avcodec/adxdec: add support for 6 channels

libavcodec/adx.h

@@ -35,9 +35,11 @@ typedef struct ADXChannelState {
     int s1,s2;
 } ADXChannelState;
 
+#define MAX_CHANNELS 6
+
 typedef struct ADXContext {
     int channels;
-    ADXChannelState prev[2];
+    ADXChannelState prev[MAX_CHANNELS];
     int header_parsed;
     int eof;
     int cutoff;

libavcodec/adxdec.c

@@ -70,7 +70,7 @@ static int adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
 
     /* channels */
     channels = buf[7];
-    if (channels <= 0 || channels > 2)
+    if (channels <= 0 || channels > MAX_CHANNELS)
         return AVERROR_INVALIDDATA;
 
     if (avctx->ch_layout.nb_channels != channels) {