[RFC, WIP, v5 08/10] media: vidtv: implement a PES packetizer

Daniel W. S. Almeida
2020-05-15T21:49:21Z

Implement the PES logic to convert encoder data into MPEG TS packets.
These TS packets can then be fed into a TS multiplexer and eventually
into userspace.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
.../media/test-drivers/vidtv/vidtv_common.h | 2 +
drivers/media/test-drivers/vidtv/vidtv_pes.c | 450 ++++++++++++++++++
drivers/media/test-drivers/vidtv/vidtv_pes.h | 186 ++++++++
3 files changed, 638 insertions(+)
create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.c
create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
index a3cb303cc7423..1a31973f3ac61 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_common.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -24,4 +24,6 @@ u32 vidtv_memset(void *to,
int c,
size_t len);

+u64 vidtv_extract_bits(u64 value, u8 start_bit, u8 nbits);
+
#endif // VIDTV_COMMON_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_pes.c b/drivers/media/test-drivers/vidtv/vidtv_pes.c
new file mode 100644
index 0000000000000..8614868972eaa
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_pes.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the logic to translate the ES data for one access unit
+ * from an encoder into MPEG TS packets. It does so by first encapsulating it
+ * with a PES header and then splitting it into TS packets.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_pes.h"
+#include "vidtv_common.h"
+#include "vidtv_ts.h"
+
+#define PRIVATE_STREAM_1_ID 0xbd /* private_stream_1. See SMPTE 302M-2007 p.6 */
+#define PES_HEADER_MAX_STUFFING_BYTES 32
+#define PES_TS_HEADER_MAX_STUFFING_BYTES 182
+
+static u32 vidtv_pes_op_get_regular_len(bool send_pts, bool send_dts)
+{
+ u32 len = 0;
+
+ /* the flags must always be sent */
+ len += sizeof(struct vidtv_pes_optional);
+
+ /* From all optionals, we might send these for now */
+ if (send_pts && send_dts)
+ len += sizeof(struct vidtv_pes_optional_pts_dts);
+ else if (send_pts)
+ len += sizeof(struct vidtv_pes_optional_pts);
+
+ return len;
+}
+
+static u32 vidtv_pes_h_get_regular_len(bool send_pts, bool send_dts)
+{
+ /* PES header length notwithstanding stuffing bytes */
+ u32 len = 0;
+
+ len += sizeof(struct vidtv_mpeg_pes);
+ len += vidtv_pes_op_get_regular_len(send_pts, send_dts);
+
+ return len;
+}
+
+static u32 vidtv_pes_write_header_stuffing(struct vidtv_mpeg_pes *pes_h,
+ struct pes_header_write_args args)
+{
+ /*
+ * This is a fixed 8-bit value equal to '1111 1111' that can be inserted
+ * by the encoder, for example to meet the requirements of the channel.
+ * It is discarded by the decoder. No more than 32 stuffing bytes shall
+ * be present in one PES packet header.
+ */
+ if (args.n_pes_h_s_bytes > PES_HEADER_MAX_STUFFING_BYTES) {
+ pr_warn_ratelimited("More than 32 stuffing bytes in PES packet header\n");
+ args.n_pes_h_s_bytes = PES_HEADER_MAX_STUFFING_BYTES;
+ }
+
+ /* gives the length of the remainder of the PES header in bytes */
+ pes_h->length += args.n_pes_h_s_bytes;
+
+ return vidtv_memset(args.dest_buf,
+ args.dest_offset,
+ args.dest_buf_sz,
+ TS_FILL_BYTE,
+ args.n_pes_h_s_bytes);
+}
+
+static u32 vidtv_pes_write_pts_dts(struct pes_header_write_args args)
