1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Vidtv serves as a reference DVB driver and helps validate the existing APIs 4 * in the media subsystem. It can also aid developers working on userspace 5 * applications. 6 * 7 * This file contains the logic to translate the ES data for one access unit 8 * from an encoder into MPEG TS packets. It does so by first encapsulating it 9 * with a PES header and then splitting it into TS packets. 10 * 11 * Copyright (C) 2020 Daniel W. S. Almeida 12 */ 13 14 #ifndef VIDTV_PES_H 15 #define VIDTV_PES_H 16 17 #include <linux/types.h> 18 19 #include "vidtv_common.h" 20 21 #define PES_MAX_LEN 65536 /* Set 'length' to 0 if greater. Only possible for video. */ 22 #define PES_START_CODE_PREFIX 0x001 /* 00 00 01 */ 23 24 /* Used when sending PTS, but not DTS */ 25 struct vidtv_pes_optional_pts { 26 u8 pts1; 27 __be16 pts2; 28 __be16 pts3; 29 } __packed; 30 31 /* Used when sending both PTS and DTS */ 32 struct vidtv_pes_optional_pts_dts { 33 u8 pts1; 34 __be16 pts2; 35 __be16 pts3; 36 37 u8 dts1; 38 __be16 dts2; 39 __be16 dts3; 40 } __packed; 41 42 /* PES optional flags */ 43 struct vidtv_pes_optional { 44 /* 45 * These flags show which components are actually 46 * present in the "optional fields" in the optional PES 47 * header and which are not 48 * 49 * u16 two:2; //0x2 50 * u16 PES_scrambling_control:2; 51 * u16 PES_priority:1; 52 * u16 data_alignment_indicator:1; // unused 53 * u16 copyright:1; 54 * u16 original_or_copy:1; 55 * u16 PTS_DTS:2; 56 * u16 ESCR:1; 57 * u16 ES_rate:1; 58 * u16 DSM_trick_mode:1; 59 * u16 additional_copy_info:1; 60 * u16 PES_CRC:1; 61 * u16 PES_extension:1; 62 */ 63 __be16 bitfield; 64 u8 length; 65 } __packed; 66 67 /* The PES header */ 68 struct vidtv_mpeg_pes { 69 __be32 bitfield; /* packet_start_code_prefix:24, stream_id: 8 */ 70 /* after this field until the end of the PES data payload */ 71 __be16 length; 72 struct vidtv_pes_optional optional[]; 73 } __packed; 74 75 /** 76 * struct pes_header_write_args - Arguments to write a PES header. 77 * @dest_buf: The buffer to write into. 78 * @dest_offset: where to start writing in the dest_buffer. 79 * @dest_buf_sz: The size of the dest_buffer 80 * @encoder_id: Encoder id (see vidtv_encoder.h) 81 * @send_pts: Should we send PTS? 82 * @pts: PTS value to send. 83 * @send_dts: Should we send DTS? 84 * @dts: DTS value to send. 85 * @stream_id: The stream id to use. Ex: Audio streams (0xc0-0xdf), Video 86 * streams (0xe0-0xef). 87 * @n_pes_h_s_bytes: Padding bytes. Might be used by an encoder if needed, gets 88 * discarded by the decoder. 89 * @access_unit_len: The size of _one_ access unit (with any headers it might need) 90 */ 91 struct pes_header_write_args { 92 void *dest_buf; 93 u32 dest_offset; 94 u32 dest_buf_sz; 95 u32 encoder_id; 96 97 bool send_pts; 98 u64 pts; 99 100 bool send_dts; 101 u64 dts; 102 103 u16 stream_id; 104 /* might be used by an encoder if needed, gets discarded by decoder */ 105 u32 n_pes_h_s_bytes; 106 u32 access_unit_len; 107 }; 108 109 /** 110 * struct pes_ts_header_write_args - Arguments to write a TS header. 111 * @dest_buf: The buffer to write into. 112 * @dest_offset: where to start writing in the dest_buffer. 113 * @dest_buf_sz: The size of the dest_buffer 114 * @pid: The PID to use for the TS packets. 115 * @continuity_counter: Incremented on every new TS packet. 116 * @wrote_pes_header: Flag to indicate that the PES header was written 117 * @n_stuffing_bytes: Padding bytes. Might be used by an encoder if needed, gets 118 * discarded by the decoder. 119 * @pcr: counter driven by a 27Mhz clock. 120 */ 121 struct pes_ts_header_write_args { 122 void *dest_buf; 123 u32 dest_offset; 124 u32 dest_buf_sz; 125 u16 pid; 126 u8 *continuity_counter; 127 bool wrote_pes_header; 128 u32 n_stuffing_bytes; 129 u64 pcr; 130 }; 131 132 /** 133 * struct pes_write_args - Arguments for the packetizer. 134 * @dest_buf: The buffer to write into. 135 * @from: A pointer to the encoder buffer containing one access unit. 136 * @access_unit_len: The size of _one_ access unit (with any headers it might need) 137 * @dest_offset: where to start writing in the dest_buffer. 138 * @dest_buf_sz: The size of the dest_buffer 139 * @pid: The PID to use for the TS packets. 140 * @encoder_id: Encoder id (see vidtv_encoder.h) 141 * @continuity_counter: Incremented on every new TS packet. 142 * @stream_id: The stream id to use. Ex: Audio streams (0xc0-0xdf), Video 143 * streams (0xe0-0xef). 144 * @send_pts: Should we send PTS? 145 * @pts: PTS value to send. 146 * @send_dts: Should we send DTS? 147 * @dts: DTS value to send. 148 * @n_pes_h_s_bytes: Padding bytes. Might be used by an encoder if needed, gets 149 * discarded by the decoder. 150 * @pcr: counter driven by a 27Mhz clock. 151 */ 152 struct pes_write_args { 153 void *dest_buf; 154 void *from; 155 u32 access_unit_len; 156 157 u32 dest_offset; 158 u32 dest_buf_sz; 159 u16 pid; 160 161 u32 encoder_id; 162 163 u8 *continuity_counter; 164 165 u16 stream_id; 166 167 bool send_pts; 168 u64 pts; 169 170 bool send_dts; 171 u64 dts; 172 173 u32 n_pes_h_s_bytes; 174 u64 pcr; 175 }; 176 177 /** 178 * vidtv_pes_write_into - Write a PES packet as MPEG-TS packets into a buffer. 179 * @args: The args to use when writing 180 * 181 * This function translate the ES data for one access unit 182 * from an encoder into MPEG TS packets. It does so by first encapsulating it 183 * with a PES header and then splitting it into TS packets. 184 * 185 * The data is then written into the buffer pointed to by 'args.buf' 186 * 187 * Return: The number of bytes written into the buffer. This is usually NOT 188 * equal to the size of the access unit, since we need space for PES headers, TS headers 189 * and padding bytes, if any. 190 */ 191 u32 vidtv_pes_write_into(struct pes_write_args *args); 192 193 #endif // VIDTV_PES_H 194