mpc8: fix maximum bands handling

In Musepack SV8 codec property tell the maximum nonzero band, but every
frame codes maximum band as a limit (i.e. strictly less than given value).
Synthesis also expects maximum nonzero band, so there's a need to convert
frame maximum band limit value.
(cherry picked from commit b56825c4

)

Conflicts:

	libavcodec/mpc8.c
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpc8.c

@@ -275,7 +275,7 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void *data,
         maxband = c->last_max_band + get_vlc2(gb, band_vlc.table, MPC8_BANDS_BITS, 2);
         if(maxband > 32) maxband -= 33;
     }
-    if(maxband >= BANDS) {
+    if(maxband > c->maxbands + 1) {
         av_log(avctx, AV_LOG_ERROR, "maxband %d too large\n",maxband);
         return AVERROR_INVALIDDATA;
     }
@@ -412,7 +412,8 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void *data,
         }
     }
 
-    ff_mpc_dequantize_and_synth(c, maxband, c->frame.data[0], avctx->channels);
+    ff_mpc_dequantize_and_synth(c, maxband - 1, c->frame.data[0],
+                                avctx->channels);
 
     c->cur_frame++;