external/srs
1
0
Fork 0
mirror of https://github.com/ossrs/srs.git synced 2025-03-09 15:49:59 +00:00
Code Issues Releases Wiki Activity

add ts PCR analysis, the tool MPEG-2-ts-packet-analysis.2.4.5.0 decode PCR wrong

Browse source
This commit is contained in:
winlin 2013-11-23 11:25:58 +08:00
parent 71015dc4a1
commit 37e53f3735
2 changed files with 158 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

105
trunk/doc/ts-PCR-analysis.txt Normal file
View file

@ -0,0 +1,105 @@
packet#7:
Adaptation fields
Adaptation_field_length: 7
discontinuity_indicator: False
random_access_indicator: True
ES_priority_indicator: False
PCR_flag: True
OPCR_flag: False
splicing_point_flag: False
transport_private_data_flag: False
adaptation_field_extension_flag: False
PCR: 50572350000
PES header
stream_id: E0 (video stream 224)
PES_packet_length: 35808
PES_scrambling: 0
PES_priority: False
data_alignment: False
copyright: False
original_or_copy: False
PTS_flag: True
DTS_flag: True
ESCR_flag: False
ES_rate_flag: False
DSM_trick_mode_flag: False
additional_copy_info_flag: False
PES_CRC_flag: False
PES_extension_flag: False
PES_header_data_length: 10
PTS: 168704280
DTS: 168700500
packet#665:
Adaptation fields
Adaptation_field_length: 7
discontinuity_indicator: False
random_access_indicator: True
ES_priority_indicator: False
PCR_flag: True
OPCR_flag: False
splicing_point_flag: False
transport_private_data_flag: False
adaptation_field_extension_flag: False
PCR: 50616225000
PES header
stream_id: E0 (video stream 224)
PES_packet_length: 29213
PES_scrambling: 0
PES_priority: False
data_alignment: False
copyright: False
original_or_copy: False
PTS_flag: True
DTS_flag: True
ESCR_flag: False
ES_rate_flag: False
DSM_trick_mode_flag: False
additional_copy_info_flag: False
PES_CRC_flag: False
PES_extension_flag: False
PES_header_data_length: 10
PTS: 168850530
DTS: 168846750
参考nginx-rtmp函数：ngx_rtmp_mpegts_write_frame
其中，nginx-rtmp写入PCR的逻辑如下：
if (f->key) {
packet[3] |= 0x20; /* adaptation */
*p++ = 7; /* size */
*p++ = 0x50; /* random access + PCR */
p = ngx_rtmp_mpegts_write_pcr(p, f->dts - NGX_RTMP_HLS_DELAY);
}
只要碰到关键帧，就写入PCR。
ngx_rtmp_mpegts_write_pcr(u_char *p, uint64_t pcr)
{
*p++ = (u_char) (pcr >> 25);
*p++ = (u_char) (pcr >> 17);
*p++ = (u_char) (pcr >> 9);
*p++ = (u_char) (pcr >> 1);
*p++ = (u_char) (pcr << 7 | 0x7e);
*p++ = 0;
return p;
}
即将高9位置0，6个reserverd置1，低33位输出（little-endian）。
nginx-rtmp写入dts的逻辑如下：
p = ngx_rtmp_mpegts_write_pts(p, 1, f->dts + NGX_RTMP_HLS_DELAY);
也就是说，
pcr = f->dts - NGX_RTMP_HLS_DELAY
f->dts = dts - NGX_RTMP_HLS_DELAY
计算出来的:
pcr = program_clock_reference_base = 168574500
dts = 168700500
168574500 = 168700500 - 63000 - 63000
可见，工具MPEG-2 TS packet analyser分析出来的pcr是不对的。
解码出来的结果：
demuxer+read packet 0006 0001128 0x47 0x41 0x00 0x35 ... 0xb6 0x9f 0x89
ts+af af flags parsed, discontinuity: 0 random: 1 priority: 0 PCR: 1 OPCR: 0 slicing: 0 private: 0 extension: 0 pcr: 168574500 opcr: 0
ts+pes stream_id: 224 size: 35808 pts: 168704280 dts: 168700500 total: 35808 header: 13 packet_size: 35795 parsed_size: 157