1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "media/formats/mp2t/ts_section_pes.h"
6
7 #include "base/logging.h"
8 #include "base/strings/string_number_conversions.h"
9 #include "media/base/bit_reader.h"
10 #include "media/base/buffers.h"
11 #include "media/formats/mp2t/es_parser.h"
12 #include "media/formats/mp2t/mp2t_common.h"
13 #include "media/formats/mp2t/timestamp_unroller.h"
14
15 static const int kPesStartCode = 0x000001;
16
IsTimestampSectionValid(int64 timestamp_section)17 static bool IsTimestampSectionValid(int64 timestamp_section) {
18 // |pts_section| has 40 bits:
19 // - starting with either '0010' or '0011' or '0001'
20 // - and ending with a marker bit.
21 // See ITU H.222 standard - PES section.
22
23 // Verify that all the marker bits are set to one.
24 return ((timestamp_section & 0x1) != 0) &&
25 ((timestamp_section & 0x10000) != 0) &&
26 ((timestamp_section & 0x100000000) != 0);
27 }
28
ConvertTimestampSectionToTimestamp(int64 timestamp_section)29 static int64 ConvertTimestampSectionToTimestamp(int64 timestamp_section) {
30 return (((timestamp_section >> 33) & 0x7) << 30) |
31 (((timestamp_section >> 17) & 0x7fff) << 15) |
32 (((timestamp_section >> 1) & 0x7fff) << 0);
33 }
34
35 namespace media {
36 namespace mp2t {
37
TsSectionPes(scoped_ptr<EsParser> es_parser,TimestampUnroller * timestamp_unroller)38 TsSectionPes::TsSectionPes(scoped_ptr<EsParser> es_parser,
39 TimestampUnroller* timestamp_unroller)
40 : es_parser_(es_parser.release()),
41 wait_for_pusi_(true),
42 timestamp_unroller_(timestamp_unroller) {
43 DCHECK(es_parser_);
44 DCHECK(timestamp_unroller_);
45 }
46
~TsSectionPes()47 TsSectionPes::~TsSectionPes() {
48 }
49
Parse(bool payload_unit_start_indicator,const uint8 * buf,int size)50 bool TsSectionPes::Parse(bool payload_unit_start_indicator,
51 const uint8* buf, int size) {
52 // Ignore partial PES.
53 if (wait_for_pusi_ && !payload_unit_start_indicator)
54 return true;
55
56 bool parse_result = true;
57 if (payload_unit_start_indicator) {
58 // Try emitting a packet since we might have a pending PES packet
59 // with an undefined size.
60 // In this case, a unit is emitted when the next unit is coming.
61 int raw_pes_size;
62 const uint8* raw_pes;
63 pes_byte_queue_.Peek(&raw_pes, &raw_pes_size);
64 if (raw_pes_size > 0)
65 parse_result = Emit(true);
66
67 // Reset the state.
68 ResetPesState();
69
70 // Update the state.
71 wait_for_pusi_ = false;
72 }
73
74 // Add the data to the parser state.
75 if (size > 0)
76 pes_byte_queue_.Push(buf, size);
77
78 // Try emitting the current PES packet.
79 return (parse_result && Emit(false));
80 }
81
Flush()82 void TsSectionPes::Flush() {
83 // Try emitting a packet since we might have a pending PES packet
84 // with an undefined size.
85 Emit(true);
86
87 // Flush the underlying ES parser.
88 es_parser_->Flush();
89 }
90
Reset()91 void TsSectionPes::Reset() {
92 ResetPesState();
93 es_parser_->Reset();
94 }
95
Emit(bool emit_for_unknown_size)96 bool TsSectionPes::Emit(bool emit_for_unknown_size) {
97 int raw_pes_size;
98 const uint8* raw_pes;
99 pes_byte_queue_.Peek(&raw_pes, &raw_pes_size);
100
101 // A PES should be at least 6 bytes.
102 // Wait for more data to come if not enough bytes.
103 if (raw_pes_size < 6)
104 return true;
105
106 // Check whether we have enough data to start parsing.
107 int pes_packet_length =
108 (static_cast<int>(raw_pes[4]) << 8) |
109 (static_cast<int>(raw_pes[5]));
110 if ((pes_packet_length == 0 && !emit_for_unknown_size) ||
111 (pes_packet_length != 0 && raw_pes_size < pes_packet_length + 6)) {
112 // Wait for more data to come either because:
113 // - there are not enough bytes,
114 // - or the PES size is unknown and the "force emit" flag is not set.
115 // (PES size might be unknown for video PES packet).
116 return true;
117 }
118 DVLOG(LOG_LEVEL_PES) << "pes_packet_length=" << pes_packet_length;
119
120 // Parse the packet.
121 bool parse_result = ParseInternal(raw_pes, raw_pes_size);
122
123 // Reset the state.
124 ResetPesState();
125
126 return parse_result;
127 }
128
ParseInternal(const uint8 * raw_pes,int raw_pes_size)129 bool TsSectionPes::ParseInternal(const uint8* raw_pes, int raw_pes_size) {
130 BitReader bit_reader(raw_pes, raw_pes_size);
131
132 // Read up to the pes_packet_length (6 bytes).
133 int packet_start_code_prefix;
134 int stream_id;
135 int pes_packet_length;
136 RCHECK(bit_reader.ReadBits(24, &packet_start_code_prefix));
137 RCHECK(bit_reader.ReadBits(8, &stream_id));
138 RCHECK(bit_reader.ReadBits(16, &pes_packet_length));
139
140 RCHECK(packet_start_code_prefix == kPesStartCode);
141 DVLOG(LOG_LEVEL_PES) << "stream_id=" << std::hex << stream_id << std::dec;
142 if (pes_packet_length == 0)
143 pes_packet_length = bit_reader.bits_available() / 8;
144
145 // Ignore the PES for unknown stream IDs.
