avcodec/vc1: more corrections for AC inverse quantization scaling

HALFQP should only be added to the inverse quantizer when the block is
coded with PQUANT. When PQUANT is equal to ALTPQUANT, the original test
for the addition of HALFQP fails. A negative value for mquant indicates
that the value was derived from VOPDQUANT.

Fixes #4372

Signed-off-by: Jerome Borsboom <jerome.borsboom@carpalis.nl>

2 files changed, 69 insertions, 61 deletions

diff --git a/libavcodec/vc1.c b/libavcodec/vc1.c
index 5fc479347e..b7050440d5 100644
--- a/libavcodec/vc1.c
+++ b/libavcodec/vc1.c
@@ -991,6 +991,7 @@ int ff_vc1_parse_frame_header_adv(VC1Context *v, GetBitContext* gb)
         v->pquantizer = 1;
         break;
     }
+    v->dquantfrm = 0;
     if (v->postprocflag)
         v->postproc = get_bits(gb, 2);
 
diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
index de06b6fb2a..7cabe49eda 100644
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -160,13 +160,13 @@ static void vc1_put_signed_blocks_clamped(VC1Context *v)
         int edges = 0;                                         \
         if (v->dqprofile == DQPROFILE_ALL_MBS) {               \
             if (v->dqbilevel) {                                \
-                mquant = (get_bits1(gb)) ? v->altpq : v->pq;   \
+                mquant = (get_bits1(gb)) ? -v->altpq : v->pq;  \
             } else {                                           \
                 mqdiff = get_bits(gb, 3);                      \
                 if (mqdiff != 7)                               \
-                    mquant = v->pq + mqdiff;                   \
+                    mquant = -v->pq - mqdiff;                  \
                 else                                           \
-                    mquant = get_bits(gb, 5);                  \
+                    mquant = -get_bits(gb, 5);                 \
             }                                                  \
         }                                                      \
         if (v->dqprofile == DQPROFILE_SINGLE_EDGE)             \
@@ -176,13 +176,13 @@ static void vc1_put_signed_blocks_clamped(VC1Context *v)
         else if (v->dqprofile == DQPROFILE_FOUR_EDGES)         \
             edges = 15;                                        \
         if ((edges&1) && !s->mb_x)                             \
-            mquant = v->altpq;                                 \
+            mquant = -v->altpq;                                \
         if ((edges&2) && s->first_slice_line)                  \
-            mquant = v->altpq;                                 \
+            mquant = -v->altpq;                                \
         if ((edges&4) && s->mb_x == (s->mb_width - 1))         \
-            mquant = v->altpq;                                 \
+            mquant = -v->altpq;                                \
         if ((edges&8) && s->mb_y == (s->mb_height - 1))        \
-            mquant = v->altpq;                                 \
+            mquant = -v->altpq;                                \
         if (!mquant || mquant > 31) {                          \
             av_log(v->s.avctx, AV_LOG_ERROR,                   \
                    "Overriding invalid mquant %d\n", mquant);  \
@@ -388,7 +388,7 @@ static inline int ff_vc1_pred_dc(MpegEncContext *s, int overlap, int pq, int n,
     int dqscale_index;
 
     /* scale predictors if needed */
-    q1 = s->current_picture.qscale_table[mb_pos];
+    q1 = FFABS(s->current_picture.qscale_table[mb_pos]);
     dqscale_index = s->y_dc_scale_table[q1] - 1;
     if (dqscale_index < 0)
         return 0;
@@ -404,12 +404,12 @@ static inline int ff_vc1_pred_dc(MpegEncContext *s, int overlap, int pq, int n,
     a = dc_val[ - wrap];
 
     if (c_avail && (n != 1 && n != 3)) {
-        q2 = s->current_picture.qscale_table[mb_pos - 1];
+        q2 = FFABS(s->current_picture.qscale_table[mb_pos - 1]);
         if (q2 && q2 != q1)
             c = (c * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
     }
     if (a_avail && (n != 2 && n != 3)) {
-        q2 = s->current_picture.qscale_table[mb_pos - s->mb_stride];
+        q2 = FFABS(s->current_picture.qscale_table[mb_pos - s->mb_stride]);
         if (q2 && q2 != q1)
             a = (a * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
     }
@@ -419,7 +419,7 @@ static inline int ff_vc1_pred_dc(MpegEncContext *s, int overlap, int pq, int n,
             off--;
         if (n != 2)
             off -= s->mb_stride;
-        q2 = s->current_picture.qscale_table[off];
+        q2 = FFABS(s->current_picture.qscale_table[off]);
         if (q2 && q2 != q1)
             b = (b * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
     }
@@ -700,6 +700,7 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
     int scale;
     int q1, q2 = 0;
     int mb_pos = s->mb_x + s->mb_y * s->mb_stride;
+    int quant = FFABS(mquant);
 
