godaddy wordpress托管,优化大师win10能用吗,软件工程考研方向有哪些,莆田做网站建设一、引言
FFmpeg源码在解析完PMT表后#xff0c;会得到该节目包含的视频和音频信息#xff0c;从而找到音视频流。TS流的音视频流包含在PES流中。FFmpeg源码通过调用函数指针tss-u.pes_filter.pes_cb指向的回调函数解析PES流的PES packet#xff1a;
/* handle one TS…一、引言
FFmpeg源码在解析完PMT表后会得到该节目包含的视频和音频信息从而找到音视频流。TS流的音视频流包含在PES流中。FFmpeg源码通过调用函数指针tss-u.pes_filter.pes_cb指向的回调函数解析PES流的PES packet
/* handle one TS packet */
static int handle_packet(MpegTSContext *ts, const uint8_t *packet, int64_t pos)
{
//...if (tss-type MPEGTS_SECTION) {//...}else {int ret;// Note: The position here points actually behind the current packet.if (tss-type MPEGTS_PES) {if ((ret tss-u.pes_filter.pes_cb(tss, p, p_end - p, is_start,pos - ts-raw_packet_size)) 0)return ret;}}return 0;
//...
} 而函数指针tss-u.pes_filter.pes_cb指向的回调函数是mpegts_push_data函数。 二、mpegts_push_data函数的定义
mpegts_push_data函数定义在FFmpeg源码本文演示用的FFmpeg源码版本为7.0.1的源文件libavformat/mpegts.c中
/* return non zero if a packet could be constructed */
static int mpegts_push_data(MpegTSFilter *filter,const uint8_t *buf, int buf_size, int is_start,int64_t pos)
{PESContext *pes filter-u.pes_filter.opaque;MpegTSContext *ts pes-ts;const uint8_t *p;int ret, len;if (!ts-pkt)return 0;if (is_start) {if (pes-state MPEGTS_PAYLOAD pes-data_index 0) {ret new_pes_packet(pes, ts-pkt);if (ret 0)return ret;ts-stop_parse 1;} else {reset_pes_packet_state(pes);}pes-state MPEGTS_HEADER;pes-ts_packet_pos pos;}p buf;while (buf_size 0) {switch (pes-state) {case MPEGTS_HEADER:len PES_START_SIZE - pes-data_index;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index PES_START_SIZE) {/* we got all the PES or section header. We can now* decide */if (pes-header[0] 0x00 pes-header[1] 0x00 pes-header[2] 0x01) {/* it must be an MPEG-2 PES stream */pes-stream_id pes-header[3];av_log(pes-stream, AV_LOG_TRACE, pid%x stream_id%#x\n, pes-pid, pes-stream_id);if ((pes-st pes-st-discard AVDISCARD_ALL (!pes-sub_st ||pes-sub_st-discard AVDISCARD_ALL)) ||pes-stream_id STREAM_ID_PADDING_STREAM)goto skip;/* stream not present in PMT */if (!pes-st) {if (ts-skip_changes)goto skip;if (ts-merge_pmt_versions)goto skip; /* wait for PMT to merge new stream */pes-st avformat_new_stream(ts-stream, NULL);if (!pes-st)return AVERROR(ENOMEM);pes-st-id pes-pid;mpegts_set_stream_info(pes-st, pes, 0, 0);}pes-PES_packet_length AV_RB16(pes-header 4);/* NOTE: zero length means the PES size is unbounded */if (pes-stream_id ! STREAM_ID_PROGRAM_STREAM_MAP pes-stream_id ! STREAM_ID_PRIVATE_STREAM_2 pes-stream_id ! STREAM_ID_ECM_STREAM pes-stream_id ! STREAM_ID_EMM_STREAM pes-stream_id ! STREAM_ID_PROGRAM_STREAM_DIRECTORY pes-stream_id ! STREAM_ID_DSMCC_STREAM pes-stream_id ! STREAM_ID_TYPE_E_STREAM) {FFStream *const pes_sti ffstream(pes-st);pes-state MPEGTS_PESHEADER;if (pes-st-codecpar-codec_id AV_CODEC_ID_NONE !pes_sti-request_probe) {av_log(pes-stream, AV_LOG_TRACE,pid%x stream_type%x probing\n,pes-pid,pes-stream_type);pes_sti-request_probe 1;}} else {pes-pes_header_size 6;pes-state MPEGTS_PAYLOAD;pes-data_index 0;}} else {/* otherwise, it should be a table *//* skip packet */
