mpegts: fuzzy crc check for not so spec compliant files

Fixes Ticket598
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegts.c

@@ -123,6 +123,7 @@ struct MpegTSContext {
     unsigned int nb_prg;
     struct Program *prg;
 
+    int8_t crc_validity[NB_PID_MAX];
 
     /** filters for various streams specified by PMT + for the PAT and PMT */
     MpegTSFilter *pids[NB_PID_MAX];
@@ -277,6 +278,7 @@ static int discard_pid(MpegTSContext *ts, unsigned int pid)
 static void write_section_data(AVFormatContext *s, MpegTSFilter *tss1,
                                const uint8_t *buf, int buf_size, int is_start)
 {
+    MpegTSContext *ts = s->priv_data;
     MpegTSSectionFilter *tss = &tss1->u.section_filter;
     int len;
 
@@ -304,10 +306,19 @@ static void write_section_data(AVFormatContext *s, MpegTSFilter *tss1,
     }
 
     if (tss->section_h_size != -1 && tss->section_index >= tss->section_h_size) {
+        int crc_valid = 1;
         tss->end_of_section_reached = 1;
-        if (!tss->check_crc ||
-            av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1,
-                   tss->section_buf, tss->section_h_size) == 0)
+
+        if (tss->check_crc){
+            crc_valid = !av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1, tss->section_buf, tss->section_h_size);
+            if (crc_valid){
+                ts->crc_validity[ tss1->pid ] = 100;
+            }else if(ts->crc_validity[ tss1->pid ] > -10){
+                ts->crc_validity[ tss1->pid ]--;
+            }else
+                crc_valid = 2;
+        }
+        if (crc_valid)
             tss->section_cb(tss1, tss->section_buf, tss->section_h_size);
     }
 }