[MPlayer-dev-eng] [PATCH] Automatic downmix

[Clément Bœsch]

On Sun, Sep 26, 2010 at 10:49:29AM +0200, Nicolas George wrote:
> Le quintidi 5 vendémiaire, an CCXIX, Clément Bœsch a écrit :
> > It's "historical"; there was a time where I needed to check the return
> > value in order to reinit or not the chain list. As I said in a previous
> > mail, I can remove it but I'm not sure it's harmless to keep it (if it
> > needs to be checked later).
> 
> I committed the patch with the return value removed. If someone needs to
> check it, it takes a few seconds to add it back, and in the meantime,
> someone who reads the code will not wonder what it is there for.
> 

OK. Then I attach two versions of the patch:
 - patch-auto-downmix-pan.diff: my naive/arbitrary values
 - patch-auto-downmix-pan-new-coeff.diff: with better values :)

I'm fine with both, but I think the second one is better. You to judge.

> Thanks for your efforts.
> 
> Regards,
> 

Thanks to you,

Regards,

-- 
Clément B.
-------------- next part --------------
Index: libaf/af.c
===================================================================
--- libaf/af.c	(revision 32355)
+++ libaf/af.c	(working copy)
@@ -21,6 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "osdep/strsep.h"
+#include "libmpcodecs/dec_audio.h"
 
 #include "af.h"
 
@@ -412,6 +413,26 @@
     return AF_OK;
 }
 
+/**
+ * Automatic downmix to stereo in case the codec does not implement it.
+ */
+static void af_downmix(af_stream_t* s)
+{
+    static const char * const downmix_strs[AF_NCH + 1] = {
+        /*                FL       FR       RL       RR          FC          LF         AL      AR */
+        [3] = "pan=2:" "0.6:0:" "0:0.6:"                     "0.4:0.4",
+        [4] = "pan=2:" "0.6:0:" "0:0.6:" "0.4:0:"  "0:0.4",
+        [5] = "pan=2:" "0.5:0:" "0:0.5:" "0.2:0:"  "0:0.2:"  "0.3:0.3",
+        [6] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:"  "0:0.2:"  "0.3:0.3:"   "0.1:0.1",
+        [7] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:"  "0:0.2:"  "0.3:0.3:"              "0.1:0:" "0:0.1",
+        [8] = "pan=2:" "0.4:0:" "0:0.4:" "0.15:0:" "0:0.15:" "0.25:0.25:" "0.1:0.1:" "0.1:0:" "0:0.1",
+    };
+    const char *af_pan_str = downmix_strs[s->input.nch];
+
+    if (af_pan_str)
+        af_append(s, s->first, af_pan_str);
+}
+
 /* Initialize the stream "s". This function creates a new filter list
    if necessary according to the values set in input and output. Input
    and output should contain the format of the current movie and the
@@ -438,6 +459,9 @@
 
   // Check if this is the first call
   if(!s->first){
+    // Append a downmix pan filter at the beginning of the chain if needed
+    if (s->input.nch != audio_output_channels && audio_output_channels == 2)
+      af_downmix(s);
     // Add all filters in the list (if there are any)
     if (s->cfg.list) {
       while(s->cfg.list[i]){
-------------- next part --------------
Index: libaf/af.c
===================================================================
--- libaf/af.c	(revision 32355)
+++ libaf/af.c	(working copy)
@@ -21,6 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "osdep/strsep.h"
+#include "libmpcodecs/dec_audio.h"
 
 #include "af.h"
 
@@ -412,6 +413,26 @@
     return AF_OK;
 }
 
+/**
+ * Automatic downmix to stereo in case the codec does not implement it.
+ */
+static void af_downmix(af_stream_t* s)
+{
+    static const char * const downmix_strs[AF_NCH + 1] = {
+        /*                 FL       FR        RL        RR          FC          LFE         AL        AR */
+        [3] = "pan=2:" ".586:0:" "0:.586:"                     ".414:.414",
+        [4] = "pan=2:" ".500:0:" "0:.500:" ".500:0:" "0:.500",
+        [5] = "pan=2:" ".369:0:" "0:.369:" ".369:0:" "0:.369:" ".261:.261",
+        [6] = "pan=2:" ".293:0:" "0:.293:" ".293:0:" "0:.293:" ".207:.207:" ".207:.207",
+        [7] = "pan=2:" ".270:0:" "0:.270:" ".270:0:" "0:.270:" ".191:.191:"              ".270:0:" "0:.270",
+        [8] = "pan=2:" ".227:0:" "0:.227:" ".227:0:" "0:.227:" ".160:.160:" ".160:.160:" ".227:0:" "0:.227",
+    };
+    const char *af_pan_str = downmix_strs[s->input.nch];
+
+    if (af_pan_str)
+        af_append(s, s->first, af_pan_str);
+}
+
 /* Initialize the stream "s". This function creates a new filter list
    if necessary according to the values set in input and output. Input
    and output should contain the format of the current movie and the
@@ -438,6 +459,9 @@
 
   // Check if this is the first call
   if(!s->first){
+    // Append a downmix pan filter at the beginning of the chain if needed
+    if (s->input.nch != audio_output_channels && audio_output_channels == 2)
+      af_downmix(s);
     // Add all filters in the list (if there are any)
     if (s->cfg.list) {
       while(s->cfg.list[i]){