skip:pes-state MPEGTS_SKIP;continue;}}break;/**********************************************//* PES packing parsing */case MPEGTS_PESHEADER:len PES_HEADER_SIZE - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index PES_HEADER_SIZE) {pes-pes_header_size pes-header[8] 9;pes-state MPEGTS_PESHEADER_FILL;}break;case MPEGTS_PESHEADER_FILL:len pes-pes_header_size - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index pes-pes_header_size) {const uint8_t *r;unsigned int flags, pes_ext, skip;flags pes-header[7];r pes-header 9;pes-pts AV_NOPTS_VALUE;pes-dts AV_NOPTS_VALUE;if ((flags 0xc0) 0x80) {pes-dts pes-pts ff_parse_pes_pts(r);r 5;} else if ((flags 0xc0) 0xc0) {pes-pts ff_parse_pes_pts(r);r 5;pes-dts ff_parse_pes_pts(r);r 5;}pes-extended_stream_id -1;if (flags 0x01) { /* PES extension */pes_ext *r;/* Skip PES private data, program packet sequence counter and P-STD buffer */skip (pes_ext 4) 0xb;skip skip 0x9;r skip;if ((pes_ext 0x41) 0x01 (r 2) (pes-header pes-pes_header_size)) {/* PES extension 2 */if ((r[0] 0x7f) 0 (r[1] 0x80) 0)pes-extended_stream_id r[1];}}/* we got the full header. We parse it and get the payload */pes-state MPEGTS_PAYLOAD;pes-data_index 0;if (pes-stream_type 0x12 buf_size 0) {int sl_header_bytes read_sl_header(pes, pes-sl, p,buf_size);pes-pes_header_size sl_header_bytes;p sl_header_bytes;buf_size - sl_header_bytes;}if (pes-stream_type STREAM_TYPE_METADATA pes-stream_id STREAM_ID_METADATA_STREAM pes-st-codecpar-codec_id AV_CODEC_ID_SMPTE_KLV buf_size 5) {/* skip metadata access unit header - see MISB ST 1402 */pes-pes_header_size 5;p 5;buf_size - 5;}if ( pes-ts-fix_teletext_pts ( pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT|| pes-st-codecpar-codec_id AV_CODEC_ID_DVB_SUBTITLE)) {AVProgram *p NULL;int pcr_found 0;while ((p av_find_program_from_stream(pes-stream, p, pes-st-index))) {if (p-pcr_pid ! -1 p-discard ! AVDISCARD_ALL) {MpegTSFilter *f pes-ts-pids[p-pcr_pid];if (f) {AVStream *st NULL;if (f-type MPEGTS_PES) {PESContext *pcrpes f-u.pes_filter.opaque;if (pcrpes)st pcrpes-st;} else if (f-type MPEGTS_PCR) {int i;for (i 0; i p-nb_stream_indexes; i) {AVStream *pst pes-stream-streams[p-stream_index[i]];if (pst-codecpar-codec_type AVMEDIA_TYPE_VIDEO)st pst;}}if (f-last_pcr ! -1 !f-discard) {// teletext packets do not always have correct timestamps,// the standard says they should be handled after 40.6 ms at most,// and the pcr error to this packet should be no more than 100 ms.