avcodec/mpc8: Unobfuscate sign-extension

[ffmpeg] / libavcodec / mpc8.c

diff --git a/libavcodec/mpc8.c b/libavcodec/mpc8.c
index 3be2f79a5a1a79d20d52bbc29fc8699f61e4d145..631bac27532d4435c81daeb7aca86a656828c66b 100644 (file)
--- a/libavcodec/mpc8.c
+++ b/libavcodec/mpc8.c
@@ -62,7 +62,7 @@ static inline int mpc8_dec_enum(GetBitContext *gb, int k, int n)
     do {
         n--;
         if (code >= C[n]) {
-            bits |= 1 << n;
+            bits |= 1U << n;
             code -= C[n];
             C -= 32;
             k--;
@@ -364,8 +364,9 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void *data,
                 for(j = 0; j < SAMPLES_PER_BAND; j += SAMPLES_PER_BAND / 2){
                     cnt = get_vlc2(gb, q1_vlc.table, MPC8_Q1_BITS, 2);
                     t = mpc8_get_mask(gb, 18, cnt);
-                    for(k = 0; k < SAMPLES_PER_BAND / 2; k++, t <<= 1)
-                        c->Q[ch][off + j + k] = (t & 0x20000) ? (get_bits1(gb) << 1) - 1 : 0;
+                    for(k = 0; k < SAMPLES_PER_BAND / 2; k++)
+                        c->Q[ch][off + j + k] = t & (1 << (SAMPLES_PER_BAND / 2 - k - 1))
+                                                ? (get_bits1(gb) << 1) - 1 : 0;
                 }
                 break;
             case 2:
@@ -383,7 +384,7 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void *data,
                 for(j = 0; j < SAMPLES_PER_BAND; j += 2){
                     t = get_vlc2(gb, q3_vlc[res - 3].table, MPC8_Q3_BITS, 2) + q3_offsets[res - 3];
                     c->Q[ch][off + j + 1] = t >> 4;
-                    c->Q[ch][off + j + 0] = (t & 8) ? (t & 0xF) - 16 : (t & 0xF);
+                    c->Q[ch][off + j + 0] = sign_extend(t, 4);
                 }
                 break;
             case 5: