avcodec/mjpegdec: rgba64 ljpeg support

Fixes Ticket2965
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mjpegdec.c

@@ -371,7 +371,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
         break;
     case 0x11111111:
         if (s->rgb)
-            s->avctx->pix_fmt = AV_PIX_FMT_ABGR;
+            s->avctx->pix_fmt = s->bits <= 8 ? AV_PIX_FMT_ABGR : AV_PIX_FMT_RGBA64;
         else {
             s->avctx->pix_fmt = s->bits <= 8 ? AV_PIX_FMT_YUVA444P : AV_PIX_FMT_YUVA444P16;
             s->avctx->color_range = s->cs_itu601 ? AVCOL_RANGE_MPEG : AVCOL_RANGE_JPEG;
@@ -868,8 +868,14 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
         if (s->nb_components == 4) {
             for(i=0; i<nb_components; i++) {
                 int c= s->comp_index[i];
-                for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
-                    ptr[4*mb_x+3-c] = buffer[mb_x][i];
+                if (s->bits <= 8) {
+                    for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
+                        ptr[4*mb_x+3-c] = buffer[mb_x][i];
+                    }
+                } else {
+                    for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
+                        ((uint16_t*)ptr)[4*mb_x+c] = buffer[mb_x][i];
+                    }
                 }
             }
         } else if (s->rct) {