// TODO: we should interpolate the PCR, not just use the last oneint64_t pcr f-last_pcr / 300;pcr_found 1;if (st) {const FFStream *const sti ffstream(st);FFStream *const pes_sti ffstream(pes-st);pes_sti-pts_wrap_reference sti-pts_wrap_reference;pes_sti-pts_wrap_behavior sti-pts_wrap_behavior;}if (pes-dts AV_NOPTS_VALUE || pes-dts pcr) {pes-pts pes-dts pcr;} else if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT pes-dts pcr 3654 9000) {pes-pts pes-dts pcr 3654 9000;} else if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_SUBTITLE pes-dts pcr 10*90000) { //10secpes-pts pes-dts pcr 3654 9000;}break;}}}}if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT !pcr_found) {av_log(pes-stream, AV_LOG_VERBOSE,Forcing DTS/PTS to be unset for a non-trustworthy PES packet for PID %d as PCR hasnt been received yet.\n,pes-pid);pes-dts pes-pts AV_NOPTS_VALUE;}}}break;case MPEGTS_PAYLOAD:do {int max_packet_size ts-max_packet_size;if (pes-PES_packet_length pes-PES_packet_length PES_START_SIZE pes-pes_header_size)max_packet_size pes-PES_packet_length PES_START_SIZE - pes-pes_header_size;if (pes-data_index 0 pes-data_index buf_size max_packet_size) {ret new_pes_packet(pes, ts-pkt);if (ret 0)return ret;pes-PES_packet_length 0;max_packet_size ts-max_packet_size;ts-stop_parse 1;} else if (pes-data_index 0 buf_size max_packet_size) {// pes packet size is ts size packet and pes data is padded with 0xff// not sure if this is legal in ts but see issue #2392buf_size max_packet_size;}if (!pes-buffer) {pes-buffer buffer_pool_get(ts, max_packet_size);if (!pes-buffer)return AVERROR(ENOMEM);}memcpy(pes-buffer-data pes-data_index, p, buf_size);pes-data_index buf_size;/* emit complete packets with known packet size* decreases demuxer delay for infrequent packets like subtitles from* a couple of seconds to milliseconds for properly muxed files. */if (!ts-stop_parse pes-PES_packet_length pes-pes_header_size pes-data_index pes-PES_packet_length PES_START_SIZE) {ts-stop_parse 1;ret new_pes_packet(pes, ts-pkt);pes-state MPEGTS_SKIP;if (ret 0)return ret;}} while (0);buf_size 0;break;case MPEGTS_SKIP:buf_size 0;break;}}return 0;
}
该函数的作用就是解析TS流中的PES流的PES packetPES包。即解析TS流中的一个PES packet。 形参filter输出型参数指向一个MpegTSFilter类型变量。 形参buf输入型参数。存放一个transport packetTS包去掉TS Header后的有效数据即ES packet的数据。 形参buf_size输入型参数。形参buf指向的缓冲区的大小。 形参is_start输入型参数。如果值为true表示该transport packet的TS Header的payload_unit_start_indicator属性的值为1说明携带的是PES的第一个包。 形参pos输入型参数文件位置指针当前位置相对于TS文件的文件首的偏移字节数 减去 188字节。 返回值返回0表示解析成功返回一个负数表示出错。 三、mpegts_push_data函数的内部实现分析
mpegts_push_data函数内部使用了状态机的设计模式会根据枚举变量pes-state的值执行不同的处理逻辑pes-state取值如下
/* TS stream handling */enum MpegTSState {MPEGTS_HEADER 0,MPEGTS_PESHEADER,MPEGTS_PESHEADER_FILL,MPEGTS_PAYLOAD,MPEGTS_SKIP,
