[FFmpeg-devel] [PATCH] avformat/mpegts: parse large PMTs with multiple tables

[Aman Gupta]

From: Aman Gupta <aman at tmm1.net>

In 9152c1e4955, the mpegts parser was taught how to parse
PMT sections which contained multiple tables. That commit
fixed parsing of PMT packets from some cable providers,
which included a special SCTE table (0xc0) before the
standard program map table (0x2).

Sometimes, however, the combined 0xc0 and 0x2 tables are
larger than a single TS packet (188 bytes). The mpegts parser
already attempts to parse sections which span multiple packets,
but still assumed that the split section only contained one
table.

This patch fixes parsing of such a sample[1].

Before:

    Input #0, mpegts, from 'combined-pmt-tids-split.ts':
      Duration: 00:00:01.26, start: 39188.931756, bitrate: 597 kb/s
      Program 1
      No Program
        Stream #0:0[0xeff]: Audio: ac3, 48000 Hz, mono, fltp, 64 kb/s
        Stream #0:1[0xefd]: Audio: mp3, 0 channels, fltp
        Stream #0:2[0xefe]: Unknown: none

After:

    Input #0, mpegts, from 'combined-pmt-tids-split.ts':
      Duration: 00:00:01.27, start: 39188.931756, bitrate: 589 kb/s
      Program 1
        Stream #0:0[0xefd]: Video: h264 ([27][0][0][0] / 0x001B), none, 59.94 fps, 59.94 tbr, 90k tbn, 180k tbc
        Stream #0:1[0xefe](eng): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, stereo, fltp, 384 kb/s
        Stream #0:2[0xeff](spa): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, mono, fltp, 64 kb/s
        Stream #0:3[0xf00]: Data: scte_35
        Stream #0:4[0xf01]: Unknown: none (ETV1 / 0x31565445)
        Stream #0:5[0xf02]: Unknown: none (ETV1 / 0x31565445)
        Stream #0:6[0xf03]: Unknown: none ([192][0][0][0] / 0x00C0)

With the patch, the PMT is parsed correctly so the streams are
created in the correct order, are associated with "Program 1",
and their codecs are set correctly.

[1] https://s3.amazonaws.com/tmm1/combined-pmt-tids-split.ts

Signed-off-by: Aman Gupta <aman at tmm1.net>
---
 libavformat/mpegts.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 5f53f77d89..a5cb17ac16 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -465,6 +465,7 @@ static void write_section_data(MpegTSContext *ts, MpegTSFilter *tss1,
             offset += tss->section_h_size;
             tss->section_h_size = -1;
         } else {
+            tss->section_h_size = -1;
             tss->end_of_section_reached = 0;
             break;
         }
-- 
2.14.2