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9200T Disk Structure - one for the techies

Discussion in 'PVR-9200 Freeview Recorder' started by Astronomy, Jul 3, 2011.

  1. Astronomy

    Astronomy New Member

    Looking for info on how the Humax 9200T disk drive is laid out. I've read both these pages:

    http://humaxdisk.wikispaces.com/Disk+Format
    http://www.mudup.co.uk/humax/9200T/

    But I am still short of information. All the info makes sense on those 2 web sites and I've even managed to download an entire program straight off the disk, however I don't know how the entries like 2.av link to the FAT entries and ultimately the data for the program. I also can't find the recorded program information.

    For example, the following data (already reversed) is from 4EC00 + 12C:
    Code:
    0000 004B 0000 004C 0000 004D 0000 004E 0000 004F 0000 0050 etc
    No problem getting from 4B to the actual data for the program but the problem is I don't know which program this is nor where the information for it is stored (e.g. "Charlie and Lola grow a plant").

    Here is the entry showing 22.av:

    Code:
    0000 0000 0000 0000 0000 0000 02AE B72A .............®·*
    0000 0000 02FA A49A 0000 0000 001B E510 .....ú¤š......å.
    0000 0000 37C6 AA00 0000 1002 0000 000B ....7ƪ.........
    0000 0000 0000 0000 0000 0000 0000 0000 ................
    3232 2E61 7600 0000 0000 0000 0000 0000 22.av...........
    0000 0000 0000 0000 0000 0000 0000 0000 ................
    0000 0000 0000 0000 0000 0000 0000 0000 ................
    0000 0000 0000 0000 0000 0000 2245 22DD ............"E"Ý
    I understand that 02AEB72A x200 is the start of the file and 37C6AA00 is the length, hence I can download the file but which file is it? Where is the name, start time, program info, etc?

    And how does "02AEB72A x200" link to the FAT entry like that shown above (probably not the FAT entry for that file)? The web site says "divide this by 5E000 to obtain 1st FAT entry position" but doing that gives E9C6 - which is what??

    Lots of questions there, hopefully some boffin will pick through it and fill in the blanks that I have. I very nearly understand the Humax disk format but lack these few details.

    Cheers
     
  2. xyz321

    xyz321 Well-Known Member

    Knowing the start and the length doesn't give you all the necessary infomation to download the file. It may not be contiguous, which is why a FAT is needed. BTW there are a couple of extra parameters in there not indicated on the web sites. 02FAA49A x200 is the position of the last block in the file - it should match the FAT, if not there is a disk corruption problem. 001BE510 is the number of 512 byte sectors allocated to the file.

    E9C6 is the offset (in words) from the start of the FAT (+1 because the initial FAT entry is used to stored the number of free blocks on disk). When you look up this FAT entry it indicates where the next block on disk is.

    In order to link 2.av to the recording details you have to look for the file _RECORD_LIST_ on the second partition. This is pretty much the contents of all the humaxrw .hre files stored as a single file. There is also 2.epg on this partition which stores the synopsis.
     
  3. Astronomy

    Astronomy New Member

    Thanks for the info, good to see what some of the other bytes tell us. The file I downloaded was contiguous (and short) but proved I understood the websites instructions.

    Still stuck on the program info though. I had a little sniff around the HDD but it's like trying to find a needle in a 500Gb haystack. There must be a reference to where the _RECORD_LIST_ is stored or even where the start of the 2nd partition is, no?

    For the FAT, 4EC00+E9C6+1 would be the first entry for that particular file? Understandable.

    Apologies if this sounds like I'm a complete beginner but I am :) But I'm an interested beginner who's only a little slow.
     
  4. xyz321

    xyz321 Well-Known Member

    The three partitions all follow the same format but the sizes of some of the structures are different e.g each FAT entry represents a smaller area on disk for the second partition. To find the partitions you need to look at the first sector on the disk. For each partition this gives the size and the starting point (see the first page in the 'mudup' link).

    At the start of each partition is a table which gives the locations and sizes of the other structures within that partition. For the first partition this is at 0x2000 (see the link ..00000002000-00000021ff). There is one important parameter not highlighted in that link. This is the 'start of FAT' parameter which has the value 0x276 for that example.

    BTW if anyone can work out how the 'CRC' is generated for this table, this could be useful. It might then be possible to have user defined partition sizes.

    Yes, and for a contiguous file it should contain E9C7.
     
  5. Astronomy

    Astronomy New Member

    Thanks again. I had a quick look in the EPG Partition but never seen it the first time hence not linking 2nd partition with epg partition, doh. Found it now though and will play around a little to see what if I can link all this stuff together.

    Cheers.