Refactor PES parser

Author: fwolter

Makefile

@@ -128,7 +128,7 @@ override CFLAGS	  += $(_CFLAGS) $(DEFINES) $(INCLUDES) \
 ### The object files (add further files here):
 
 OBJS = $(PLUGIN).o audio.o buf2rgb.o codec_audio.o codec_video.o config.o drmbuffer.o drmdevice.o drmplane.o grab.o h264parser.o \
-	logger.o mediaplayer.o queue.o ringbuffer.o softhddevice.o softhdmenu.o softhdosd.o threads.o videorender.o videostream.o
+	logger.o mediaplayer.o pes.o queue.o ringbuffer.o softhddevice.o softhdmenu.o softhdosd.o threads.o videorender.o videostream.o
 
 ifeq ($(GLES),1)
 OBJS += openglosd.o

pes.cpp

@@ -0,0 +1,180 @@
+/**
+ * @file pes.cpp
+ * PES packet parser implementation
+ *
+ * @license{AGPLv3
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.}
+ */
+
+#include "pes.h"
+
+#include "vdr/remux.h"
+
+extern "C"
+{
+#include <libavutil/avutil.h>
+}
+
+/**
+ * Construct a PES packet parser
+ *
+ * @param data Pointer to the raw PES packet data
+ * @param size Size of the PES packet in bytes
+ */
+cPes::cPes(const uint8_t *data, int size)
+	: m_data(data), m_size(size)
+{
+}
+
+/**
+ * Parse the PES packet to detect the video codec
+ *
+ * Analyzes the PES payload to identify the codec type (MPEG2, H.264, or HEVC).
+ * This method looks for codec-specific start codes and stream type identifiers
+ * in the payload. The detected codec can be retrieved using GetCodec().
+ *
+ * Supported codecs:
+ * - MPEG2 (AV_CODEC_ID_MPEG2VIDEO)
+ * - H.264 (AV_CODEC_ID_H264)
+ * - HEVC (AV_CODEC_ID_HEVC)
+ *
+ * @note This method must be called before GetCodec()
+ */
+void cPes::Parse() {
+	int pesPayloadStart = PesPayloadOffset(m_data);
+
+	if (pesPayloadStart + START_CODE_PREFIX_LEN + 1 >= (unsigned int)m_size)
+		return;
+
+	uint32_t firstThreePesPayloadBytes = ReadBytes(pesPayloadStart, START_CODE_PREFIX_LEN);
+	const uint8_t *codecPayload = &m_data[pesPayloadStart + START_CODE_PREFIX_LEN];
+
+	// Looking for the MPEG2 start code and stream type
+	if (firstThreePesPayloadBytes == START_CODE_PREFIX && codecPayload[0] == MPEG2_STREAM_TYPE)
+		m_codec = AV_CODEC_ID_MPEG2VIDEO;
+	// Looking for the H.264/HEVC start code. It can have an optional leading zero byte.
+	else if (ReadBytes(pesPayloadStart + 1, START_CODE_PREFIX_LEN) == START_CODE_PREFIX) {
+		codecPayload++;
+		m_payloadHasLeadingZero = true;
+	} else if (firstThreePesPayloadBytes != START_CODE_PREFIX)
+		return; // no start code found
+
+	if (m_size > &codecPayload[7] - m_data) {
+		if (     codecPayload[0] == H264_STREAM_TYPE && (codecPayload[1] == 0x10 || codecPayload[1] == 0xF0 || codecPayload[7] == 0x64))
+			m_codec = AV_CODEC_ID_H264;
+		else if (codecPayload[0] == HEVC_STREAM_TYPE && (codecPayload[1] == 0x10 || codecPayload[1] == 0x50 || codecPayload[7] == 0x40))
+			m_codec = AV_CODEC_ID_HEVC;
+	}
+}
+
+uint32_t cPes::ReadBytes(int offset, int count)
+{
+	uint32_t value = 0;
+
+	for (int i = 0; i < count; i++) {
+		value <<= 8;
+		value |= m_data[offset + i];
+	}
+
+	return value;
+}
+
+/**
+ * Check if the PES header is valid
+ *
+ * Validates that the PES packet has a valid header by checking:
+ * - The packet is long enough to contain a header
+ * - The start code prefix (0x000001) is present
+ *
+ * @return true if the header is valid, false otherwise
+ */
+bool cPes::IsHeaderValid()
+{
+	return PesLongEnough(m_size) && ReadBytes(0, 3) == START_CODE_PREFIX;
+}
+
+/**
+ * Check if this is a video stream
+ *
+ * Determines if the PES packet contains a video stream based on the stream ID.
+ * Video streams have stream IDs in the range 0xE0-0xEF according to
+ * H.222.0 03/2017 Table 2-22.
+ *
+ * @return true if this is a video stream, false otherwise
+ */
+bool cPes::IsVideoStream()
+{
+	// The low nibble is the stream number
+	return (GetStreamId() & 0xF0) == 0xE0;
+}
+
+/**
+ * Check if this is an audio stream
+ *
+ * Determines if the PES packet contains an audio stream based on the stream ID.
+ * Audio streams have stream IDs in the range 0xC0-0xCF according to
+ * H.222.0 03/2017 Table 2-22.
+ *
+ * @return true if this is an audio stream, false otherwise
+ */
+bool cPes::IsAudioStream()
+{
+	// The low nibble is the stream number
+	return (GetStreamId() & 0xF0) == 0xC0;
+}
+
+/**
+ * Get the Presentation Time Stamp (PTS) from the PES header
+ *
+ * Extracts the PTS value from the PES packet header if present.
+ * The PTS indicates when the decoded content should be presented.
+ *
+ * @return The PTS value in 90 kHz units, or AV_NOPTS_VALUE if no PTS is present
+ */
+int64_t cPes::GetPts()
+{
+	if (!PesHasPts(m_data))
+		return AV_NOPTS_VALUE;
+
+	return PesGetPts(m_data);
+}
+
+/**
+ * Get a pointer to the PES payload data
+ *
+ * Returns a pointer to the start of the payload data, skipping the PES header.
+ * For H.264/HEVC streams with a leading zero byte, the leading zero is also skipped.
+ *
+ * @return Pointer to the payload data
+ */
+const uint8_t *cPes::GetPayload()
+{
+	int headerLen = PesPayloadOffset(m_data);
+
+	if (m_payloadHasLeadingZero)
+		headerLen++; // Skip the leading zero byte for H.264/HEVC
+
+	return &m_data[headerLen];
+}
+
+/**
+ * Get the size of the PES payload
+ *
+ * Calculates the size of the payload by subtracting the header size
+ * (and optional leading zero for H.264/HEVC) from the total packet size.
+ *
+ * @return Size of the payload in bytes
+ */
+int cPes::GetPayloadSize()
+{
+	return m_size - (GetPayload() - m_data);
+}

