[MPlayer-dev-eng] [PATCH] Proof of concept extrasurround plugin

Kis Gergely kisg at lme.linux.hu
Thu Apr 4 22:03:40 CEST 2002


Hi,

I made the thing work.

WHAT'S NEW:
-> Every previously known bugs fixed.
-> The plugin now respects the -channels switch of mplayer and acts 
   accordingly. (The sochans switch has been removed.) 
   4 and 6 channel output is supported. 
-> Included "quick workaround" for ao_plugin.c bug that prevented 6 channel
    output in many cases. This is not a true fix, it may cause problems for 
    you. 
-> Debug output enabled. Note the word "experimental".

TODO: 
-> Use the same lowpass filter as in the original surround part of the plugin. 
    I couldn't figure the firfilter thingie out, so I stole^H^H^H^H^H reused
    the simple RC lowpass filter from sox.
-> Discover and fix the bugs

KNOWN BUGS:
-> Quick workaround for ao_plugin.c may cause problems.

Patch is attached, or can be downloaded from
http://www.inf.bme.hu/~kisg/mplayer.

Please Anders look at the bug in ao_plugin.c

Thanks,
kisg

-------------- next part --------------
? cfg-mplayer.h.kisg4
? libao2/audio_plugin.h.kisg4
? libao2/pl_surround.c.kisg1
? libao2/pl_surround.c.kisg2
Index: libao2/ao_plugin.c
===================================================================
RCS file: /cvsroot/mplayer/main/libao2/ao_plugin.c,v
retrieving revision 1.15
diff -u -r1.15 ao_plugin.c
--- libao2/ao_plugin.c	12 Mar 2002 06:32:02 -0000	1.15
+++ libao2/ao_plugin.c	4 Apr 2002 20:06:18 -0000
@@ -229,9 +229,17 @@
   int tmp = get_space();
   int ret_len =(tmp<len)?tmp:len;
   if(ret_len){
+    
+    if (ret_len%2 != 0) {
+      ret_len += 1;
+    } 
+    
     // Filter data
     ao_plugin_data.len=ret_len;
     ao_plugin_data.data=data;
+    
+    fprintf(stderr,"ao_plugin: I send ao_plugin_data.len = %d data to the plugins\n",ao_plugin_data.len);
+    
     while(plugin(i))
       plugin(i++)->play();
     // Copy data to output buffer
Index: libao2/pl_surround.c
===================================================================
RCS file: /cvsroot/mplayer/main/libao2/pl_surround.c,v
retrieving revision 1.9
diff -u -r1.9 pl_surround.c
--- libao2/pl_surround.c	24 Dec 2001 18:54:58 -0000	1.9
+++ libao2/pl_surround.c	4 Apr 2002 20:06:18 -0000
@@ -64,6 +64,7 @@
   int passthrough;      // Just be a "NO-OP"
   int msecs;            // Rear channel delay in milliseconds
   int16_t* databuf;     // Output audio buffer
+  int databuf_len;      // Output audio buffer length in samples
   int16_t* Ls_delaybuf; // circular buffer to be used for delaying Ls audio
   int16_t* Rs_delaybuf; // circular buffer to be used for delaying Rs audio
   int delaybuf_len;     // delaybuf buffer length in samples
@@ -72,10 +73,16 @@
   int rate;             // input data rate
   int format;           // input format
   int input_channels;   // input channels
+  int output_channels;  // output channels
+  float lowp_cutoff;    // cutoff freq for the lowpass filter
+  double lowp_A, lowp_B; // parameters for lowpass filter
+  double lowp_outm1;	// output for lowpass filter (??)
 
 } pl_surround_t;
 
-static pl_surround_t pl_surround={0,20,NULL,NULL,NULL,0,0,NULL,0,0,0};
+static pl_surround_t pl_surround={0,20,NULL,0,NULL,NULL,0,0,NULL,0,0,0,0,0,0,0,0};
+
+extern int audio_output_channels;
 
 // to set/get/query special features/parameters
 static int control(int cmd,int arg){
@@ -89,9 +96,20 @@
       free(pl_surround.databuf);  pl_surround.databuf = NULL;
     }
     // Allocate output buffer
-    pl_surround.databuf = calloc(ao_plugin_data.len, 1);
+    
+    fprintf(stderr, "pl_surround: We can produce: audio_plugin_data.len = %d\n",ao_plugin_data.len);
+    
+    pl_surround.databuf_len = ao_plugin_data.len / sizeof(int16_t) / pl_surround.output_channels;
+    
+    fprintf(stderr, "pl_surround: This means pl_surround.databuf_len = %d\n",pl_surround.databuf_len);
+    
+    pl_surround.databuf = calloc(pl_surround.databuf_len*pl_surround.output_channels, sizeof(int16_t));
     // Return back smaller len so we don't get overflowed...
-    ao_plugin_data.len /= 2;
+    // ao_plugin_data.len /= 2;
+    ao_plugin_data.len = pl_surround.databuf_len * sizeof(int16_t) * pl_surround.input_channels;
+
+    fprintf(stderr, "pl_surround: We can receive: audio_plugin_data.len = %d\n",ao_plugin_data.len);
+    
     return CONTROL_OK;
   }
   return -1;
@@ -113,6 +131,12 @@
     return 1;
   }
 