+{
+ u32 nbytes = 0; /* the number of bytes written by this function */
+
+ struct vidtv_pes_optional_pts pts = {0};
+ struct vidtv_pes_optional_pts_dts pts_dts = {0};
+ void *op = NULL;
+ size_t op_sz = 0;
+
+ if (!args.send_pts && args.send_dts)
+ return 0;
+
+ /* see ISO/IEC 13818-1 : 2000 p. 32 */
+
+ if (args.send_pts && args.send_dts) {
+ pts_dts.three = 0x3;
+
+ pts_dts.pts1 = (args.pts & GENMASK(32, 30)) >> 30;
+ pts_dts.marker1 = 0x1;
+ pts_dts.pts2 = (args.pts & GENMASK(29, 15)) >> 15;
+ pts_dts.marker2 = 0x1;
+ pts_dts.pts3 = args.pts & GENMASK(14, 0);
+ pts_dts.marker3 = 0x1;
+
+ pts_dts.one = 0x1;
+
+ pts_dts.dts1 = (args.dts & GENMASK(32, 30)) >> 30;
+ pts_dts.marker1 = 0x1;
+ pts_dts.dts2 = (args.dts & GENMASK(29, 15)) >> 15;
+ pts_dts.marker2 = 0x1;
+ pts_dts.dts3 = args.dts & GENMASK(14, 0);
+ pts_dts.marker3 = 0x1;
+
+ op = &pts_dts;
+ op_sz = sizeof(pts_dts);
+
+ } else if (args.send_pts) {
+ pts.two = 0x2;
+ pts_dts.pts1 = (args.pts & GENMASK(32, 30)) >> 30;
+ pts_dts.marker1 = 0x1;
+ pts_dts.pts2 = (args.pts & GENMASK(29, 15)) >> 15;
+ pts_dts.marker2 = 0x1;
+ pts_dts.pts3 = args.pts & GENMASK(14, 0);
+ pts_dts.marker3 = 0x1;
+
+ op = &pts;
+ op_sz = sizeof(pts);
+ }
+
+ /* copy PTS/DTS optional */
+ nbytes += vidtv_memcpy(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ op,
+ op_sz);
+
+ return nbytes;
+}
+
+static u32 vidtv_pes_write_h(struct pes_header_write_args args)
+{
+ u32 nbytes = 0; /* the number of bytes written by this function */
+
+ struct vidtv_mpeg_pes pes_header = {0};
+ struct vidtv_pes_optional pes_optional = {0};
+ struct pes_header_write_args pts_dts_args = args;
+
+ pes_header.packet_start_code_prefix = PES_START_CODE_PREFIX;
+
+ pes_header.stream_id = (args.is_s302m_pkt) ?
+ PRIVATE_STREAM_1_ID :
+ args.stream_id;
+
+ pes_header.length = vidtv_pes_op_get_regular_len(args.send_pts,
+ args.send_dts);
+
+ pes_optional.two = 0x2;
+
+ pes_optional.PTS_DTS = (args.send_pts && args.send_dts) ?
+ 0x3 :
+ (args.send_pts) ?
+ 0x2 :
+ 0x0;
+
+ /* copy header */
+
+ nbytes += vidtv_memcpy(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ &pes_header,
+ sizeof(pes_header));
+
+ /* copy optional header */
+ nbytes += vidtv_memcpy(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ &pes_optional,
+ sizeof(pes_optional));
+
+ pts_dts_args.dest_offset = args.dest_offset + nbytes;
+ nbytes += vidtv_pes_write_pts_dts(pts_dts_args);
+
+ /* write any PES header stuffing */
+ nbytes += vidtv_pes_write_header_stuffing(&pes_header, args);
+
+ return nbytes;
+}
+
+static u32 vidtv_pes_write_stuffing(struct vidtv_mpeg_ts *ts_h,
+ void *dest_buf,
+ u32 dest_offset,
+ u32 n_stuffing_bytes,
+ u32 buf_sz)
+{
+ /*
+ * For Transport Stream packets carrying PES packets, stuffing is
+ * needed when there is insufficient PES packet data to completely
+ * fill the Transport Stream packet payload bytes. Stuffing is
+ * accomplished by defining an adaptation field longer than the sum of
+ * the lengths of the data elements in it, so that the payload bytes
+ * remaining after the adaptation field exactly accommodates the
+ * available PES packet data. The extra space in the adaptation field
+ * is filled with stuffing bytes.