}; mpegts_push_data函数中首先判断形参is_start的值如果为true说明携带的是PES的第一个包。让pes-state赋值为MPEGTS_HEADER if (is_start) {if (pes-state MPEGTS_PAYLOAD pes-data_index 0) {ret new_pes_packet(pes, ts-pkt);if (ret 0)return ret;ts-stop_parse 1;} else {reset_pes_packet_state(pes);}pes-state MPEGTS_HEADER;pes-ts_packet_pos pos;} 下面分情况讨论。 一pes-state的值为MPEGTS_HEADER
pes-state的值为MPEGTS_HEADER时mpegts_push_data函数会执行下面代码块解析该PES packet的PES packet header中的固定长度部分 switch (pes-state) {case MPEGTS_HEADER:len PES_START_SIZE - pes-data_index;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index PES_START_SIZE) {/* we got all the PES or section header. We can now* decide */if (pes-header[0] 0x00 pes-header[1] 0x00 pes-header[2] 0x01) {/* it must be an MPEG-2 PES stream */pes-stream_id pes-header[3];av_log(pes-stream, AV_LOG_TRACE, pid%x stream_id%#x\n, pes-pid, pes-stream_id);if ((pes-st pes-st-discard AVDISCARD_ALL (!pes-sub_st ||pes-sub_st-discard AVDISCARD_ALL)) ||pes-stream_id STREAM_ID_PADDING_STREAM)goto skip;/* stream not present in PMT */if (!pes-st) {if (ts-skip_changes)goto skip;if (ts-merge_pmt_versions)goto skip; /* wait for PMT to merge new stream */pes-st avformat_new_stream(ts-stream, NULL);if (!pes-st)return AVERROR(ENOMEM);pes-st-id pes-pid;mpegts_set_stream_info(pes-st, pes, 0, 0);}pes-PES_packet_length AV_RB16(pes-header 4);/* NOTE: zero length means the PES size is unbounded */if (pes-stream_id ! STREAM_ID_PROGRAM_STREAM_MAP pes-stream_id ! STREAM_ID_PRIVATE_STREAM_2 pes-stream_id ! STREAM_ID_ECM_STREAM pes-stream_id ! STREAM_ID_EMM_STREAM pes-stream_id ! STREAM_ID_PROGRAM_STREAM_DIRECTORY pes-stream_id ! STREAM_ID_DSMCC_STREAM pes-stream_id ! STREAM_ID_TYPE_E_STREAM) {FFStream *const pes_sti ffstream(pes-st);pes-state MPEGTS_PESHEADER;if (pes-st-codecpar-codec_id AV_CODEC_ID_NONE !pes_sti-request_probe) {av_log(pes-stream, AV_LOG_TRACE,pid%x stream_type%x probing\n,pes-pid,pes-stream_type);pes_sti-request_probe 1;}} else {pes-pes_header_size 6;pes-state MPEGTS_PAYLOAD;pes-data_index 0;}} else {/* otherwise, it should be a table *//* skip packet */
skip:pes-state MPEGTS_SKIP;continue;}} 宏PES_START_SIZE定义在libavformat/mpegts.c中值为6表示PES packet header中的固定长度部分总共占6个字节
#define PES_START_SIZE 6 上述代码块中首先将该PES packet的PES packet header中的固定长度部分拷贝到数组pes-header中 len PES_START_SIZE - pes-data_index;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len; 判断PES packet header中的packet_start_code_prefix属性的值是否为0x000001如果是说明这是PES packet读取stream_id属性的值赋值给变量pes-stream_id /* we got all the PES or section header. We can now* decide */if (pes-header[0] 0x00 pes-header[1] 0x00 pes-header[2] 0x01) {/* it must be an MPEG-2 PES stream */pes-stream_id pes-header[3];av_log(pes-stream, AV_LOG_TRACE, pid%x stream_id%#x\n, pes-pid, pes-stream_id);//...
