avcodec/mpeg12dec: Add CPB coded side data

This fixes mpeg2video stream copies to mpeg muxer like this:
  ffmpeg -i xdcamhd.mxf -c:v copy output.mpg
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/mpeg12dec.c

@@ -1399,6 +1399,7 @@ static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
     MpegEncContext *s = &s1->mpeg_enc_ctx;
     int horiz_size_ext, vert_size_ext;
     int bit_rate_ext;
+    AVCPBProperties *cpb_props;
 
     skip_bits(&s->gb, 1); /* profile and level esc*/
     s->avctx->profile       = get_bits(&s->gb, 3);
@@ -1430,6 +1431,12 @@ static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
     ff_dlog(s->avctx, "sequence extension\n");
     s->codec_id = s->avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
 
+    if (cpb_props = ff_add_cpb_side_data(s->avctx)) {
+        cpb_props->buffer_size = s1->rc_buffer_size;
+        if (s->bit_rate != 0x3FFFF*400)
+            cpb_props->max_bitrate = s->bit_rate;
+    }
+
     if (s->avctx->debug & FF_DEBUG_PICT_INFO)
         av_log(s->avctx, AV_LOG_DEBUG,
                "profile: %d, level: %d ps: %d cf:%d vbv buffer: %d, bitrate:%"PRId64"\n",

tests/ref/fate/mxf-probe-d10

@@ -50,6 +50,9 @@ DISPOSITION:clean_effects=0
 DISPOSITION:attached_pic=0
 DISPOSITION:timed_thumbnails=0
 TAG:file_package_umid=0x060A2B340101010501010D1313000000AE86B200913105800000080046A54011
+[SIDE_DATA]
+side_data_type=CPB properties
+[/SIDE_DATA]
 [/STREAM]
 [STREAM]
 index=1

tests/ref/fate/ts-demux

@@ -15,7 +15,7 @@
 1,       5760,       5760,     2880,     1536, 0xbab5129c
 1,       8640,       8640,     2880,     1536, 0x602f034b, S=1,        1, 0x00bd00bd
 1,      11520,      11520,     2880,      906, 0x69cdcbcd
-0,      32037,      36541,     1501,   114336, 0x37a215a8, S=1,        1, 0x00e000e0
+0,      32037,      36541,     1501,   114336, 0x37a215a8, S=2,        1, 0x00e000e0,       24, 0x663d0b52
 0,      33538,      33538,     1501,    12560, 0xb559a3d4, F=0x0, S=1,        1, 0x00e000e0
 0,      35040,      35040,     1501,    12704, 0x2614adf4, F=0x0, S=1,        1, 0x00e000e0
 0,      36541,      41046,     1501,    51976, 0x9ff1dbfe, F=0x0, S=1,        1, 0x00e000e0