diff --git a/libavcodec/sgidec.c b/libavcodec/sgidec.c
index e5b3c59..f6af1c1 100644
--- a/libavcodec/sgidec.c
+++ b/libavcodec/sgidec.c
@@ -123,26 +123,33 @@ static int read_rle_sgi(unsigned char* out_buf, const uin$
  * @return 0 if read success, otherwise return -1.
  */
 static int read_uncompressed_sgi(unsigned char* out_buf, uint8_t* out_end,
-                const uint8_t *in_buf, const uint8_t *in_end, SgiState* s)
+                                 GetByteContext *g, SgiState* s)
 {
     int x, y, z;
-    const uint8_t *ptr;
     unsigned int offset = s->height * s->width * s->bytes_per_channel;
+    GetByteContext gp[4];

     /* Test buffer size. */
-    if (offset * s->depth > in_end - in_buf) {
+    if (offset * s->depth > bytestream2_get_bytes_left(g)) {
        return -1;
     }

+    for (z = 0; z < s->depth; z++) {
+        gp[z] = *g;
+        bytestream2_skip(&gp[z], z * offset);
+    }
+
     for (y = s->height - 1; y >= 0; y--) {
         out_end = out_buf + (y * s->linesize);
-        for (x = s->width; x > 0; x--) {
-            ptr = in_buf += s->bytes_per_channel;
-            for(z = 0; z < s->depth; z ++) {
-                memcpy(out_end, ptr, s->bytes_per_channel);
-                out_end += s->bytes_per_channel;
-                ptr += offset;
-            }
+        if (s->bytes_per_channel == 1) {
+            for (x = s->width; x > 0; x--)
+                for (z = 0; z < s->depth; z++)
+                    *out_end++ = bytestream2_get_byte(&gp[z]);
+        } else {
+            uint16_t *out_line = (uint16_t *)out_end;
+            for (x = s->width; x > 0; x--)
+                for (z = 0; z < s->depth; z++)
+                    *out_line++ = bytestream2_get_be16(&gp[z]);
         }
     }
     return 0;
@@ -228,7 +235,9 @@ static int decode_frame(AVCodecContext *avctx,
     if (rle) {
         ret = read_rle_sgi(out_end, in_buf, in_end, s);
     } else {
-        ret = read_uncompressed_sgi(out_buf, out_end, in_buf, in_end, s);
+        GetByteContext g;
+        bytestream2_init(&g, in_buf, in_end - in_buf);
+        ret = read_uncompressed_sgi(out_buf, out_end, &g, s);
     }

     if (ret == 0) {