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

[Christophe Gisquet]

Hi,

the attached patch improves the decoding of ticket #3692 by following
S268M-2003.

Unfortunately, that probably means ffmpeg's dpx encoder is not
compliant to these specifications.

-- 
Christophe

From 4ba2ec15c9a111fb4e20523d5a8fa337bedee92d Mon Sep 17 00:00:00 2001
From: Christophe Gisquet <christophe.gisq...@gmail.com>
Date: Wed, 13 Aug 2014 00:37:00 +0200
Subject: [PATCH 1/3] dpx: use aligned line starts

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 | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/libavcodec/dpx.c b/libavcodec/dpx.c
index 5f05cd8..2fa549c 100644
--- a/libavcodec/dpx.c
+++ b/libavcodec/dpx.c
@@ -77,7 +77,7 @@ static int decode_frame(AVCodecContext *avctx,
 
     unsigned int offset;
     int magic_num, endian;
-    int x, y, i, ret;
+    int x, y, stride, i, ret;
     int w, h, bits_per_color, descriptor, elements, packing, total_size;
     int encoding;
 
@@ -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 +203,11 @@ 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.
+    stride = FFALIGN(stride, 4);
+    total_size = stride*avctx->height;
+
     switch (1000 * descriptor + 10 * bits_per_color + endian) {
     case 6081:
     case 6080:
@@ -308,6 +313,8 @@ 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 +324,7 @@ 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


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