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