Format of channels.dat

[UPollaehne]

Hi,

 

in the ShortCutter_Source.zip I found a description of the channels.dat structure.

First tests with Java were successful to the point that there was one byte at the end which I do not know what to do.

 

So my question is: Is the field Encrypted of TChannel a Byte or a Word?

[Griga]

The following facts have to be considered when accessing the channels.dat:

 

- The Delphi Compiler does a 4-bytes-alignment for all DWord values. So if a value that occupies only one byte is followed by a DWord or Integer, there will be up to three unused bytes in between (e.g. after the first member "Tunertype", an enumerated type, that is coded as a byte, and the subsequent DWord Frequency).

 

Word values are aligned at 2-byte-boundaries respectively.

 

- The "Short String" type that is used in the structure consists of 1 length byte, followed by the characters. Thus String[25] occupies 26 bytes - the length byte and a maximum of 25 characters (some or all of them may be unused).

 

- The "Encrypted" member is a byte that contains the following information:

 

Bit 0 set: Channel is encrypted.

Bit 1 set: EPG is excluded from the "What's Now" tab.

Bit 2 set: Channel provides RDS (radio text).

 

I hope it helps...

[UPollaehne]

I hope it helps...

<{POST_SNAPBACK}>

Oh yes, this helps a lot. Many thanks.

I knew that Pascal strings start with a length byte but I was not aware of the padding bytes.

 

BTW:

• An enumeration in Delphi depends on the MINENUMSIZE (default 1 Byte).
  
• A DWord hast 2 Words.
  
• A Word has 2 Bytes.
  
• DWord and Word types are stored in Intel (Little Endian) order.
  

So, in the light of this new knowledge I have to count bytes...

 

And additional thanks for the description of the "Encrypted" byte.

Edited May 8, 2006 by UPollaehne

[Griga]

An enumeration in Delphi is stored as DWord.

No. Depends on the MINENUMSIZE compiler directive. The default is 1 byte (used in DVBViewer), which means enumerations with up to 256 values are stored as a byte.

[UPollaehne]

No. Depends on the MINENUMSIZE compiler directive. The default is 1 byte (used in DVBViewer), which means enumerations with up to 256 values are stored as a byte.

<{POST_SNAPBACK}>

Thanks for the correction (I edited my posting). This clearly shows that I have to thoroughly look up the different types used in this structure.

 

But the other statements hold true?

[Griga]

Yes

[UPollaehne]

After getting around the Java-Does-Not-Have-Unsigned-Types issue I finally have a working reader but there remain some quirks:

 

There is an extra byte at the end of each channel definition.

 

There is a discrepancy between the FEC value stored in the channels.dat and the value exported to an INI file. While there is value 0 in the DAT file the exported INI contains -1. But reading the Channel ShortCutter source I do not know what a value of 0 does mean for FEC.

 

The GE does not export NetworkID and SatModulation to INI files whereas the Pro does.

[Guest Lars_MQ]

NetworkID and SatModulation to INI files whereas the Pro does.

The NID more the ONID (OriginalNetworkID)(word value) will be important in the future. The SatModulation (byte) is for upcoming DVB-S2 cards. The NID is present in the channelsdat, the SatModulation is in one of the unused bytes, I'll have to lookup which one...

[UPollaehne]

The NID more the ONID (OriginalNetworkID)(word value) will be important in the future. The SatModulation (byte) is for upcoming DVB-S2 cards. The NID is present in the channelsdat, the SatModulation is in one of the unused bytes, I'll have to lookup which one...

<{POST_SNAPBACK}>

 

It would be really nice to know which one. Thanks in advance.

[Guest Lars_MQ]

  AVFormat: Byte; 
   FEC: Byte; 
   SatModulation: Byte;

It's the byte after FEC

[UPollaehne]

  AVFormat: Byte; 
   FEC: Byte; 
   SatModulation: Byte;

It's the byte after FEC

<{POST_SNAPBACK}>

Thanks, and this AVFormat is the AC3 marker?

[Griga]

AVFormat:

 

Low Nibble = 0: MP2 audio stream

Low Nibble = 1: AC3 audio stream

 

High Nibble = 0: MPEG2 video stream

High Nibble = 1: H.264 video stream

 

Other values are reserved for additional audio/video formats.

[xck3001]

Is there a way to detect if a channel is DVB-S2 by COM? ITuner has no property "SatModulation" ...

[xck3001]

OK, seems like I can't access it directly with ITuner, but by GetChannelList()[i,10] it get's transmitted. And I'm using GetChannelList() anyway

[xck3001]

Hm, seems to be a little problematic:

For Premiere HD (which should be DVB-S2) I get SatModulation = 1, the same for Premiere 1 (which is normal DVB-S).

 

For Sat1HD and Pro7HD it works: SatModulation is 2.

 

Why does the value differ from these two DVB-S2 HDTV channels? Is the encryption a problem?

Normal viewing the Premiere HD channel in DVBViewer works, so an incorrect configured channel shouldn't be the problem.

Edited April 28, 2007 by xck3001