[FFmpeg-devel] [PATCH v11 09/14] lavc/mjpegdec: Enable decoding of single-component bayer images

[velocityra at gmail.com]

From: Nick Renieris <velocityra at gmail.com>

Signed-off-by: Nick Renieris <velocityra at gmail.com>
---
 libavcodec/mjpegdec.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index 6391107f78..94cf73549d 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -412,13 +412,21 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
         return AVERROR_PATCHWELCOME;
     }
 
-    /* Lossless JPEGs encoded in DNGs are commonly bayer-encoded. They contain 2
-       interleaved components and the width stored in their SOF3 markers is the
-       width of each one.  We only output a single component, therefore we need
-       to adjust the output image width. */
-    if (s->lossless == 1 && nb_components == 2) {
-        s->bayer = 1;
-        width *= 2;
+    /* Lossless JPEGs encoded in DNGs are commonly bayer-encoded. */
+    if (s->lossless) {
+        if (nb_components == 1) {
+            /* They can contain 1 component, which is double the width and half the height
+               of the final image (rows are interleaved).  We don't handle the decoding in
+               this file, but leave that to the DNG decoder. */
+            s->bayer = 1;
+        } else if (nb_components == 2) {
+            /* Or they can contain 2 interleaved components and the width stored in their
+               SOF3 markers is the width of each one.  We only output a single component,
+               therefore we need to adjust the output image width.  We handle the
+               deinterleaving (but not the debayering) in this file. */
+            s->bayer = 1;
+            width *= 2;
+        }
     }
 
     /* if different size, realloc/alloc picture */
@@ -1184,10 +1192,15 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
                 ptr[3*mb_x + 0] = buffer[mb_x][1] + ptr[3*mb_x + 1];
                 ptr[3*mb_x + 2] = buffer[mb_x][2] + ptr[3*mb_x + 1];
             }
-        } else if (s->bayer && nb_components == 2) {
-            for (mb_x = 0; mb_x < width; mb_x++) {
-                ((uint16_t*)ptr)[2*mb_x + 0] = buffer[mb_x][0];
-                ((uint16_t*)ptr)[2*mb_x + 1] = buffer[mb_x][1];
+        } else if (s->bayer) {
+            if (nb_components == 1) {
+                for (mb_x = 0; mb_x < width; mb_x++)
+                    ((uint16_t*)ptr)[mb_x] = buffer[mb_x][0];
+            } else if (nb_components == 2) {
+                for (mb_x = 0; mb_x < width; mb_x++) {
+                    ((uint16_t*)ptr)[2*mb_x + 0] = buffer[mb_x][0];
+                    ((uint16_t*)ptr)[2*mb_x + 1] = buffer[mb_x][1];
+                }
             }
         } else {
             for(i=0; i<nb_components; i++) {
-- 
2.21.0.windows.1