146 // See ITU H.222 Table 2-22 "Stream_id assignments"
147 bool is_audio_stream_id = ((stream_id & 0xe0) == 0xc0);
148 bool is_video_stream_id = ((stream_id & 0xf0) == 0xe0);
149 if (!is_audio_stream_id && !is_video_stream_id)
150 return true;
151
152 // Read up to "pes_header_data_length".
153 int dummy_2;
154 int PES_scrambling_control;
155 int PES_priority;
156 int data_alignment_indicator;
157 int copyright;
158 int original_or_copy;
159 int pts_dts_flags;
160 int escr_flag;
161 int es_rate_flag;
162 int dsm_trick_mode_flag;
163 int additional_copy_info_flag;
164 int pes_crc_flag;
165 int pes_extension_flag;
166 int pes_header_data_length;
167 RCHECK(bit_reader.ReadBits(2, &dummy_2));
168 RCHECK(dummy_2 == 0x2);
169 RCHECK(bit_reader.ReadBits(2, &PES_scrambling_control));
170 RCHECK(bit_reader.ReadBits(1, &PES_priority));
171 RCHECK(bit_reader.ReadBits(1, &data_alignment_indicator));
172 RCHECK(bit_reader.ReadBits(1, ©right));
173 RCHECK(bit_reader.ReadBits(1, &original_or_copy));
174 RCHECK(bit_reader.ReadBits(2, &pts_dts_flags));
175 RCHECK(bit_reader.ReadBits(1, &escr_flag));
176 RCHECK(bit_reader.ReadBits(1, &es_rate_flag));
177 RCHECK(bit_reader.ReadBits(1, &dsm_trick_mode_flag));
178 RCHECK(bit_reader.ReadBits(1, &additional_copy_info_flag));
179 RCHECK(bit_reader.ReadBits(1, &pes_crc_flag));
180 RCHECK(bit_reader.ReadBits(1, &pes_extension_flag));
181 RCHECK(bit_reader.ReadBits(8, &pes_header_data_length));
182 int pes_header_start_size = bit_reader.bits_available() / 8;
183
184 // Compute the size and the offset of the ES payload.
185 // "6" for the 6 bytes read before and including |pes_packet_length|.
186 // "3" for the 3 bytes read before and including |pes_header_data_length|.
187 int es_size = pes_packet_length - 3 - pes_header_data_length;
188 int es_offset = 6 + 3 + pes_header_data_length;
189 RCHECK(es_size >= 0);
190 RCHECK(es_offset + es_size <= raw_pes_size);
191
192 // Read the timing information section.
193 bool is_pts_valid = false;
194 bool is_dts_valid = false;
195 int64 pts_section = 0;
196 int64 dts_section = 0;
197 if (pts_dts_flags == 0x2) {
198 RCHECK(bit_reader.ReadBits(40, &pts_section));
199 RCHECK((((pts_section >> 36) & 0xf) == 0x2) &&
200 IsTimestampSectionValid(pts_section));
201 is_pts_valid = true;
202 }
203 if (pts_dts_flags == 0x3) {
204 RCHECK(bit_reader.ReadBits(40, &pts_section));
205 RCHECK(bit_reader.ReadBits(40, &dts_section));
206 RCHECK((((pts_section >> 36) & 0xf) == 0x3) &&
207 IsTimestampSectionValid(pts_section));
208 RCHECK((((dts_section >> 36) & 0xf) == 0x1) &&
209 IsTimestampSectionValid(dts_section));
210 is_pts_valid = true;
211 is_dts_valid = true;
212 }
213
214 // Convert and unroll the timestamps.
215 base::TimeDelta media_pts(kNoTimestamp());
216 DecodeTimestamp media_dts(kNoDecodeTimestamp());
217 if (is_pts_valid) {
218 int64 pts = timestamp_unroller_->GetUnrolledTimestamp(
219 ConvertTimestampSectionToTimestamp(pts_section));
220 media_pts = base::TimeDelta::FromMicroseconds((1000 * pts) / 90);
221 }
222 if (is_dts_valid) {
223 int64 dts = timestamp_unroller_->GetUnrolledTimestamp(
224 ConvertTimestampSectionToTimestamp(dts_section));
225 media_dts = DecodeTimestamp::FromMicroseconds((1000 * dts) / 90);
226 }
227
228 // Discard the rest of the PES packet header.
229 // TODO(damienv): check if some info of the PES packet header are useful.
230 DCHECK_EQ(bit_reader.bits_available() % 8, 0);
231 int pes_header_remaining_size = pes_header_data_length -
232 (pes_header_start_size - bit_reader.bits_available() / 8);
233 RCHECK(pes_header_remaining_size >= 0);
234
235 // Read the PES packet.
236 DVLOG(LOG_LEVEL_PES)
237 << "Emit a reassembled PES:"
238 << " size=" << es_size
239 << " pts=" << media_pts.InMilliseconds()
240 << " dts=" << media_dts.InMilliseconds()
241 << " data_alignment_indicator=" << data_alignment_indicator;
242 return es_parser_->Parse(&raw_pes[es_offset], es_size, media_pts, media_dts);
243 }
244
ResetPesState()245 void TsSectionPes::ResetPesState() {
246 pes_byte_queue_.Reset();
247 wait_for_pusi_ = true;
248 }
249
250 } // namespace mp2t
251 } // namespace media
252