+ *
+ */
+
+ /* the number of bytes written by this function */
+ u32 nbytes = 0;
+ struct vidtv_mpeg_ts_adaption ts_adap = {0};
+
+ if (!n_stuffing_bytes)
+ return nbytes;
+
+ ts_h->adaptation_field = 1;
+
+ if (n_stuffing_bytes > PES_TS_HEADER_MAX_STUFFING_BYTES) {
+ pr_warn_ratelimited("More than %d stuffing bytes for a PES packet",
+ PES_TS_HEADER_MAX_STUFFING_BYTES);
+
+ n_stuffing_bytes = PES_TS_HEADER_MAX_STUFFING_BYTES;
+ }
+
+ /* the AF will only be its 'length' field with a value of zero */
+ if (n_stuffing_bytes == 1) {
+ nbytes += vidtv_memset(dest_buf,
+ dest_offset + nbytes,
+ buf_sz,
+ 0,
+ n_stuffing_bytes);
+
+ return nbytes;
+ }
+
+ n_stuffing_bytes -= sizeof(ts_adap);
+
+ /* length _immediately_ following 'adaptation_field_length' */
+ ts_adap.length = sizeof(ts_adap) -
+ sizeof(ts_adap.length) +
+ n_stuffing_bytes;
+
+ /* write the adap after the TS header */
+ nbytes += vidtv_memcpy(dest_buf,
+ dest_offset + nbytes,
+ buf_sz,
+ &ts_adap,
+ sizeof(ts_adap));
+
+ /* write the stuffing bytes */
+ nbytes += vidtv_memset(dest_buf,
+ dest_offset + nbytes,
+ buf_sz,
+ TS_FILL_BYTE,
+ n_stuffing_bytes);
+
+ return nbytes;
+}
+
+static u32 vidtv_pes_write_ts_h(struct pes_ts_header_write_args args)
+{
+ /* number of bytes written by this function */
+ u32 nbytes = 0;
+ struct vidtv_mpeg_ts ts_header = {0};
+
+ ts_header.sync_byte = TS_SYNC_BYTE;
+ ts_header.tei = 0;
+ ts_header.pid = args.pid;
+ ts_header.priority = 0;
+ ts_header.scrambling = 0; /* not scrambled */
+ ts_header.adaptation_field = 0;
+ ts_header.payload = 1;
+
+ ts_header.payload_start = (!args.wrote_pes_header) ? 1 : 0;
+ ts_header.continuity_counter = *args.continuity_counter;
+
+ /*
+ * This will trigger a discontinuity if the buffer is full, which is
+ * what we want: the continuity counter will be incremented but nothing
+ * will get copied by vidtv_memcpy/vidtv_memset, effectively dropping
+ * the packet.
+ */
+ vidtv_ts_inc_cc(args.continuity_counter);
+
+ /* write the TS header */
+ nbytes += vidtv_memcpy(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ &ts_header,
+ sizeof(ts_header));
+
+ /* write stuffing, if any */
+ nbytes += vidtv_pes_write_stuffing(&ts_header,
+ args.dest_buf,
+ args.dest_offset + nbytes,
+ args.n_stuffing_bytes,
+ args.dest_buf_sz);
+
+ return nbytes;
+}
+
+u32 vidtv_pes_write_into(struct pes_write_args args)
+{
+ u32 nbytes_past_boundary = (args.dest_offset % TS_PACKET_LEN);
+ bool aligned = (nbytes_past_boundary == 0);
+
+ struct pes_ts_header_write_args ts_header_args = {0};
+ struct pes_header_write_args pes_header_args = {0};
+
+ /* number of bytes written by this function */
+ u32 nbytes = 0;
+ u32 remaining_len = args.access_unit_len;
+
+ bool wrote_pes_header = false;
+
+ /* whether we need to stuff the TS packet to align the buffer */
+ bool stuff = false;
+
+ u32 available_space = 0;
+ u32 payload_write_len = 0;
+ u32 num_stuffing_bytes = 0;
+
+ /* Just a sanity check, should not really happen because we stuff the
+ * TS packet when we finish writing the PES data, but if this happens
+ * then we have messed up the logic somewhere.
+ *
+ * Also note that, unlike packets for PSI data, we need to carry PES
+ * packets aligned with the payload of transport packets, that is the
+ * first byte of each PES header must be the first byte in the payload
+ * of a transport packet. As a consequence, the last byte of a PES
+ * packet must be the last byte of the payload of a transport packet.
+ */
+ if (!aligned) {
+ pr_warn_ratelimited("Cannot start a PES packet in a misaligned buffer\n");
+
+ /* forcibly align and hope for the best */
+ nbytes += vidtv_memset(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ TS_FILL_BYTE,
+ TS_PACKET_LEN - nbytes_past_boundary);
+
+ aligned = true;
+ }
+
+ if (args.send_dts && !args.send_pts) {
+ pr_warn_ratelimited("forbidden value '01' for PTS_DTS flags\n");
+ args.send_pts = true;
+ args.pts = args.dts;
+ }
+
+ /* see SMPTE 302M clause 6.4 */
+ if (args.is_s302m_pkt) {
+ args.send_dts = false;
+ args.send_pts = true;
+ }
+
+ while (remaining_len) {
+ /*
+ * The amount of space initially available in the TS packet.
+ * if this is the beginning of the PES packet, we need to
+ * take into account the space needed for the TS header _and_
+ * for the PES header
+ */
+ available_space = (!wrote_pes_header) ?
+ TS_PAYLOAD_LEN -
+ vidtv_pes_h_get_regular_len(args.send_pts,
+ args.send_dts) :
+ TS_PAYLOAD_LEN;
+
+ /* if the encoder has inserted stuffing bytes in the PES
+ * header, account for them.
