riff: add ISMP/timecode tag.

doc/ffprobe.texi

@@ -410,7 +410,7 @@ MOV timecode is extracted from tmcd track, so is available in the tmcd
 stream metadata (@option{-show_streams}, see @var{TAG:timecode}).
 
 @item
-DV and GXF timecodes are available in format metadata
+DV, GXF and AVI timecodes are available in format metadata
 (@option{-show_format}, see @var{TAG:timecode}).
 
 @end itemize

doc/general.texi

@@ -890,6 +890,7 @@ performance on systems without hardware floating point support).
 
 @multitable @columnfractions .4 .1 .1
 @item Codec/format      @tab Read   @tab Write
+@item AVI               @tab X      @tab X
 @item DV                @tab X      @tab X
 @item GXF               @tab X      @tab X
 @item MOV               @tab X      @tab

libavformat/riff.c

@@ -389,6 +389,7 @@ const AVMetadataConv ff_riff_info_conv[] = {
     { "IPRD", "album"     },
     { "IPRT", "track"     },
     { "ISFT", "encoder"   },
+    { "ISMP", "timecode"  },
     { "ITCH", "encoded_by"},
     { 0 },
 };
@@ -396,7 +397,7 @@ const AVMetadataConv ff_riff_info_conv[] = {
 const char ff_riff_tags[][5] = {
     "IARL", "IART", "ICMS", "ICMT", "ICOP", "ICRD", "ICRP", "IDIM", "IDPI",
     "IENG", "IGNR", "IKEY", "ILGT", "ILNG", "IMED", "INAM", "IPLT", "IPRD",
-    "IPRT", "ISBJ", "ISFT", "ISHP", "ISRC", "ISRF", "ITCH",
+    "IPRT", "ISBJ", "ISFT", "ISHP", "ISMP", "ISRC", "ISRF", "ITCH",
     {0}
 };