adpcm: ADPCM IMA SMJPEG stereo decoding

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/adpcm.c

@@ -473,7 +473,7 @@ static int get_nb_samples(AVCodecContext *avctx, GetByteContext *gb,
         case AV_CODEC_ID_ADPCM_4XM:
         case AV_CODEC_ID_ADPCM_IMA_ISS:     header_size = 4 * ch;      break;
         case AV_CODEC_ID_ADPCM_IMA_AMV:     header_size = 8;           break;
-        case AV_CODEC_ID_ADPCM_IMA_SMJPEG:  header_size = 4;           break;
+        case AV_CODEC_ID_ADPCM_IMA_SMJPEG:  header_size = 4 * ch;      break;
     }
     if (header_size > 0)
         return (buf_size - header_size) * 2 / ch;
@@ -1153,20 +1153,22 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data,
         }
         break;
     case AV_CODEC_ID_ADPCM_IMA_SMJPEG:
-        c->status[0].predictor = sign_extend(bytestream2_get_be16u(&gb), 16);
-        c->status[0].step_index = bytestream2_get_byteu(&gb);
+        for (i = 0; i < avctx->channels; i++) {
+        c->status[i].predictor = sign_extend(bytestream2_get_be16u(&gb), 16);
+        c->status[i].step_index = bytestream2_get_byteu(&gb);
         bytestream2_skipu(&gb, 1);
-        if (c->status[0].step_index > 88u) {
+        if (c->status[i].step_index > 88u) {
             av_log(avctx, AV_LOG_ERROR, "ERROR: step_index = %i\n",
-                   c->status[0].step_index);
+                   c->status[i].step_index);
             return AVERROR_INVALIDDATA;
         }
+        }
 
         for (n = nb_samples >> (1 - st); n > 0; n--) {
             int v = bytestream2_get_byteu(&gb);
 
-            *samples++ = adpcm_ima_qt_expand_nibble(&c->status[0], v >> 4, 3);
-            *samples++ = adpcm_ima_qt_expand_nibble(&c->status[0], v & 0xf, 3);
+            *samples++ = adpcm_ima_qt_expand_nibble(&c->status[0 ], v >> 4, 3);
+            *samples++ = adpcm_ima_qt_expand_nibble(&c->status[st], v & 0xf, 3);
         }
         break;
     case AV_CODEC_ID_ADPCM_CT: