cleanup

adding AVVideoFrame
 moving quality, pict_type, key_frame, qscale_table, ... to AVVideoFrame
 removing obsolete variables in AVCodecContext
 skiping of MBs in b frames
 correctly initalizing AVCodecContext
 picture buffer cleanup

Originally committed as revision 1302 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/swf.c

@@ -482,6 +482,8 @@ static int swf_read_header(AVFormatContext *s, AVFormatParameters *ap)
                 st = av_mallocz(sizeof(AVStream));
                 if (!st)
                     return -ENOMEM;
+                avcodec_get_context_defaults(&st->codec);
+
                 if (v & 0x01)
                     st->codec.channels = 2;
                 else