     /* Get DC differential */
     if (n < 4) {
@@ -712,7 +713,7 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
         return -1;
     }
     if (dcdiff) {
-        const int m = (mquant == 1 || mquant == 2) ? 3 - mquant : 0;
+        const int m = (quant == 1 || quant == 2) ? 3 - quant : 0;
         if (dcdiff == 119 /* ESC index value */) {
             dcdiff = get_bits(gb, 8 + m);
         } else {
@@ -724,7 +725,7 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
     }
 
     /* Prediction */
-    dcdiff += ff_vc1_pred_dc(&v->s, v->overlap, mquant, n, v->a_avail, v->c_avail, &dc_val, &dc_pred_dir);
+    dcdiff += ff_vc1_pred_dc(&v->s, v->overlap, quant, n, v->a_avail, v->c_avail, &dc_val, &dc_pred_dir);
     *dc_val = dcdiff;
 
     /* Store the quantized DC coeff, used for prediction */
@@ -738,7 +739,7 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
     if (!a_avail && !c_avail)
         use_pred = 0;
 
-    scale = mquant * 2 + ((mquant == v->pq) ? v->halfpq : 0);
+    scale = quant * 2 + ((mquant < 0) ? 0 : v->halfpq);
 
     ac_val  = s->ac_val[0][s->block_index[n]];
     ac_val2 = ac_val;
@@ -804,11 +805,12 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
                 ac_val += 8;
             }
             /* scale predictors if needed*/
+            q1 = FFABS(q1) * 2 + ((q1 < 0) ? 0 : v->halfpq) - 1;
+            if (q1 < 1)
+                return AVERROR_INVALIDDATA;
+            if (q2)
+                q2 = FFABS(q2) * 2 + ((q2 < 0) ? 0 : v->halfpq) - 1;
             if (q2 && q1 != q2) {
-                q1 = q1 * 2 + ((q1 == v->pq) ? v->halfpq : 0) - 1;
-                if (q1 < 1)
-                    return AVERROR_INVALIDDATA;
-                q2 = q2 * 2 + ((q2 == v->pq) ? v->halfpq : 0) - 1;
                 for (k = 1; k < 8; k++)
                     block[k << sh] += (ac_val[k] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18;
             } else {
@@ -827,7 +829,7 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
             if (block[k]) {
                 block[k] *= scale;
                 if (!v->pquantizer)
-                    block[k] += (block[k] < 0) ? -mquant : mquant;
+                    block[k] += (block[k] < 0) ? -quant : quant;
             }
 
     } else { // no AC coeffs
@@ -846,18 +848,19 @@ static int vc1_decode_i_block_adv(VC1Context *v, int16_t block[64], int n,
                 ac_val2 += 8;
             }
             memcpy(ac_val2, ac_val, 8 * 2);
+            q1 = FFABS(q1) * 2 + ((q1 < 0) ? 0 : v->halfpq) - 1;
+            if (q1 < 1)
+                return AVERROR_INVALIDDATA;
+            if (q2)
+                q2 = FFABS(q2) * 2 + ((q2 < 0) ? 0 : v->halfpq) - 1;
             if (q2 && q1 != q2) {
-                q1 = q1 * 2 + ((q1 == v->pq) ? v->halfpq : 0) - 1;
-                q2 = q2 * 2 + ((q2 == v->pq) ? v->halfpq : 0) - 1;
-                if (q1 < 1)
-                    return AVERROR_INVALIDDATA;
                 for (k = 1; k < 8; k++)
                     ac_val2[k] = (ac_val2[k] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18;
             }
             for (k = 1; k < 8; k++) {
                 block[k << sh] = ac_val2[k] * scale;
                 if (!v->pquantizer && block[k << sh])
-                    block[k << sh] += (block[k << sh] < 0) ? -mquant : mquant;
+                    block[k << sh] += (block[k << sh] < 0) ? -quant : quant;
             }
         }
     }
@@ -890,15 +893,16 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
     int use_pred = s->ac_pred;
     int scale;
     int q1, q2 = 0;
+    int quant = FFABS(mquant);
 
     s->bdsp.clear_block(block);
 
