small spelling/grammar fixes

Originally committed as revision 17718 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/imgresample.c

@@ -575,7 +575,7 @@ void sws_freeContext(struct SwsContext *ctx)
  * Otherwise, frees context and gets a new one.
  *
  * Be warned that srcFilter, dstFilter are not checked, they are
- * asumed to remain valid.
+ * assumed to remain valid.
  */
 struct SwsContext *sws_getCachedContext(struct SwsContext *ctx,
                         int srcW, int srcH, int srcFormat,

libavcodec/mpegvideo.h

@@ -600,7 +600,7 @@ typedef struct MpegEncContext {
     int broken_link;         ///< no_output_of_prior_pics_flag
     uint8_t *vbv_delay_ptr;  ///< pointer to vbv_delay in the bitstream
 
-    /* MPEG2 specific - I wish I had not to support this mess. */
+    /* MPEG-2-specific - I wished not to have to support this mess. */
     int progressive_sequence;
     int mpeg_f_code[2][2];
     int picture_structure;
@@ -635,7 +635,7 @@ typedef struct MpegEncContext {
     int rtp_mode;
 
     uint8_t *ptr_lastgob;
-    int swap_uv;//vcr2 codec is mpeg2 varint with UV swaped
+    int swap_uv;             //vcr2 codec is an MPEG-2 variant with U and V swapped
     DCTELEM (*pblocks[12])[64];
 
     DCTELEM (*block)[64]; ///< points to one of the following blocks