+  if (audio_output_channels != 4 && audio_output_channels != 6) {
+    fprintf(stderr, "pl_surround: I'm dumb and can only output 4 or 6 channel sound, using passtrough mode\n");
+    pl_surround.passthrough = 1;
+    return 1;    
+  }
+
   pl_surround.passthrough = 0;
 
   /* Store info on input format to expect */
@@ -120,9 +144,16 @@
   pl_surround.format=ao_plugin_data.format;
   pl_surround.input_channels=ao_plugin_data.channels;
 
+  /* Store info on output channel number */
+  pl_surround.output_channels = audio_output_channels;
+
+
   // Input 2 channels, output will be 4 - tell ao_plugin
-  ao_plugin_data.channels    = 4;
-  ao_plugin_data.sz_mult    /= 2;
+//  ao_plugin_data.channels    = 4;
+//  ao_plugin_data.sz_mult    /= 2;
+
+  ao_plugin_data.channels    = pl_surround.output_channels;
+  ao_plugin_data.sz_mult    /= pl_surround.output_channels / pl_surround.input_channels;
 
   // Figure out buffer space (in int16_ts) needed for the 15msec delay
   // Extra 31 samples allow for lowpass filter delay (taps-1)
@@ -137,6 +168,16 @@
   pl_surround.filter_coefs_surround = calc_coefficients_7kHz_lowpass(pl_surround.rate);
   //dump_filter_coefficients(pl_surround.filter_coefs_surround);
   //testfilter(pl_surround.filter_coefs_surround, 32, pl_surround.rate);
+  
+  pl_surround.lowp_cutoff = 7000;
+  if (pl_surround.lowp_cutoff > pl_surround.rate / 2) {
+    // Cutoff rate must be < sample rate / 2 (Nyquist rate)
+    pl_surround.lowp_cutoff = pl_surround.rate / 2 - 1;
+  } 
+  pl_surround.lowp_B = exp ((-2.0 * M_PI * (pl_surround.lowp_cutoff / pl_surround.rate)));
+  pl_surround.lowp_A = 1 - pl_surround.lowp_B;
+  pl_surround.lowp_outm1 = 0.0;
+  
   return 1;
 }
 
@@ -161,6 +202,7 @@
   pl_surround.delaybuf_pos = 0;
   memset(pl_surround.Ls_delaybuf, 0, sizeof(int16_t)*pl_surround.delaybuf_len);
   memset(pl_surround.Rs_delaybuf, 0, sizeof(int16_t)*pl_surround.delaybuf_len);
+  pl_surround.lowp_outm1 = 0;
 }
 
 // The beginnings of an active matrix...
@@ -181,11 +223,11 @@
 
   if (pl_surround.passthrough) return 1;
 
-  // fprintf(stderr, "pl_surround: play %d bytes, %d samples\n", ao_plugin_data.len, samples);
 
   samples  = ao_plugin_data.len / sizeof(int16_t) / pl_surround.input_channels;
   out = pl_surround.databuf;  in = (int16_t *)ao_plugin_data.data;
 
+  fprintf(stderr, "pl_surround: play %d bytes, %d samples\n", ao_plugin_data.len, samples);
   // Testing - place a 1kHz tone on Lt and Rt in anti-phase: should decode in S
   //sinewave(in, samples, pl_surround.input_channels, 1000, 0.0, pl_surround.rate);
   //sinewave(&in[1], samples, pl_surround.input_channels, 1000, PI, pl_surround.rate);
@@ -222,6 +264,26 @@
 #else
     out[3] = -out[2];
 #endif
+    if (pl_surround.output_channels == 6) {
+    
+	int32_t avg;
+	double d;
+	avg = (out[0] + out[1]) / 2;
+	
+	d = pl_surround.lowp_A * avg + pl_surround.lowp_B * pl_surround.lowp_outm1;
+
+	if (d > 32767L) {
+	    d = 32767L;
+	}
+	if (d < -32768L) {
+	    d = -32768L;
+	}
+	pl_surround.lowp_outm1 = d;
+	out[5] = d;
+	// Only 4.1 output, center speaker remains silent
+	out[4] = 0;
+    }
+    
     // calculate and save surround for 20msecs time
 #ifdef SPLITREAR
     pl_surround.Ls_delaybuf[pl_surround.delaybuf_pos] =
@@ -235,7 +297,7 @@
     pl_surround.delaybuf_pos %= pl_surround.delaybuf_len;
 
     // next samples...
-    in = &in[pl_surround.input_channels];  out = &out[4];
+    in = &in[pl_surround.input_channels];  out = &out[pl_surround.output_channels];
   }
 
   // Show some state
@@ -243,6 +305,6 @@
   
   // Set output block/len
   ao_plugin_data.data=pl_surround.databuf;
-  ao_plugin_data.len=samples*sizeof(int16_t)*4;
+  ao_plugin_data.len=samples*sizeof(int16_t)*pl_surround.output_channels;
   return 1;
 }
? libavcodec/.depend
? libavcodec/README.MPlayer


More information about the MPlayer-dev-eng mailing list