     /* XXX: Guard against dumb values of mquant */
-    mquant = av_clip_uintp2(mquant, 5);
+    quant = av_clip_uintp2(quant, 5);
 
     /* Set DC scale - y and c use the same */
-    s->y_dc_scale = s->y_dc_scale_table[mquant];
-    s->c_dc_scale = s->c_dc_scale_table[mquant];
+    s->y_dc_scale = s->y_dc_scale_table[quant];
+    s->c_dc_scale = s->c_dc_scale_table[quant];
 
     /* Get DC differential */
     if (n < 4) {
@@ -911,7 +915,7 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
         return -1;
     }
     if (dcdiff) {
-        const int m = (mquant == 1 || mquant == 2) ? 3 - mquant : 0;
+        const int m = (quant == 1 || quant == 2) ? 3 - quant : 0;
         if (dcdiff == 119 /* ESC index value */) {
             dcdiff = get_bits(gb, 8 + m);
         } else {
@@ -923,7 +927,7 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
     }
 
     /* Prediction */
-    dcdiff += ff_vc1_pred_dc(&v->s, v->overlap, mquant, n, a_avail, c_avail, &dc_val, &dc_pred_dir);
+    dcdiff += ff_vc1_pred_dc(&v->s, v->overlap, quant, n, a_avail, c_avail, &dc_val, &dc_pred_dir);
     *dc_val = dcdiff;
 
     /* Store the quantized DC coeff, used for prediction */
@@ -944,7 +948,7 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
     ac_val = s->ac_val[0][s->block_index[n]];
     ac_val2 = ac_val;
 
-    scale = mquant * 2 + ((mquant == v->pq) ? v->halfpq : 0);
+    scale = quant * 2 + ((mquant < 0) ? 0 : v->halfpq);
 
     if (dc_pred_dir) //left
         ac_val -= 16;
@@ -988,12 +992,12 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
         /* apply AC prediction if needed */
         if (use_pred) {
             /* scale predictors if needed*/
+            q1 = FFABS(q1) * 2 + ((q1 < 0) ? 0 : v->halfpq) - 1;
+            if (q1 < 1)
+                return AVERROR_INVALIDDATA;
+            if (q2)
+                q2 = FFABS(q2) * 2 + ((q2 < 0) ? 0 : v->halfpq) - 1;
             if (q2 && q1 != q2) {
-                q1 = q1 * 2 + ((q1 == v->pq) ? v->halfpq : 0) - 1;
-                q2 = q2 * 2 + ((q2 == v->pq) ? v->halfpq : 0) - 1;
-
-                if (q1 < 1)
-                    return AVERROR_INVALIDDATA;
                 if (dc_pred_dir) { // left
                     for (k = 1; k < 8; k++)
                         block[k << v->left_blk_sh] += (ac_val[k] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18;
@@ -1022,7 +1026,7 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
             if (block[k]) {
                 block[k] *= scale;
                 if (!v->pquantizer)
-                    block[k] += (block[k] < 0) ? -mquant : mquant;
+                    block[k] += (block[k] < 0) ? -quant : quant;
             }
 