} 如果在之前解析PMT表的时候没有找到该PES流对应的音视频流跳过本次循环 /* stream not present in PMT */if (!pes-st) {if (ts-skip_changes)goto skip;if (ts-merge_pmt_versions)goto skip; /* wait for PMT to merge new stream */pes-st avformat_new_stream(ts-stream, NULL);if (!pes-st)return AVERROR(ENOMEM);pes-st-id pes-pid;mpegts_set_stream_info(pes-st, pes, 0, 0);} 读取PES_packet_length属性的值赋值给变量pes-PES_packet_length pes-PES_packet_length AV_RB16(pes-header 4);/* NOTE: zero length means the PES size is unbounded */ 通过PES packet header中的stream_id的值判断PES packet header中是否存在Optional PES header如果存在让pes-state赋值为MPEGTS_PESHEADER if (pes-stream_id ! STREAM_ID_PROGRAM_STREAM_MAP pes-stream_id ! STREAM_ID_PRIVATE_STREAM_2 pes-stream_id ! STREAM_ID_ECM_STREAM pes-stream_id ! STREAM_ID_EMM_STREAM pes-stream_id ! STREAM_ID_PROGRAM_STREAM_DIRECTORY pes-stream_id ! STREAM_ID_DSMCC_STREAM pes-stream_id ! STREAM_ID_TYPE_E_STREAM) {FFStream *const pes_sti ffstream(pes-st);pes-state MPEGTS_PESHEADER;if (pes-st-codecpar-codec_id AV_CODEC_ID_NONE !pes_sti-request_probe) {av_log(pes-stream, AV_LOG_TRACE,pid%x stream_type%x probing\n,pes-pid,pes-stream_type);pes_sti-request_probe 1;}} else {pes-pes_header_size 6;pes-state MPEGTS_PAYLOAD;pes-data_index 0;} 二pes-state的值为MPEGTS_PESHEADER
pes-state的值为MPEGTS_PESHEADER时mpegts_push_data函数会执行下面代码块 /**********************************************//* PES packing parsing */case MPEGTS_PESHEADER:len PES_HEADER_SIZE - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index PES_HEADER_SIZE) {pes-pes_header_size pes-header[8] 9;pes-state MPEGTS_PESHEADER_FILL;}break; 宏PES_HEADER_SIZE定义在libavformat/mpegts.c中值为9表示PES packet header中的固定长度部分 Optional PES header中的PES_header_data_length属性之前的部分包含PES_header_data_length属性总共占9个字节
#define PES_HEADER_SIZE 9 上述代码块中首先将该PES packet的Optional PES header中的PES_header_data_length属性之前的部分包含PES_header_data_length属性拷贝到pes-header pes-data_index指向的缓冲区中 len PES_HEADER_SIZE - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len; 读取Optional PES header中的PES_header_data_length属性赋值给变量pes-pes_header_size。让变量pes-state赋值为MPEGTS_PESHEADER_FILL if (pes-data_index PES_HEADER_SIZE) {pes-pes_header_size pes-header[8] 9;pes-state MPEGTS_PESHEADER_FILL;} 三pes-state的值为MPEGTS_PESHEADER_FILL
pes-state的值为MPEGTS_PESHEADER_FILL时mpegts_push_data函数会执行下面代码块 len pes-pes_header_size - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len;if (pes-data_index pes-pes_header_size) {const uint8_t *r;unsigned int flags, pes_ext, skip;flags pes-header[7];r pes-header 9;pes-pts AV_NOPTS_VALUE;pes-dts AV_NOPTS_VALUE;if ((flags 0xc0) 0x80) {pes-dts pes-pts ff_parse_pes_pts(r);r 5;} else if ((flags 0xc0) 0xc0) {pes-pts ff_parse_pes_pts(r);r 5;pes-dts ff_parse_pes_pts(r);r 5;}pes-extended_stream_id -1;if (flags 0x01) { /* PES extension */pes_ext *r;/* Skip PES private data, program packet sequence counter and P-STD buffer */skip (pes_ext 4) 0xb;skip skip 0x9;r skip;if ((pes_ext 0x41) 0x01 (r 2) (pes-header