martin.dauskardt at gmx
Jun 7, 2009, 12:40 AM
Views: 763
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V4L2_CID_MPEG_VIDEO_ASPECT vs. Wide-screen signaling
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The pvrinput plugin for vdr reads a PES stream from an mpeg encoder card and
converts it into a Transport stream, which is needed by vdr.
The PES stream should include all available vbi data, because we embedd vbi
into the mpeg stream using
vbifmt.fmt.sliced.service_set = V4L2_SLICED_VBI_625;
vbifmt.type = V4L2_BUF_TYPE_SLICED_VBI_CAPTURE;
The plugin also sets V4L2_CID_MPEG_VIDEO_ASPECT to a fix value, which results
for example in a 4:3 format.
Since some time I recognize that analogue broadcastings (for example RTL) have
a 16:9 anarmorphic format, so the TV needs to stretch it. Unfortunately the
TV does not detect the anarmorphic format. It seems that the 4:3 setting from
V4L2_CID_MPEG_VIDEO_ASPECT overrides any wss data.
What is the relation between this mpeg control and the wss vbi data? Should I
really change V4L2_CID_MPEG_VIDEO_ASPECT every time the wss data bit
switches?
Furthermore, I am not sure if the PES to TS conversion handles the vbi data
properly. It works for Teletext, but maybe something is missing to make sure
that also the wss vbi data gets inserted into the transport stream.
This is the current code (I shortend it so that it contains only the vbi
stuff):
void cPvrReadThread::PesToTs(uint8_t * Data, uint32_t Length) {
uint8_t stream_id;
bool first = true;
uint32_t i;
const short PayloadSize = TS_SIZE - 4;
uint32_t Payload_Count = Length / PayloadSize;
uint32_t Payload_Rest = Length % PayloadSize;
stream_id = Data[3];
switch (stream_id) {
case 0xBD: {
uint8_t * payload_data;
uint16_t payload_length;
uint32_t pos = 0;
uint32_t ts_pos = 0;
memset(ts_buffer, 0, TS_SIZE);
ts_buffer[0] = TS_SYNC_BYTE;
ts_buffer[1] = kTeletextPid >> 8;
ts_buffer[2] = kTeletextPid & 0xFF;
ts_buffer[3] = 0x10 | text_counter;
payload_length = Length - 9 - Data[8];
payload_data = Data + 9 + Data[8];
if (memcmp(payload_data, "itv0", 4) == 0)
pos = 12;
else
if (memcmp(payload_data, "ITV0", 4) == 0)
pos = 4;
else
return;
while (pos + 43 <= payload_length) {
if ((payload_data[pos] & 0x0F) == 0x01) {
ts_buffer[4+ts_pos*46] = 0x02; // data_unit_id
ts_buffer[5+ts_pos*46] = 0x2C; // data_unit_length
ts_buffer[6+ts_pos*46] = 0x00; // field_parity, line_offset
ts_buffer[7+ts_pos*46] = 0xE4; // framing_code
for (int j = 0; j < 42; j++) {
ts_buffer[8 + ts_pos * 46 + j] = kInvTab[payload_data[pos + 1 +
j]];
}
ts_pos++;
if (ts_pos == 4) {
ts_pos = 0;
PutData(ts_buffer, TS_SIZE);
text_counter = (text_counter + 1) & 15;
memset(ts_buffer, 0, TS_SIZE);
ts_buffer[0] = TS_SYNC_BYTE;
ts_buffer[1] = kTeletextPid >> 8;
ts_buffer[2] = kTeletextPid & 0xFF;
ts_buffer[3] = 0x10 | text_counter;
}
}
pos += 43;
}
if (ts_pos > 0) {
PutData(ts_buffer, TS_SIZE);
text_counter = (text_counter + 1) & 15;
}
break; // end: case 0xBD:
}
} // end: switch (stream_id)
}
Any help is welcome.
Greets,
Martin
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V4L2_CID_MPEG_VIDEO_ASPECT vs. Wide-screen signaling
