[FFmpeg-devel] [PATCH 1/4] dpx: use aligned line starts

[Christophe Gisquet]

SMPTE 268M-2003 specifies that each line starts at a 4-bytes boundary.
Therefore, modify correspondingly the input buffer strides and size.

Partially fixes ticket #3692: DLAD_8b_3c_big.dpx still has inverted
colors, which might be related to endianness.
---
 libavcodec/dpx.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/libavcodec/dpx.c b/libavcodec/dpx.c
index 5f05cd8..8cd7d73 100644
--- a/libavcodec/dpx.c
+++ b/libavcodec/dpx.c
@@ -77,8 +77,8 @@ static int decode_frame(AVCodecContext *avctx,
 
     unsigned int offset;
     int magic_num, endian;
-    int x, y, i, ret;
-    int w, h, bits_per_color, descriptor, elements, packing, total_size;
+    int x, y, stride, i, ret;
+    int w, h, bits_per_color, descriptor, elements, packing;
     int encoding;
 
     unsigned int rgbBuffer = 0;
@@ -175,24 +175,24 @@ static int decode_frame(AVCodecContext *avctx,
 
     switch (bits_per_color) {
     case 8:
-        total_size = avctx->width * avctx->height * elements;
+        stride = avctx->width * elements;
         break;
     case 10:
         if (!packing) {
             av_log(avctx, AV_LOG_ERROR, "Packing to 32bit required\n");
             return -1;
         }
-        total_size = (avctx->width * elements + 2) / 3 * 4 * avctx->height;
+        stride = (avctx->width * elements + 2) / 3 * 4;
         break;
     case 12:
         if (!packing) {
             av_log(avctx, AV_LOG_ERROR, "Packing to 16bit required\n");
             return -1;
         }
-        total_size = 2 * avctx->width * avctx->height * elements;
+        stride = 2 * avctx->width * elements;
         break;
     case 16:
-        total_size = 2 * avctx->width * avctx->height * elements;
+        stride = 2 * avctx->width * elements;
         break;
     case 1:
     case 32:
@@ -203,6 +203,20 @@ static int decode_frame(AVCodecContext *avctx,
         return AVERROR_INVALIDDATA;
     }
 
+    // Table 3c: Runs will always break at scan line boundaries. Packing
+    // will always break to the next 32-bit word at scan-line boundaries.
+    // Unfortunately, the encoder produced invalid files, so attempt
+    // to detect it
+    if (FFALIGN(stride, 4)*avctx->height + (int64_t)offset > avpkt->size) {
+        // Alignment seems unappliable, try without
+        if (stride*avctx->height + (int64_t)offset > avpkt->size) {
+            av_log(avctx, AV_LOG_ERROR, "Overread buffer. Invalid header?\n");
+            return AVERROR_INVALIDDATA;
+        }
+    } else {
+        stride = FFALIGN(stride, 4);
+    }
+
     switch (1000 * descriptor + 10 * bits_per_color + endian) {
     case 6081:
     case 6080:
@@ -266,10 +280,6 @@ static int decode_frame(AVCodecContext *avctx,
     for (i=0; i<AV_NUM_DATA_POINTERS; i++)
         ptr[i] = p->data[i];
 
-    if (total_size + (int64_t)offset > avpkt->size) {
-        av_log(avctx, AV_LOG_ERROR, "Overread buffer. Invalid header?\n");
-        return AVERROR_INVALIDDATA;
-    }
     switch (bits_per_color) {
     case 10:
         for (x = 0; x < avctx->height; x++) {
@@ -308,6 +318,8 @@ static int decode_frame(AVCodecContext *avctx,
                 // For 12 bit, ignore alpha
                 if (elements == 4)
                     buf += 2;
+                // Jump to next aligned position
+                buf += stride - 6*avctx->width;
             }
             for (i = 0; i < 3; i++)
                 ptr[i] += p->linesize[i];
@@ -317,7 +329,7 @@ static int decode_frame(AVCodecContext *avctx,
         elements *= 2;
     case 8:
         av_image_copy_plane(ptr[0], p->linesize[0],
-                            buf, elements * avctx->width,
+                            buf, stride,
                             elements * avctx->width, avctx->height);
         break;
     }
-- 
1.9.2.msysgit.0