clamp intra matrix to 8bit for mjpeg (workaround for qscale>=25)

Originally committed as revision 451 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/common.h

@@ -902,4 +902,6 @@ void *av_mallocz(int size);
 /* math */
 int ff_gcd(int a, int b);
 
+#define CLAMP_TO_8BIT(d) ((d > 0xff) ? 0xff : (d < 0) ? 0 : d)
+
 #endif

libavcodec/mjpeg.c

@@ -388,6 +388,8 @@ void mjpeg_picture_header(MpegEncContext *s)
 {
     put_marker(&s->pb, SOI);
 
+    if (!s->mjpeg_data_only_frames)
+    {
     jpeg_put_comments(s);    
 
     if (s->mjpeg_write_tables) jpeg_table_header(s);
@@ -425,6 +427,7 @@ void mjpeg_picture_header(MpegEncContext *s)
 #else
     put_bits(&s->pb, 8, 0); /* select matrix */
 #endif
+    }
 
     /* scan header */
     put_marker(&s->pb, SOS);

libavcodec/mpegvideo.c

@@ -427,6 +427,7 @@ int MPV_encode_init(AVCodecContext *avctx)
         s->out_format = FMT_MJPEG;
         s->intra_only = 1; /* force intra only for jpeg */
         s->mjpeg_write_tables = 1; /* write all tables */
+	s->mjpeg_data_only_frames = 0; /* write all the needed headers */
         s->mjpeg_vsample[0] = 2; /* set up default sampling factors */
         s->mjpeg_vsample[1] = 1; /* the only currently supported values */
         s->mjpeg_vsample[2] = 1; 
@@ -1658,7 +1659,7 @@ static void encode_picture(MpegEncContext *s, int picture_number)
         /* for mjpeg, we do include qscale in the matrix */
         s->intra_matrix[0] = default_intra_matrix[0];
         for(i=1;i<64;i++)
-            s->intra_matrix[i] = (default_intra_matrix[i] * s->qscale) >> 3;
+            s->intra_matrix[i] = CLAMP_TO_8BIT((default_intra_matrix[i] * s->qscale) >> 3);
         convert_matrix(s->q_intra_matrix, s->q_intra_matrix16, 
                        s->q_intra_matrix16_bias, s->intra_matrix, s->intra_quant_bias);
     }

libavcodec/mpegvideo.h

@@ -332,6 +332,7 @@ typedef struct MpegEncContext {
     int mjpeg_hsample[3]; /* horizontal sampling factors, default = {2, 1, 1} */
     int mjpeg_write_tables; /* do we want to have quantisation- and
 			       huffmantables in the jpeg file ? */
+    int mjpeg_data_only_frames; /* frames only with SOI, SOS and EOI markers */
 
     /* MSMPEG4 specific */
     int mv_table_index;