+ */
+ available_space -= args.n_pes_h_s_bytes;
+
+ /* whether we need to stuff the TS packet to align the buffer */
+ stuff = remaining_len < available_space;
+
+ /*
+ * how much of the _actual_ payload we should write in this
+ * packet.
+ */
+ payload_write_len = (stuff) ?
+ remaining_len :
+ available_space;
+
+ num_stuffing_bytes = available_space - payload_write_len;
+
+ /* write ts header */
+ ts_header_args.dest_buf = args.dest_buf;
+ ts_header_args.dest_offset = args.dest_offset + nbytes;
+ ts_header_args.dest_buf_sz = args.dest_buf_sz;
+ ts_header_args.pid = args.pid;
+ ts_header_args.continuity_counter = args.continuity_counter;
+ ts_header_args.wrote_pes_header = wrote_pes_header;
+ ts_header_args.n_stuffing_bytes = num_stuffing_bytes;
+
+ nbytes += vidtv_pes_write_ts_h(ts_header_args);
+
+ if (!wrote_pes_header) {
+ /* write the PES header only once */
+ pes_header_args.dest_buf = args.dest_buf;
+
+ pes_header_args.dest_offset = args.dest_offset +
+ nbytes;
+
+ pes_header_args.dest_buf_sz = args.dest_buf_sz;
+ pes_header_args.is_s302m_pkt = args.is_s302m_pkt;
+ pes_header_args.send_pts = args.send_pts;
+ pes_header_args.pts = args.pts;
+ pes_header_args.send_dts = args.send_dts;
+ pes_header_args.dts = args.dts;
+ pes_header_args.stream_id = args.stream_id;
+ pes_header_args.n_pes_h_s_bytes = args.n_pes_h_s_bytes;
+
+ nbytes += vidtv_pes_write_h(pes_header_args);
+ wrote_pes_header = true;
+ }
+
+ /* write as much of the payload as we possibly can */
+ nbytes += vidtv_memcpy(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ args.from,
+ payload_write_len);
+
+ args.from += payload_write_len;
+ args.dest_offset += nbytes;
+
+ /* Sanity check for underflow. Should not really happen. */
+ if (remaining_len - payload_write_len > remaining_len) {
+ pr_err_ratelimited("Underflow detected\n");
+
+ /* recompute the alignment */
+ nbytes_past_boundary = (args.dest_offset + nbytes) %
+ TS_PACKET_LEN;
+
+ /* forcibly align */
+ nbytes += vidtv_memset(args.dest_buf,
+ args.dest_offset + nbytes,
+ args.dest_buf_sz,
+ TS_FILL_BYTE,
+ TS_PACKET_LEN -
+ nbytes_past_boundary);
+
+ /* bailing out is the best that we can do */
+ return nbytes;
+ }
+
+ remaining_len -= payload_write_len;
+ }
+
+ return nbytes;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_pes.h b/drivers/media/test-drivers/vidtv/vidtv_pes.h
new file mode 100644
index 0000000000000..f2cf3872db545
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_pes.h
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the logic to translate the ES data for one access unit
+ * from an encoder into MPEG TS packets. It does so by first encapsulating it
+ * with a PES header and then splitting it into TS packets.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_PES_H
+#define VIDTV_PES_H
+
+#include <asm/byteorder.h>
+#include <linux/types.h>
+
+#include "vidtv_common.h"
+
+#define PES_MAX_LEN 65536 /* Set 'length' to 0 if greater */
+#define PES_START_CODE_PREFIX 0x001 /* 00 00 01 */
+
+struct vidtv_pes_optional_pts {
+ struct {
+ #if defined(__LITTLE_ENDIAN_BITFIELD)
+ u8 marker3:1; /* always 0x1 */
+ u16 pts3:15;
+ u8 marker2:1; /* always 0x1 */
+ u16 pts2:15;
+ u8 marker1:1; /* always 0x1 */
+ u8 pts1:3;
+ u8 two:4; /* always 0010b */
+ #elif defined(__BIG_ENDIAN_BITFIELD)
+ u8 two:4; /* always 0010b */
+ u8 pts1:3;
+ u8 marker1:1; /* always 0x1 */