pes-pes_header_size)) {/* PES extension 2 */if ((r[0] 0x7f) 0 (r[1] 0x80) 0)pes-extended_stream_id r[1];}}/* we got the full header. We parse it and get the payload */pes-state MPEGTS_PAYLOAD;pes-data_index 0;if (pes-stream_type 0x12 buf_size 0) {int sl_header_bytes read_sl_header(pes, pes-sl, p,buf_size);pes-pes_header_size sl_header_bytes;p sl_header_bytes;buf_size - sl_header_bytes;}if (pes-stream_type STREAM_TYPE_METADATA pes-stream_id STREAM_ID_METADATA_STREAM pes-st-codecpar-codec_id AV_CODEC_ID_SMPTE_KLV buf_size 5) {/* skip metadata access unit header - see MISB ST 1402 */pes-pes_header_size 5;p 5;buf_size - 5;}if ( pes-ts-fix_teletext_pts ( pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT|| pes-st-codecpar-codec_id AV_CODEC_ID_DVB_SUBTITLE)) {AVProgram *p NULL;int pcr_found 0;while ((p av_find_program_from_stream(pes-stream, p, pes-st-index))) {if (p-pcr_pid ! -1 p-discard ! AVDISCARD_ALL) {MpegTSFilter *f pes-ts-pids[p-pcr_pid];if (f) {AVStream *st NULL;if (f-type MPEGTS_PES) {PESContext *pcrpes f-u.pes_filter.opaque;if (pcrpes)st pcrpes-st;} else if (f-type MPEGTS_PCR) {int i;for (i 0; i p-nb_stream_indexes; i) {AVStream *pst pes-stream-streams[p-stream_index[i]];if (pst-codecpar-codec_type AVMEDIA_TYPE_VIDEO)st pst;}}if (f-last_pcr ! -1 !f-discard) {// teletext packets do not always have correct timestamps,// the standard says they should be handled after 40.6 ms at most,// and the pcr error to this packet should be no more than 100 ms.// TODO: we should interpolate the PCR, not just use the last oneint64_t pcr f-last_pcr / 300;pcr_found 1;if (st) {const FFStream *const sti ffstream(st);FFStream *const pes_sti ffstream(pes-st);pes_sti-pts_wrap_reference sti-pts_wrap_reference;pes_sti-pts_wrap_behavior sti-pts_wrap_behavior;}if (pes-dts AV_NOPTS_VALUE || pes-dts pcr) {pes-pts pes-dts pcr;} else if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT pes-dts pcr 3654 9000) {pes-pts pes-dts pcr 3654 9000;} else if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_SUBTITLE pes-dts pcr 10*90000) { //10secpes-pts pes-dts pcr 3654 9000;}break;}}}}if (pes-st-codecpar-codec_id AV_CODEC_ID_DVB_TELETEXT !pcr_found) {av_log(pes-stream, AV_LOG_VERBOSE,Forcing DTS/PTS to be unset for a non-trustworthy PES packet for PID %d as PCR hasnt been received yet.\n,pes-pid);pes-dts pes-pts AV_NOPTS_VALUE;}}}break; 上述代码块中首先将该PES packet的Optional PES header中的可选字段占用的总字节数以及包含在此PES packet header的任何填充字节拷贝到pes-header pes-data_index指向的缓冲区中 len pes-pes_header_size - pes-data_index;if (len 0)return AVERROR_INVALIDDATA;if (len buf_size)len buf_size;memcpy(pes-header pes-data_index, p, len);pes-data_index len;p len;buf_size - len; 读取Optional PES header中的PTS_DTS_flags、ESCR_flag、ES_rate_flag、DSM_trick_mode_flag、additional_copy_info_flag、PES_CRC_flag、PES_extension_flag这7个属性这7个属性加起来总共1个字节赋值给变量flags const uint8_t *r;unsigned int flags, pes_ext, skip;flags pes-header[7];r pes-header 9;pes-pts AV_NOPTS_VALUE;pes-dts AV_NOPTS_VALUE; 如果Optional PES header中的PTS_DTS_flags属性的值为10表示PES packet header中会存在PTS。