iff: check for pbm tag

more robust
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/iff.c

@@ -541,18 +541,20 @@ static int decode_frame_ilbm(AVCodecContext *avctx,
                 }
             }
         }
-    } else if (avctx->pix_fmt == PIX_FMT_PAL8 || avctx->pix_fmt == PIX_FMT_GRAY8) { // IFF-PBM
-        for(y = 0; y < avctx->height; y++ ) {
-            uint8_t *row = &s->frame.data[0][y * s->frame.linesize[0]];
-            memcpy(row, buf, FFMIN(avctx->width, buf_end - buf));
-            buf += avctx->width + (avctx->width % 2); // padding if odd
-        }
-    } else { // IFF-PBM: HAM to PIX_FMT_BGR32
-        for (y = 0; y < avctx->height; y++) {
-            uint8_t *row = &s->frame.data[0][ y*s->frame.linesize[0] ];
-            memcpy(s->ham_buf, buf, FFMIN(avctx->width, buf_end - buf));
-            buf += avctx->width + (avctx->width & 1); // padding if odd
-            decode_ham_plane32((uint32_t *) row, s->ham_buf, s->ham_palbuf, s->planesize);
+    } else if (avctx->codec_tag == MKTAG('P','B','M',' ')) { // IFF-PBM
+        if (avctx->pix_fmt == PIX_FMT_PAL8 || avctx->pix_fmt == PIX_FMT_GRAY8) {
+            for(y = 0; y < avctx->height; y++ ) {
+                uint8_t *row = &s->frame.data[0][y * s->frame.linesize[0]];
+                memcpy(row, buf, FFMIN(avctx->width, buf_end - buf));
+                buf += avctx->width + (avctx->width % 2); // padding if odd
+            }
+        } else { // IFF-PBM: HAM to PIX_FMT_BGR32
+            for (y = 0; y < avctx->height; y++) {
+                uint8_t *row = &s->frame.data[0][ y*s->frame.linesize[0] ];
+                memcpy(s->ham_buf, buf, FFMIN(avctx->width, buf_end - buf));
+                buf += avctx->width + (avctx->width & 1); // padding if odd
+                decode_ham_plane32((uint32_t *) row, s->ham_buf, s->ham_palbuf, s->planesize);
+            }
         }
     }
 
@@ -630,16 +632,18 @@ static int decode_frame_byterun1(AVCodecContext *avctx,
                 }
             }
         }
-    } else if (avctx->pix_fmt == PIX_FMT_PAL8 || avctx->pix_fmt == PIX_FMT_GRAY8) { // IFF-PBM
-        for(y = 0; y < avctx->height ; y++ ) {
-            uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
-            buf += decode_byterun(row, avctx->width, buf, buf_end);
-        }
-    } else { // IFF-PBM: HAM to PIX_FMT_BGR32
-        for (y = 0; y < avctx->height ; y++) {
-            uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
-            buf += decode_byterun(s->ham_buf, avctx->width, buf, buf_end);
-            decode_ham_plane32((uint32_t *) row, s->ham_buf, s->ham_palbuf, s->planesize);
+    } else if (avctx->codec_tag == MKTAG('P','B','M',' ')) { // IFF-PBM
+        if (avctx->pix_fmt == PIX_FMT_PAL8 || avctx->pix_fmt == PIX_FMT_GRAY8) {
+            for(y = 0; y < avctx->height ; y++ ) {
+                uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
+                buf += decode_byterun(row, avctx->width, buf, buf_end);
+            }
+        } else { // IFF-PBM: HAM to PIX_FMT_BGR32
+            for (y = 0; y < avctx->height ; y++) {
+                uint8_t *row = &s->frame.data[0][y*s->frame.linesize[0]];
+                buf += decode_byterun(s->ham_buf, avctx->width, buf, buf_end);
+                decode_ham_plane32((uint32_t *) row, s->ham_buf, s->ham_palbuf, s->planesize);
+            }
         }
     }