         if (use_pred) i = 63;
@@ -1033,11 +1037,12 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
         if (dc_pred_dir) { // left
             if (use_pred) {
                 memcpy(ac_val2, ac_val, 8 * 2);
+                q1 = FFABS(q1) * 2 + ((q1 < 0) ? 0 : v->halfpq) - 1;
+                if (q1 < 1)
+                    return AVERROR_INVALIDDATA;
+                if (q2)
+                    q2 = FFABS(q2) * 2 + ((q2 < 0) ? 0 : v->halfpq) - 1;
                 if (q2 && q1 != q2) {
-                    q1 = q1 * 2 + ((q1 == v->pq) ? v->halfpq : 0) - 1;
-                    q2 = q2 * 2 + ((q2 == v->pq) ? v->halfpq : 0) - 1;
-                    if (q1 < 1)
-                        return AVERROR_INVALIDDATA;
                     for (k = 1; k < 8; k++)
                         ac_val2[k] = (ac_val2[k] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18;
                 }
@@ -1045,11 +1050,12 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
         } else { // top
             if (use_pred) {
                 memcpy(ac_val2 + 8, ac_val + 8, 8 * 2);
+                q1 = FFABS(q1) * 2 + ((q1 < 0) ? 0 : v->halfpq) - 1;
+                if (q1 < 1)
+                    return AVERROR_INVALIDDATA;
+                if (q2)
+                    q2 = FFABS(q2) * 2 + ((q2 < 0) ? 0 : v->halfpq) - 1;
                 if (q2 && q1 != q2) {
-                    q1 = q1 * 2 + ((q1 == v->pq) ? v->halfpq : 0) - 1;
-                    q2 = q2 * 2 + ((q2 == v->pq) ? v->halfpq : 0) - 1;
-                    if (q1 < 1)
-                        return AVERROR_INVALIDDATA;
                     for (k = 1; k < 8; k++)
                         ac_val2[k + 8] = (ac_val2[k + 8] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18;
                 }
@@ -1062,13 +1068,13 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n,
                 for (k = 1; k < 8; k++) {
                     block[k << v->left_blk_sh] = ac_val2[k] * scale;
                     if (!v->pquantizer && block[k << v->left_blk_sh])
-                        block[k << v->left_blk_sh] += (block[k << v->left_blk_sh] < 0) ? -mquant : mquant;
+                        block[k << v->left_blk_sh] += (block[k << v->left_blk_sh] < 0) ? -quant : quant;
                 }
             } else { // top
                 for (k = 1; k < 8; k++) {
                     block[k << v->top_blk_sh] = ac_val2[k + 8] * scale;
                     if (!v->pquantizer && block[k << v->top_blk_sh])
-                        block[k << v->top_blk_sh] += (block[k << v->top_blk_sh] < 0) ? -mquant : mquant;
+                        block[k << v->top_blk_sh] += (block[k << v->top_blk_sh] < 0) ? -quant : quant;
                 }
             }
             i = 63;
@@ -1093,6 +1099,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
     int scale, off, idx, last, skip, value;
     int ttblk = ttmb & 7;
     int pat = 0;
+    int quant = FFABS(mquant);
 
     s->bdsp.clear_block(block);
 
@@ -1113,7 +1120,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
         if (ttblk == TT_4X8_RIGHT || ttblk == TT_4X8_LEFT)
             ttblk = TT_4X8;
     }
-    scale = 2 * mquant + ((v->pq == mquant) ? v->halfpq : 0);
+    scale = quant * 2 + ((mquant < 0) ? 0 : v->halfpq);
 
     // convert transforms like 8X4_TOP to generic TT and SUBBLKPAT
     if (ttblk == TT_8X4_TOP || ttblk == TT_8X4_BOTTOM) {
@@ -1140,7 +1147,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
                 idx = v->zzi_8x8[i++];
             block[idx] = value * scale;
             if (!v->pquantizer)
-                block[idx] += (block[idx] < 0) ? -mquant : mquant;
+                block[idx] += (block[idx] < 0) ? -quant : quant;
         }
         if (!skip_block) {
             if (i == 1)
@@ -1168,7 +1175,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
                     idx = ff_vc1_adv_interlaced_4x4_zz[i++];
                 block[idx + off] = value * scale;
                 if (!v->pquantizer)
-                    block[idx + off] += (block[idx + off] < 0) ? -mquant : mquant;
+                    block[idx + off] += (block[idx + off] < 0) ? -quant : quant;
             }
             if (!(subblkpat & (1 << (3 - j))) && !skip_block) {
                 if (i == 1)
@@ -1195,7 +1202,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
                     idx = ff_vc1_adv_interlaced_8x4_zz[i++] + off;
                 block[idx] = value * scale;
                 if (!v->pquantizer)
-                    block[idx] += (block[idx] < 0) ? -mquant : mquant;
+                    block[idx] += (block[idx] < 0) ? -quant : quant;
             }
             if (!(subblkpat & (1 << (1 - j))) && !skip_block) {
                 if (i == 1)
@@ -1222,7 +1229,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
                     idx = ff_vc1_adv_interlaced_4x8_zz[i++] + off;
                 block[idx] = value * scale;
                 if (!v->pquantizer)
-                    block[idx] += (block[idx] < 0) ? -mquant : mquant;
+                    block[idx] += (block[idx] < 0) ? -quant : quant;
             }
             if (!(subblkpat & (1 << (1 - j))) && !skip_block) {
                 if (i == 1)
@@ -1549,8 +1556,8 @@ static int vc1_decode_p_mb_intfr(VC1Context *v)
             GET_MQUANT();
             s->current_picture.qscale_table[mb_pos] = mquant;
             /* Set DC scale - y and c use the same (not sure if necessary here) */
-            s->y_dc_scale = s->y_dc_scale_table[mquant];
-            s->c_dc_scale = s->c_dc_scale_table[mquant];
+            s->y_dc_scale = s->y_dc_scale_table[FFABS(mquant)];
+            s->c_dc_scale = s->c_dc_scale_table[FFABS(mquant)];
             dst_idx = 0;
             for (i = 0; i < 6; i++) {
                 v->a_avail = v->c_avail          = 0;
@@ -1711,8 +1718,8 @@ static int vc1_decode_p_mb_intfi(VC1Context *v)
         GET_MQUANT();
         s->current_picture.qscale_table[mb_pos] = mquant;
         /* Set DC scale - y and c use the same (not sure if necessary here) */
-        s->y_dc_scale = s->y_dc_scale_table[mquant];
-        s->c_dc_scale = s->c_dc_scale_table[mquant];
+        s->y_dc_scale = s->y_dc_scale_table[FFABS(mquant)];
+        s->c_dc_scale = s->c_dc_scale_table[FFABS(mquant)];
         v->s.ac_pred  = v->acpred_plane[mb_pos] = get_bits1(gb);
         mb_has_coeffs = idx_mbmode & 1;
         if (mb_has_coeffs)
@@ -1989,8 +1996,8 @@ static void vc1_decode_b_mb_intfi(VC1Context *v)
         GET_MQUANT();
         s->current_picture.qscale_table[mb_pos] = mquant;
         /* Set DC scale - y and c use the same (not sure if necessary here) */
-        s->y_dc_scale = s->y_dc_scale_table[mquant];
-        s->c_dc_scale = s->c_dc_scale_table[mquant];
+        s->y_dc_scale = s->y_dc_scale_table[FFABS(mquant)];
+        s->c_dc_scale = s->c_dc_scale_table[FFABS(mquant)];
         v->s.ac_pred  = v->acpred_plane[mb_pos] = get_bits1(gb);
         mb_has_coeffs = idx_mbmode & 1;
         if (mb_has_coeffs)
@@ -2218,8 +2225,8 @@ static int vc1_decode_b_mb_intfr(VC1Context *v)
         GET_MQUANT();
         s->current_picture.qscale_table[mb_pos] = mquant;
         /* Set DC scale - y and c use the same (not sure if necessary here) */
-        s->y_dc_scale = s->y_dc_scale_table[mquant];
-        s->c_dc_scale = s->c_dc_scale_table[mquant];
+        s->y_dc_scale = s->y_dc_scale_table[FFABS(mquant)];
+        s->c_dc_scale = s->c_dc_scale_table[FFABS(mquant)];
         dst_idx = 0;
         for (i = 0; i < 6; i++) {
             v->a_avail = v->c_avail          = 0;
@@ -2687,8 +2694,8 @@ static void vc1_decode_i_blocks_adv(VC1Context *v)
 
             s->current_picture.qscale_table[mb_pos] = mquant;
             /* Set DC scale - y and c use the same */
-            s->y_dc_scale = s->y_dc_scale_table[mquant];
-            s->c_dc_scale = s->c_dc_scale_table[mquant];
+            s->y_dc_scale = s->y_dc_scale_table[FFABS(mquant)];
+            s->c_dc_scale = s->c_dc_scale_table[FFABS(mquant)];
 
             for (k = 0; k < 6; k++) {
                 v->mb_type[0][s->block_index[k]] = 1;