some more work on teletext single-page parsing

1 files changed, 216 insertions, 7 deletions

diff --git a/lib/dvb/teletext.cpp b/lib/dvb/teletext.cpp
index e05891c4..17020bb3 100644
--- a/lib/dvb/teletext.cpp
+++ b/lib/dvb/teletext.cpp
@@ -1,33 +1,242 @@
 #include <lib/base/eerror.h>
 #include <lib/dvb/teletext.h>
 #include <lib/dvb/idemux.h>
+#include <lib/gdi/gpixmap.h>
+
+/*
+ This is a very simple en300 706 telext decoder.
+ 
+ It can only decode a single page at a time, thus it's only used
+ for subtitles.
+ 
+ */
 
 DEFINE_REF(eDVBTeletextParser);
 
+	/* we asumme error free transmission! */
+static inline unsigned char decode_odd_parity(unsigned char *b)
+{
+	int i;
+	unsigned char res = 0;
+	for (i=0; i<7; ++i)
+		if (*b & (0x80 >> i))
+			res |= 1<<i;
+	return res;
+}
+
+static inline unsigned char decode_hamming_84(unsigned char *b)
+{
+	unsigned char res = 0;
+	res |= (*b << 3) & 8;
+	res |= (*b     ) & 4;
+	res |= (*b >> 3) & 2;
+	res |= (*b >> 6) & 1;
+	return res;
+}
+
+static inline unsigned long decode_hamming_2418(unsigned char *b)
+{
+	unsigned long h24 = b[0] | (b[1] << 8) | (b[2] << 16);
+	
+	return
+		((h24 & 0x000004) >> 2) |
+		((h24 & 0x000070) >> 3) |
+		((h24 & 0x007f00) >> 4) |
+		((h24 & 0x7f0000) >> 5);
+}
+
 eDVBTeletextParser::eDVBTeletextParser(iDVBDemux *demux)
 {
-	setStreamID(0xBD); // as per en 300 472
+	setStreamID(0xBD); /* as per en 300 472 */
+	
+	setPage(0x150);
 	
 	if (demux->createPESReader(eApp, m_pes_reader))
 		eDebug("failed to create PES reader!");
 	else
 		m_pes_reader->connectRead(slot(*this, &eDVBTeletextParser::processData), m_read_connection);
-		
+}
+
+eDVBTeletextParser::~eDVBTeletextParser()
+{
 }
 
 void eDVBTeletextParser::processPESPacket(__u8 *pkt, int len)
 {
-	eDebug("GOT TELETEXT PACKET:");
-	int i;
-	for (i=0; i<16; ++i)
-		eDebugNoNewLine("%02x ", pkt[i]);
-	eDebug("<");
+	unsigned char *p = pkt;
+	
+	p += 4; len -= 4; /* start code, already be verified by pes parser */
+	p += 2; len -= 2; /* length, better use the argument */	
+	
+	p += 3; len -= 3; /* pes header */
+	
+	p += 0x24; len -= 0x24; /* skip header */
+	
+//	eDebug("data identifier: %02x", *p);
+	
+	p++; len--;
+	
+	while (len > 2)
+	{
+		unsigned char data_unit_id = *p++;
+		unsigned char data_unit_length = *p++;
+		len -= 2;
+		
+		if (len < data_unit_length)
+		{
+			eDebug("data_unit_length > len");
+			break;
+		}
+		
+		if (data_unit_length != 44)
+		{
+			eDebug("illegal data unit length %d", data_unit_length);
+			break;
+		}
+		
+		unsigned char line_offset = *p++; len--;
+		unsigned char framing_code = *p++; len--;
+
+		int magazine_and_packet_address = decode_hamming_84(p++); len--;
+		magazine_and_packet_address |= decode_hamming_84(p++)<<4; len--;
+		
+		unsigned char *data = p; p += 40; len -= 40;
+		
+		if (framing_code != 0xe4) /* no teletxt data */
+			continue;
+		
+		m_M = magazine_and_packet_address & 7;
+		m_Y = magazine_and_packet_address >> 3;
+//		eDebug("line %d, framing code: %02x, M=%02x, Y=%02x", line_offset, framing_code, M, Y);
+		
+		if (m_Y == 0) /* page header */
+		{
+			m_C = 0;
+			
+			m_S1 = decode_hamming_84(data + 2); /* S1 */
+			int S2C4 = decode_hamming_84(data + 3);
+			
+			m_S2 = S2C4 & 7;
+			m_C |= (S2C4 & 8) ? (1<<4) : 0;
+			
+			m_S3 = decode_hamming_84(data + 4);
+			
+			int S4C5C6 = decode_hamming_84(data + 5);
+			
+			m_S4 = S4C5C6 & 3;
+			m_C |= (S4C5C6 & 0xC) << 3;
+			
+			m_C |= decode_hamming_84(data + 6) << 7;
+			m_C |= decode_hamming_84(data + 7) << 11;
+			
+				/* page on the same magazine? end current page. */
+			if ((m_M == m_page_M) && (m_page_open))
+			{
+				handlePageEnd();
+				m_page_open = 0;
+			}
+			
+			m_X = decode_hamming_84(data+1) * 0x10 + decode_hamming_84(data);
+			
+				/* correct page on correct magazine? open page. */
+			if ((m_M == m_page_M) && (m_X == m_page_X))
+			{
+				handlePageStart();
+				m_page_open = 1;
+				handleLine(data + 8, 32);
+			}
+		} else
+		{
+			/* data for the selected page? */
+			if ((m_M == m_page_M) && m_page_open)
+				handleLine(data, 40);
+		}
+	}
 }
 