+ u16 pts2:15;
+ u8 marker2:1; /* always 0x1 */
+ u16 pts3:15;
+ u8 marker3:1; /* always 0x1 */
+ #else
+ #error "Unknown bit ordering"
+ #endif
+ } __packed;
+} __packed;
+
+struct vidtv_pes_optional_pts_dts {
+ struct {
+ #if defined(__LITTLE_ENDIAN_BITFIELD)
+ u8 marker6:1; /* always 0x1 */
+ u16 dts3:15;
+ u8 marker5:1; /* always 0x1 */
+ u16 dts2:15;
+ u8 marker4:1; /* always 0x1 */
+ u8 dts1:3;
+ u8 one:4; /* always 0001b */
+ u8 marker3:1; /* always 0x1 */
+ u16 pts3:15;
+ u8 marker2:1; /* always 0x1 */
+ u16 pts2:15;
+ u8 marker1:1; /* always 0x1 */
+ u8 pts1:3;
+ u8 three:4; /* always 0011b */
+ #elif defined(__BIG_ENDIAN_BITFIELD)
+ u8 three:4; /* always 0011b */
+ u8 pts1:3;
+ u8 marker1:1; /* always 0x1 */
+ u16 pts2:15;
+ u8 marker2:1; /* always 0x1 */
+ u16 pts3:15;
+ u8 marker3:1; /* always 0x1 */
+ u8 one:4; /* always 0001b */
+ u8 dts1:3;
+ u8 marker4:1; /* always 0x1 */
+ u16 dts2:15;
+ u8 marker5:1; /* always 0x1 */
+ u16 dts3:15;
+ u8 marker6:1; /* always 0x1 */
+ #else
+ #error "Unknown bit ordering"
+ #endif
+ } __packed;
+} __packed;
+
+struct vidtv_pes_optional {
+ union {
+ __be16 bitfield;
+ struct {
+ u16 two:2; /* always 0x2*/
+ u16 PES_scrambling_control:2;
+ u16 PES_priority:1;
+ u16 data_alignment_indicator:1; /* ununsed for us */
+ u16 copyright:1;
+ u16 original_or_copy:1;
+ u16 PTS_DTS:2;
+ /* These flags show which components are actually
+ * present in the "optinal fields" in the optinal PES
+ * header and which are not. Vidtv currently does
+ * not need any of these.
+ */
+ u16 ESCR:1;
+ u16 ES_rate:1;
+ u16 DSM_trick_mode:1;
+ u16 additional_copy_info:1;
+ u16 PES_CRC:1;
+ u16 PES_extension:1;
+ } __packed;
+ } __packed;
+ u8 length;
+} __packed;
+
+struct vidtv_mpeg_pes {
+ union {
+ __be32 bitfield;
+ struct {
+ /* These two together make the 32-bit start-code */
+ u32 packet_start_code_prefix:24;
+ u32 stream_id:8;
+ } __packed;
+ } __packed;
+ /* after this field until the end of the PES data payload */
+ u16 length;
+ struct vidtv_pes_optional optional[];
+} __packed;
+
+struct pes_header_write_args {
+ void *dest_buf;
+ u32 dest_offset;
+ u32 dest_buf_sz;
+ bool is_s302m_pkt;
+
+ bool send_pts;
+ u64 pts;
+
+ bool send_dts;
+ u64 dts;
+
+ u16 stream_id;
+ /* might be used by an encoder if needed, gets discarded by decoder */
+ u32 n_pes_h_s_bytes;
+};
+
+struct pes_ts_header_write_args {
+ void *dest_buf;
+ u32 dest_offset;
+ u32 dest_buf_sz;
+ u16 pid;
+ u8 *continuity_counter;
+ bool wrote_pes_header;
+ u32 n_stuffing_bytes;
+};
+
+struct pes_write_args {
+ void *dest_buf; /* pointer to a program mux buffer */
+ void *from; /* pointer to the encoder buffer */
+
+ /* the size of one access unit (with any headers it might need) */
+ u32 access_unit_len;
+
+ u32 dest_offset; /* where to start writing in the program mux buffer */
+ u32 dest_buf_sz; /* how big is the program mux buffer */
+ u16 pid; /* TS packet ID */
+
+ /* use SMPTE 302M to packetize the data */
+ bool is_s302m_pkt;
+
+ u8 *continuity_counter; /* incremented for every TS packet */
+
+ /* Examples: Audio streams (0xc0-0xdf), Video streams (0xe0-0xef) */
+ u16 stream_id;
+
+ bool send_pts;
+ u64 pts;
+
+ bool send_dts;
+ u64 dts;
+
+ /* might be used by an encoder if needed, gets discarded by decoder */
+ u32 n_pes_h_s_bytes;
+};
+
+u32 vidtv_pes_write_into(struct pes_write_args args);
+
+#endif // VIDTV_PES_H
--
2.26.2