读取PTS的值赋值给变量pes-pts让pes-dts也等于PTS if ((flags 0xc0) 0x80) {pes-dts pes-pts ff_parse_pes_pts(r);r 5;} 如果PTS_DTS_flags属性的值为11PES packet header中会同时存在PTS和DTS读取PTS的值赋值给变量pes-pts读取DTS的值赋值给变量pes-dts if ((flags 0xc0) 0x80) {//...} else if ((flags 0xc0) 0xc0) {pes-pts ff_parse_pes_pts(r);r 5;pes-dts ff_parse_pes_pts(r);r 5;} 如果PES_extension_flag属性的值为1表示PES packet header有PES_extension域解析PES_extension域 if (flags 0x01) { /* PES extension */pes_ext *r;/* Skip PES private data, program packet sequence counter and P-STD buffer */skip (pes_ext 4) 0xb;skip skip 0x9;r skip;if ((pes_ext 0x41) 0x01 (r 2) (pes-header pes-pes_header_size)) {/* PES extension 2 */if ((r[0] 0x7f) 0 (r[1] 0x80) 0)pes-extended_stream_id r[1];}} 至此mpegts_push_data函数已解析完整个PES packet header让变量pes-state赋值为MPEGTS_PAYLOAD /* we got the full header. We parse it and get the payload */pes-state MPEGTS_PAYLOAD;pes-data_index 0; 四pes-state的值为MPEGTS_PAYLOAD
pes-state的值为MPEGTS_PAYLOAD时mpegts_push_data函数会执行下面代码块
case MPEGTS_PAYLOAD:do {int max_packet_size ts-max_packet_size;if (pes-PES_packet_length pes-PES_packet_length PES_START_SIZE pes-pes_header_size)max_packet_size pes-PES_packet_length PES_START_SIZE - pes-pes_header_size;if (pes-data_index 0 pes-data_index buf_size max_packet_size) {ret new_pes_packet(pes, ts-pkt);if (ret 0)return ret;pes-PES_packet_length 0;max_packet_size ts-max_packet_size;ts-stop_parse 1;} else if (pes-data_index 0 buf_size max_packet_size) {// pes packet size is ts size packet and pes data is padded with 0xff// not sure if this is legal in ts but see issue #2392buf_size max_packet_size;}if (!pes-buffer) {pes-buffer buffer_pool_get(ts, max_packet_size);if (!pes-buffer)return AVERROR(ENOMEM);}memcpy(pes-buffer-data pes-data_index, p, buf_size);pes-data_index buf_size;/* emit complete packets with known packet size* decreases demuxer delay for infrequent packets like subtitles from* a couple of seconds to milliseconds for properly muxed files. */if (!ts-stop_parse pes-PES_packet_length pes-pes_header_size pes-data_index pes-PES_packet_length PES_START_SIZE) {ts-stop_parse 1;ret new_pes_packet(pes, ts-pkt);pes-state MPEGTS_SKIP;if (ret 0)return ret;}} while (0);buf_size 0;break; 上述代码块的主要作用就是将该PES packet的PES packet data bytesPES包的负载拷贝到pes-buffer-data pes-data_index指向的缓冲区中 memcpy(pes-buffer-data pes-data_index, p, buf_size);pes-data_index buf_size; ts-pkt指向一个AVPacket类型的变量让ts-pkt得到该PES packet的数据 /* emit complete packets with known packet size* decreases demuxer delay for infrequent packets like subtitles from* a couple of seconds to milliseconds for properly muxed files. */if (!ts-stop_parse pes-PES_packet_length pes-pes_header_size pes-data_index pes-PES_packet_length PES_START_SIZE) {ts-stop_parse 1;ret new_pes_packet(pes, ts-pkt);pes-state MPEGTS_SKIP;if (ret 0)return ret;}
