flac: make FLAC_CHMODE_* constants consecutive

libavcodec/flac.c

@@ -55,8 +55,9 @@ int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
     if (fi->ch_mode < FLAC_MAX_CHANNELS) {
         fi->channels = fi->ch_mode + 1;
         fi->ch_mode = FLAC_CHMODE_INDEPENDENT;
-    } else if (fi->ch_mode <= FLAC_CHMODE_MID_SIDE) {
+    } else if (fi->ch_mode < FLAC_MAX_CHANNELS + FLAC_CHMODE_MID_SIDE) {
         fi->channels = 2;
+        fi->ch_mode -= FLAC_MAX_CHANNELS - 1;
     } else {
         av_log(avctx, AV_LOG_ERROR + log_level_offset,
                "invalid channel mode: %d\n", fi->ch_mode);

libavcodec/flac.h

@@ -37,10 +37,10 @@
 #define FLAC_MIN_FRAME_SIZE    11
 
 enum {
-    FLAC_CHMODE_INDEPENDENT =  0,
-    FLAC_CHMODE_LEFT_SIDE   =  8,
-    FLAC_CHMODE_RIGHT_SIDE  =  9,
-    FLAC_CHMODE_MID_SIDE    = 10,
+    FLAC_CHMODE_INDEPENDENT = 0,
+    FLAC_CHMODE_LEFT_SIDE   = 1,
+    FLAC_CHMODE_RIGHT_SIDE  = 2,
+    FLAC_CHMODE_MID_SIDE    = 3,
 };
 
 enum {

libavcodec/flacenc.c

@@ -1001,15 +1001,8 @@ static int estimate_stereo_mode(int32_t *left_ch, int32_t *right_ch, int n)
     for (i = 1; i < 4; i++)
         if (score[i] < score[best])
             best = i;
-    if (best == 0) {
-        return FLAC_CHMODE_INDEPENDENT;
-    } else if (best == 1) {
-        return FLAC_CHMODE_LEFT_SIDE;
-    } else if (best == 2) {
-        return FLAC_CHMODE_RIGHT_SIDE;
-    } else {
-        return FLAC_CHMODE_MID_SIDE;
-    }
+
+    return best;
 }
 
 
@@ -1081,7 +1074,7 @@ static void write_frame_header(FlacEncodeContext *s)
     if (frame->ch_mode == FLAC_CHMODE_INDEPENDENT)
         put_bits(&s->pb, 4, s->channels-1);
     else
-        put_bits(&s->pb, 4, frame->ch_mode);
+        put_bits(&s->pb, 4, frame->ch_mode + FLAC_MAX_CHANNELS - 1);
 
     put_bits(&s->pb, 3, 4); /* bits-per-sample code */
     put_bits(&s->pb, 1, 0);