 int eDVBTeletextParser::start(int pid)
 {
+	m_page_open = 0;
+
 	if (m_pes_reader)
 		return m_pes_reader->start(pid);
 	else
 		return -1;
 }
+
+void eDVBTeletextParser::handlePageStart()
+{
+	if (m_C & (1<<4)) /* erase flag set */
+		m_subtitle_page.clear();
+}
+
+void eDVBTeletextParser::handleLine(unsigned char *data, int len)
+{
+	if (!m_Y) /* first line is page header, we don't need that. */
+		return;
+
+	int last_was_white = 1, color = -1;
+	
+	std::string text;
+	
+	for (int i=0; i<len; ++i)
+	{
+		unsigned char b = decode_odd_parity(data + i);
+	
+		if (b < 0x10) /* spacing attribute */
+		{
+			if (b < 8) /* colors */
+			{
+				if (b != color) /* new color is split into a new string */
+				{
+					if (color != -1)
+						addSubtitleString(color, text);
+					text = "";
+					color = b;
+				}
+			}
+				/* ignore other attributes */
+		} else
+		{
+				/* no more than one whitespace, only printable chars */
+			if (((!last_was_white) || (b != ' ')) && (b >= 0x20))
+			{
+				text += b;
+				last_was_white = b == ' ';
+			}
+		}
+	}
+	addSubtitleString(color, text);
+}
+
+void eDVBTeletextParser::handlePageEnd()
+{
+	addSubtitleString(-1, ""); /* end last line */ 
+	sendSubtitlePage();  /* send assembled subtitle page to display */
+}
+
+void eDVBTeletextParser::setPage(int page)
+{
+	m_page_M = (page >> 8) & 7; /* magazine to look for */
+	m_page_X = page & 0xFF;     /* page number */
+}
+
+void eDVBTeletextParser::addSubtitleString(int color, const std::string &string)
+{
+	if ((color != m_subtitle_color) && !m_subtitle_text.empty())
+	{
+		m_subtitle_page.m_elements.push_back(eDVBTeletextSubtitlePageElement(gRGB(0, 0xff, 0), m_subtitle_text));
+		m_subtitle_text = "";
+	} else if (!m_subtitle_text.empty() && m_subtitle_text[m_subtitle_text.size()-1] != ' ')
+		m_subtitle_text += " ";
+	
+	m_subtitle_color = color;
+	m_subtitle_text += string;
+}
+
+void eDVBTeletextParser::sendSubtitlePage()
+{
+	eDebug("subtitle page:");
+	for (unsigned int i = 0; i < m_subtitle_page.m_elements.size(); ++i)
+		eDebug("%s", m_subtitle_page.m_elements[i].m_text.c_str());
+}