i < filter->nb_outputs; i++) {
+        AVFilterLink *outlink = filter->outputs[i];
+        int best_idx;
+
+        if (outlink->type != AVMEDIA_TYPE_VIDEO ||
+            outlink->in_formats->nb_formats < 2)
+            continue;
+
+        best_idx = find_best_pix_fmt_match(outlink, desc, format);
+
+        if (best_idx > -1)
+            FFSWAP(int, outlink->in_formats->formats[0],
+                   outlink->in_formats->formats[best_idx]);
+    }
+}

I'm not so sure I like how the scoring is implemented here. The most
logical to me would be a strict layered matching. Ideally, my preference
would be, in order or priority:

- preserve alpha only if the input has alpha

Can be done.

- preserve average, non-alpha, bit depth

You end up with 16bits gray while 8bits gray is more than enough.

Yeah, I suppose preserving color if input has color could be the top priority.


- preserve colorspace

Ok

- preserve individual component (including alpha) bit depths, if applicable

Ok, I can extend what I put there, that part seems working quite well.

- preserve component ordering/packing

Something like this could still be done within a scoring system.

I'll update the rules soon.

lu




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