From 9152c1e495551535886cfd7a8d7c0a206691443e Mon Sep 17 00:00:00 2001 From: Aman Gupta Date: Wed, 9 May 2018 14:20:48 -0700 Subject: [PATCH] avformat/mpegts: parse sections with multiple tables Fixes PMT parsing in some mpegts streams which contain multiple tables within the PMT pid. Previously, the parser assumed only one table was present in each packet, and discarded the rest of the section data after attempting to parse the first table. A similar issue was documented in the BeyondTV software[1], which helped me diagnose the same bug in the ffmpeg mpegts demuxer. I also tried DVBInspector, libdvbpsi's dvbinfo, and tstools' tsinfo to help debug. The former two properly read PMTs with multiple tables, whereas the last has the same bug as ffmpeg. I've created a minimal sample[2] which contains the combined PMT. Here's what ffmpeg probe shows before and after this patch: Before: Input #0, mpegts, from 'combined-pmt-tids.ts': Duration: 00:00:01.08, start: 4932.966167, bitrate: 741 kb/s Program 1 No Program Stream #0:0[0xf9d]: Audio: ac3, 48000 Hz, mono, fltp, 96 kb/s Stream #0:1[0xf9b]: Audio: mp3, 0 channels, fltp Stream #0:2[0xf9c]: Unknown: none After: Input #0, mpegts, from 'combined-pmt-tids.ts': Duration: 00:00:01.11, start: 4932.966167, bitrate: 718 kb/s Program 1 Stream #0:0[0xf9b]: Video: mpeg2video ([2][0][0][0] / 0x0002), none(tv, top first), 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc Stream #0:1[0xf9c](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 384 kb/s Stream #0:2[0xf9d](spa): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, mono, fltp, 96 kb/s 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] http://forums.snapstream.com/vb/showpost.php?p=343816&postcount=201 [2] https://s3.amazonaws.com/tmm1/combined-pmt-tids.ts Signed-off-by: Aman Gupta Signed-off-by: Michael Niedermayer --- libavformat/mpegts.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c index 0d1dda1c36..3c9f9421cb 100644 --- a/libavformat/mpegts.c +++ b/libavformat/mpegts.c @@ -391,7 +391,8 @@ static void write_section_data(MpegTSContext *ts, MpegTSFilter *tss1, const uint8_t *buf, int buf_size, int is_start) { MpegTSSectionFilter *tss = &tss1->u.section_filter; - int len; + uint8_t *cur_section_buf = NULL; + int len, offset; if (is_start) { memcpy(tss->section_buf, buf, buf_size); @@ -408,23 +409,26 @@ static void write_section_data(MpegTSContext *ts, MpegTSFilter *tss1, tss->section_index += len; } + offset = 0; + cur_section_buf = tss->section_buf; + while (cur_section_buf - tss->section_buf < MAX_SECTION_SIZE && cur_section_buf[0] != 0xff) { /* compute section length if possible */ - if (tss->section_h_size == -1 && tss->section_index >= 3) { - len = (AV_RB16(tss->section_buf + 1) & 0xfff) + 3; + if (tss->section_h_size == -1 && tss->section_index - offset >= 3) { + len = (AV_RB16(cur_section_buf + 1) & 0xfff) + 3; if (len > MAX_SECTION_SIZE) return; tss->section_h_size = len; } if (tss->section_h_size != -1 && - tss->section_index >= tss->section_h_size) { + tss->section_index >= offset + tss->section_h_size) { int crc_valid = 1; tss->end_of_section_reached = 1; if (tss->check_crc) { - crc_valid = !av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1, tss->section_buf, tss->section_h_size); + crc_valid = !av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1, cur_section_buf, tss->section_h_size); if (tss->section_h_size >= 4) - tss->crc = AV_RB32(tss->section_buf + tss->section_h_size - 4); + tss->crc = AV_RB32(cur_section_buf + tss->section_h_size - 4); if (crc_valid) { ts->crc_validity[ tss1->pid ] = 100; @@ -434,10 +438,18 @@ static void write_section_data(MpegTSContext *ts, MpegTSFilter *tss1, crc_valid = 2; } if (crc_valid) { - tss->section_cb(tss1, tss->section_buf, tss->section_h_size); + tss->section_cb(tss1, cur_section_buf, tss->section_h_size); if (crc_valid != 1) tss->last_ver = -1; } + + cur_section_buf += tss->section_h_size; + offset += tss->section_h_size; + tss->section_h_size = -1; + } else { + tss->end_of_section_reached = 0; + break; + } } }