avcodec/mjpegdec: Support RGBA lpegs

Fixes Ticket896
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mjpegdec.c

@@ -337,7 +337,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
             return AVERROR_INVALIDDATA;
         }
     } else{
-        if (s->v_max == 1 && s->h_max == 1 && s->lossless==1 && nb_components==3)
+        if (s->v_max == 1 && s->h_max == 1 && s->lossless==1 && (nb_components==3 || nb_components==4))
             s->rgb = 1;
         else if (!s->lossless)
             s->rgb = 0;
@@ -368,6 +368,15 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
         }
         av_assert0(s->nb_components == 3);
         break;
+    case 0x11111111:
+        if (s->rgb)
+            s->avctx->pix_fmt = AV_PIX_FMT_ABGR;
+        else {
+            s->avctx->pix_fmt = /*s->cs_itu601 ?*/ AV_PIX_FMT_YUVA444P/* : AV_PIX_FMT_YUVJA444P*/;
+            s->avctx->color_range = s->cs_itu601 ? AVCOL_RANGE_MPEG : AVCOL_RANGE_JPEG;
+        }
+        av_assert0(s->nb_components == 4);
+        break;
     case 0x12121100:
     case 0x22122100:
         s->avctx->pix_fmt = s->cs_itu601 ? AV_PIX_FMT_YUV444P : AV_PIX_FMT_YUVJ444P;
@@ -774,7 +783,7 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
 {
     int i, mb_x, mb_y;
     uint16_t (*buffer)[4];
-    int left[3], top[3], topleft[3];
+    int left[4], top[4], topleft[4];
     const int linesize = s->linesize[0];
     const int mask     = (1 << s->bits) - 1;
     int resync_mb_y = 0;
@@ -786,7 +795,7 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
                    (unsigned)s->mb_width * 4 * sizeof(s->ljpeg_buffer[0][0]));
     buffer = s->ljpeg_buffer;
 
-    for (i = 0; i < 3; i++)
+    for (i = 0; i < 4; i++)
         buffer[0][i] = 1 << (s->bits - 1);
 
     for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
@@ -795,7 +804,7 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
         if (s->interlaced && s->bottom_field)
             ptr += linesize >> 1;
 
-        for (i = 0; i < 3; i++)
+        for (i = 0; i < 4; i++)
             top[i] = left[i] = topleft[i] = buffer[0][i];
 
         for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
@@ -805,7 +814,7 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
                 s->restart_count = s->restart_interval;
                 resync_mb_x = mb_x;
                 resync_mb_y = mb_y;
-                for(i=0; i<3; i++)
+                for(i=0; i<4; i++)
                     top[i] = left[i]= topleft[i]= 1 << (s->bits - 1);
             }
             if (mb_y == resync_mb_y || mb_y == resync_mb_y+1 && mb_x < resync_mb_x || !mb_x)
@@ -832,8 +841,14 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int nb_components, int p
                 skip_bits(&s->gb, 16); /* skip RSTn */
             }
         }
-
-        if (s->rct) {
+        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];
+                }
+            }
+        } else if (s->rct) {
             for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                 ptr[3*mb_x + 1] = buffer[mb_x][0] - ((buffer[mb_x][1] + buffer[mb_x][2] - 0x200) >> 2);
                 ptr[3*mb_x + 0] = buffer[mb_x][1] + ptr[3*mb_x + 1];
@@ -867,7 +882,7 @@ static int ljpeg_decode_yuv_scan(MJpegDecodeContext *s, int predictor,
 
     point_transform += bits - s->bits;
 
-    av_assert0(nb_components>=1 && nb_components<=3);
+    av_assert0(nb_components>=1 && nb_components<=4);
 
     for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
         for (mb_x = 0; mb_x < s->mb_width; mb_x++) {