Update AAC decoder wrapper to latest FDK API for output channel count

Rename decoder parameter for the maximum number of PCM output channels,
 according to FDK AAC decoder interface, as defined in aacdecoder_lib.h

Bug 9428126

Change-Id: I2f0f6ca848bdbc8657d8dea589b03238245c0eaf
diff --git a/media/libstagefright/codecs/aacdec/SoftAAC2.cpp b/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
index f842e27..2f5eff4 100644
--- a/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
+++ b/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
@@ -30,7 +30,7 @@
 #define DRC_DEFAULT_MOBILE_REF_LEVEL 64  /* 64*-0.25dB = -16 dB below full scale for mobile conf */
 #define DRC_DEFAULT_MOBILE_DRC_CUT   127 /* maximum compression of dynamic range for mobile conf */
 #define DRC_DEFAULT_MOBILE_DRC_BOOST 127 /* maximum compression of dynamic range for mobile conf */
-#define MAX_CHANNEL_COUNT            6  /* maximum number of audio channels that can be decoded */
+#define MAX_CHANNEL_COUNT            8  /* maximum number of audio channels that can be decoded */
 // names of properties that can be used to override the default DRC settings
 #define PROP_DRC_OVERRIDE_REF_LEVEL  "aac_drc_reference_level"
 #define PROP_DRC_OVERRIDE_CUT        "aac_drc_cut"
@@ -296,8 +296,11 @@
         if (!(property_get("media.aac_51_output_enabled", value, NULL) &&
                 (!strcmp(value, "1") || !strcasecmp(value, "true")))) {
             ALOGI("Downmixing multichannel AAC to stereo");
-            aacDecoder_SetParam(mAACDecoder, AAC_PCM_OUTPUT_CHANNELS, 2);
+            aacDecoder_SetParam(mAACDecoder, AAC_PCM_MAX_OUTPUT_CHANNELS, 2);
             mStreamInfo->numChannels = 2;
+            // By default, the decoder creates a 5.1 channel downmix signal
+            // for seven and eight channel input streams. To enable 6.1 and 7.1 channel output
+            // use aacDecoder_SetParam(mAACDecoder, AAC_PCM_MAX_OUTPUT_CHANNELS, -1)
         }
     }
 }