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

[Clément Bœsch]

On Sat, Sep 25, 2010 at 01:56:57PM +0200, Reimar Döffinger wrote:
> On Sat, Sep 25, 2010 at 01:37:53PM +0200, Clément Bœsch wrote:
> > +    return af_pan_str ? af_append(s, s->first, af_pan_str) : NULL;
> 
> Something like
> if (af_pan_str)
>     return af_append...
> return NULL;
> or the other way around might be more readable, but it doesn't really matter.
> 

Ok, done.

> > @@ -438,6 +457,9 @@
> >  
> >    // 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){      // To make automatic format conversion work
> >        if(!af_append(s,s->first,"dummy"))
> 
> I think this should now be
> if (!s->first && !af_append...
> the dummy filter should only be inserted if there's no other filters.
> I changed the code in SVN a bit so you won't have to change this.

Well, if I understand it well, I don't have to change something; new
version attached.

Regards,

-- 
Clément B.
-------------- next part --------------
Index: libaf/af.c
===================================================================
--- libaf/af.c	(revision 32347)
+++ 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 +413,27 @@
     return AF_OK;
 }
 
+/**
+ * Automatic downmix to stereo in case the codec does not implement it.
+ */
+static af_instance_t *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)
+        return af_append(s, s->first, af_pan_str);
+    return NULL;
+}
+
 /* 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 +460,9 @@
 
   // 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]){