pes.h

@@ -0,0 +1,86 @@
+/**
+ * @file pes.h
+ * PES packet parser header
+ *
+ * @copyright (c) 2025 by Andreas Baierl. All Rights Reserved.
+ *
+ * @license{AGPLv3
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.}
+ */
+
+#ifndef __SOFTHDDEVICE_PES_H
+#define __SOFTHDDEVICE_PES_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+extern "C"
+{
+#include <libavcodec/avcodec.h>
+}
+
+/**
+ * @brief Convert AVCodecID to a human-readable string
+ *
+ * @param c The codec ID to convert
+ * @return A string representation of the codec ID
+ */
+constexpr const char* to_string(AVCodecID c) {
+    switch (c) {
+        case AV_CODEC_ID_NONE: return "None";
+        case AV_CODEC_ID_MPEG2VIDEO: return "MPEG2";
+        case AV_CODEC_ID_H264: return "H.264";
+        case AV_CODEC_ID_HEVC: return "HEVC";
+		default: return "Unknown codec";
+    }
+}
+
+/**
+ * PES packet parser class
+ *
+ * This class parses PES (Packetized Elementary Stream) packets
+ * to extract header information, video codec, PTS, and payload data.
+ */
+class cPes
+{
+public:
+	cPes(const uint8_t *data, int size);
+	void Parse();
+	bool IsHeaderValid();
+	bool IsVideoStream();
+	bool IsAudioStream();
+	AVCodecID GetCodec() { return m_codec; }
+	int64_t GetPts();
+	const uint8_t *GetPayload();
+	int GetPayloadSize();
+
+	private:
+	uint32_t ReadBytes(int offset, int count);
+	uint8_t GetStreamId() { return m_data[3]; }
+	AVCodecID ParseCodec();
+
+	// According to H.222.0 03/2017 Table 2-21 packet_start_code_prefix
+	// And also according to H.264/HEVC payload
+	static constexpr uint32_t START_CODE_PREFIX = 0x00'0001;
+	static constexpr uint32_t START_CODE_PREFIX_LEN = 3;
+
+	static constexpr uint8_t MPEG2_STREAM_TYPE = 0xB3;
+	static constexpr uint8_t H264_STREAM_TYPE = 0x09;
+	static constexpr uint8_t HEVC_STREAM_TYPE = 0x46;
+
+	const uint8_t *m_data;   ///< pointer to the raw PES packet data
+	int m_size;              ///< size of the PES packet
+	bool m_payloadHasLeadingZero = false;   ///< flag indicating if codec payload has leading zero byte for H.264/HEVC
+	AVCodecID m_codec = AV_CODEC_ID_NONE; ///< detected codec ID
+};
+
+#endif